The unc-86 gene product couples cell lineage and cell identity in C. elegans

The C. elegans gene unc-86 is required in several distinct neuroblast lineages for daughter cells to become different from their mothers, and is also required for the specification of particular neural identities. Consistent with the fact that unc-86 encodes a POU domain protein, we find that the unc-86 protein is localized to the nucleus. In the affected lineages, unc-86 protein appears within a few minutes after cell division in the nuclei of those daughter cells that are transformed by unc-86 mutations. Thus, expression of unc-86 protein is dependent on cell lineage. unc-86 protein is not asymmetrically segregated at further divisions. unc-86 protein also appears shortly after cell division in the nuclei of particular identified differentiating neurons; at least some of these neurons are nonfunctional in unc-86 mutants.     

hUNC93B1: a novel human gene representing a new gene family and encoding an unc-93-like protein

We have identified a novel human gene UNC93B1 encoding a protein related to unc-93 of Caenorhabditis elegans. The combined sequence derived from several cDNA clones is 2282 bp and comparison with genomic sequence shows that the gene contains 11 exons. The longest open reading frame encodes a deduced sequence of 597 amino acids. Homology analysis shows that the hUNC93B1 gene is highly conserved and related to sequences in Arabidopsis thaliana, C. elegans, Drosophila melanogaster, chicken and mouse. Structural analysis of the deduced amino acid sequence of hUNC93B1 points to possible existence of multiple membrane-spanning domains. hUNC93B1 protein also displays some similarities to the bacterial ABC-2 type transporter signature and to ion transporters of Deinococcus radiodurans and Helicobacter pylori. As revealed by Northern analysis, the level of expression varies significantly between tissues, with the highest level detected in the heart. The gene was mapped to chromosomal band 11q13 by fluorescence in situ hybridization. We suggest that this gene is a member of a novel hUNC93B-related gene family.     

The Unc-8 and Sup-40 Genes Regulate Ion Channel Function in Caenorhabditis Elegans Motorneurons

Two Caenorhabditis elegans genes, unc-8 and sup-40, have been newly identified, by genetic criteria, as regulating ion channel function in motorneurons. Two dominant unc-8 alleles cause motorneuron swelling similar to that of other neuronal types in dominant mutants of the deg-1 gene family, which is homologous to a mammalian gene family encoding amiloride-sensitive sodium channel subunits. As for previously identified deg-1 family members, unc-8 dominant mutations are recessively suppressed by mutations in the mec-6 gene, which probably encodes a second type of channel component. An unusual dominant mutation, sup-41 (lb125), also co-suppresses unc-8 and deg-1, suggesting the existence of yet another common component of ion channels containing unc-8 or deg-1 subunits. Dominant, transacting, intragenic suppressor mutations have been isolated for both unc-8 and deg-1, consistent with the idea that, like their mammalian homologues, the two gene products function as multimers. The sup-40 (lb130) mutation dominantly suppresses unc-8 motorneuron swelling and produces a novel swelling phenotype in hypodermal nuclei. sup-40 may encode an ion channel component or regulator that can correct the osmotic defect caused by abnormal unc-8 channels.