Figure 3.

Roles of Rac1 and Cdc42 in protrusive activity in the SE. (A) Scanning electron micrographs of an E9.5 mouse embryo showing membrane ruffles at the site of spinal neural fold apposition. Blue arrow indicates the direction of zippering of the spinal neural tube. Right sided image is an enlargement of the orange boxed region. (B) Summary of the roles, regulation, and requirement of different types of protrusions during spinal neurulation, as described in ref. 14. Rac1 is essential for the formation of membrane ruffles in SE cells at late neurulation, and their absence results in neural tube defects, whereas Cdc42 regulates formation of filopodia by SE cells during early neurulation.