Multiple requirements for Hes 1 during early eye formation.

During embryogenesis, multiple developmental processes are integrated through their precise temporal regulation. Hes1 is a transcriptional repressor that regulates the timing of mammalian retinal neurogenesis. However, roles for Hes1 in early eye development have not been well defined.

Precocious retinal neurons: Pax6 controls timing of differentiation and determination of cell type.

The transcription factor Pax6 plays a pivotal role in eye development, as eye morphogenesis is arrested at a primitive optic vesicle stage in homozygous Pax6 mutant mouse embryos. The arrested optic vesicle development has led to the assumption that cellular differentiation programs are unable to initiate. Contrary to this, we found that neurogenesis in Pax6 mutant optic vesicles was not arrested, but instead accelerated as numerous neurons differentiated precociously, more than a day earlier than normal.