Fig. 2: Defective spermatogenesis in Kdm2a iKO mice.

A PAS-stained section showing stage VIII seminiferous tubules of Ctrl and Kdm2a iKO males at 3, 6, 9, 12 and 15 d post first tamoxifen treatment. Arrowheads indicate apoptotic cells. Scale bar = 25 μm; n = 1 for 3 d and 6 d; n = 3 for subsequent time points. B Stage VI tubule of iKO male at 9 d (n = 3) containing Intermediate spermatogonia (arrowheads), indicative of delayed proliferation. Scale bar = 35 μm. C Stage IX tubule of iKO male at 9 d (n = 3) containing retarded preleptotenes (black arrowheads) and apoptotic spermatocytes (red arrowheads). Scale bar = 35 μm. D, E Stage-specific percentages of seminiferous tubules with apoptotic cells near the basal membrane at 9 d (n = 3) (D) and 12 d (n = 3) (E). We examined two testis cross sections per animal (373 to 573 tubules per testis). n = 3 per genotype, per time point. Two-sample, two-sided Wilcoxon tests were performed between the indicated groups. (nd) non determined, (ns) P > 0.05; (*) P < 0.05; (**) P < 0.01; (***) P < 0.001; (****) P < 0.0001. Center lines in box plots represent median values, while lower and upper lines indicate the interquartile range (IQR; from the 25th to 75th percentile). F Stage IV tubule of iKO male at 12 d (n = 3) showing morphologically abnormal (black arrowheads) and apoptotic (red arrowheads) pachytene spermatocytes. Scale bar = 35 μm. G Scheme summarizing aberrant phenotypes in Kdm2a iKO testes in relation to the timing of loss of KDM2A protein expression and of developmental progression of male germ cells (as determined by staging of seminiferous tubules).