By identifying the mRNA products of stage-and cell-specific gene expression directly in histologic specimens, in 냐셔 hybridization provides a powerful tool to demonstrate the cellular mechanisms regulating spermatogenesis. Nur77 is a member of the growth factor-inducible "immediate early" genes and is highly homologous to sequences of members of the steroid/thyroid hormone receptor gene superfamily. We investigated a putative role for nur77 during spermatogenesis by probing for its expression using in 냐셔 hybridization in mouse testes. Expression of the nur77 gene was restricted to the round spermatids in stage IV through VI. The identificantion of nur77 as a discretely, temporally expressed gene during germ cell differentiation indicates its pivotal function in spermatogenesis. Its abnormal expression may be important in definding a specific cause of unexplained testicular failure in some patients.