OVARIES OF EWES HOMOZYGOUS FOR THE X-LINKED INVERDALE GENE (FECX(1)) ARE DEVOID OF SECONDARY AND TERTIARY FOLLICLES BUT CONTAIN MANY ABNORMAL STRUCTURES

Ewes homozygous (II) for the Inverdale prolificacy gene (FecX(I)) loca ted on the X chromosome are infertile with ''streak'' ovaries. The aim s of this study were to examine the ovarian morphology and plasma and tissue (or extracellular fluid) hormone concentrations in II ewes in c omparison to control (++) animals. All II animals (n = 11) were found to contain no normal ovarian follicles beyond the primary stage of dev elopment despite their being similar in number of germ cells to the + ewes. The II animals had high plasma gonadotropin levels and undetect able estradiol and progesterone, and in addition 6 of 9 ewes had undet ectable plasma inhibin concentrations. 11 ewes contained large numbers of oocyte-free follicles (''nodules'') that were often found as clust ers in the innermost regions of the cortex. In addition, 6 of 11 ewes contained abnormal luteal- or granulosa cell-like structures and other unusual formations. In three II animals the abnormal structures were visible on the ovarian surface, and the plasma inhibin concentrations in these ewes were significantly higher than in the ++ ewes (p < 0.05) . Collectively these findings suggest that two copies of the FecX(I) m utation impair the resumption of growth of primordial follicles and ma y in some instances lead to the development of abnormal structures hav ing a morphology consistent with that observed for ovarian tumors.