introducing-gene-knockout-directly-into-amastigote-stage-trypanosoma

Introducing a Gene Knockout Directly Into the Amastigote Stage of <em>Trypanosoma cruzi</em> Using the CRISPR/Cas9 System

Trypanosoma cruzi is a pathogenic protozoan parasite that causes Chagas&#8217; disease mainly in Latin America. In order to identify a novel drug target ...

National Institute of Advanced Industrial Science and Technology (AIST)

Na+/K+ ATPase is a plasma membrane-localized sodium pump that maintains the ion gradients between the extracellular and intracellular environments, which in turn controls the cellular resting membrane potential.Recent evidence suggests that the pump is also localized at synapses and regulates synaptic efficacy.However, its precise function at the synapse is unknown. Here we show that two mutations in the alpha subunit of the eat-6 Na+/K+ ATPase in Caenorhabditis elegans dramatically increase the sensitivity to acetylcholine(Ach) agonists and alter the localization of nicotinic Ach receptors at the neuromuscular junction (NMJ).These defects can be rescued by mutated EAT-6 proteins which lack its pump activity, suggesting the presence of a novel function for Ach signaling. The Na+/K+ ATPase accumulates at postsynaptic sites and appears to surround Ach receptors to maintain rigid clusters at the NMJ. Our findings suggest a pump activity-independent, allele-specific role for Na+/K+ ATPase on postsynaptic organization and synaptic efficacy.

Na+/K+ ATPase regulates the expression and localization of acetylcholine receptors in a pump activity-independent manner.

Cell migration and axon guidance require proper regulation of the actin cytoskeleton in response to extracellular guidance cues. Rho/Rac small GTPases are essential regulators of actin remodeling. Caenorhabditis elegans CED-10 is a Rac1 homolog that is required for various cellular morphological changes and migration events and is under the control of several guidance signaling pathways. There is still considerable uncertainty regarding events following the activation of guidance receptors by extracellular signals and the regulation of actin dynamics based on spatiotemporally restricted Rac activity. Here we show that the VPS9 domain protein RIN-1 acts as a novel effector for CED-10 in C. elegans. The orthologous mammalian Rin1 protein has previously been identified as an effector for Ras GTPase and is now known to function as a guanine nucleotide exchange factor for Rab5 GTPase. We found that RIN-1 specifically binds to the GTP-bound form of CED-10 and that mutations in rin-1 cause significant defects in migration and axon guidance of restricted neuronal cell types including AVM and HSN neurons, in contrast to the various defects observed in ced-10 mutants. Our analyses place RIN-1 in the Slit-Robo genetic pathway that regulates repulsive signaling for dorsoventral axon guidance. In rin-1 mutants, actin accumulated on both the ventral and dorsal sides of the developing HSN neuron, in contrast to its ventral accumulation in wild type. These results strongly suggest that RIN-1 acts as an effector for CED-10/Rac1 and regulates actin remodeling in response to restricted guidance cues. 

The novel Rac effector RIN-1 regulates neuronal cell migration and axon pathfinding in C. elegans.

Recently, advances in next-generation sequencing technologies have enabled genome-wide analyses of epigenetic modifications; however, it remains difficult to analyze the states of histone modifications at a single-cell resolution in living multicellular organisms because of the heterogeneity within cellular populations. Here we describe a simple method to visualize histone modifications on the specific sequence of target locus at a single-cell resolution in living , by combining the LacO/LacI system and a genetically-encoded H4K20me1-specific probe, "mintbody". We demonstrate that Venus-labeled mintbody and mTurquoise2-labeled LacI can co-localize on an artificial chromosome carrying both the target locus and LacO sequences, where H4K20me1 marks the target locus. We demonstrate that our visualization method can precisely detect H4K20me1 depositions on the  gene sequences on the artificial chromosome, to which the dosage compensation complex binds to regulate sex determination. The degree of H4K20me1 deposition on the  sequences on the artificial chromosome correlated strongly with sex, suggesting that, using the artificial chromosome, this method can reflect context-dependent changes of H4K20me1 on endogenous genomes. Furthermore, we demonstrate live imaging of H4K20me1 depositions on the artificial chromosome. Combined with ChIP assays, this mintbody-LacO/LacI visualization method will enable analysis of developmental and context-dependent alterations of locus-specific histone modifications in specific cells and elucidation of the underlying molecular mechanisms.

Article	Year
Na+/K+ ATPase regulates the expression and localization of acetylcholine receptors in a pump activity-independent manner. Molecular and cellular neurosciences\| PubMed ID: 18599311	2008
The novel Rac effector RIN-1 regulates neuronal cell migration and axon pathfinding in C. elegans. Development (Cambridge, England)\| PubMed ID: 23900541	2013
A Simple Method for Visualization of Locus-Specific H4K20me1 Modifications in Living Single Cells. G3 (Bethesda, Md.)\| PubMed ID: 29724885	2018

Motomichi Doi

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