According to Eric Vilain and colleagues at UCLA.
Here's a brief summary of the preliminary findings, presented at the annual meeting of the American Society of Human Genetics.
Michael Balter, (October 8, 2015, Science)
And here's the abstract of the presentation.
Abstract:
Sexual orientation is one of the most pronounced sex differences in the animal kingdom. Although upwards of 95% of the general population is heterosexual, a small but significant proportion of individuals (3-5%) is homosexual. Male sexual orientation has been linked to several genomic loci, with Xq28 and 8p12 being the most replicated. As with other complex traits, environmental factors may also play an important role. Firstly, monozygotic twins show substantial levels of discordance for this trait. Secondly, each male pregnancy a woman has increases the chance that her next son will be homosexual by 33% (the fraternal birth order effect). Thirdly, early life androgen exposure in women is associated with increased rates of non-heterosexual identity. Taken together, the evidence suggests a role for non-genetic and, possibly, epigenetic influences on sexual orientation. Our aim in this study was to create a predictive model for sexual orientation using epigenetic markers. We created our model based on genome-wide DNA methylation patterns in 37 monozygotic male twin pairs that were discordant for sexual orientation. 10 monozygotic twin pairs concordant for homosexuality were included as a control population. Genomic sites where methylation occurred were consolidated into short regions based on proximity and correlation of their methylation patterns to increase the signal to noise ratio. We then applied the Fuzzy Forest algorithm to our data set. Briefly, regions were clustered into modules using Weighted Gene Co-expression Network Analysis and recursive feature elimination was performed with the random forest algorithm (RF) to identify regions most relevant to sexual orientation. The highest prediction accuracy was achieved using information from just 9 regions. Some of these regions were associated with the regulatory domains of two genes, CIITA and KIF1A. The former is a transcriptional regulator that is sometimes referred to as the master control factor of class II major histocompatibility complex genes. The latter is a neuron-specific transport protein that is important for movement of synaptic vesicle precursors along axons. Our results demonstrate that studies of the epigenome can yield new insights into the biological underpinnings of sexual orientation and provide strong support to the hypothesis that epigenetics is involved in sexual orientation. To our knowledge, this is the first example of a biomarker-based predictive model for sexual orientation.
Here's a brief summary of the preliminary findings, presented at the annual meeting of the American Society of Human Genetics.
Michael Balter, (October 8, 2015, Science)
And here's the abstract of the presentation.
Abstract:
Sexual orientation is one of the most pronounced sex differences in the animal kingdom. Although upwards of 95% of the general population is heterosexual, a small but significant proportion of individuals (3-5%) is homosexual. Male sexual orientation has been linked to several genomic loci, with Xq28 and 8p12 being the most replicated. As with other complex traits, environmental factors may also play an important role. Firstly, monozygotic twins show substantial levels of discordance for this trait. Secondly, each male pregnancy a woman has increases the chance that her next son will be homosexual by 33% (the fraternal birth order effect). Thirdly, early life androgen exposure in women is associated with increased rates of non-heterosexual identity. Taken together, the evidence suggests a role for non-genetic and, possibly, epigenetic influences on sexual orientation. Our aim in this study was to create a predictive model for sexual orientation using epigenetic markers. We created our model based on genome-wide DNA methylation patterns in 37 monozygotic male twin pairs that were discordant for sexual orientation. 10 monozygotic twin pairs concordant for homosexuality were included as a control population. Genomic sites where methylation occurred were consolidated into short regions based on proximity and correlation of their methylation patterns to increase the signal to noise ratio. We then applied the Fuzzy Forest algorithm to our data set. Briefly, regions were clustered into modules using Weighted Gene Co-expression Network Analysis and recursive feature elimination was performed with the random forest algorithm (RF) to identify regions most relevant to sexual orientation. The highest prediction accuracy was achieved using information from just 9 regions. Some of these regions were associated with the regulatory domains of two genes, CIITA and KIF1A. The former is a transcriptional regulator that is sometimes referred to as the master control factor of class II major histocompatibility complex genes. The latter is a neuron-specific transport protein that is important for movement of synaptic vesicle precursors along axons. Our results demonstrate that studies of the epigenome can yield new insights into the biological underpinnings of sexual orientation and provide strong support to the hypothesis that epigenetics is involved in sexual orientation. To our knowledge, this is the first example of a biomarker-based predictive model for sexual orientation.
