A fork head/HNF-3 homolog expressed in the pharynx and intestine of the Caenorhabditis elegans embryo.

We have cloned a member of the fork head/HNF-3 family of transcription factors from the nematode Caenorhabditis elegans. Within the predicted DNA binding domain, this gene, called Ce-fkh-1, is 75-78% identical to the Drosophila fork head and rat liver HNF-3 alpha, beta, and gamma genes. Ce-fkh-1 mRNA is highly enriched in embryos. The Ce-fkh-1 gene produces three major transcripts: the longest mRNA retains its original 5'-end but two shorter mRNAs are trans-spliced at the beginning of exons 2 and 3, respectively. In situ hybridization and transgenic Ce-fkh-1::lacZ reporter constructs indicate that the Ce-fkh-1 gene is expressed in both pharynx and intestine of the embryo, beginning at the midproliferation stage. A second phase of Ce-fkh-1 expression occurs in cells of the larval somatic gonad. The pharynx-gut expression of Ce-fkh-1 in the C. elegans embryo is compared with expression of fork head throughout the gut of Drosophila embryos and with expression of HNF-3 (alpha beta gamma) in the endoderm of mammalian embryos. Such conserved patterns of gene expression point to universal features of gastrulation and of digestive tract formation.