A conserved LIM protein that affects muscular adherens junction integrity and mechanosensory function in Caenorhabditis elegans

We describe here the molecular and functional characterization of the Caeno rhabditis elegans unc-97 gene, whose gene product constitutes a novel compo nent of muscular adherens junctions. UNC-97 and homologues from several oth er species define the PINCH family, a family of LIM proteins whose modular composition of five LIM domains implicates them as potential adapter molecu les. unc-97 expression is restricted to tissue types that attach to the hyp odermis, specifically body wall muscles, vulval muscles, and mechanosensory neurons. In body wall muscles, the UNC-97 protein colocalizes with the bet a-integrin PAT-3 to the focal adhesion-like attachment sites of muscles. Pa rtial and complete loss-of-function studies demonstrate that UNC-97 affects the structural integrity of the integrin containing muscle adherens juncti ons and contributes to the mechanosensory functions of touch neurons. The e xpression of a Drosophila homologue of unc-97 in two integrin containing ce ll types, muscles, and muscle-attached epidermal cells, suggests that unc-9 7 function in adherens junction assembly and stability has been conserved a cross phylogeny. In addition to its localization to adherens junctions UNC- 97 can also be detected in the nucleus, suggesting multiple functions for t his LIM domain protein.