THE RETINOBLASTOMA GENE FAMILY IS DIFFERENTIALLY EXPRESSED DURING EMBRYOGENESIS

We report differential expression of the RBI tumor suppressor gene and the homologous genes p107 and p130 during embryogenesis. Abundant RBI transcripts were detected during neurogenesis, hematopoiesis, myogene sis, lens development and in the ganglion cell layer of the embryonic retina, prior to and during differentiation, The expression pattern of RBI mirrored the defects in RBI mutant mice (RB-/-), In the heart, lu ng, kidney and intestine, p107, but not RBI, was expressed, In the liv er and the central nervous system p107 and RBI were co-expressed, cons istent with the accelerated cell death observed in RB-/-; p107(-/-) do uble knock-out mice, In the central nervous system, p107 expression wa s restricted to proliferating cells surrounding the ventricles, while RBI was expressed in areas of both proliferating and differentiating c ells, In contrast to RBI and p107, expression of p130 was low througho ut embryogenesis. In situ hybridization and Western blot analyses show ed that the expression of p107 and p130 was not markedly altered in RB -/- embryos compared to control litter-mates, Our results suggest that members of RBI gene family have distinct, but overlapping roles in em bryogenesis, with p107 and RBI possibly having redundant functions in the central nervous system and liver.