Maintaining the male germline: regulation of spermatogonial stem cells

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   Figure 1

   Photomicrographs of cross-sections of seminiferous tubules in an adult mouse testis used for immunohistochemical analysis. (A) Control hematoxylin counter-stained mouse testis section with no primary antibody incubation. (B) Immunohistorchemistry staining for PLZF. Undifferentiated spermatogonia positive for PLZF (arrows) are found along the basement membrane preferentially localized to the interstitial space. The image also demonstrates that not all seminiferous tubules contain PLZF-positive spermatogonia. Cells with positive stain in the interstitial space are non-specific, while staining in seminferous tubules is specific for PLZF based on controls. (C) Immunohistochemistry staining for GDNF. Somatic and germ cells are positive for GDNF in all seminiferous tubules regardless of stage. (D) Immunohistochemistry for RET. Spermatogonia along the basement membrane are positive for RET (arrows) with some expression visualized in Sertoli cells. No counterstain was used to assist in the visualization of RET-positive cells. (E) Immunohistochemistry staining for phosphorylation-specific Tyrosine 1062 (Y-1062) residue of RET in germ and somatic cells. The importance of intracellular signaling via Y-1062 in RET has been demonstrated for spermatogonial stem cell self-renewal in mammals. The image illustrates that expression of RET phosphorylated in Y-1062 is heterogeneous among seminiferous tubules. Spermatogonia positive for RET-Y-1062 staining are indicated with an arrow, and negative spermatogonia in the adjacent tubule are indicated with an arrowhead. Scale bar is 50 μm in all panels. Images are representative of independent experiments (n=3).
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   Figure 2

   Diagram is a model of spermatogonial stem cell and somatic cells contributing to the SSC niche. This model demonstrates the sources of potential autocrine, paracrine, and environmental cues that may influence spermatogonial stem cell fate in the mammalian testis.

• © 2010 Society for Endocrinology