H-Y antigen

Association with spermatogenesis

It has been shown that male mice lacking in the H-Y antigen, hence lacking in the gene producing it, have also lost genetic information responsible for spermatogenesis. This result also identified a gene on the mouse Y chromosome, distinct from the testis-determining gene, that was essential for spermatogenesis, thus raising the possibility that the very product of this "spermatogenesis gene" is the H-Y antigen.

Male homosexuality and the birth order effect

Among humans, it has been observed that men with more older brothers tend to have a higher chance of being homosexual (see Fraternal birth order and male sexual orientation). For every additional older brother, a man's chance of being homosexual can rise by up to 33%. One theory to explain this involves H-Y antigens, which suggests that a maternal immune reaction to these antigens has, to an extent, an inhibitory effect on the masculinization of the brain, and therefore, the more male foetuses that the mother of a man has had, the greater the maternal immune response towards him and thus the greater the inhibitory effect on brain masculinization, which is believed to be a factor in sexual orientation.

This hypothesis is supported by evidence that older sisters have no discernible influence on the sexual orientation of later-born males, which would be expected since H-Y antigen is male tissue specific, the 'probable involvement of H-Y antigen in the development of sex-typical traits, and the detrimental effects of immunization of female mice to H-Y antigen on the reproductive performance of subsequent male offspring'. More specifically, recent research (Jan 2018) has found maternal antibodies to the neuroligin NLGN4Y protein, a Y-chromosome protein important in male fetal brain development, to be involved in the fraternal birth order effect.

References

References

1. "H-Y Antigen". Wolters Kluwer.
2. (2000). "Genome: The Autobiography of a Species in 23 Chapters.". Harper and Collins.
3. Dare, Tom. (8 October 2013). "Vaccination and immunity for iGCSE Biology". YouTube.
4. (January 2018). "Male homosexuality and maternal immune responsivity to the Y-linked protein NLGN4Y". Proceedings of the National Academy of Sciences of the United States of America.
5. (June 1996). "H-Y antigens". Human Genetics.
6. (1998). "The serologically detected H-Y antigen revisited". Cytogenetics and Cell Genetics.
7. (April 1997). "H-Y antigen and homosexuality in men". Journal of Theoretical Biology.
8. (1986). "Spermatogenic failure in male mice lacking H-Y antigen". Nature.