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Extreme skewing of X chromosome inactivation in mothers of homosexual men.

Bocklandt S, Horvath S, Vilain E, Hamer DH

Department of Human Genetics, University of California, Los Angeles, CA, USA.

Human sexual preference is a sexually dimorphic trait with a substantial genetic component. Linkage of male sexual orientation to markers on the X chromosome has been reported in some families. Here, we measured X chromosome inactivation ratios in 97 mothers of homosexual men and 103 age-matched control women without gay sons. The number of women with extreme skewing of X-inactivation was significantly higher in mothers of gay men (13/97=13%) compared to controls (4/103=4%) and increased in mothers with two or more gay sons (10/44=23%). Our findings support a role for the X chromosome in regulating sexual orientation in a subgroup of gay men.

Published 3 February 2006 in Hum Genet, 118(6): 691-4.
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