Cdc42 GTPase and Rac1 GTPase act downstream of p120 catenin and require GTP exchange during gastrulation of zebrafish mesoderm.

BACKGROUND: We investigated the roles of p120 catenin, Cdc42, Rac1, and RhoA GTPases in regulating migration of presomitic mesoderm cells in zebrafish embryos. p120 catenin has dual roles: It binds the intracellular and juxtamembrane region of cadherins to stabilize cadherin-mediated adhesion with the aid of RhoA GTPase, and it activates Cdc42 GTPase and Rac1 GTPase in the cytosol to initiate cell motility. RESULTS: During gastrulation of zebrafish embryos, knockdown of the synthesis of zygotic p120 catenin δ1 mRNAs with a splice-site morpholino caused lateral widening and anterior-posterior shortening of the presomitic mesoderm and somites and a shortened anterior-posterior axis. These phenotypes indicate a cell-migration effect. Co-injection of low amounts of wild-type Cdc42 or wild-type Rac1 or dominant-negative RhoA mRNAs, but not constitutively-active Cdc42 mRNA, rescued these p120 catenin δ1-depleted embryos. CONCLUSIONS: These downstream small GTPases require appropriate spatiotemporal stimulation or cycling of GTP to guide mesodermal cell migration. A delicate balance of Rho GTPases and p120 catenin underlies normal development.

Contribution of Rho kinase to blood pressure elevation and vasoconstrictor responsiveness in type 2 diabetic Goto-Kakizaki rats.

OBJECTIVES: The RhoA-Rho kinase (ROCK) pathway contributes to a number of diabetic complications including cardiomyopathy and nephropathy. In this study, we investigated whether it contributes to elevated blood pressure and vascular contractile dysfunction in type 2 diabetes. METHODS: Blood pressure was measured in Goto-Kakizaki rats, a nonobese model of type 2 diabetes, before and after treatment with the ROCK inhibitor fasudil. Vasoconstrictor responsiveness in the absence and presence of ROCK inhibitors as well as ROCK pathway activity was measured in isolated mesenteric resistance vessels from these animals. RESULTS: Blood pressure was elevated in diabetic rats compared with age-matched Wistar controls, and was normalized by treatment with fasudil. Contractile responses of mesenteric arteries from diabetic rats to phenylephrine and U-46619, as well as relaxant responses to acetylcholine, were unaltered. However, vasoconstrictor responses were more sensitive to ROCK inhibition with either Y-27632 or H-1152 than were responses of control arteries. No differences were found in expression of RhoA, ROCK1, or ROCK2 or in basal ROCK activity between arteries from control and diabetic rats. U-46619 produced a similar magnitude of increase in ROCK activity that was completely blocked by H-1152 in arteries from both groups of animals. CONCLUSION: These data suggest that ROCK contributes to the increase in blood pressure in type 2 diabetic Goto-Kakizaki rats, and that vasoconstrictor responses of small mesenteric arteries from these animals are more dependent on ROCK than are responses of control arteries.