However, D1pas1 mRNA is expressed inspermatocytes, but not in spermatogonia [36], and D1pas1 KO germ cells arrest in late pachytene spermatocytes [40], indicating that the spermatogenic failure in D1pas1 KO mice is milder than that in AZFa-deleted SCOS patients. This evidence concerns the gene USP9Y and small cell osteogenic sarcoma.