Our lab uses Caenorhabditis elegans as a model organism to study actin/myosin contractile networks that are employed for morphogenic changes in animal development. We focus on the contraction of the epidermal cells responsible for elongating the ovoid embryo into a worm-shaped tube.Previous research in our lab determined the key players (and their regulatory relationships) involved in worm embryonic contraction, including the worm homologs of vertebrate LET-502/Rho-binding kinase, MEL-11/myosin phosphatase, FEM-2/protein phosphatase 2c and non-muscle myosin. Furthermore, parallel pathways generate contraction:
mel-11 and
let-502 are involved in one pathway, while
fem-2 and
pak-1 are involved in a different pathway.Only the lateral epidermal cells contract during elongation, and localized activity of a Rho GEF (guanine exchange factor) could contribute to this asymmetry. We found that loss of the C. elegans Rho GEF encoded by
rhgf-2 results in arrest during early elongation. Genetically,
rhgf-2 acts as an activator of
let-502/Rho-binding kinase, in parallel to
fem-2/PP2c phosphatase. Although expressed throughout the embryo, RHGF-2 in the lateral cells can mediate elongation. The Rho GAP (GTPase activating protein) RGA-2 is known to prevent contraction in the dorsal and ventral epidermis. In the absence of both
rhgf-2 and
rga-2, elongation still occurs, although this still requires
let-502(+).Recently, by screening for genetic interactions, a new player has been identified: the gene ZK185.1, which encodes a protein with a Cys-His Zinc finger. Three alleles are known but no phenotypes are exhibited for any of them. Currently double mutants are being constructed between the three alleles and mutations of known genes in the contraction pathway to determine where ZK185.1 acts in elongation. GFP reporters using CRISPR will be generated to visualise where ZK185.1 is acting. .