![]() ![]() ![]() elegans has an almost invariant cell division pattern ( Sulston et al. ![]() The Caenorhabditis elegans embryo is an ideal system for exploring the mechanisms of morphogenesis. For example, little is known about the factors needed for sending and receiving the signals that initiate cell migrations for changing cell adhesiveness to allow both migrations past neighboring cells and anchoring of cells to new locations and for initiating, executing, and strengthening cell shape changes in the embryo. A great deal is known about the mechanisms of cellular differentiation, but the mechanisms controlling cell shape changes and the cell movements that occur during morphogenesis are less well understood. Our findings suggest that GEX-2 and GEX-3 may function at cell boundaries to regulate cell migrations and cell shape changes required for proper morphogenesis and development.Įmbryogenesis requires two at least partially distinct processes, the generation of cellular diversity, or differentiation, and the organization of cells into a functional body, or morphogenesis. GEX-2 and GEX-3 are highly conserved, with vertebrate homologs implicated in binding the small GTPase Rac and a GEX-3 Drosophila homolog, HEM2/NAP1/KETTE, that interacts genetically with Rac pathway mutants. GEX-2 and GEX-3 proteins colocalize to cell boundaries and appear to directly interact. Postembryonically gex-3 activity is required for egg laying and for proper morphogenesis of the gonad. The external hypodermal cells fail to spread over and enclose the embryo and instead cluster on the dorsal side. In the absence of gex-2 and gex-3 activities, cells differentiate properly but fail to become organized. Here we describe two genes, gex-2 and gex-3, whose activities are necessary for initial steps of body morphogenesis in Caenorhabditis elegans. During body morphogenesis precisely coordinated cell movements and cell shape changes organize the newly differentiated cells of an embryo into functional tissues. ![]()
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