Vertebrate neural cell-fate determination: Lessons from the retina

Postmitotic neurons are produced from a pool of cycling progenitors in an o rderly fashion during development. Studies of cell-fate determination in th e vertebrate retina have uncovered several fundamental principles by which this is achieved. Most notably, a model for vertebrate cell-fate determinat ion has been proposed that combines findings on the relative roles of extri nsic and intrinsic regulators in controlling cell-fate choices. At the hear t of the model is the proposal that progenitors pass through intrinsically determined competence states, during which they are capable of giving rise to a limited subset of cell types under the influence of extrinsic signals.