The Caenorhabditis elegans nonmuscle myosin genes nmy-1 and nmy-2 function as redundant components of the let-502/Rho-binding kinase and mel-11/myosin phosphatase pathway during embryonic morphogenesis.
Rho-binding kinase and the myosin phosphatase targeting subunit regulate nonmuscle contractile events in higher eukaryotes. Genetic evidence indicates that the C. elegans homologs regulate embryonic morphogenesis by controlling the actin-mediated epidermal cell shape changes that transform the spherical embryo into a long, thin worm. LET-502/Rho-binding kinase triggers elongation while MEL-11/myosin phosphatase targeting subunit inhibits this contractile event. We describe mutations in the nonmuscle myosin heavy chain gene nmy-1 that were isolated as suppressors of the mel-11 hypercontraction phenotype. However, a nmy-1 null allele displays elongation defects less severe than mutations in let-502 or in the single nonmuscle myosin light chain gene mlc-4. This results because nmy-1 is partially redundant with another nonmuscle myosin heavy chain, nmy-2, which was previously known only for its role in anterior/posterior polarity and cytokinesis in the early embryo. At the onset of elongation, NMY-1 forms filamentous-like structures similar to actin, and LET-502 is interspersed with these structures, where it may trigger contraction. MEL-11, which inhibits elongation, is initially cytoplasmic. In response to LET-502 activity, MEL-11 becomes sequestered away from the contractile apparatus, to the plasma membrane, when elongation commences. Upon completion of morphogenesis, MEL-11 again appears in the cytoplasm where it may halt actin/myosin contraction.
Piekny
Alisa J
AJ
Genes and Development Research Group and Department of Biochemistry and Molecular Biology, University of Calgary, 3330 Hospital Dr NW, Calgary, AB, Canada, T2N 4N1.
Johnson
Jacque-Lynne F
JL
Cham
Gwendolyn D
GD
Mains
Paul E
PE
D000199:Actins / Q000378:metabolism; D000818:Animals; D019521:Body Patterning; D017173:Caenorhabditis elegans / Q000033:anatomy & histology / Q000196:embryology* / Q000235:genetics* / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins; D009024:Morphogenesis; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D043263:Myosin-Light-Chain Phosphatase / Q000378:metabolism*; D009218:Myosins / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D011110:Polymorphism, Genetic; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D054460:rho-Associated Kinases
D000199:Actins; D029742:Caenorhabditis elegans Proteins; D047908:Intracellular Signaling Peptides and Proteins; C480836:NMY-1 protein, C elegans; C480837:NMY-2 protein, C elegans; C515856:LET-502 protein, C elegans; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; C468369:MEL-11 protein, C elegans; D043263:Myosin-Light-Chain Phosphatase; D018995:Myosin Heavy Chains; D009218:Myosins