The characterization of gene expression in cells via measurement of mRNA levels is a useful tool in determining how the transcriptional machinery of the cell is affected by external signals (e.g. drug treatment), or how cells differ between a healthy state and a diseased state. With the advent and continuous refinement of next-generation DNA sequencing technology, RNA-sequencing (RNA-seq) has become an increasingly popular method of transcriptome analysis to catalog all species of transcripts, to determine the transcriptional structure of all expressed genes and to quantify the changing expression levels of the total set of transcripts in a given cell, tissue or organism1,2 . RNA-seq is gradually replacing DNA microarrays as a preferred method for transcriptome analysis because it has the advantages of profiling a complete transcriptome, providing a digital type datum (copy number of any transcript) and not relying on any known genomic sequence3.
Here, we present a complete and detailed protocol to apply RNA-seq to profile transcriptomes in human pulmonary microvascular endothelial cells with or without thrombin treatment. This protocol is based on our recent published study entitled "RNA-seq Reveals Novel Transcriptome of Genes and Their Isoforms in Human Pulmonary Microvascular Endothelial Cells Treated with Thrombin,"4 in which we successfully performed the first complete transcriptome analysis of human pulmonary microvascular endothelial cells treated with thrombin using RNA-seq. It yielded unprecedented resources for further experimentation to gain insights into molecular mechanisms underlying thrombin-mediated endothelial dysfunction in the pathogenesis of inflammatory conditions, cancer, diabetes, and coronary heart disease, and provides potential new leads for therapeutic targets to those diseases.
The descriptive text of this protocol is divided into four parts. The first part describes the treatment of human pulmonary microvascular endothelial cells with thrombin and RNA isolation, quality analysis and quantification. The second part describes library construction and sequencing. The third part describes the data analysis. The fourth part describes an RT-PCR validation assay. Representative results of several key steps are displayed. Useful tips or precautions to boost success in key steps are provided in the Discussion section. Although this protocol uses human pulmonary microvascular endothelial cells treated with thrombin, it can be generalized to profile transcriptomes in both mammalian and non-mammalian cells and in tissues treated with different stimuli or inhibitors, or to compare transcriptomes in cells or tissues between a healthy state and a disease state.
23 Related JoVE Articles!
High-throughput Screening and Biosensing with Fluorescent C. elegans Strains
Institutions: University of Florida, Mount Desert Island Biological Laboratory.
High-throughput screening (HTS) is a powerful approach for identifying chemical modulators of biological processes. However, many compounds identified in screens using cell culture models are often found to be toxic or pharmacologically inactive in vivo1-2
. Screening in whole animal models can help avoid these pitfalls and streamline the path to drug development.
is a multicellular model organism well suited for HTS. It is small (<1 mm) and can be economically cultured and dispensed in liquids. C. elegans
is also one of the most experimentally tractable animal models permitting rapid and detailed identification of drug mode-of-action3
We describe a protocol for culturing and dispensing fluorescent strains of C. elegans
for high-throughput screening of chemical libraries or detection of environmental contaminants that alter the expression of a specific gene. Large numbers of developmentally synchronized worms are grown in liquid culture, harvested, washed, and suspended at a defined density. Worms are then added to black, flat-bottomed 384-well plates using a peristaltic liquid dispenser. Small molecules from a chemical library or test samples (e.g., water, food, or soil) can be added to wells with worms. In vivo
, real-time fluorescence intensity is measured with a fluorescence microplate reader. This method can be adapted to any inducible gene in C. elegans
for which a suitable reporter is available. Many inducible stress and developmental transcriptional pathways are well defined in C. elegans
and GFP transgenic reporter strains already exist for many of them4
. When combined with the appropriate transgenic reporters, our method can be used to screen for pathway modulators or to develop robust biosensor assays for environmental contaminants.
We demonstrate our C. elegans
culture and dispensing protocol with an HTS assay we developed to monitor the C. elegans
cap ‘n’ collar transcription factor SKN-1. SKN-1 and its mammalian homologue Nrf2 activate cytoprotective genes during oxidative and xenobiotic stress5-10
. Nrf2 protects mammals from numerous age-related disorders such as cancer, neurodegeneration, and chronic inflammation and has become a major chemotherapeutic target11-13
.Our assay is based on a GFP transgenic reporter for the SKN-1 target gene gst
, which encodes a glutathione-s transferase6
. The gst
-4 reporter is also a biosensor for xenobiotic and oxidative chemicals that activate SKN-1 and can be used to detect low levels of contaminants such as acrylamide and methyl-mercury15-16
Neuroscience, Issue 51, High-Throughput screening, C. elegans, biosensor, drug discovery, Nrf2, small molecule, oxidant
Automated Separation of C. elegans Variably Colonized by a Bacterial Pathogen
Institutions: University of California, Berkeley.
The wormsorter is an instrument analogous to a FACS machine that is used in studies of Caenorhabditis elegans
, typically to sort worms based on expression of a fluorescent reporter. Here, we highlight an alternative usage of this instrument, for sorting worms according to their degree of colonization by a GFP-expressing pathogen. This new usage allowed us to address the relationship between colonization of the worm intestine and induction of immune responses. While C. elegans
immune responses to different pathogens have been documented, it is still unknown what initiates them. The two main possibilities (which are not mutually exclusive) are recognition of pathogen-associated molecular patterns, and detection of damage caused by infection. To differentiate between the two possibilities, exposure to the pathogen must be dissociated from the damage it causes. The wormsorter enabled separation of worms that were extensively-colonized by the Gram-negative pathogen Pseudomonas aeruginosa
, with the damage likely caused by pathogen load, from worms that were similarly exposed, but not, or marginally, colonized. These distinct populations were used to assess the relationship between pathogen load and the induction of transcriptional immune responses. The results suggest that the two are dissociated, supporting the possibility of pathogen recognition.
Immunology, Issue 85, Innate Immunity, C. elegans, Pseudomonas aeruginosa, wormsorter, pathogen recognition
Osmotic Avoidance in Caenorhabditis elegans: Synaptic Function of Two Genes, Orthologues of Human NRXN1 and NLGN1, as Candidates for Autism
Institutions: Facultad de Ciencias, Universidad de Córdoba, Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC).
Neurexins and neuroligins are cell adhesion molecules present in excitatory and inhibitory synapses, and they are required for correct neuron network function1
. These proteins are found at the presynaptic and postsynaptic membranes 2
. Studies in mice indicate that neurexins and neurologins have an essential role in synaptic transmission 1
. Recent reports have shown that altered neuronal connections during the development of the human nervous system could constitute the basis of the etiology of numerous cases of autism spectrum disorders 3
could be used as an experimental tool to facilitate the study of the functioning of synaptic components, because of its simplicity for laboratory experimentation, and given that its nervous system and synaptic wiring has been fully characterized. In C
. elegans nrx-1
genes are orthologous to human NRXN1
genes which encode alpha-neurexin-1 and neuroligin-1 proteins, respectively. In humans and nematodes, the organization of neurexins and neuroligins is similar in respect to functional domains.
The head of the nematode contains the amphid, a sensory organ of the nematode, which mediates responses to different stimuli, including osmotic strength. The amphid is made of 12 sensory bipolar neurons with ciliated dendrites and one presynaptic terminal axon 4
. Two of these neurons, named ASHR and ASHL are particularly important in osmotic sensory function, detecting water-soluble repellents with high osmotic strength 5
. The dendrites of these two neurons lengthen to the tip of the mouth and the axons extend to the nerve ring, where they make synaptic connections with other neurons determining the behavioral response 6
To evaluate the implications of neurexin and neuroligin in high osmotic strength avoidance, we show the different response of C. elegans mutants defective in nrx-1
genes, using a method based on a 4M fructose ring 7
. The behavioral phenotypes were confirmed using specific RNAi clones 8
. In C. elegans
, the dsRNA required to trigger RNAi can be administered by feeding 9
. The delivery of dsRNA through food induces the RNAi interference of the gene of interest thus allowing the identification of genetic components and network pathways.
Neuroscience, Microbiology, Issue 34, synapse, osmotic sensitivity, Caenorhabditis elegans, neurexin, neuroligin, autism, neuroscience
Isolation and In vitro Activation of Caenorhabditis elegans Sperm
Institutions: Rutgers University.
Males and hermaphrodites are the two naturally found sexual forms in the nematode C. elegans
. The amoeboid sperm are produced by both males and hermaphrodites. In the earlier phase of gametogenesis, the germ cells of hermaphrodites differentiate into limited number of sperm - around 300 - and are stored in a small 'bag' called the spermatheca. Later on, hermaphrodites continually produce oocytes1
. In contrast, males produce exclusively sperm throughout their adulthood. The males produce so much sperm that it accounts for >50% of the total cells in a typical adult worm2
. Therefore, isolating sperm from males is easier than from that of hermaphrodites.
Only a small proportion of males are naturally generated due to spontaneous non-disjunction of X chromosome3
. Crossing hermaphrodites with males or more conveniently, the introduction of mutations to give rise to Him (High Incidence of Males) phenotype are some of strategies through which one can enrich the male population3
Males can be easily distinguished from hermaphrodites by observing the tail morphology4
. Hermaphrodite's tail is pointed, whereas male tail is rounded with mating structures.
Cutting the tail releases vast number of spermatids stored inside the male reproductive tract. Dissection is performed under a stereo microscope using 27 gauge needles. Since spermatids are not physically connected with any other cells, hydraulic pressure expels internal contents of male body, including spermatids2
Males are directly dissected on a small drop of 'Sperm Medium'. Spermatids are sensitive to alteration in the pH. Hence, HEPES, a compound with good buffering capacity is used in sperm media. Glucose and other salts present in sperm media help maintain osmotic pressure to maintain the integrity of sperm.
Post-meiotic differentiation of spermatids into spermatozoa is termed spermiogenesis or sperm activation. Shakes5
, and Nelson6
previously showed that round spermatids can be induced to differentiate into spermatozoa by adding various activating compounds including Pronase E. Here we demonstrate in vitro
spermiogenesis of C. elegans
spermatids using Pronase E.
Successful spermiogenesis is pre-requisite for fertility and hence the mutants defective in spermiogenesis are sterile. Hitherto several mutants have been shown to be defective specifically in spermiogenesis process7
. Abnormality found during in vitro
activation of novel Spe (Spermatogenesis defective) mutants would help us discover additional players participating in this event.
Developmental Biology, Issue 47, spermatid, spermatozoa, spermiogenesis, protease, pseudopod, nematode
RNAi Mediated Gene Knockdown and Transgenesis by Microinjection in the Necromenic Nematode Pristionchus pacificus
Institutions: California State University.
Although it is increasingly affordable for emerging model organisms to obtain completely sequenced genomes, further in-depth gene function and expression analyses by RNA interference and stable transgenesis remain limited in many species due to the particular anatomy and molecular cellular biology of the organism. For example, outside of the crown group Caenorhabditis
that includes Caenorhabditis elegans3
, stably transmitted transgenic lines in non-Caenorhabditis
species have not been reported in this specious phylum (Nematoda), with the exception of Strongyloides stercoralis4
and Pristionchus pacificus5
. To facilitate the expanding role of P. pacificus
in the study of development, evolution, and behavior6-7
, we describe here the current methods to use microinjection for making transgenic animals and gene knock down by RNAi. Like the gonads of C. elegans
and most other nematodes, the gonads of P. pacificus
is syncitial and capable of incorporating DNA and RNA into the oocytes when delivered by direct microinjection. Unlike C. elegans
however, stable transgene inheritance and somatic expression in P. pacificus
requires the addition of self genomic DNA digested with endonucleases complementary to the ends of target transgenes and coinjection markers5
. The addition of carrier genomic DNA is similar to the requirement for transgene expression in Strongyloides stercoralis4
and in the germ cells of C. elegans
. However, it is not clear if the specific requirement for the animals' own genomic DNA is because P. pacificus
soma is very efficient at silencing non-complex multi-copy genes or that extrachromosomal arrays in P. pacificus
require genomic sequences for proper kinetochore assembly during mitosis. The ventral migration of the two-armed (didelphic) gonads in hermaphrodites further complicates the ability to inject both gonads in individual worms8
. We also demonstrate the use of microinjection to knockdown a dominant mutant (roller,tu92
) by injecting double-stranded RNA (dsRNA) into the gonads to obtain non-rolling F1
progeny. Unlike C. elegans
, but like most other nematodes, P. pacificus
PS312 is not receptive to systemic RNAi via feeding and soaking and therefore dsRNA must be administered by microinjection into the syncitial gonads. In this current study, we hope to describe the microinjection process needed to transform a Ppa-egl-4
promoter::GFP fusion reporter and knockdown a dominant roller prl-1 (tu92)
mutant in a visually informative protocol.
Developmental Biology, Issue 56, RNA interference, Pristionchus pacificus, microinjection, transgenesis, Caenorhabditis elegans, developmental biology, behavior, gene expression
Paradigms for Pharmacological Characterization of C. elegans Synaptic Transmission Mutants
Institutions: University of Alabama.
The nematode, Caenorhabditis elegans, has become an expedient model for studying neurotransmission. C. elegans is unique among animal models, as the anatomy and connectivity of its nervous system has been determined from electron micrographs and refined by pharmacological assays. In this video, we describe how two complementary neural stimulants, an acetylcholinesterase inhibitor, called aldicarb, and a gamma-aminobutyric acid (GABA) receptor antagonist, called pentylenetetrazole (PTZ), may be employed to specifically characterize signaling at C. elegans neuromuscular junctions (NMJs) and facilitate our understanding of antagonistic neural circuits.
Of 302 C. elegans neurons, nineteen GABAergic D-type motor neurons innervate body wall muscles (BWMs), while four GABAergic neurons, called RMEs, innervate head muscles. Conversely, thirty-nine motor neurons express the excitatory neurotransmitter, acetylcholine (ACh), and antagonize GABA transmission at BWMs to coordinate locomotion. The antagonistic nature of GABAergic and cholinergic motor neurons at body wall NMJs was initially determined by laser ablation and later buttressed by aldicarb exposure. Acute aldicarb exposure results in a time-course or dose-responsive paralysis in wild-type worms. Yet, loss of excitatory ACh transmission confers resistance to aldicarb, as less ACh accumulates at worm NMJs, leading to less stimulation of BWMs. Resistance to aldicarb may be observed with ACh-specific or general synaptic function mutants. Consistent with antagonistic GABA and ACh transmission, loss of GABA transmission, or a failure to negatively regulate ACh release, confers hypersensitivity to aldicarb. Although aldicarb exposure has led to the isolation of numerous worm homologs of neurotransmission genes, aldicarb exposure alone cannot efficiently determine prevailing roles for genes and pathways in specific C. elegans motor neurons. For this purpose, we have introduced a complementary experimental approach, which uses PTZ.
Neurotransmission mutants display clear phenotypes, distinct from aldicarb-induced paralysis, in response to PTZ. Wild-type worms, as well as mutants with specific inabilities to release or receive ACh, do not show apparent sensitivity to PTZ. However, GABA mutants, as well as general synaptic function mutants, display anterior convulsions in a time-course or dose-responsive manner. Mutants that cannot negatively regulate general neurotransmitter release and, thus, secrete excessive amounts of ACh onto BWMs, become paralyzed on PTZ. The PTZ-induced phenotypes of discrete mutant classes indicate that a complementary approach with aldicarb and PTZ exposure paradigms in C. elegans may accelerate our understanding of neurotransmission. Moreover, videos demonstrating how we perform pharmacological assays should establish consistent methods for C. elegans research.
Neuroscience, Issue 18, epilepsy, seizure, Caenorhabditis elegans, genetics, worm, nematode, aldicarb, pentylenetetrazole, synaptic, GABA
Identification of Key Factors Regulating Self-renewal and Differentiation in EML Hematopoietic Precursor Cells by RNA-sequencing Analysis
Institutions: The University of Texas Graduate School of Biomedical Sciences at Houston.
Hematopoietic stem cells (HSCs) are used clinically for transplantation treatment to rebuild a patient's hematopoietic system in many diseases such as leukemia and lymphoma. Elucidating the mechanisms controlling HSCs self-renewal and differentiation is important for application of HSCs for research and clinical uses. However, it is not possible to obtain large quantity of HSCs due to their inability to proliferate in vitro
. To overcome this hurdle, we used a mouse bone marrow derived cell line, the EML (Erythroid, Myeloid, and Lymphocytic) cell line, as a model system for this study.
RNA-sequencing (RNA-Seq) has been increasingly used to replace microarray for gene expression studies. We report here a detailed method of using RNA-Seq technology to investigate the potential key factors in regulation of EML cell self-renewal and differentiation. The protocol provided in this paper is divided into three parts. The first part explains how to culture EML cells and separate Lin-CD34+ and Lin-CD34- cells. The second part of the protocol offers detailed procedures for total RNA preparation and the subsequent library construction for high-throughput sequencing. The last part describes the method for RNA-Seq data analysis and explains how to use the data to identify differentially expressed transcription factors between Lin-CD34+ and Lin-CD34- cells. The most significantly differentially expressed transcription factors were identified to be the potential key regulators controlling EML cell self-renewal and differentiation. In the discussion section of this paper, we highlight the key steps for successful performance of this experiment.
In summary, this paper offers a method of using RNA-Seq technology to identify potential regulators of self-renewal and differentiation in EML cells. The key factors identified are subjected to downstream functional analysis in vitro
and in vivo
Genetics, Issue 93, EML Cells, Self-renewal, Differentiation, Hematopoietic precursor cell, RNA-Sequencing, Data analysis
Enhanced Northern Blot Detection of Small RNA Species in Drosophila Melanogaster
Institutions: Institut de Génétique et de Biologie Moléculaire et Cellulaire, Istituto Italiano di Tecnologia.
The last decades have witnessed the explosion of scientific interest around gene expression control mechanisms at the RNA level. This branch of molecular biology has been greatly fueled by the discovery of noncoding RNAs as major players in post-transcriptional regulation. Such a revolutionary perspective has been accompanied and triggered by the development of powerful technologies for profiling short RNAs expression, both at the high-throughput level (genome-wide identification) or as single-candidate analysis (steady state accumulation of specific species). Although several state-of-art strategies are currently available for dosing or visualizing such fleeing molecules, Northern Blot assay remains the eligible approach in molecular biology for immediate and accurate evaluation of RNA expression. It represents a first step toward the application of more sophisticated, costly technologies and, in many cases, remains a preferential method to easily gain insights into RNA biology. Here we overview an efficient protocol (Enhanced Northern Blot) for detecting weakly expressed microRNAs (or other small regulatory RNA species) from Drosophila melanogaster
whole embryos, manually dissected larval/adult tissues or in vitro
cultured cells. A very limited amount of RNA is required and the use of material from flow cytometry-isolated cells can be also envisaged.
Molecular Biology, Issue 90, Northern blotting, Noncoding RNAs, microRNAs, rasiRNA, Gene expression, Gcm/Glide, Drosophila melanogaster
RNA-Seq Analysis of Differential Gene Expression in Electroporated Chick Embryonic Spinal Cord
Institutions: Universidade de São Paulo.
electroporation of the chick neural tube is a fast and inexpensive method for identification of gene function during neural development. Genome wide analysis of differentially expressed transcripts after such an experimental manipulation has the potential to uncover an almost complete picture of the downstream effects caused by the transfected construct. This work describes a simple method for comparing transcriptomes from samples of transfected embryonic spinal cords comprising all steps between electroporation and identification of differentially expressed transcripts. The first stage consists of guidelines for electroporation and instructions for dissection of transfected spinal cord halves from HH23 embryos in ribonuclease-free environment and extraction of high-quality RNA samples suitable for transcriptome sequencing. The next stage is that of bioinformatic analysis with general guidelines for filtering and comparison of RNA-Seq datasets in the Galaxy public server, which eliminates the need of a local computational structure for small to medium scale experiments. The representative results show that the dissection methods generate high quality RNA samples and that the transcriptomes obtained from two control samples are essentially the same, an important requirement for detection of differential expression genes in experimental samples. Furthermore, one example is provided where experimental overexpression of a DNA construct can be visually verified after comparison with control samples. The application of this method may be a powerful tool to facilitate new discoveries on the function of neural factors involved in spinal cord early development.
Developmental Biology, Issue 93, chicken embryo, in ovo electroporation, spinal cord, RNA-Seq, transcriptome profiling, Galaxy workflow
Using RNA-mediated Interference Feeding Strategy to Screen for Genes Involved in Body Size Regulation in the Nematode C. elegans
Institutions: Borough of Manhattan Community College, City Universtiy of New York (CUNY), Queens College, The City University of New York (CUNY), Queens College, The City University of New York (CUNY).
Double-strand RNA-mediated interference (RNAi) is an effective strategy to knock down target gene expression1-3
. It has been applied to many model systems including plants, invertebrates and vertebrates. There are various methods to achieve RNAi in vivo4,5
. For example, the target gene may be transformed into an RNAi vector, and then either permanently or transiently transformed into cell lines or primary cells to achieve gene knockdown effects; alternatively synthesized double-strand oligonucleotides from specific target genes (RNAi oligos) may be transiently transformed into cell lines or primary cells to silence target genes; or synthesized double-strand RNA molecules may be microinjected into an organism. Since the nematode C. elegans
uses bacteria as a food source, feeding the animals with bacteria expressing double-strand RNA against target genes provides a viable strategy6
. Here we present an RNAi feeding method to score body size phenotype. Body size in C. elegans
is regulated primarily by the TGF- β - like ligand DBL-1, so this assay is appropriate for identification of TGF-β signaling components7
. We used different strains including two RNAi hypersensitive strains to repeat the RNAi feeding experiments. Our results showed that rrf-3
strain gave us the best expected RNAi phenotype. The method is easy to perform, reproducible, and easily quantified. Furthermore, our protocol minimizes the use of specialized equipment, so it is suitable for smaller laboratories or those at predominantly undergraduate institutions.
Developmental Biology, Issue 72, Genetics, Cellular Biology, Molecular Biology, Biochemistry, Basic Protocols, RNAi feeding technique, genetic screen, TGF-beta, body size, C. elegans, Caenorhabditis elegans, RNA-mediated Interference, RNAi, RNA, DNA, gene expression knock down, animal model
Methods for Studying the Mechanisms of Action of Antipsychotic Drugs in Caenorhabditis elegans
Institutions: Harvard Medical School, McLean Hospital.
is a simple genetic organism amenable to large-scale forward and reverse genetic screens and chemical genetic screens. The C. elegans
genome includes potential antipsychotic drug (APD) targets conserved in humans, including genes encoding proteins required for neurotransmitter synthesis and for synaptic structure and function. APD exposure produces developmental delay and/or lethality in nematodes in a concentration-dependent manner. These phenotypes are caused, in part, by APD-induced inhibition of pharyngeal pumping1,2
. Thus, the developmental phenotype has a neuromuscular basis, making it useful for pharmacogenetic studies of neuroleptics. Here we demonstrate detailed procedures for testing APD effects on nematode development and pharyngeal pumping. For the developmental assay, synchronized embryos are placed on nematode growth medium (NGM) plates containing APDs, and the stages of developing animals are then scored daily. For the pharyngeal pumping rate assay, staged young adult animals are tested on NGM plates containing APDs. The number of pharyngeal pumps per unit time is recorded, and the pumping rate is calculated. These assays can be used for studying many other types of small molecules or even large molecules.
Neuroscience, Issue 84, antipsychotic drug, Caenorhabditis elegans, clozapine, developmental delay, lethality, nematode, pharmacogenetics, pharyngeal pumping, schizophrenia
Biochemical and High Throughput Microscopic Assessment of Fat Mass in Caenorhabditis Elegans
Institutions: Massachusetts General Hospital and Harvard Medical School, Massachusetts Institute of Technology.
The nematode C. elegans
has emerged as an important model for the study of conserved genetic pathways regulating fat metabolism as it relates to human obesity and its associated pathologies. Several previous methodologies developed for the visualization of C. elegans
triglyceride-rich fat stores have proven to be erroneous, highlighting cellular compartments other than lipid droplets. Other methods require specialized equipment, are time-consuming, or yield inconsistent results. We introduce a rapid, reproducible, fixative-based Nile red staining method for the accurate and rapid detection of neutral lipid droplets in C. elegans
. A short fixation step in 40% isopropanol makes animals completely permeable to Nile red, which is then used to stain animals. Spectral properties of this lipophilic dye allow it to strongly and selectively fluoresce in the yellow-green spectrum only when in a lipid-rich environment, but not in more polar environments. Thus, lipid droplets can be visualized on a fluorescent microscope equipped with simple GFP imaging capability after only a brief Nile red staining step in isopropanol. The speed, affordability, and reproducibility of this protocol make it ideally suited for high throughput screens. We also demonstrate a paired method for the biochemical determination of triglycerides and phospholipids using gas chromatography mass-spectrometry. This more rigorous protocol should be used as confirmation of results obtained from the Nile red microscopic lipid determination. We anticipate that these techniques will become new standards in the field of C. elegans
Genetics, Issue 73, Biochemistry, Cellular Biology, Molecular Biology, Developmental Biology, Physiology, Anatomy, Caenorhabditis elegans, Obesity, Energy Metabolism, Lipid Metabolism, C. elegans, fluorescent lipid staining, lipids, Nile red, fat, high throughput screening, obesity, gas chromatography, mass spectrometry, GC/MS, animal model
A Method for Culturing Embryonic C. elegans Cells
Institutions: University of Miami .
is a powerful model system, in which genetic and molecular techniques are easily applicable. Until recently though, techniques that require direct access to cells and isolation of specific cell types, could not be applied in C. elegans
. This limitation was due to the fact that tissues are confined within a pressurized cuticle which is not easily digested by treatment with enzymes and/or detergents. Based on early pioneer work by Laird Bloom, Christensen and colleagues 1
developed a robust method for culturing C. elegans
embryonic cells in large scale. Eggs are isolated from gravid adults by treatment with bleach/NaOH and subsequently treated with chitinase to remove the eggshells. Embryonic cells are then dissociated by manual pipetting and plated onto substrate-covered glass in serum-enriched media. Within 24 hr of isolation cells begin to differentiate by changing morphology and by expressing cell specific markers. C. elegans
cells cultured using this method survive for up 2 weeks in vitro
and have been used for electrophysiological, immunochemical, and imaging analyses as well as they have been sorted and used for microarray profiling.
Developmental Biology, Issue 79, Eukaryota, Biological Phenomena, Cell Physiological Phenomena, C. elegans, cell culture, embryonic cells
Visualizing Neuroblast Cytokinesis During C. elegans Embryogenesis
Institutions: Concordia University.
This protocol describes the use of fluorescence microscopy to image dividing cells within developing Caenorhabditis elegans
embryos. In particular, this protocol focuses on how to image dividing neuroblasts, which are found underneath the epidermal cells and may be important for epidermal morphogenesis. Tissue formation is crucial for metazoan development and relies on external cues from neighboring tissues. C. elegans
is an excellent model organism to study tissue morphogenesis in vivo
due to its transparency and simple organization, making its tissues easy to study via microscopy. Ventral enclosure is the process where the ventral surface of the embryo is covered by a single layer of epithelial cells. This event is thought to be facilitated by the underlying neuroblasts, which provide chemical guidance cues to mediate migration of the overlying epithelial cells. However, the neuroblasts are highly proliferative and also may act as a mechanical substrate for the ventral epidermal cells. Studies using this experimental protocol could uncover the importance of intercellular communication during tissue formation, and could be used to reveal the roles of genes involved in cell division within developing tissues.
Neuroscience, Issue 85, C. elegans, morphogenesis, cytokinesis, neuroblasts, anillin, microscopy, cell division
Large-scale Gene Knockdown in C. elegans Using dsRNA Feeding Libraries to Generate Robust Loss-of-function Phenotypes
Institutions: University of Massachusetts, Amherst, University of Massachusetts, Amherst, University of Massachusetts, Amherst.
RNA interference by feeding worms bacteria expressing dsRNAs has been a useful tool to assess gene function in C. elegans
. While this strategy works well when a small number of genes are targeted for knockdown, large scale feeding screens show variable knockdown efficiencies, which limits their utility. We have deconstructed previously published RNAi knockdown protocols and found that the primary source of the reduced knockdown can be attributed to the loss of dsRNA-encoding plasmids from the bacteria fed to the animals. Based on these observations, we have developed a dsRNA feeding protocol that greatly reduces or eliminates plasmid loss to achieve efficient, high throughput knockdown. We demonstrate that this protocol will produce robust, reproducible knock down of C. elegans
genes in multiple tissue types, including neurons, and will permit efficient knockdown in large scale screens. This protocol uses a commercially available dsRNA feeding library and describes all steps needed to duplicate the library and perform dsRNA screens. The protocol does not require the use of any sophisticated equipment, and can therefore be performed by any C. elegans
Developmental Biology, Issue 79, Caenorhabditis elegans (C. elegans), Gene Knockdown Techniques, C. elegans, dsRNA interference, gene knockdown, large scale feeding screen
Culturing Caenorhabditis elegans in Axenic Liquid Media and Creation of Transgenic Worms by Microparticle Bombardment
Institutions: University of Maryland, University of Maryland.
In this protocol, we present the required materials, and the procedure for making modified C. elegans
Habituation and Reproduction media (mCeHR). Additionally, the steps for exposing and acclimatizing C. elegans
grown on E. coli
to axenic liquid media are described. Finally, downstream experiments that utilize axenic C. elegans
illustrate the benefits of this procedure. The ability to analyze and determine C. elegans
nutrient requirement was illustrated by growing N2 wild type worms in axenic liquid media with varying heme concentrations. This procedure can be replicated with other nutrients to determine the optimal concentration for worm growth and development or, to determine the toxicological effects of drug treatments. The effects of varied heme concentrations on the growth of wild type worms were determined through qualitative microscopic observation and by quantitating the number of worms that grew in each heme concentration. In addition, the effect of varied nutrient concentrations can be assayed by utilizing worms that express fluorescent sensors that respond to changes in the nutrient of interest. Furthermore, a large number of worms were easily produced for the generation of transgenic C. elegans
using microparticle bombardment.
Molecular Biology, Issue 90, C. elegans, axenic media, transgenics, microparticle bombardment, heme, nutrition
Quantitative and Automated High-throughput Genome-wide RNAi Screens in C. elegans
Institutions: Université de la Méditerranée.
RNA interference is a powerful method to understand gene function, especially when conducted at a whole-genome scale and in a quantitative context. In C. elegans
, gene function can be knocked down simply and efficiently by feeding worms with bacteria expressing a dsRNA corresponding to a specific gene 1
. While the creation of libraries of RNAi clones covering most of the C. elegans
opened the way for true functional genomic studies (see for example 4-7
), most established methods are laborious. Moy and colleagues have developed semi-automated protocols that facilitate genome-wide screens 8
. The approach relies on microscopic imaging and image analysis.
Here we describe an alternative protocol for a high-throughput genome-wide screen, based on robotic handling of bacterial RNAi clones, quantitative analysis using the COPAS Biosort (Union Biometrica (UBI)), and an integrated software: the MBioLIMS (Laboratory Information Management System from Modul-Bio) a technology that provides increased throughput for data management and sample tracking. The method allows screens to be conducted on solid medium plates. This is particularly important for some studies, such as those addressing host-pathogen interactions in C. elegans
, since certain microbes do not efficiently infect worms in liquid culture.
We show how the method can be used to quantify the importance of genes in anti-fungal innate immunity in C. elegans
. In this case, the approach relies on the use of a transgenic strain carrying an epidermal infection-inducible fluorescent reporter gene, with GFP under the control of the promoter of the antimicrobial peptide gene nlp 29
and a red fluorescent reporter that is expressed constitutively in the epidermis. The latter provides an internal control for the functional integrity of the epidermis and nonspecific transgene silencing9
. When control worms are infected by the fungus they fluoresce green. Knocking down by RNAi a gene required for nlp 29
expression results in diminished fluorescence after infection. Currently, this protocol allows more than 3,000 RNAi clones to be tested and analyzed per week, opening the possibility of screening the entire genome in less than 2 months.
Molecular Biology, Issue 60, C. elegans, fluorescent reporter, Biosort, LIMS, innate immunity, Drechmeria coniospora
A Protocol to Infect Caenorhabditis elegans with Salmonella typhimurium
Institutions: Florida Atlantic University.
In the last decade, C. elegans
has emerged as an invertebrate organism to study interactions between hosts and pathogens, including the host defense against gram-negative bacterium Salmonella typhimurium. Salmonella
establishes persistent infection in the intestine of C. elegans
and results in early death of infected animals. A number of immunity mechanisms have been identified in C. elegans
to defend against Salmonella
infections. Autophagy, an evolutionarily conserved lysosomal degradation pathway, has been shown to limit the Salmonella
replication in C. elegans
and in mammals. Here, a protocol is described to infect C. elegans
with Salmonella typhimurium
, in which the worms are exposed to Salmonella
for a limited time, similar to Salmonella
infection in humans. Salmonella
infection significantly shortens the lifespan of C. elegans
. Using the essential autophagy gene bec-1
as an example, we combined this infection method with C. elegans
RNAi feeding approach and showed this protocol can be used to examine the function of C. elegans
host genes in defense against Salmonella
infection. Since C. elegans
whole genome RNAi libraries are available, this protocol makes it possible to comprehensively screen for C. elegans
genes that protect against Salmonella
and other intestinal pathogens using genome-wide RNAi libraries.
Immunology, Issue 88, C. elegans, Salmonella typhimurium, autophagy, infection, pathogen, host, RNAi
Methods to Assess Subcellular Compartments of Muscle in C. elegans
Institutions: University of Nottingham.
Muscle is a dynamic tissue that responds to changes in nutrition, exercise, and disease state. The loss of muscle mass and function with disease and age are significant public health burdens. We currently understand little about the genetic regulation of muscle health with disease or age. The nematode C. elegans
is an established model for understanding the genomic regulation of biological processes of interest. This worm’s body wall muscles display a large degree of homology with the muscles of higher metazoan species. Since C. elegans
is a transparent organism, the localization of GFP to mitochondria and sarcomeres allows visualization of these structures in vivo
. Similarly, feeding animals cationic dyes, which accumulate based on the existence of a mitochondrial membrane potential, allows the assessment of mitochondrial function in vivo
. These methods, as well as assessment of muscle protein homeostasis, are combined with assessment of whole animal muscle function, in the form of movement assays, to allow correlation of sub-cellular defects with functional measures of muscle performance. Thus, C. elegans
provides a powerful platform with which to assess the impact of mutations, gene knockdown, and/or chemical compounds upon muscle structure and function. Lastly, as GFP, cationic dyes, and movement assays are assessed non-invasively, prospective studies of muscle structure and function can be conducted across the whole life course and this at present cannot be easily investigated in vivo
in any other organism.
Developmental Biology, Issue 93, Physiology, C. elegans, muscle, mitochondria, sarcomeres, ageing
Mapping Bacterial Functional Networks and Pathways in Escherichia Coli using Synthetic Genetic Arrays
Institutions: University of Toronto, University of Toronto, University of Regina.
Phenotypes are determined by a complex series of physical (e.g.
protein-protein) and functional (e.g.
gene-gene or genetic) interactions (GI)1
. While physical interactions can indicate which bacterial proteins are associated as complexes, they do not necessarily reveal pathway-level functional relationships1. GI screens, in which the growth of double mutants bearing two deleted or inactivated genes is measured and compared to the corresponding single mutants, can illuminate epistatic dependencies between loci and hence provide a means to query and discover novel functional relationships2
. Large-scale GI maps have been reported for eukaryotic organisms like yeast3-7
, but GI information remains sparse for prokaryotes8
, which hinders the functional annotation of bacterial genomes. To this end, we and others have developed high-throughput quantitative bacterial GI screening methods9, 10
Here, we present the key steps required to perform quantitative E. coli
Synthetic Genetic Array (eSGA) screening procedure on a genome-scale9
, using natural bacterial conjugation and homologous recombination to systemically generate and measure the fitness of large numbers of double mutants in a colony array format.
Briefly, a robot is used to transfer, through conjugation, chloramphenicol (Cm) - marked mutant alleles from engineered Hfr (High frequency of recombination) 'donor strains' into an ordered array of kanamycin (Kan) - marked F- recipient strains. Typically, we use loss-of-function single mutants bearing non-essential gene deletions (e.g.
the 'Keio' collection11
) and essential gene hypomorphic mutations (i.e.
alleles conferring reduced protein expression, stability, or activity9, 12, 13
) to query the functional associations of non-essential and essential genes, respectively. After conjugation and ensuing genetic exchange mediated by homologous recombination, the resulting double mutants are selected on solid medium containing both antibiotics. After outgrowth, the plates are digitally imaged and colony sizes are quantitatively scored using an in-house automated image processing system14
. GIs are revealed when the growth rate of a double mutant is either significantly better or worse than expected9
. Aggravating (or negative) GIs often result between loss-of-function mutations in pairs of genes from compensatory pathways that impinge on the same essential process2
. Here, the loss of a single gene is buffered, such that either single mutant is viable. However, the loss of both pathways is deleterious and results in synthetic lethality or sickness (i.e.
slow growth). Conversely, alleviating (or positive) interactions can occur between genes in the same pathway or protein complex2
as the deletion of either gene alone is often sufficient to perturb the normal function of the pathway or complex such that additional perturbations do not reduce activity, and hence growth, further. Overall, systematically identifying and analyzing GI networks can provide unbiased, global maps of the functional relationships between large numbers of genes, from which pathway-level information missed by other approaches can be inferred9
Genetics, Issue 69, Molecular Biology, Medicine, Biochemistry, Microbiology, Aggravating, alleviating, conjugation, double mutant, Escherichia coli, genetic interaction, Gram-negative bacteria, homologous recombination, network, synthetic lethality or sickness, suppression
A Restriction Enzyme Based Cloning Method to Assess the In vitro Replication Capacity of HIV-1 Subtype C Gag-MJ4 Chimeric Viruses
Institutions: Emory University, Emory University.
The protective effect of many HLA class I alleles on HIV-1 pathogenesis and disease progression is, in part, attributed to their ability to target conserved portions of the HIV-1 genome that escape with difficulty. Sequence changes attributed to cellular immune pressure arise across the genome during infection, and if found within conserved regions of the genome such as Gag, can affect the ability of the virus to replicate in vitro
. Transmission of HLA-linked polymorphisms in Gag to HLA-mismatched recipients has been associated with reduced set point viral loads. We hypothesized this may be due to a reduced replication capacity of the virus. Here we present a novel method for assessing the in vitro
replication of HIV-1 as influenced by the gag
gene isolated from acute time points from subtype C infected Zambians. This method uses restriction enzyme based cloning to insert the gag
gene into a common subtype C HIV-1 proviral backbone, MJ4. This makes it more appropriate to the study of subtype C sequences than previous recombination based methods that have assessed the in vitro
replication of chronically derived gag-pro
sequences. Nevertheless, the protocol could be readily modified for studies of viruses from other subtypes. Moreover, this protocol details a robust and reproducible method for assessing the replication capacity of the Gag-MJ4 chimeric viruses on a CEM-based T cell line. This method was utilized for the study of Gag-MJ4 chimeric viruses derived from 149 subtype C acutely infected Zambians, and has allowed for the identification of residues in Gag that affect replication. More importantly, the implementation of this technique has facilitated a deeper understanding of how viral replication defines parameters of early HIV-1 pathogenesis such as set point viral load and longitudinal CD4+ T cell decline.
Infectious Diseases, Issue 90, HIV-1, Gag, viral replication, replication capacity, viral fitness, MJ4, CEM, GXR25
DNA-affinity-purified Chip (DAP-chip) Method to Determine Gene Targets for Bacterial Two component Regulatory Systems
Institutions: Lawrence Berkeley National Laboratory.
methods such as ChIP-chip are well-established techniques used to determine global gene targets for transcription factors. However, they are of limited use in exploring bacterial two component regulatory systems with uncharacterized activation conditions. Such systems regulate transcription only when activated in the presence of unique signals. Since these signals are often unknown, the in vitro
microarray based method described in this video article can be used to determine gene targets and binding sites for response regulators. This DNA-affinity-purified-chip method may be used for any purified regulator in any organism with a sequenced genome. The protocol involves allowing the purified tagged protein to bind to sheared genomic DNA and then affinity purifying the protein-bound DNA, followed by fluorescent labeling of the DNA and hybridization to a custom tiling array. Preceding steps that may be used to optimize the assay for specific regulators are also described. The peaks generated by the array data analysis are used to predict binding site motifs, which are then experimentally validated. The motif predictions can be further used to determine gene targets of orthologous response regulators in closely related species. We demonstrate the applicability of this method by determining the gene targets and binding site motifs and thus predicting the function for a sigma54-dependent response regulator DVU3023 in the environmental bacterium Desulfovibrio vulgaris
Genetics, Issue 89, DNA-Affinity-Purified-chip, response regulator, transcription factor binding site, two component system, signal transduction, Desulfovibrio, lactate utilization regulator, ChIP-chip
A Strategy to Identify de Novo Mutations in Common Disorders such as Autism and Schizophrenia
Institutions: Universite de Montreal, Universite de Montreal, Universite de Montreal.
There are several lines of evidence supporting the role of de novo
mutations as a mechanism for common disorders, such as autism and schizophrenia. First, the de novo
mutation rate in humans is relatively high, so new mutations are generated at a high frequency in the population. However, de novo
mutations have not been reported in most common diseases. Mutations in genes leading to severe diseases where there is a strong negative selection against the phenotype, such as lethality in embryonic stages or reduced reproductive fitness, will not be transmitted to multiple family members, and therefore will not be detected by linkage gene mapping or association studies. The observation of very high concordance in monozygotic twins and very low concordance in dizygotic twins also strongly supports the hypothesis that a significant fraction of cases may result from new mutations. Such is the case for diseases such as autism and schizophrenia. Second, despite reduced reproductive fitness1
and extremely variable environmental factors, the incidence of some diseases is maintained worldwide at a relatively high and constant rate. This is the case for autism and schizophrenia, with an incidence of approximately 1% worldwide. Mutational load can be thought of as a balance between selection for or against a deleterious mutation and its production by de novo
mutation. Lower rates of reproduction constitute a negative selection factor that should reduce the number of mutant alleles in the population, ultimately leading to decreased disease prevalence. These selective pressures tend to be of different intensity in different environments. Nonetheless, these severe mental disorders have been maintained at a constant relatively high prevalence in the worldwide population across a wide range of cultures and countries despite a strong negative selection against them2
. This is not what one would predict in diseases with reduced reproductive fitness, unless there was a high new mutation rate. Finally, the effects of paternal age: there is a significantly increased risk of the disease with increasing paternal age, which could result from the age related increase in paternal de novo
mutations. This is the case for autism and schizophrenia3
. The male-to-female ratio of mutation rate is estimated at about 4–6:1, presumably due to a higher number of germ-cell divisions with age in males. Therefore, one would predict that de novo
mutations would more frequently come from males, particularly older males4
. A high rate of new mutations may in part explain why genetic studies have so far failed to identify many genes predisposing to complexes diseases genes, such as autism and schizophrenia, and why diseases have been identified for a mere 3% of genes in the human genome. Identification for de novo
mutations as a cause of a disease requires a targeted molecular approach, which includes studying parents and affected subjects. The process for determining if the genetic basis of a disease may result in part from de novo
mutations and the molecular approach to establish this link will be illustrated, using autism and schizophrenia as examples.
Medicine, Issue 52, de novo mutation, complex diseases, schizophrenia, autism, rare variations, DNA sequencing