The pharynx (or foregut) of the nematode Caenorhabditis elegans is involved in initiation of digestion and transportation of its food source. We previously showed that pharyngeal gland cells secrete mucin-like proteins (PHAT proteins) that aid in transportation of the bacteria along the lumen. We identified
hlh-6 as a critical regulator of phat gene expression and subsequent gland function. Mutations in
hlh-6 result in a starvation phenotype presumably due to the lack of PHAT protein coating and lubricating the pharyngeal lumen. However, not all gland expressed genes are dependent on
hlh-6 for expression and three out of five glands are still present in
hlh-6 mutants, suggesting the presence of other gland gene regulators and potentially other gland functions. By identifying other gland transcription factors and examining their mutant phenotype we hope to further our understanding of the development and function(s) of these cells. Searching for cis-acting elements in
hlh-6 independent gland genes will lead to the identification of an
hlh-6 independent transcription factor. A list of all known gland expressed genes was compiled by searches of the literature and available expression databases (NEXTDB, the BC Gene Expression Database, the Hope Lab Expression Database). The promoters of these genes were then examined for the presence of a consensus
hlh-6 binding motif. Thirty genes had promoters lacking a probable HLH-6 binding site and were classified as possible
hlh-6-independent genes. Reporters were made for ten of these genes and we are currently testing which of these reporters are indeed
hlh-6 independent by examining their expression in
hlh-6 mutants. Once we have a list of confirmed
hlh-6-independent gland genes, the promoters of these genes will be examined computationally for the presence of shared motifs. The gland expression of one gene (B0507.1) has been shown to be only partially dependent on
hlh-6. Further analysis of this promoter has identified a critical region of 60 bp in the B0507.1 promoter that is responsible for the
hlh-6 independent gland expression. We are currently defining the specific cis-acting element(s) within this region, which may suggest probable trans-acting factors. From the list of all known gland expressed genes, ten are transcription factors (zinc finger and nuclear hormone receptor families) and eight do not contain probable HLH-6 binding sites. As a complementary approach we are examining the expression of known HLH-6 independent genes in mutants for these transcription factors.