REDUCED FERTILITY IN MICE DEFICIENT FOR THE POU PROTEIN SPERM-1

Members of the POU-homeodomain gene family encode transcriptional regu latory molecules that play important roles in terminal differentiation of many organ systems. Sperm-1 (Sprm-1) is a POU domain factor that i s exclusively expressed in the differentiating male germ cell. We show here that the Sprm-1 protein is expressed in the haploid spermatid an d that 129/Sv Sprm-1 (-/-) mice are subfertile when compared with wild -type or heterozygous littermates yet exhibit normal testicular morpho logy and produce normal numbers of mobile spermatozoa. Our data sugges t that the Sprm-1 protein plays a discrete regulatory function in the haploid spermatid, which is required for the optimal function, but not the terminal differentiation, of the male germ cell.