Ablation of RXR in spermatogonia induces age-related testis degeneration.

<p>(A,B) Periodic acid-Schiff stains illustrating overviews and (C-H) details of germ cell associations in the seminiferous epithelium of 12 week-old control and <i>Rxra;b;g</i>^{<i>Sgp–/–</i>} testes, as indicated. Normal gem cell associations at epithelial stage VII (C) coexist with abnormal associations mimicking, to some extent, this epithelial stage, but lacking: pachytene spermatocytes (D,H), preleptotene spermatocytes (E,G) and round spermatids (F,H). (I,J) Hematoxylin and eosin stain showing overviews of 12 month-old control and <i>Rxra;b;g</i>^{<i>Sgp–/–</i>} testes: seminiferous tubules containing only spermatogonia and Sertoli cells represent the end-stage of degeneration in the mutant testes. PR and P, preleptotene and pachytene spermatocytes, respectively; St7 and St16, step 7 and 16 spermatids, respectively; T2, tubule sections lacking generation(s) of germ cells around their entire circumference; T3, tubule sections with disorganization of the germ cell layer; T4, tubule sections containing only spermatogonia and Sertoli cells. Germ cell populations present in a given seminiferous tubule cross-section are highlighted by colored bars: red, preleptotene spermatocytes; green, pachytene spermatocytes; blue, step 7 (round) spermatids; purple, step 16 (elongated, mature) spermatids. Roman numerals indicate the stages of the seminiferous epithelium cycle. Scale bar, 80 μm (A,B and I,J) and 30 μm (C-H).