GJA1 and Azoospermia: Such mice had hypotrophic testes because of severe germ cell deficiency.7 Grafting of the testes of connexin-43 knockout fetuses under the renal capsules of adult males resulted in germ cell deficiency in seminiferous epithelium.8 The critical role of connexin-43 has also been reported in human spermatogenesis, as it was reduced in infertile men with azoospermia.9