Bisphenol A regulates rare minnow testicular vitellogenin expression via reducing its promoter Er recruitment

Vitellogenins (Vtgs) are major precursor of the egg-yolk proteins. They are synthesized in liver of adult female ovipara, but normally silent in males. For their sensitive response to estrogen, Vtgs are usually used as biomarkers for environmental estrogenic compounds. In the present study, three vtg subtypes (vtg1, vtg2 and vtg3) were proved to present in the testis of rare minnow Gobiocypris rarus for the first time. Immunohistochemistry result showed that Vtg proteins mainly deposit in spermatogonium and spermatocytes. Following 225μg/L bisphenol A (BPA) exposure 1, 3 and 9 weeks, testicular vtg mRNAs were mostly significantly decreased. The further chromatin immunoprecipitation showed that BPA could decrease estrogen receptor (Er) recruitment in vtg promoter, which possibly reduced Er's transcription activation effect on vtgs. However, different from the continuously decreased vtg mRNA levels, testicular Vtg protein levels were recovered at week 9. Considering the induced hepatic Vtg expression, testicular Vtgs may be replenished by the induced hepatic Vtgs under BPA exposure.