Casprs are members of the Neurexins superfamily, a group of transmembrane proteins that mediate cell-cell interactions in the nervous system. The Caspr proteins mediate axon-glia and glia-glia interactions and in vertebrates, they are also found in other tissues in addition to the nervous system. Two Caspr proteins, encodes by WO3D8.6 and F20B10.1 are found in Caenorhabditis elegans . Both proteins contain several EGF and Laminin-G domains in their large extracellular region but lack the characteristic discoidin-like domain that is found in all mammalian Casprs. A transgenic line expressing GFP reporter construct fused to the promoter region of W03D8.6 revealed that this gene is expressed exclusively by epithelia of intestinal cells, as well as in socket and sheath cells of the inner labial sensilla. Whole mount immunofluorescence staining confirmed that W03D8.6 gene product is expressed by intestine epithelia, where it is confined to the basolateral membranes. We therefore termed W03D8.6 Intexin ( itx ). Disruption of Intexin expression by RNA interference (RNAi) was examined in wild type N2 strain, as well as in 2 other transgenic lines:
jam-1::GFP (JcIs1) and
cdh-3::GFP (arIs51). Preliminary characterization of the RNAi effect revealed that the abrogation of Intexin expression did not disrupts organogenesis or integrity of the intestine at any developmental stage. Nevertheless, in JcIs1 the expression of
jam-1::GFP, was dramatically impaired such that no GFP could be detected in these worms. This effect was specific and was exclusively observed in the gut epithelia. The expression of
jam-1::GFP in other epithelial tissues such as the hyodermis and pharynx remained intact. In contrast, the expression of cadherin--3 was not affected by Intexin RNAi. These results suggest that Intexin may be required to delineate the apico-lateral domain of gut epithelia where adherence junctions typically assemble. Ultrastructural studies are underway to study the affect of intexin RNAi on the morphology of these junctions, as well as to determine the exact localization of Intexin in ensheathing glial cells.