Cloning and expression characterization of the chicken Piwil1 gene

Piwi gene involves in the germline stem cells self-renewal, transposon silencing and post-transcriptional gene regulation in the majority of organisms; however, the biological function of Piwi gene in poultry remains unclear. Here we cloned the Piwi-like 1 (Piwil1) gene and characterized its expression in the Langshan chickens during the development. The results showed that the PIWIL1 protein was the homolog of mice MIWI and human HIWI proteins (100 % identity), and encoded a cytoplasmic protein including the two conserved domains PAZ and PIWI. In males, the expression of Piwil1 gene showed a bimodal distribution in the gonads during embryogenesis with peaks at embryonic 14.5 and 17.5-18.5 days respectively. After puberty, the expression of Piwil1 gene increased sharply and reached a high level at the sexual maturity. The mRNA expression of Piwil1 gene at 27 weeks of age is 35-40 times that of 0 week of age, indicating that the high expression of Piwil1 gene was essential to maintain the spermatogenesis. In females, the expression of Piwil1 gene showed a unimodal distribution in the embryonic gonads. A strong peak appeared at E16.5-17.5d when the primary oocytes have entered the prophase I of meiosis. Subsequently, the expression of Piwil1 gene decreased gradually and kept at the low level during the embryogenesis. So Piwil1 gene was likely to play an important role during the meiosis I. This report filled in partly the gap of the Piwi gene researches in poultry and defined our research directions in future.