Regulating proliferation during retinal development

Recent studies have shown that components of the cell-cycle machinery can h ave diverse and unexpected roles in the retina. Cyclin-kinase inhibitors, f or example, have been implicated as regulators of cell-fate decisions durin g histogenesis and reactive gliosis in the adult tissue after injury Also, various mechanisms have been identified that can compensate for extra round s of cell division when the normal timing of the cell-cycle exit is perturb ed. Surprisingly, distinct components of the cell-cycle machinery seem to b e used during different stages of development, and different organisms migh t rely on distinct pathways. Such detailed studies on the regulation of pro liferation in complex multicellular tissues during development have not onl y advanced our knowledge of the ways in which proliferation is controlled, but might also help us to understand the degenerative disorders that are as sociated with gliosis and some types of tumorigenesis.