Identification of sperm-bearing female-specific chromosome in the sex-reversed chicken.

Sexual differentiation in the female chick embryo was phenotypically reversed to the male sex by injection of an aromatase inhibitor (Fadrozole, 0.1 mg/egg) into the embryo at day 5 of incubation. The birds were raised to 10 months of age, and the morphology of the gonads of sex-reversed hens were examined by the light-microscopic morphology, and the presence of the W chromosome gene was determined by fluorescence in situ hybridization (FISH) technique and used for PCR analysis of a single isolated sperm. The sex-reversed hens possessed two testes with a fully developed oviduct on the left side. The testes contained essentially the same cellular components as those of normal testes, although sperm counts were low. FISH analysis revealed numerous spermatids and several sperm bearing W-chromosomes, indicating that the second meiosis occurred normally but that the transformation from the spermatid to the spermatozoon is partially impaired. PCR analysis using the DNA of a single sperm also indicates that sperm-carrying the W chromosome were produced.