THESIS
2016
xvii leaves, 116 pages : illustrations (some color) ; 30 cm
Abstract
Caenorhabditis elegans male tail consists of nine pairs of sensory rays which are embedded in a
cuticular fan. Each ray comprises simple cell components, a structural cell and two neuronal cells,
surrounded by hypodermis syncytium. Male sensory ray formation requires coordination of
transcription factors and their downstream targets. Yet, little is known about the final executor
genes. nsy-4, a C. elegans claudin-like gene, was identified to be involved in ray formation from a
genome-wide RNAi screen in our lab. nsy-4 (RNAi) males display a ray missing phenotype and the
depletion of its activity primarily affects the ray assembly process since the structural cells are already
differentiated. nsy-4 translational reporter reveals its subcellular localization at the ray cell junctio...[
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Caenorhabditis elegans male tail consists of nine pairs of sensory rays which are embedded in a
cuticular fan. Each ray comprises simple cell components, a structural cell and two neuronal cells,
surrounded by hypodermis syncytium. Male sensory ray formation requires coordination of
transcription factors and their downstream targets. Yet, little is known about the final executor
genes. nsy-4, a C. elegans claudin-like gene, was identified to be involved in ray formation from a
genome-wide RNAi screen in our lab. nsy-4 (RNAi) males display a ray missing phenotype and the
depletion of its activity primarily affects the ray assembly process since the structural cells are already
differentiated. nsy-4 translational reporter reveals its subcellular localization at the ray cell junctional
region. Knockdown of nsy-4 in ray hypodermal or structural cells alone is sufficient to give ray
missing males. Like its claudin homologs in vertebrates, NSY-4 contains a functional PDZ binding
motif and intracellular C-terminus, which are dispensable for correct localization. These results
suggest that NSY-4 functions similarly as its vertebrate counterparts and possibly mediates cell-cell
adhesion for ray assembly. NSY-4 also requires HMR-1, the classical cadherin, for its correct
localization, and the two co-localize in ray tips. hmr-1 and nys-4 double knockdown enhances the ray
missing phenotype, implying an interaction between the two proteins. In addition, homeobox
transcription factor ceh-43 knockdown reduces nsy-4 activity via a transcriptional reporter assay,
pointing nsy-4 as a downstream target of ceh-43. Given these results, we propose NSY-4 as a core
adhesive molecule in ray cell junctions for the formation of C. elegans male sensory ray. This study on NSY-4 reveals information about roles of claudin-like proteins in nematode organ formation and
provides insights for how their vertebrate counterparts may work in cellular association process.
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