Abstract：Male germline stem cells (mGSCs) present low differentiation degree, with the ability of self-renewal and differentiating into sperms, are the foundation of males producing sperms. The study of regulation factors and mechanism of mGSCs self-renewal, proliferation and differentiation is of great significance to the understanding of spermatogenesis. E-cadherin is an important regulation factor of the microenvironment of stem cells, which plays a complex role in the mGSCs regulation, including stem cells self-renewal, proliferation and differentiation, etc. E-cadherin helps mGSCs anchores in the niche, mediating cell-niche signaling transmission, at the same time providing polarizing signals guiding stem cells undergo symmetric cell division or asymmetric division, affecting mGSCs continuous, long-term self-renewal. Ensuring that only undifferentiated, functional stem cells are kept in the niche, stem cells in differentiating lose the competitive advantage and leave. The microenvironment can regulate the self-renewal and differentiation of mGSCs. Continuous research of germline stem cell niche is expected to reveal the regulatory mechanisms between self-renewal and differentiation of mGSCs. Sequence alignment found that the mRNA sequence and the amino acid sequence of E-cadherin were highly conserved in a variety of species. In order to confirm the E-cadherin expression status in dairy goat (Capra hircus) testis, immunohistochemical staining found that as a cell membrane protein, E-cadherin widely expressed in dairy goat testis. Addationally, E-cadherin expression quantity of cells at the basement of seminiferous tubules, where mGSCs usually localized, was obviously higher than that of other cells in the seminiferous tubules. Those results indicated that E-cadherin, as an important component of dairy goat mGSCs microenvironment, played an important role in maintaining the microenvironment of male spermatogonial stem cell niche. For further research, the E-cadherin-GFP mammalian over-expression vector was transfected into mGSCs-I-SB, a dairy goat male germ stem cell cell line we had established, to explore the effects of E-cadherin on mGSCs. Gene expression changes of E-cadherin and other marker genes associated with cell proliferation and pluripotency were tested by qRT-PCR, Western blot and immunofluorescence staining. The result showed that E-cadherin expression quantity increased obviously, and the expression of octamer-binding transcription factor 4 (OCT4), integrin alpha-6 (CD49f), glial cell line-derived neurotrophic factor family receptor alpha-1 (GFRa1), promyeloeytie leukaemia zinc-finger (PLZF) and proliferating cell nuclear antigen (PCNA), genes associated with cell self-renewal, proliferation and pluripotency maintenance were also raised in E-cadherin overexpression (0CDH1) dairy goat mGSCs groups compared with control groups (Con). Immunofluorescence staining detection found that those genes colocalized with E-cadherin-GFP. These results indicated that E-cadherin promoted dairy goat mGSCs self-renewal, proliferation and pluripotency maintenance. The study of the influence of E-cadherin on dairy goat mGSCs will provide a molecular basis for further study of cell self-renewal, proliferation and differentiation processes, which will be useful for establishing stable male germline stem cell lines.
