“…Many bHLH homologs are expressed in the vertebrate retina, but only Ascl1 and Neurog2 are expressed in mitotically active progenitors (Jasoni et al, 1994;Jasoni and Reh, 1996;Perron et al, 1998;Yan et al, 2001;Marquardt, et al, 2001;Ma and Wang, 2006;Le et al, 2006;Nelson and Reh, 2008). While the functions of proneural bHLH genes have been extensively investigated with respect to their role in retinal cell fate specification (reviewed by Cepko, 1999;Vetter and Brown, 2001;Yan et al, 2005;Ohsawa and Kageyama, 2007;Harada et al, 2007), their function in the regulation Notch ligands have not been described in the developing retina. Recently, we found in the developing chick retina that the expression pattern and expression kinetics of Dll1 during synchronized progenitor differentiation most closely matched that of Ascl1, similar to observations in the frog retina (Perron et al, 1998).…”