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...[ Read more ]

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.