Localization and expression of CTRP6 in ovary and its regulation by FSH in porcine granulosa cells

C1q/tumor necrosis factor-related protein 6 (CTRP6) is a newly identified adiponectin paralog with modulating effects on metabolism and inflammation. CTRP6 transcript is detected in human ovarian tissue. However, the expression pattern and function of CTRP6 on ovary have been rarely studied. In the present study, we preliminarily examined the structure feature and function of CTRP6 in porcine granulosa cells. The results indicated that the signaling peptide of CTRP6 was located at among positions 21 and 22, and the phosphorylation sites were at 15 (Ser), 4 (Thr) and 4 (Tyr), respectively. Meanwhile, CTRP6 was extremely homologous in livestock and chiropteran. The qPCR results showed that CTRP6 was moderately expressed in porcine follicle. Immunohistochemistry manifested that CTRP6 was presented in various types of ovarian cells. Immunofluorescence revealed that CTRP6 was located in cytoplasm in primary porcine granulosa cells. ELISA results showed that the concentration of CTRP6 in the follicular fluid was gradually decreased with the growth of antral follicle. In addition FSH increased CTRP6 expression levels in a time- and dose-dependent manner in primary porcine granulosa cells, while LH had no effect on CTRP6 basal gene expression, which suggesting CTRP6 is an FSH-responsive gene in porcine granulosa cells. Our findings imply that the CTRP6 may be a candidate gene to regulate folliculogenesis and reproductive performance.