Effects of the Booroola gene (FecB(B)) on bodymass, testis development and hormone concentrations during fetal life.

In female fetuses the Booroola gene (FecB(B)) is known to affect germ cell development and consequently the pattern of ovarian follicular growth during fetal and post-natal life. However in males, the role of this gene during fetal development is unknown. The aims of the study reported here were to examine the effects of the FecB(B) gene on development of male fetuses with respect to body and organ mass for example, pituitary gland, adrenal and mesonephros), testes development, including numbers of germ cells, and also the plasma concentrations or tissue contents of the reproductive hormones (FSH, LH and testosterone) at days 40, 55, 75, 90 and 135 of gestation. The FecB(B) gene was found to influence litter size, bodymass, crown-rump length and testis mass at most stages of gestation. Some effects were also noted on the mesonephros at days 40 and 55 and on the pituitary and adrenal at days 90 or 135 of gestation. However, the FecB(B) gene was not observed to have an effect on the patterns of germ cell development, on pituitary content or plasma concentrations of immunoreactive or bioactive FSH or immunoreactive LH or testicular content of testosterone. When embryo transfer experiments were performed to eliminate the effects of litter size at days 40, 90 and 135 of gestation nearly all of the differences in bodymass, crown-rump length and organ mass disappeared. The only exception to this was at day 90 when bodymass continued to be lighter and crown-rump lengths smaller in the BB/B + fetuses compared with the +2 fetuses; the significance of this finding remains unknown. It is concluded that for Booroola male fetuses there are no direct effects of the FecB(B) gene on pituitary gonadotrophin function or testicular development after sexual differentiation. Moreover, although there may be temporal differences around day 90 of gestation, there are no long-term, direct effects of the FecB(B) gene on total body, adrenal, testis or pituitary mass. Collectively these findings for the male are similar to those for female fetuses except with regard to germ cell development.