Notch pathway is required for protection against heat stress in spermatogonial stem cells in medaka

Trpv4-mediated apoptosis of Leydig cells induced by high temperature regulates sperm development and motility in zebrafish

Exposure of testes to high-temperature environment results in defective spermatogenesis. Zebrafish exposed to high temperature exhibited apoptosis not only in germ cells but also in Leydig cells, as expected from studies using mice or salmon. However, the role of testicular somatic cells in spermatogenesis defects remains unclear. We found that in Leydig cells the Trpv4 gene encoding the temperature sensitive ion channel was specifically upregulated in high temperature. High temperature also reduced hormone synthesis in Leydig cells and led to a prompt downregulation of sperm motility. In the Trpv4 null mutant, neither Leydig cell-specific apoptosis nor decreased sperm motility was observed under high temperature. These results indicate that Leydig cell specific-apoptosis is induced via Trpv4 by high temperature. Notably this Trpv4-dependent mechanism was specific to Leydig cells and did not operate in germ cells. Because sperm exposed to high temperature exhibited compromised genome stability, we propose that temperature sensing leading to apoptosis in Leydig cells evolved to actively suppress generation of offspring with unstable genome.