AbstractTo identify candidate genes for poor sperm morphology, we have screened for genes expressed during spermiogenesis. We identified 10 new members of the cysteine‐rich perinuclear theca (CYPT) family showing that this family contains at least 15 members, which also includes the casein kinase II target genes. Based on similarity the CYPT sequences could be divided into two groups, Cypt1–10 and the novel members Cypt12–15. The 5′‐end of the CYPT family is highly similar to exon1A and part of the first intron of Zfy2. Seven CYPT genes mapped to the X chromosome; six contained an intron and one was intron‐less. One CYPT gene mapped to chromosome 3 and one mapped to chromosome 9 which were both intron‐less. The upstream region of the CYPT family and Zfy2 genes is conserved. For some the conservation extended over a large region, however, only about 150 nucleotides is conserved among all CYPT members and Zfy2. Nevertheless, the short conserved promoter leads to essentially identical expression profiles for the CYPT family members and Zfy2, which was clearly different from the profile of Zfy1. Expression of the CYPT family and Zfy2 preceded the expression of other spermatid‐specific genes such as the transition proteins and the protamines. In situ hybridization revealed a low expression in pachytene spermatocytes from stages IX–X followed by a strong upregulation in spermatids from stage VI with maximum expression in spermatids in stages VII–VIII. The CYPT family may function in the remodeling of the spermatid nucleus before condensation of the DNA. Mol. Reprod. Dev. © 2006 Wiley‐Liss, Inc.