Expression and Localization of Fas-Associated Factor 1 in Testicular Tissues of Different Ages and Ovaries at Different Reproductive Cycle Phases of Bos grunniens

SIMPLE SUMMARY: In order to explore the biological role of Fas-associated factor 1 (FAF1) in testes and ovaries of domestic yaks, we examined the mRNA, protein expression and tissue localization of FAF1 in the ovaries of different ages and reproductive cycles in domestic yaks. The results showed that FAF1 mRNA and protein were expressed differently in the ovaries of testes of different ages and different reproductive cycles, mainly expressed in sperm, sperm cells, spermatogonia, primary spermatoblasts, supporting cells, testesian stromal cells and periductalcells in the testes, germinal epithelial cells, granule cells, cumulus cells, follicular membrane cells and luteal cells of ovarian tissues, and it was speculated that FAF1 may be closely related to the testicular development, spermatogenesis and testosterone secretion of male domestic yaks, and to the follicular atresia of female domestic yaks. Development, maturation and luteal lysis physiological processes are related, which provides a basis for further exploration of FAF1 in the reproductive physiological function of domestic yaks. ABSTRACT: Fas-associated factor 1 (FAF1), a member of the Fas family, is involved in biological processes such as apoptosis, inflammation, cell proliferation and proteostasis. This study aimed to explore the biological role of FAF1 in testicular tissue at different ages (juveniles (1 and 2 years old), adults (3, 4, 6, and 7 years old) and old-aged animals (11 years old)) and ovaries during different reproductive cycle phases (follicular, luteal, and pregnancy phases). FAF1 mRNA, relative protein expression and protein expression localization were determined in testes and ovaries using real-time quantification, WB and immunohistochemistry (IHC), respectively. Real-time quantification of testis tissues showed that the relative expression of FAF1 mRNA in testis tissues at 3, 4 and 7 years of age was significantly higher than of those in other ages, and in ovarian tissues was significantly higher in luteal phase ovaries than those in follicular and pregnancy phase ovaries; follicular phase ovaries were the lowest. WB of testis tissues showed that the relative protein expression of FAF1 protein was significantly higher at 11 and 7 years of age; in ovarian tissue, the relative protein expression of FAF1 protein was significantly higher in follicular phase ovaries than in luteal and pregnancy phase ovaries, and lowest in luteal phase ovaries. The relative protein expression of FAF1 at 3, 4 and 7 years of age was the lowest. IHC showed that FAF1 was mainly expressed in spermatozoa, spermatocytes, spermatogonia and supporting cells; in ovarian tissue, FAF1 was expressed in ovarian germ epithelial cells, granulosa cells, cumulus cells and luteal cells. The IHC results showed that FAF1 mRNA and protein were significantly differentially expressed in testes of different ages and ovarian tissues of different reproductive cycle phases, revealing the significance of FAF1 in the regulation of male and female B. grunniens reproductive physiology. Furthermore, our results provide a basis for the further exploration of FAF1 in the reproductive physiology of B. grunniens.