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Abstract

In species with seasonal breeding, male specimens undergo substantial testicularregression during the nonbreeding period of the year. However, the molecularmechanisms that control this biological process are largely unknown. Here, wereport a transcriptomic analysis on the Iberian mole,Talpa occidentalis, in which thedesquamation of live, nonapoptotic germ cells is the major cellular event responsiblefor testis regression. By comparing testes at different reproductive states (active,regressing, and inactive), we demonstrate that the molecular pathways controllingthe cell adhesion function in the seminiferous epithelium, such as the MAPK, ERK,and TGF‐βsignaling, are altered during the regression process. In addition, inactivetestes display a global upregulation of genes associated with immune response,indicating a selective loss of the“immune privilege”that normally operates insexually active testes. Interspecies comparative analyses using analogous data fromthe Mediterranean pine vole, a rodent species where testis regression is controlledby halting meiosis entry, revealed a common gene expression signature in theregressed testes of these two evolutionary distant species. Our study advances inthe knowledge of the molecular mechanisms associated to gonadal seasonalbreeding, highlighting the existence of a conserved transcriptional program of testisinvolution across mammalian clades.