Skip to content
Articles by Ryan Thummel in JoVE
-
In vivo Elektroporation af Morpholinos i den voksne zebrafisk Retina
Ryan Thummel1, Travis J. Bailey2,3, David R. Hyde2,3
1Departments of Anatomy and Cell Biology and Ophthalmology, Wayne State University School of Medicine, 2Department of Biological Sciences, University of Notre Dame, 3Center for Zebrafish Research, University of Notre Dame
En metode til betinget Knockdown et mål protein udtryk i den voksne zebrafisk nethinden er beskrevet, hvilket indebærer intravitrealt injektion antisense morpholinos og electroporating dem ind i nethinden. Den resulterende protein er slået ned i flere dage, hvilket giver mulighed for test af protein rolle i regenerere eller intakte nethinden.
-
In vivo elektroporation af Morpholinos i Regenerating Adult zebrafisk Tail Fin
David R. Hyde1, Alan R. Godwin2, Ryan Thummel3
1Department of Biological Sciences, Center for Zebrafish Research, University of Notre Dame, 2Department of Microbiology, Immunology, and Pathology, Colorado State University, 3Departments of Anatomy and Cell Biology and Ophthalmology, Wayne State University School of Medicine
Vi beskriver en fremgangsmåde til konditionelt knockdown ekspressionen af et målprotein i voksne zebrafisk fin regenerering. Denne teknik involverer mikro-injektion, og elektroporering antisense oligonucleotid morpholinos i fin væv, som tillader afprøvning af proteinets rolle i forskellige stadier af fin regenerering, herunder sårheling, blastema dannelse og regenerative udvækst.
-
Other articles by Ryan Thummel on PubMed
-
Differences in Expression Pattern and Function Between Zebrafish Hoxc13 Orthologs: Recruitment of Hoxc13b into an Early Embryonic Role
Developmental Biology.
Oct, 2004 |
Pubmed ID: 15385162 Vertebrate Hox genes are generally believed to initiate expression at the primitive streak or early neural plate stages. The timing and spatial restrictions of the Hox expression patterns during these stages correlate well with their demonstrated role in axial patterning. Here we demonstrate that one zebrafish hoxc13 ortholog, hoxc13a, has an expression pattern in the developing tail bud that is consistent with the gene playing a role in axial patterning. However, the second hoxc13 ortholog, hoxc13b, is maternally expressed and is detectable in every cell of early cleavage embryos through gastrulae. In addition, both transcript and protein are detectable at these stages. At 19 h post fertilization (hpf), hoxc13b expression is up-regulated in the tail bud, becoming restricted to the tail bud by 24 hpf. Importantly, by 24 hpf, hoxc13b morphants show a specific developmental delay, which can be rescued by co-injecting synthetic capped hoxc13a or hoxc13b message. These data suggest some functional divergence due to altered expression patterns of the two hoxc13 orthologs after duplication. Further characterization of the hoxc13b morphant delay reveals that it is biphasic in nature, with the first phase of the delay occurring before gastrulation, suggesting a new role for vertebrate Hox genes before their conserved role in axial patterning. The extent of the delay does not change through 20 hpf; however, an additional delay emerges at this time. Notably, this second phase of the delay correlates with hoxc13b expression pattern becoming restricted to the tail bud.
-
Matrix Metalloproteinase Expression and Function During Fin Regeneration in Zebrafish: Analysis of MT1-MMP, MMP2 and TIMP2
Matrix Biology : Journal of the International Society for Matrix Biology.
Jun, 2005 |
Pubmed ID: 15935631 Matrix metalloproteinases (MMPs) play key roles in the turnover of extracellular matrix (ECM) and, thereby, function as key regulators of cell-ECM interactions during development. In spite of their importance during developmental processes, relatively little has been reported about the role of these metalloproteinases during limb development and regeneration. To approach the problem of cell-ECM interactions during limb (fin) regeneration, we have utilized zebrafish as an experimental model. Based on previous MMP cloning studies from our laboratory, the current study has focused on the expression of membrane-type 1 metalloproteinase (MT1-MMP), gelatinase A (MMP-2) and endogenous tissue inhibitor 2 of metalloproteinases (TIMP-2) during fin regeneration in adult zebrafish. In situ analysis indicated co-expression of zmt1-mmp, zmmp-2, and ztimp-2 mRNA transcripts in regenerating caudal fins. In situ gelatin-zymography confirmed the presence of active metalloproteinases in regenerating fins. zmt1-mmp, zmmp-2, and ztimp-2 mRNA transcripts were expressed in the blastema and basal epithelium during caudal fin regeneration while expression of type IV collagen [zcol-IV(a5)] transcripts (a basal lamina component) was restricted to the basal epithelium. Fin outgrowth was greatly reduced in the presence of GM6001 (an inhibitor of MMP activity) indicating the importance of these enzymes during fin regeneration. Previous studies by Itoh (EMBO, 2001) indicated that expression of a vertebrate MT1-MMP construct containing only the hemopexin-transmembrane-cytoplasmic domains (MT1HPX) resulted in blockage of MT1-MMP homophilic complex formation and subsequent inhibition of pro-MMP-2 activation. Interference with homophilic complex formation was attributed to expression of the hemopexin domain at the cell surface. Building upon these earlier findings, the current study found that ectopic expression of MT1HPX in fin regenerates inhibited the regeneration process and resulted in a reduction in cell proliferation in the blastema. Taken together, these results indicate that MMPs have an important role during fin regeneration in zebrafish.
-
-
Inhibition of Zebrafish Fin Regeneration Using in Vivo Electroporation of Morpholinos Against Fgfr1 and Msxb
Developmental Dynamics : an Official Publication of the American Association of Anatomists.
Feb, 2006 |
Pubmed ID: 16273523 Increased interest in using zebrafish as a model organism has led to a resurgence of fin regeneration studies. This has allowed for the identification of a large number of gene families, including signaling molecules and transcription factors, which are expressed during regeneration. However, in cases where no specific inhibitor is available for the gene product of interest, determination of a functional role for these genes has been difficult. Here we demonstrate that in vivo electroporation of morpholino oligonucleotides is a feasible approach for protein knock-down during fin regeneration. Morpholino oligonucleotides against fgfr1 and msxb were utilized and knock-down of both proteins resulted in reduced fin outgrowth. Importantly, Fgfr1 knock-down phenocopied outgrowth inhibition obtained with an Fgfr1 inhibitor. Furthermore, this method provided direct evidence for a functional role for msxb in caudal fin regeneration. Finally, knock-down of Fgfr1, but not Msxb, affected the blastemal expression of msxc, suggesting this technique can be used to determine epistasis in genetic pathways affecting regeneration. Thus, this convenient reverse genetic approach allows researchers to quickly (1) assess the function of genes known to be expressed during fin regeneration, (2) screen genes for functional relevance during fin regeneration, and (3) assign genes to the molecular pathways underlying fin regeneration.
-
Two Different Transgenes to Study Gene Silencing and Re-expression During Zebrafish Caudal Fin and Retinal Regeneration
TheScientificWorldJournal.
2006 |
Pubmed ID: 17205188 We used the 500-bp Xenopus ef1-alpha promoter and the 2-kb zebrafish histone 2A.F/Z promoter to generate several independent transgenic zebrafish lines expressing EGFP. While both promoters drive ubiquitous EGFP expression in early zebrafish development, they are systematically silenced in several adult tissues, including the retina and caudal fin. However, EGFP expression is temporarily renewed in the adult during either caudal fin or retinal regeneration. In the Tg(H2A.F/Z:EGFP)nt line, EGFP is moderately expressed in both the wound epithelium and blastema of the regenerating caudal fin. In the Tg(ef1-alpha:EGFP)nt line, EGFP expression is reinitiated and restricted to the blastema of the regenerating caudal fin and colabels with BrdU, PCNA, and msxc-positive cells. Thus, these two ubiquitous promoters drive EGFP transgene expression in different cell populations during caudal fin regeneration. We further analyzed the ability of the ef1-alpha:EGFP transgene to label nonterminally differentiated cells during adult tissue regeneration. First, we demonstrated that the transgene is highly methylated in adult zebrafish caudal fin tissue, but not during fin regeneration, implicating methylation as a potential means of transgene silencing in this line. Next, we determined that the ef1-alpha:EGFP transgene is also re-expressed during adult retinal regeneration. Specifically, the ef1-alpha:EGFP transgene colabels with PCNA in the Müller glia, a specialized cell that is the source of neuronal progenitors during zebrafish retinal regeneration. Thus, we concluded that Tg(ef1-alpha:EGFP)nt line visually marks nonterminally differentiated cells in multiple adult regeneration environments and may prove to be a useful marker in tissue regeneration studies in zebrafish.
-
-
Generation and Characterization of Transgenic Zebrafish Lines Using Different Ubiquitous Promoters
Transgenic Research.
Apr, 2008 |
Pubmed ID: 17968670 Two commonly used promoters to ubiquitously express transgenes in zebrafish are the Xenopus laevis elongation factor 1 alpha promoter (XlEef1a1) and the zebrafish histone variant H2A.F/Z (h2afv) promoter. Recently, transgenes utilizing these promoters were shown to be silenced in certain adult tissues, particularly the central nervous system. To overcome this limitation, we cloned the promoters of four zebrafish genes that likely are transcribed ubiquitously throughout development and into the adult. These four genes are the TATA box binding protein gene, the taube nuss-like gene, the eukaryotic elongation factor 1-gamma gene, and the beta-actin-1 gene. We PCR amplified approximately 2.5 kb upstream of the putative translational start site of each gene and cloned each into a Tol2 expression vector that contains the EGFP reporter transgene. We used these four Tol2 vectors to independently generate stable transgenic fish lines for analysis of transgene expression during development and in the adult. We demonstrated that all four promoters drive a very broad pattern of EGFP expression throughout development and the adult. Using the retina as a well-characterized component of the CNS, all four promoters appeared to drive EGFP expression in all neuronal and non-neuronal cells of the adult retina. In contrast, the h2afv promoter failed to express EGFP in the adult retina. When we examined EGFP expression in the various cells of the blood cell lineage, we observed that all four promoters exhibited a more heterogenous expression pattern than either the XlEef1a1 or h2afv promoters. While these four ubiquitous promoters did not express EGFP in all the adult blood cells, they did express EGFP throughout the CNS and in broader expression patterns in the adult than either the XlEef1a1 or h2afv promoters. For these reasons, these four promoters will be valuable tools for expressing transgenes in adult zebrafish.
-
Inhibition of Müller Glial Cell Division Blocks Regeneration of the Light-damaged Zebrafish Retina
Developmental Neurobiology.
Feb, 2008 |
Pubmed ID: 18161852 The adult zebrafish retina possesses a robust regenerative response. In the light-damaged retina, Müller glial cell divisions precede regeneration of rod and cone photoreceptors. Neuronal progenitors, which arise from the Müller glia, continue to divide and use the Müller glial cell processes to migrate to the outer nuclear layer and replace the lost photoreceptors. We tested the necessity of Müller glial cell division for photoreceptor regeneration. As knockdown tools were unavailable for use in the adult zebrafish retina, we developed a method to conditionally inhibit the expression of specific proteins by in vivo electroporation of morpholinos. We determined that two separate morpholinos targeted against the proliferating cell nuclear antigen (PCNA) mRNA reduced PCNA protein levels. Furthermore, injection and in vivo electroporation of PCNA morpholinos immediately prior to starting intense light exposure inhibited both Müller glial cell proliferation and neuronal progenitor marker Pax6 expression. PCNA knockdown additionally resulted in decreased expression of glutamine synthetase in Müller glia and Müller glial cell death, while amacrine and ganglion cells were unaffected. Finally, histological and immunological methods showed that long-term effects of PCNA knockdown resulted in decreased numbers of Müller glia and the failure to regenerate rod photoreceptors, short single cones, and long single cones. These data suggest that Müller glial cell division is necessary for proper photoreceptor regeneration in the light-damaged zebrafish retina and are consistent with the Müller glia serving as the source of neuronal progenitor cells in regenerating teleost retinas.
-
-
Connexin43 (GJA1) is Required in the Population of Dividing Cells During Fin Regeneration
Developmental Biology.
May, 2008 |
Pubmed ID: 18406403 In zebrafish, mutations in the gap junction gene connexin43 lead to short bony fin ray segments that give rise to the short fin phenotype. The sof(b123) mutant exhibits fins that are half the length of wild-type fins and have reduced levels of cx43 mRNA. We find that sof(b123) regenerating fins exhibit reduced levels of cell proliferation. Interestingly, the number of dividing cells per unit length of fin growth is similar between wild-type and mutant fins, suggesting that the number of cells that enter the cell cycle is specifically affected in sof(b123). Expression of cx43 is identified in mitotic cells, which further suggests that Cx43 may contribute to establishing or maintaining the population of dividing cells. Indeed, missense alleles exhibiting high or low levels of gap junctional communication reveal a correlation between defects in direct cell-cell communication, cell proliferation, and segment length. Finally, targeted gene knockdown of cx43 in adult regenerating fins recapitulates the sof(b123) phenotype, revealing that the loss of Cx43 is sufficient to reduce both cell proliferation and segment length. We hypothesize that the level of gap junctional intercellular communication among dividing cells regulates the level of cell proliferation and ultimately regulates bone growth.
-
-
Characterization of Müller Glia and Neuronal Progenitors During Adult Zebrafish Retinal Regeneration
Experimental Eye Research.
Nov, 2008 |
Pubmed ID: 18718467 The adult zebrafish retina exhibits a robust regenerative response following light-induced photoreceptor cell death. This response is initiated by the Müller glia proliferating in the inner nuclear layer (INL), which gives rise to neuronal progenitor cells that continue to divide and migrate to the outer nuclear layer (ONL), where they differentiate into rod and cone photoreceptors. We previously conducted a microarray analysis of retinal gene expression at 16, 31, 51, 68, and 96 h of constant intense-light treatment to identify genes and their corresponding proteins that may be involved in the generation and proliferation of the neuronal progenitor cells. We examined the expression of two candidate transcription factors, Pax6 and Ngn1, and one candidate transgene, olig2:EGFP, in the regenerating light-damaged retina. We compared the temporal and spatial expression patterns of these markers relative to PCNA (proliferating cell nuclear antigen), an established marker for proliferating cells in the zebrafish retina, and the Tg(gfap:EGFP) nt11 transgenic line that specifically labels Müller glial cells. We found that Müller glial cells dedifferentiate during regeneration, based on the loss of cell-specific markers such as GFAP (glial fibrillary acidic protein) and glutamine synthetase following their reentry into the cell cycle to produce neuronal progenitors. Pax6 expression was first detected in the proliferating neuronal progenitors by 51 h of constant light treatment, which is significantly after the Müller glia first reenter the cell cycle after 31h of light. This suggests that Pax6 expression increases in neuronal progenitors, rather than in the proliferating Müller glia. EGFP expression from the olig2 promoter was first detected by 68 h of constant light treatment in the dedifferentiated Müller glia, with Pax6 expressed in the closely associated proliferating neuronal progenitors migrating to the ONL. Both Pax6 and olig2 expression persisted until 3 days post-light treatment, when the neuronal progenitors begin differentiating into new rod and cone photoreceptors. Ngn1 protein expression was initially detected in proliferating neuronal progenitors at 68 h of light treatment. However, Ngn1 expression persisted in a subset of the INL nuclei until 17 days post-light treatment. Using the Tg(gfap:EGFP) nt11 transgenic line, Ngn1 was localized to the Müller glial nuclei that were reestablished following the regenerative response. These markers, therefore, can be used to identify different cell types at particular stages of retinal regeneration: neuronal progenitor formation, proliferation, and the reestablishment of the Müller glia cells. These markers will be important to further characterize the regeneration response in other retinal damage models and to elucidate the defects associated with mutants and morphants that disrupt the regeneration response.
-
CNTF Induces Photoreceptor Neuroprotection and Müller Glial Cell Proliferation Through Two Different Signaling Pathways in the Adult Zebrafish Retina
Experimental Eye Research.
Jun, 2009 |
Pubmed ID: 19450453 Ciliary neurotrophic factor (CNTF) acts in several processes in the vertebrate retina, including neuroprotection of photoreceptors in the stressed adult retina and regulation of neuronal progenitor cell proliferation during retinal development. However, the signaling pathway it utilizes (Jak/Stat, MAPK, or Akt) in these processes is ambiguous. Because dark-adapted albino zebrafish exhibit light-induced rod and cone cell death and subsequently regenerate the lost photoreceptor cells, zebrafish should be a useful model to study the role of CNTF in both neuroprotection and neuronal progenitor cell proliferation. We therefore investigated the potential roles of CNTF in both the undamaged and light-damaged adult zebrafish retinas. Intraocular injection of CNTF suppressed light-induced photoreceptor cell death, which then failed to exhibit the regeneration response that is marked by proliferating Müller glia and neuronal progenitor cells. Inhibiting the MAPK signaling pathway, but neither the Stat3 nor Akt pathways, significantly reduced the CNTF-mediated neuroprotection of light-induced photoreceptor cell death. Intraocular injection of CNTF into non-light-treated (undamaged) eyes mimicked constant intense light treatment by increasing Stat3 expression in Müller glia followed by increasing the number of proliferating Müller glia and neuronal progenitors. Knockdown of Stat3 expression in the CNTF-injected non-light-treated retinas significantly reduced the number of proliferating Müller glia, while coinjection of CNTF with either MAPK or Akt inhibitors did not inhibit the CNTF-induced Müller glia proliferation. Thus, CNTF utilizes a MAPK-dependant signaling pathway in neuroprotection of light-induced photoreceptor cell death and a Stat3-dependant signaling pathway to stimulate Müller glia proliferation.
-
-
Pax6a and Pax6b Are Required at Different Points in Neuronal Progenitor Cell Proliferation During Zebrafish Photoreceptor Regeneration
Experimental Eye Research.
May, 2010 |
Pubmed ID: 20152834 The light-damaged zebrafish retina results in the death of photoreceptor cells and the subsequent regeneration of the missing rod and cone cells. Photoreceptor regeneration initiates with asymmetric Müller glial cell division to produce neuronal progenitor cells, which amplify, migrate to the outer nuclear layer (ONL), and differentiate into both classes of photoreceptor cells. In this study, we examined the role of the Pax6 protein in regeneration. In zebrafish, there are two Pax6 proteins, one encoded by the pax6a gene and the other encoded by the pax6b gene. We intravitreally injected and electroporated morpholinos that were complementary to either the pax6a or pax6b mRNA to knockdown the translation of the corresponding protein. Loss of Pax6b expression did not affect Müller glial cell division, but blocked the subsequent first cell division of the neuronal progenitors. In contrast, the paralogous Pax6a protein was required for later neuronal progenitor cell divisions, which maximized the number of neuronal progenitors. Without neuronal progenitor cell amplification, proliferation of resident ONL rod precursor cells, which can only regenerate rods, increased inversely proportional to the number of INL neuronal progenitor cells. This confirmed that Müller glial-derived neuronal progenitor cells are necessary to regenerate cones and that distinct mechanisms selectively regenerate rod and cone photoreceptors. This work also defines distinct roles for Pax6a and Pax6b in regulating neuronal progenitor cell proliferation in the adult zebrafish retina and increases our understanding of the molecular pathways required for photoreceptor cell regeneration.
-
-
The Loss of Vacuolar Protein Sorting 11 (vps11) Causes Retinal Pathogenesis in a Vertebrate Model of Syndromic Albinism
Investigative Ophthalmology & Visual Science.
May, 2011 |
Pubmed ID: 21622697 Purpose: To establish the zebrafish platinum mutant as a model for studying vision defects caused by syndromic albinism diseases such as Chediak-Higashi syndrome, Griscelli syndrome, and Hermansky-Pudlak syndrome (HPS). Methods: Bulked segregant analysis and candidate gene sequencing revealed that the zebrafish platinum mutation is a single nucleotide insertion in the vps11 (vacuolar protein sorting 11) gene. Expression of vps11 was determined by RT-PCR and in situ hybridization. Mutants were analyzed for pigmentation defects and retinal pathology by histology, immunohistochemistry, and transmission electron microscopy. Results: Phenocopy and rescue experiments determined that a loss of Vps11 results in the platinum phenotype. Expression of vps11 appeared ubiquitous during zebrafish development, with stronger expression in the developing retina and retinal pigmented epithelium (RPE). Zebrafish platinum mutants exhibited reduced pigmentation in the body and retinal pigmented epithelium (RPE), however, melanophore development, migration, and dispersion occurred normally. RPE, photoreceptors, and inner retinal neurons formed normally in zebrafish platinum mutants. However, a gradual loss of RPE, an absence of mature melanosomes and the subsequent degradation of RPE/photoreceptor interdigitation was observed. Conclusions: These data show that Vps11 is not required for normal retinal development or initiation of melanin biosynthesis, but is required for melanosome maturation and healthy maintenance of the RPE and photoreceptors.
-
FGF Signaling Regulates Rod Photoreceptor Cell Maintenance and Regeneration in Zebrafish
Experimental Eye Research.
Nov, 2011 |
Pubmed ID: 21945172 Fgf signaling is required for many biological processes involving the regulation of cell proliferation and maintenance, including embryonic patterning, tissue homeostasis, wound healing, and cancer progression. Although the function of Fgf signaling is suggested in several different regeneration models, including appendage regeneration in amphibians and fin and heart regeneration in zebrafish, it has not yet been studied during zebrafish photoreceptor cell regeneration. Here we demonstrate that intravitreal injections of FGF-2 induced rod precursor cell proliferation and photoreceptor cell neuroprotection during intense light damage. Using the dominant-negative Tg(hsp70:dn-fgfr1) transgenic line, we found that Fgf signaling was required for homeostasis of rod, but not cone, photoreceptors. Even though fgfr1 is expressed in both rod and cone photoreceptors, we found that Fgf signaling differentially affected the regeneration of cone and rod photoreceptors in the light-damaged retina, with the dominant-negative hsp70:dn-fgfr1 transgene significantly repressing rod photoreceptor regeneration without affecting cone photoreceptors. These data suggest that rod photoreceptor homeostasis and regeneration is Fgf-dependent and that rod and cone photoreceptors in adult zebrafish are regulated by different signaling pathways.
-
Using the Tg(nrd:egfp)/albino Zebrafish Line to Characterize in Vivo Expression of Neurod
PloS One.
2012 |
Pubmed ID: 22235264 In this study, we used a newly-created transgenic zebrafish, Tg(nrd:egfp)/albino, to further characterize the expression of neurod in the developing and adult retina and to determine neurod expression during adult photoreceptor regeneration. We also provide observations regarding the expression of neurod in a variety of other tissues. In this line, EGFP is found in cells of the developing and adult retina, pineal gland, cerebellum, olfactory bulbs, midbrain, hindbrain, neural tube, lateral line, inner ear, pancreas, gut, and fin. Using immunohistochemistry and in situ hybridization, we compare the expression of the nrd:egfp transgene to that of endogenous neurod and to known retinal cell types. Consistent with previous data based on in situ hybridizations, we show that during retinal development, the nrd:egfp transgene is not expressed in proliferating retinal neuroepithelium, and is expressed in a subset of retinal neurons. In contrast to previous studies, nrd:egfp is gradually re-expressed in all rod photoreceptors. During photoreceptor regeneration in adult zebrafish, in situ hybridization reveals that neurod is not expressed in Müller glial-derived neuronal progenitors, but is expressed in photoreceptor progenitors as they migrate to the outer nuclear layer and differentiate into new rod photoreceptors. During photoreceptor regeneration, expression of the nrd:egfp matches that of neurod. We conclude that Tg(nrd:egfp)/albino is a good representation of endogenous neurod expression, is a useful tool to visualize neurod expression in a variety of tissues and will aid investigating the fundamental processes that govern photoreceptor regeneration in adults.
-
-
Get cutting-edge science videos from JoVE sent straight to your inbox every month.
