Role of p27 accumulation in the gonadal hypoplasia of Skp2-deficient mice. (A) Macroscopic comparison of the testes of wild-type, Skp2-/-, p27-/-, and Skp2-/-
;p27-/- mice. (B) Histology of the testis of Skp2-/-
;p27-/- mice (4 months of age) showing pronounced recovery of germ cell production compared with that apparent in parental Skp2-/- mice. Scale bars, 100 μm. Arrowheads in B indicate seminiferous tubules with a deficiency of germ cells. (C-E) Histology of embryonic testis (15.5 days postcoitum). Severe deficiency of gonocytes (arrowheads) was evident in Skp2-/- embryos (C) compared with wild-type embryos (D). However, the gonocyte population had recovered substantially in Skp2-/-;p27-/- embryos (E). Scale bars, 100 μm. (F) Immunoblot analysis of lysates of the testes of Skp2-/- or wild-type embryos (15.5 days postcoitum) with antibodies to p27 and to β-actin (loading control).