| Abstract: |
Hibris (Hbs) is a transmembrane immunoglobulin-like protein that shows extensive homology to Drosophila Sticks and stones (Sns) and human kidney protein Nephrin. Hbs is expressed in embryonic visceral, somatic and pharyngeal mesoderm among other tissues. In the somatic mesoderm, Hbs is restricted to fusion competent myoblasts and is regulated by Notch and Ras signaling pathways. Embryos that lack or overexpress hbs show a partial block of myoblast fusion, followed by abnormal muscle morphogenesis. Abnormalities in visceral mesoderm are also observed. In vivo mapping of functional domains suggests that the intracellular domain mediates Hbs activity. Hbs and its paralog, Sns, co-localize at the cell membrane of fusion-competent myoblasts. The two proteins act antagonistically: loss of sns dominantly suppresses the hbs myoblast fusion and visceral mesoderm phenotypes, and enhances Hbs overexpression phenotypes. Data from a P-homed enhancer reporter into hbs and colocalization studies with Sns suggest that hbs is not continuously expressed in all fusion-competent myoblasts during the fusion process. We propose that the temporal pattern of hbs expression within fusion-competent myoblasts may reflect previously undescribed functional differences within this myoblast population. |
| Keywords: |
signal transduction; controlled study; unclassified drug; mutation; dose response; nonhuman; protein domain; animal cell; phenotype; animals; animal tissue; cell function; gene overexpression; gene expression; embryo; membrane proteins; gene product; notch receptor; drosophila; morphogenesis; immunoglobulin; in vivo study; cell differentiation; cell population; data base; animalia; cloning, molecular; embryo, nonmammalian; gene expression regulation, developmental; gene mapping; kidney; amino acid sequence; molecular sequence data; sequence homology, amino acid; receptors, notch; gene repression; membrane protein; cell membrane; reporter gene; gene loss; base sequence; gene control; ras protein; developmental disorder; ras proteins; sequence homology; cell level; mesoderm; drosophila proteins; gene location; viscera; myoblast fusion; cell fusion; myoblast; gene activity; immunoglobulins; observation; pharynx; muscle, skeletal; muscle development; enhancer region; hibris protein; nephrin; human; priority journal; article; insect proteins; hbs; sticks and stones
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