Fertility of Y-TIR.B6 sex-reversal females with XX orthotopic ovarian transplants

When the Y chromosome of Mus musculus domesticus (Y-TIR) was introduced ont o the C57BL/6J (B6) mouse background, testis development was impaired and h alf of the XY progeny (Y-TIR.B6) developed a female phenotype. Y-TIR.B6 fet al ovaries showed massive death of medullary oocytes and, after birth, prod uced abnormal levels of steroid hormones, exhibited irregular estrous cycle s, and failed to become fertile. In this study we examined whether alterati ons during perinatal development observed in Y-TIR.B6 ovaries permanently i mpaired the establishment of the hypothalamus-pituitary-ovary axis (HPOa). 86 fetal and postnatal ovaries at different stages (fetal, infantile, or ad ult) were transplanted orthotopically (to the ovarian bursa) to either ovar iectomized 86 normal females or Y-TIR.B6 sex-reversal females. Percentage o f pregnancy, litter size, and capacity to feed pups were recorded. Reciproc ally, XYTIR.B6 ovaries were orthotopically transplanted into 86 females. Af ter crossing with fertile males, several Y-TIR.B6 sex-reversal females with 86 ovarian transplants at all ages became pregnant, had offspring, and fed their pups. On the other hand, none of the 86 female hosts with XYTIR ovar ies became pregnant. Results demonstrated that Y-TIR.B6 sex-reversal female s maintain a functional HPOa and that their failure to reproduce is primari ly due to an ovarian defect.