Relationship between brain cell proliferation and aromatase expression during thermolabile sex determination/ differentiation period in pejerrey fish

The present work shows that brain aromatase gene expression during the period of sex determination/differentiation was significantly enhanced in pejerrey larvae at masculinizing (29C, MPT) compared to feminizing (17C, FPT) temperatures. Analysis by immunocytochemistry (ICC) showed that aromatase expressing cells were evidenced first in the pituitary (2 weeks after hatching, WAH) and then in periventricular brain cells (4 WAH). Larvae at FT exhibited higher brain cell proliferation at 4 WAH compared with those at MPT as determined by both BrdU and PCNA ICC. Our results suggest that temperature exerts a strong effect on pejerrey brain aromatase expression and that estradiol (E2) is required for the masculinization of larval brain.