Beschreibung:
<jats:p>Myc family members play crucial roles in regulating cell proliferation, size, differentiation, and survival during development. We found that N-myc is expressed in retinal progenitor cells, where it regulates proliferation in a cell-autonomous manner. In addition, N-myc coordinates the growth of the retina and eye. Specifically, the retinas of <jats:italic>N-myc</jats:italic>-deficient mice are hypocellular but are precisely proportioned to the size of the eye. N-myc represses the expression of the cyclin-dependent kinase inhibitor p27Kip1 but acts independently of cyclin D1, the major D-type cyclin in the developing mouse retina. Acute inactivation of <jats:italic>N-myc</jats:italic> leads to increased expression of p27Kip1, and simultaneous inactivation of <jats:italic>p27Kip1</jats:italic> and <jats:italic>N-myc</jats:italic> rescues the hypocellular phenotype in <jats:italic>N-myc</jats:italic>-deficient retinas. N-myc is not required for retinal cell fate specification, differentiation, or survival. These data represent the first example of a role for a Myc family member in retinal development and the first characterization of a mouse model in which the hypocellular retina is properly proportioned to the other ocular structures. We propose that N-myc lies upstream of the cell cycle machinery in the developing mouse retina and thus coordinates the growth of both the retina and eye through extrinsic cues.</jats:p>