Trypsin regulates meiotic initiation in the Japanese eel (Anguilla japonica) by promoting the uptake of taurine into germ cells during spermatogenesis.

Meiosis is a unique and critical process in reproduction. Although the key molecular components of meiosis have been identified, the molecular mechanisms regulating the entry into this pathway remain unclear. We previously demonstrated that a progestin in teleost fish, 17alpha, 20beta-dihydroxy-4-pregnen-3-one, is essential for meiotic initiation, and up-regulates taurine synthesis and the production of trypsin in Sertoli cells. In the present study, we found that trypsin promotes the uptake of taurine into germ cells through the up-regulation of solute carrier family 6 (neurotransmitter transporter, taurine), member 6 (Slc6a6) expression. We further found that this up-regulation of the taurine signal is required for Spo11a expression and meiotic initiation.