CREB1 and cystic fibrosis: Consistent with its down-regulationin CF mice and CFTR-inhibited primarily cultured Sertoli cells, CBEB was alsodecreased in human azoospermia testes (Fig. 4C&D), suggesting thatthe CFTR-dependent CREB pathway may be important for spermatogenesis in humanand that defect in this pathway may represent a possible mechanism underlyingthe pathogenesis of azoospermia.