Photoperiodic regulation of Wnts in spermatogenesis of Brandt's vole (Lasiopodomys brandtii).

Photoperiod regulates spermatogenesis in seasonal breeders, yet its molecular mechanisms remain unclear. The Wnt signaling pathway is critical for spermatogenesis in non-seasonal breeders, but its role in photoperiodic spermatogenesis in seasonal breeders is unexplored. To investigate this, we exposed male Brandt's voles (Lasiopodomys brandtii), a strict seasonal breeder, to long-photoperiod (LP, 16L:8D) and short-photoperiod (SP, 8L:16D) from the embryonic stage. Testis volume was markedly larger in LP than in SP from 4 to 10 weeks after birth. RNA-seq analysis of 151 Wnt pathway genes revealed differential expression, with Wnt5a, Wnt6, Wnt7a, and Wnt9a downregulated and Wnt7a upregulated in LP compared to SP. RT-qPCR and Western blotting confirmed these patterns. Immunofluorescence analysis showed that WNT7A and WNT9A were localized to pachytene and diplotene spermatocytes at 4 weeks and to elongating spermatid heads at 10 weeks. WNT6 and WNT5A appeared as perinuclear foci in early spermatocytes at 4 weeks, with WNT6 subsequently shifting to spermatid nuclei at 10 weeks. These findings indicate that prenatal and postnatal photoperiodic exposure, potentially mediated through both maternal and direct pathways, is associated with distinct spatiotemporal expression patterns of WNT5A, WNT6, WNT7A, and WNT9A, suggesting their potential involvement in seasonal reproduction.