Genetic factors contributing to defective spermatogonial differentiation in juvenile spermatogonial depletion...

Male mice that are homozygous for the juvenile spermatogonial depletion (jsd) mutation in the Utp14b gene undergo several waves of spermatogenesis. However, spermatogonial differentiation ceases and in adults, spermatogonia are the only germ cells that remain. To understand further the blockage in spermatogonial differentiation in Utp14b(jsd) mutant mice, we correlated the rate and severity of spermatogonial depletion and the restoration of spermatogenesis following the suppression of testosterone or elevation of testicular temperature with the genetic background. Testes from Utp14b(jsd) mutant mice on B6, C3H, and mixed C3H-B6-129 (HB129) genetic backgrounds all showed steady decreases in the numbers of normal spermatogonia between 8 wk and 20 wk of age. The percentages of tubules with differentiating germ cells were higher and the spermatogonia were more advanced in C3H- background than in B6- or HB129-background Utp14b(jsd) mice. Genetic crosses showed that the source of the Y chromosome was a major factor in determining the severity of spermatogonial depletion in Utp14b(jsd) mutant mice. When Utp14b(jsd) mutants were subjected to total androgen ablation or unilateral cryptorchidization, spermatogenic development recovered markedly in the C3H and HB129 background but showed less recovery in the B6-background mice. The differences noted between the strains in terms of the severity of spermatogonial depletion were not dependent upon testosterone level or scrotal temperature but correlated with the magnitudes of the effects of elevated temperature on normal and Utp14b(jsd) mutant spermatogenic cells. Thus, the abilities of germ cells in certain strains to survive elevated temperatures may be related to their abilities to maintain some degree of differentiation potential after the Utp14b(jsd) gene is mutated.