Appearance of H-W (H-Y) antigen in the gonads of oestradiol sex-reversed male chicken embryos.

Abstract

THERE is evidence that H–Y antigen has a major role in testis differentiation in mammals1–3. Presumably, this antigen is the essential factor for the development of the undifferentiated gonadal anlage into a testis. Antiserum to H-–Y antigen, raised in highly inbred strains of mice and rats, exhibits cross-reactivity with cells derived from non-mammalian vertebrates like birds, amphibians and fish4,5. In these animals, the cross-reaction is strong in the heterogametic sex. This means that in birds with the ZZ/ZW mechanism of sex determination the female types as positive, as also occurs in the toad Xenopus laevis; on the other hand, in the frog genus Rana and the cyprinodont fish Lebistes and Xiphophorus, which have the XX/XY mechanism of sex determination, the male types as positive. This correlation with the heterogametic sex favours the assumption that the cross-reacting antigen ‘H–Y’ or ‘H–W’ in non-mammalian vertebrates has a similar function to that occurring in mammals for the differentiation of the heterogametic gonad, that is, the ovary in ZW, and the testis in XY animals. In contrast to placental mammals, in the other vertebrates it is possible to influence gonadal differentiation by sex steroid hormones (for review, see ref. 6). In the embryonic male (ZZ) bird, application of oestrogens leads to the development of an ovotestis, in amphibians and fish, treatment with steroid hormone of the opposite sex causes complete sex reversal. If H–Y (H–W) is the differentiation antigen for the heterogametic gonad, and if on the other hand sex reversal can be achieved by the steroid hormone of the opposite sex, the question arises whether the hormone acts by way of the H–Y (H–W) antigen. Therefore, we have converted embryonic male chickens using oestrogen to develop an ovotestis, and then tested them for the presence of cross-reactivity with rat anti-H–Y antiserum. We report here that, indeed, the normally antigen-negative testis becomes antigen-positive after hormonal treatment. Thus, the gene for this antigen must be present in the genome of both sexes.