Dynamic regulation of LARG in blastopore closure and archenteron formation during Xenopus laevis gastrulation

Rho GTPases have important roles in regulating cell migration and are activated by Rho-specific guanine nucleotide exchange factors (RhoGEFs). However, the role of leukemia-associated RhoGEF (LARG), responding to G∧12/13 family, has not been studied in vertebrate development. Here, the in vivo biochemical function of LARG was examined during early embryonic development in African frog Xenopus laevis. Gain-of-function study was performed by injecting the RNA of full-length xLARG to 2 cell-stage embryos. The ectopic expression of this protein resulted in the defect of blastopore closure during early embryogenesis. Expression of the dominant-negative form caused the defect in cell movement and following archenteron formation during late gastrulation, which is represented by the blister formation in the ventral side of the embryos. The phenotype was rescued by co-expressing the mutant with Rho or wild type xLARG, confirming the specificity of the dominant-negative activity of xLARG mutant. In this study, I showed for the first time that the spatiotemporal expression of xLARG is very dynamic and specifically regulated in early Xenopus embryonic development and xLARG may mediate Gα∧13 signal to activate Rho to exert its function in gastrulation movement and archenteron formation. My results implicate that the dynamic regulation of maternal and zygotic xLARG expression and its biochemical activity is necessary for proper gastrulation.