EXPRESSION OF GONADOTROPIN SUBUNIT GENES IN SHEEP THAT WERE HOMOZYGOUS CARRIERS AND NONCARRIERS OF THE BOOROOLA FECUNDITY GENE FEC(B)

Homozygous carriers (BB) of the Booroola fecundity gene Fec(B) are cha racterized by high plasma concentrations of immunoreactive or biologic ally active FSH and, to a lesser extent, of immunoreactive LH, relativ e to non-carriers (++). Bovine cDNA probes for the alpha gonadotrophin , FSH beta and LH beta genes were used to investigate Fec(B)-specific differences in the mRNA species for the gonadotrophin subunits in pitu itaries obtained from ++ and BE mid-luteal phase ovary-intact ewes, ov ariectomized ewes and ovary-intact or ovariectomized ewes with hypotha lamic-pituitary disconnection (HPD) given the same regimen of pulsatil e GnRH. No Fec(B)-specific differences in the number or size of mRNA t ranscripts detected by northern blotting were noted for any of these g enes. Densitometry of the northern blots revealed no significant Fec(B )-specific differences in the relative amounts of mRNA encoding a gona dotrophin, FSH beta or LH beta in the pituitaries from any of the expe rimental groups of ++ and BB sheep. Furthermore, there were no signifi cant Fec(B)-specific differences in the pituitary content of FSH or LH in these animals, despite significantly higher plasma concentrations of FSH in the ovary-intact and ovariectomized HPD groups. These data s how that whereas the Fec(B) gene causes increased plasma concentration s of FSH, no consistent effects can be demonstrated on pituitary gonad otrophin content or on gonadotrophin subunit gene transcription, using northern analysis. We suggest that the increased FSH secretion observ ed in Fec(B)-carriers does not arise from an effect of the Fec(B) gene on the size or stability of the gonadotrophin subunit mRNA, but is mo re likely to arise from differences in post-translational modification or secretion of the FSH protein in Fec(B)-carriers.