Transcription regulatory networks in Caenorhabditis elegans

bar-1 encodes a beta-catenin; during C. elegans development, BAR-1 likely functions as a transcriptional coactivator whose activity is required for Q neuroblast migration, P12 cell fate specification, and P3.p through P8.p vulval cell fate specification at two different stages of development; in specifying vulval cell fates, bar-1 interacts with Wnt and MAPK signaling pathways to regulate proper expression of the LIN-39 homeodomain transcription factor, overexpresion of which can partially rescue the bar-1 mutant phenotype; in yeast two-hybrid assays, BAR-1 interacts strongly with the POP-1/TCF transcription factor, and when fused to the Gal4 DNA binding domain, BAR-1 can function in yeast as a transcriptional coactivator; during larval development, BAR-1 expression begins in P3.p through P8.p at the late L1 stage and then disappears from these cells by the mid-L3 stage; BAR-1 is also expressed in P12, in the seam cells, and in cells of the somatic gonad; BAR-1 subcellular localization, assessed using an integrated transgene, reveals localization to the cytoplasm, nucleus, and cell junctions; genetic mosaic analyses indicate that, in P4.p and in P12, bar-1 acts cell autonomously to specify cell fates.

The F37A4.9 gene encodes a protein with a meprin-associated Traf homology (MATH) domain that may be involved in apoptosis.

bbs-8 encodes a tetratricopeptide repeat (TPR)-containing protein that is orthologous to the human Bardet-Biedl syndrome protein, BBS8; in C. elegans, bbs-8 activity is required for cilia biogenesis and function; accordingly, bbs-8 mutant animals display odorant chemotaxis defects and exhibit both aberrant motility and abnormal localization of at least two intraflagellar transport (IFT) protein markers; a BBS-8::GFP translational fusion is expressed exclusively in ciliated head and tail neurons, where it localizes predominantly to the base of cilia, known as the ciliary transition zone; BBS-8::GFP is also observed moving bidirectionally (anterograde and retrograde) along the ciliary axoneme; DNA sequences upstream of bbs-8 contain X box DNA binding sites, suggesting that bbs-8 expression may be regulated by the DAF-19 RFX-type transcription factor.

bcat-1 encodes a branched-chain amino acid aminotransferase that, by homology, is predicted to catalyze the first reaction in the catabolism of essential branched-chain amino acids such as leucine, isoleucine, and valine; in C. elegans, large-scale RNA-mediated interference (RNAi) screens indicate that bcat-1 activity is required for embryonic and larval development.