GLI1 localization in the germinal epithelial cells alternates between cytoplasm and nucleus: Upregulation in transgenic mice blocks spermatogenesis in pachytene

The zinc finger transcription factor GLI1 is the mediator of signaling by m embers of the Hedgehog (Hh) family. Male mice in which Desert hedgehog (Dhh ), an Hh homologue expressed in Sertoli cells of the testis, was knocked ou t are sterile, suggesting that the Dhh/GLI1 pathway plays a role in spermat ogenesis. Using an antiserum raised against human GLI1, we found that durin g the first round of spermatogenesis, GLI1 expression is initially cytoplas mic, then shifts to the nuclei of Sertoli and germ cells, and finally shift s back to the cytoplasm. in the adult mouse testis, GLI1 expression localiz ed to the nuclei of germ cells, beginning with pachytene cells and persisti ng through round spermatids. Localization of GLI1 in elongating spermatids shifted from the nucleus to the cytoplasm and became associated with microt ubules. We also examined a line of transgenic mice that overexpressed human GLI1. Male mice in this line were sterile. Spermatogenesis was blocked at the pachytene stage, and a subset of the morphologically indistinguishable pachytene cells underwent apoptosis. Patched-2, which is a Dhh receptor, an d Fused, another component of the signal transduction pathway, are expresse d in Leydig cells and in primary and secondary spermatocytes. Expression of GLI1 in the same cell types as Patched-2 and Fused and the disruption of s permatogenesis by GLI1 overexpression suggest that GLI1 is the mediator of the Dhh signal in the testis, and that it may be a regulator of spermatogen esis.