title: pix-1 controls early elongation in parallel with mel-11 and let-502 in Caenorhabditis elegans.
abstract: Cell shape changes are crucial for metazoan development. During Caenorhabditis elegans embryogenesis, epidermal cell shape changes transform ovoid embryos into vermiform larvae. This process is divided into two phases: early and late elongation. Early elongation involves the contraction of filamentous actin bundles by phosphorylated non-muscle myosin in a subset of epidermal (hypodermal) cells. The genes controlling early elongation are associated with two parallel pathways. The first one involves the rho-1/RHOA-specific effector let-502/Rho-kinase and mel-11/myosin phosphatase regulatory subunit. The second pathway involves the CDC42/RAC-specific effector pak-1. Late elongation is driven by mechanotransduction in ventral and dorsal hypodermal cells in response to body-wall muscle contractions, and involves the CDC42/RAC-specific Guanine-nucleotide Exchange Factor (GEF) pix-1, the GTPase ced-10/RAC and pak-1. In this study, pix-1 is shown to control early elongation in parallel with let-502/mel-11, as previously shown for pak-1. We show that pix-1, pak-1 and let-502 control the rate of elongation, and the antero-posterior morphology of the embryos. In particular, pix-1 and pak-1 are shown to control head, but not tail width, while let-502 controls both head and tail width. This suggests that let-502 function is required throughout the antero-posterior axis of the embryo during early elongation, while pix-1/pak-1 function may be mostly required in the anterior part of the embryo. Supporting this hypothesis we show that low pix-1 expression level in the dorsal-posterior hypodermal cells is required to ensure high elongation rate during early elongation.
authors.affiliation: Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Martin
authors.affiliation: Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada.
authors.forename: Sharon
authors.initials: S
authors.lastname: Harel
authors.affiliation: Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada.
authors.forename: Bernard
authors.initials: B
authors.lastname: Nkengfac
authors.affiliation: Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada.
authors.forename: Karim
authors.initials: K
authors.lastname: Hamiche
authors.affiliation: Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Neault
authors.affiliation: Department of Chemistry, Pharmaqam, Biomed, Université du Québec à Montréal (UQÀM), Montréal, Québec, Canada.
authors.forename: Sarah
authors.initials: S
authors.lastname: Jenna
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000502:physiology*; D002352:Carrier Proteins / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D040542:Mechanotransduction, Cellular / Q000235:genetics; D009154:Mutation; D043263:Myosin-Light-Chain Phosphatase / Q000502:physiology*; D010641:Phenotype; D010766:Phosphorylation; D015398:Signal Transduction; D054460:rho-Associated Kinases / Q000502:physiology*
chemical_list: D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D020662:Guanine Nucleotide Exchange Factors; C534515:PIX-1 protein, C elegans; D049452:Green Fluorescent Proteins; C515856:LET-502 protein, C elegans; D054460:rho-Associated Kinases; C468369:MEL-11 protein, C elegans; D043263:Myosin-Light-Chain Phosphatase
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