Oocyte-like cells induced from mouse spermatogonial stem cells

We report that mouse male SSCs can be converted into oocyte-like cells in culture. These SSCs-derived oocytes (SSC-Oocs) were similar in size to normal mouse mature oocytes. They expressed oocyte-specific markers and gave rise to embryos through parthenogenesis. Interestingly, the Y- and X-linked testis-specific genes in these SSC-Oocs were significantly down-regulated or turned off, while oocyte-specific X-linked genes were activated. The gene expression profile appeared to switch to that of the oocyte across the X chromosome. Furthermore, these oocyte-like cells lost paternal imprinting but acquired maternal imprinting.Our data demonstrate that SSCs might maintain the potential to be reprogrammed into oocytes with corresponding epigenetic reversals. This study provides not only further evidence for the remarkable plasticity of SSCs but also a potential system for dissecting molecular and epigenetic regulations in germ cell fate determination and imprinting establishment during gametogenesis.Despite the different genotypes of germ cells in males with XY cells and females with XX cells, both types of germ cells share the same progenitors, namely, primordial germ cells (PGCs). The differentiation of PGCs into either the male or female phenotype takes place in the sex glands at later stages of embryonic development, and sexual differentiation of the germ cells is controlled by the somatic environment of the gonad rather than the sex chromosome constitution of the germ cells themselves [1-3]. Somatic mutation of sex-determining genes contributes to the sex reversal of XY germ cells to oogonia during gonad development; thus, the fate of XY male germ cells varies in response to environmental signaling in the gonad [4]. A few recent studies have demonstrated that spermatogonial stem cells (SSCs), which are the progeny of PGCs/gonocytes, can be reprogrammed into embryonic stem-like cells in vitro without transgene manipulation [5-9], indicating that SSCs retain remarkable