Hedgehog signaling pathway regulates gene expression profiling of epididymal principal cells through the primary cilium

Background. Primary cilia (PC) are solitary antennae present at the cell surface. These non-motile cilia play an important role in organ development and tissue homeostasis through the transduction of the Hedgehog (Hh) signaling pathway. We recently revealed the presence of PC in the epithelium of the developing epididymis, an organ of the male reproductive system whose dysfunction triggers male infertility. Acknowledging that systemic blockade of the Hh pathway trigger epididymal dysfunctions in vivo, our main goals were 1) to portray the epididymal Hh environment, 2) to determine the direct responsiveness of epididymal epithelial cells to Hh, and 3) to define the contribution of PC to the transduction of this pathway. Results. The Hh ligands Indian and Sonic hedgehog (Ihh and Shh) were respectively located in principal and clear cells of the mouse epididymis by immunofluorescent staining. The propensity of epididymal principal cells to respond to Hh signaling was assessed on immortalized epididymal DC2 cells by western-blot, confocal imaging and 3D-reconstruction. Our results indicate that epididymal principal cells secrete Ihh and expose PC that co-localize with the conventional acetylated tubulin/Arl13b ciliary markers, as well as with GLI3 Hh signaling factor. Gene expression microarray profiling indicated that the expression of 43 and 248 genes was respectively and significantly modified following pharmacological treatment of DC2 cells with the Hh agonist SAG (250 nM) or the Hh antagonist cyclopamine (20 µM) compared with the control. Among Hh target genes identified, 6.7 % presented perfect matches for GLI-transcription factor consensus sequences, and the majority belonged to interferon-dependent immune response and lipocalin 2 pathways. Finally, the contribution of epididymal PC to the transduction of canonical Hh pathway was validated by ciliobrevinD treatment, which induced a significant decrease of PC length and the expressional reduction of Hh signalling targets. Conclusions. All together our data indicate that PC from epithelial principal cells regulate gene expression profile through a possible autocrine Hh signaling. This provides new hypotheses regarding the potential contribution of PC and Hh signaling in intercellular cross-talk and immunological regulation of the epididymis.

9

Girardet L, Bernet A, Calvo E, Soulet D, Joly-Beauparlant C, Droit A, Cyr DG, Belleannée C