NF-kappa B is developmentally regulated during spermatogenesis in mice

To analyze NF-kappaB activity in the testis, we used murine transgenic line s carrying a LacZ reporter gene under the control of a NF-kappaB-responsive promoter (Schmidt-Ullrich et al, [1996] Dev 122:2117-2128), We constructed three independent lines containing the promoter of the gene encoding p105, the precursor of the p50 subunit, This promoter contains three NF-kappaB-b inding sites in its proximal part. Our results show that in adult mice, the beta -galactosidase activity which reflects nuclear NF-kappaB activity, is first detected in spermatocytes at the pachytene stage and remains activat ed in the following steps of germ cell differentiation and maturation. Usin g transgenic mice carrying a p105nlslacZ construct with the 3 NF-kappaB sit es mutated in the p105 promoter, we found a significant reduction in the tr ansgene activity, confirming the important role of NF-kappaB in the activat ion of the transgene, To confirm the stage of induction during spermatogene sis, we analysed the beta -galactosidase activity in the testes from prepub eral mice in which cells synchrouneously enter meiosis, We detected the tra nsgene activity at 18 days after birth, corresponding to the pachytene stag e in spermatocytes, In nuclear extracts prepared from prepuberal mice, we f ound a peak of NF-kappaB DNA-binding activity made of p50 and p65 subunits at day 18 after birth, which remains high in the later stages. Further anal ysis showed that I kappaB alpha and beta, but not epsilon are expressed in the testes. Altogether, these data suggest that NF-kappaB factors are stage specifically controlled and may play a role during the development of sper m cells. (C) 2000 Wiley-Liss, Inc.