Figure 5. Expression of the LacZ gene in double transgenic Kera-Cre/Rosa26R mice during spermatogenesis. Whole mount X-gal staining of testes collected from 20-(A), 30-(B), and 60 day-old (C) bitransgenic mice showed positive reaction in primary and secondary spermatocytes and spermatids. No β-gal activity was found in adult single Rosa26R transgenic testes and 10-day-old testes of double Kera-Cre/Rosa26R mice (data not shown). Leydig cells (arrowheads) have endogenous β-gal activity. Testicular cell suspensions prepared from a Kera-Cre/Rosa26R mouse were subjected to May–Grünwald-Giemsa stain after X-gal staining. Positive X-gal staining (arrow) was observed in the primary spermatocytes (D), primary spermatocytes in meiotic division (E), spermatids (F), and round spermatids (G).