MOLECULAR-CLONING AND DEVELOPMENTAL EXPRESSION OF MOUSE P130, A MEMBER OF THE RETINOBLASTOMA GENE FAMILY

With sequence homology to the SV40 T antigen-binding domain of the ret inoblastoma protein (Rb), p107 and p130 constitute two additional memb ers of che Rb family, To explore the potential function of p130 in mou se development, we cloned the full-length mouse cDNA for p130 and char acterized p130 mRNA expression in mice. The deduced mouse p130 protein sequence shares a higher degree of similarity with mouse p107 than wi th mouse Rb, In adult mice, p130 mRNA is found in all tissues examined , Levels of p130 mRNA vary among different adult tissues, with the hig hest level in testis. Within testis, p130 mRNA is found predominantly in Leydig cells, Additionally, p130 expression in testis correlates wi th sexual maturation, suggesting p130 is important for the development of testis and, in particular, Leydig cells, In situ hybridization sho ws that in post coitus day 12.5 and 14.5 mouse embryos, distribution o f p130 mRNA is quite uniform with the exception of a few tissues. Litt le differences in mRNA levels of either p130 or p107 were found betwee n normal and Rb-deficient embryos, suggesting that p130 and p107 are e xpressed independently of Rb. Our data are consistent with the hypothe sis that p130 and p107 do not compensate for the loss of Rb and suppor t the view that p130 is related to, yet distinct from, the RB gene.