Dynamin-dependent endocytosis is necessary for convergent-extension movements in Xenopus animal cap explants

Cadherin cell-cell adhesion molecules are important determinants of morphogenesis and tissue patterning. C-cadherin plays a key role in the cell-upon-cell movements seen during Xenopus gastrulation. In particular, regulated changes in C-cadherin adhesion critically influence convergence-extension movements, thereby determining organization of the body plan. It is also predicted that remodelling of cadherin adhesive contacts is important for such cell-on-cell movements to occur. The recent demonstration that Epithelial (E-) cadherin is capable of undergoing endocytic trafficking to and from the cell surface presents a potential mechanism for rapid remodelling of such adhesive contacts. To test the potential role for C-cadherin endocytosis during convergence-extension, we expressed in early Xenopus embryos a dominantly-inhibitory mutant of the GTPase, dynamin, a key regulator of clathrin-mediated endocytosis. We report that this dynamin mutant significantly blocked the elongation of animal cap explants in response to activin, accompanied by inhibition of C-cadherin endocytosis. We propose that dynamin-dependent endocytosis of C-cadherin plays an important role in remodelling adhesive contacts during convergence-extension movements in the early Xenopus embryo.

N-terminal Slit2 promotes survival and neurite extension in cultured peripheral neurons

To investigate the effect of the N-terminal Slit2 protein on neuronal survival and development, recombinant human N-terminal Slit2 (N-Slit2) was assayed against isolated embryonic chick dorsal root ganglion sensory, ciliary ganglion and paravertebral sympathetic neurons. N-Slit2 promoted significant levels of neuronal survival and neurite extension in all of these populations. The protein was also assayed against postnatal mouse dorsal root ganglion neurons and found to promote neuronal survival in a similar manner. These findings suggest the Slit proteins may play an important role during development of the nervous system, mediating cellular survival in addition to the well documented role these proteins play in axonal and neuronal chemorepulsion.