Transgene-mediated rescue of spermatogenesis in Cldn11-null mice.

Claudins comprise a large family of tight junction (TJ) proteins that are often expressed broadly during development and in adult tissues and constitute the physical barriers that occlude the paracellular space in polarized epithelia. In mouse testis, the integrity of TJs is critical to normal spermatogenesis and is dependent on CLDN11 expression. In the current study, we have generated multiple transgenic mouse lines in which steady-state levels of transgene-derived Cldn11 mRNA are up to fourfold greater than endogenous gene expression. Spermatogenesis in all founder mice harboring two copies of the endogenous Cldn11 gene is normal. These animals breed well, indicating that transgene overexpression, at least at the level of mRNA, is well tolerated by Sertoli cells. In addition, we demonstrate that the promoter/enhancer of the transgene, comprising 5 kb of genomic sequence upstream of exon 1 of the mouse Cldn11 gene, is sufficient to rescue azoospermia in Cldn11-null mice. Finally, using transient transgenic mice, we narrow the location of Sertoli cell-specific cis regulatory elements to a 2-kb region upstream of the Cldn11 transcription start site. Together, these data provide essential information for further investigation of the biological regulation of CLDN11 TJs in the testis.