Temporal and spatial differential expression of chicken germlinespecific proteins cDAZL, CDH and CVH during gametogenesis

The Deleted in Azoospermia-Like (DAZL) protein coded by Dazl gene is a germline-specific RNA-binding protein essential for gametogenesis in vertebrates, and the chicken Dazl gene has also been identified in primordial germ cells (PGCs). However, the temporal and spatial expression of chicken DAZL (cDAZL) and its molecular role in germ cell development remain enigmatic. Here, we investigated the subcellular distribution and expression of cDAZL at the various stages by using a polyclonal antibody raised against its C-terminal region and compared them with those of additional germline-specific proteins chicken vasa homologue (CVH) and chicken dead end homologue (CDH). Western blot analysis for cDAZL revealed a single band in the embryonic gonads and premature chicken testis, whereas no band was detected in the premature chicken ovary. Fluorescent immunohistochemistry revealed that cDAZL was present in the nucleus and cytoplasm of circulating PGCs. Cells positive for cDAZL and CVH coexisted in the embryonic gonads and premature chicken testis, in which they were distributed near the basement membrane of seminiferous tubules. Of interest, cDAZL was not found in the premature chicken ovary, whereas CVH and CDH were present in germ cells. Collectively, three germline-specific proteins are expressed in chicken germ cells, but their patterns of expression are temporally and spatially distinct.