The secretin family of serpentine receptors is an ancient family that has members in C. elegans, Drosophila, and vertebrates . Our alignment data suggests at least five member genes in the common ancestor of these lineages. Further duplications of each of the genes within the individual lineages lead to further expansion of the family . The five subfamily branches with their C. elegans members are flamingo-cefla
(f15b9.7), latrophilin(
lat-1(
b0457.1) and
lat-2(
b0286.2)), calcitonin receptor
(c13b9.4), corticotrophin releasing factor receptor
(zk643.3), and secretin receptor
(c18b12.2). Most of the studied members of this family are involved in regulated secretion in response to a peptide ligand. We are currently attempting to understand the organismal biology of this family in C. elegans by expression and phenotypic analysis and by linking these receptors to the peptide ligands that activate them. One of the aspects that we are focusing on is the latrophilin subfamily. Lat-1 expression starts after gastrulation and continues into the adult. It is expressed in the hypodermal, pharyngeal and some neuronal cells in the embryo. During larval development it is expressed in mechanosensory and interneurons in the head and tail, gland cell in pharynx, gonadal sheath cells, spermatheca, uterine epithelial cells and intestinal cells. We are focusing on the following aspects of the expression pattern: expression in alternating dorsal hypodermal cells during intercalation, expression and localization to the apical surface in the pharyngeal primordium cells, expression in ventral cord neurons and gland cell in the dauer, and expression in the reproductive organs. Phenotypes from RNAi have correlated with some of these expression patterns. These include elongation defects, abnormal pharyngeal development and attachment, small eggs, and ovulation defects in the injected animal. Lat-2 is expressed in the
g1 gland cell and arcade cells in the head in which it localizes to the syncitial end of the process, and the expression cycles with the molts.