Fig. 1.

Testes of Stra8-cre; Sin3a^Δ/fl male mice have reduced weights but contain equivalent numbers of undifferentiated spermatogonia and cycling, premeiotic germ cells. A. Schematic illustration denoting the expression patterns of Stra8-cre and Vasa-cre transgenes in mouse spermatogonia: the former is initially expressed in a subset of Type A aligned (A_al) undifferentiated cells (dashed green line) and continues its expression through late Type B differentiating cells (solid green line), while the latter is expressed throughout all spermatogonial stages – undifferentiated A single (A_s), A paired (A_pr), A_al, and differentiating A₁–A₄, Intermediate (In), and B (solid red line). Matings of these cre driver mice with floxed Sin3a (Sin3a^fl/fl) mice generate SSKO (Stra8-cre; Sin3a^Δ/fl) and VSKO (Vasa-cre; Sin3a^Δ/fl) conditional gene-targeted mice, respectively. B. 6-wk-old SSKO male mice have testis weight/body weight ratios that are 46.5% reduced compared to littermate controls (N=7, ***p<0.001). C and D. Seminiferous tubule cross-sections of 6-wk-old testes stained with hematoxylin and eosin (H+E) reveal germ cells at all stages of development in SSKO and controls; arrowheads identify enlarged, multinucleated germ cells in SSKO tubules. E and F. Cross-sections of 6-wk-old seminiferous tubules immunostained for germ cell marker GCNA1. G and H. Cross-sections of 6-wk-old seminiferous tubules immunostained for germline stem cell marker PLZF (arrows). I and J. Seminiferous tubule cross-sections of 6-wk-old males injected with BrdU, examined 48 h later with anti-BrdU antibodies. Scale bars = 50μm.