Requirement for a functional Rb-1 gene in murine development

RB-1, a gene the mutation of which has been linked to retinoblastoma, produces different homozygous and heterozygous effects when inactivated in mouse embryos. Heterozygous mice survive to term and exhibit neither physical abnormalities nor the growth of retinoblastoma tumors. On the other hand, homozygous mouse embryos die before birth and exhibit an array of neural and hematopoietic abnormalities.