Expression of p53 protein in spermatogenesis is confined to the tetraploid pachytene primary spermatocytes.

The various steps of differentiation and maturation in spermatogenesis are well characterized and offer a convenient system to explore the possibility that p53 plays a role in cell differentiation in vivo. In situ hybridization experiments indicate that the p53 gene is expressed in tetraploid primary spermatocytes at the meiotic pachytene stage of the first round of spermatogenesis in young mice. An analysis of spermatogenic cells treated with anti-p53 antibodies reveals that the p53 protein is expressed in a discrete tetraploid cell population, with size and cellular structure parameters characteristic of midpachytene spermatocytes. The specific kinetics of p53 expression in the first round of spermatogenesis and its localization in adult testicular sections, coupled with the fact that the protein is expressed in the largest cells with lower DNA density, suggest that p53 expression is confined to the tetraploid primary spermatocytes of the meiotic pachytene phase. These observations identify p53 protein as a potential member of the meiosis control protein family.