Molecular cloning and tissue expression of the CCNG1 gene in sheep]

The CCNG1 gene encodes cyclin G1, which is an important cell cycle regulator and has been reported to be involved in reproductive biological processes, such as oocyte maturation and granule cell proliferation in mammals. But the study of CCNG1 in sheep has been rarely reported. To examine the effects of CCNG1 on estrous control and seasonal breeding in sheep, we first cloned and characterized the expression level of the sheep CCNG1 gene. Then by Real-time PCR, we detected and analyzed the expressions of CCNG1 gene at mRNA levels in the hypothalamus-pituitary-ovary (HPO) axis in different stages of an estrous cycle in Duo Lang sheep (non-seasonal breeding) and Merino sheep (seasonal breeding). The results showed that the open reading frame of the sheep CCNG1 gene is 885 bp in length and encodes 294 amino acids. Bioinformatic analysis indicated that the secondary structure of the sheep CCNG1 protein contained multiple phosphorylation sites and some Protein Kinase C phosphorylation sites. CCNG1 mRNA was identified in all tissues tested, with the levels in ovary and kidney higher than others. The expression profiles of CCNG1 in the HPO axis in different stages of an estrous cycle were similar in different sheep breeds: the expression levels of CCNG1 in the ovary, uterus, pineal gland and pituitary gland all peaked in the estrus phase. But there were significant differences for expression change extent of CCNG1 in ovaries in the oestrus and metestrus phase between different sheep breeds. The results suggested that CCNG1 probably participated in the regulation of estrous behavior and seasonal reproduction through controling the growth and development of follicles in sheep.