Becoming glial in the neural retina

During development of the vertebrate neural retina, multipotent stem cells give rise to retinal neurons as well as to Muller cells, the principal glia l population in the retina. Recent studies have shed light upon the extrace llular and intracellular signaling pathways that regulate Muller glial cell genesis. Emerging evidence demonstrates that activation of the Notch signa ling pathway can play a role in regulating Muller cell development as well as gliogenesis in other parts of the central nervous system. Cyclin depende nt kinase (CDK) inhibitors of the Cip/Kip subfamily are cell cycle regulato rs that can regulate progenitor proliferation during retinal development, b ut also regulate the proliferation of Muller glia when they become activate d in response to stress or injury. Surprisingly this class of proteins can also promote the development of Muller glia. In this review we discuss the role of both Notch and the CDK inhibitors in regulating Muller cell develop ment. (C) 2001 Wiley-Liss, Inc.