October 8, 2015

expert reaction to conference presentation (unpublished work) on epigenetics and male sexual orientation

In the presentation of their unpublished work at the American Society of Human Genetics 2015 annual meeting, a research group report their attempt to develop a way of using markers of modification of genes to predict sexual orientation in men.

Dr Ewan Birney, Co-Director, European Bioinformatics Institute, said:

“It is very hard to assess this work from an abstract and press release, and these claims need careful scrutiny. From the abstract, it is unclear whether the scientists have looked carefully at confounding factors, i.e., other things which associate with sexual orientation and might be the cause of this correlation.

“Furthermore, it seems as if their use of the word “predict” is in a specific data science way (about the ability of the statistical model) rather than the likely broader interpretation, i.e., the ability to predict someone’s sexuality ahead of puberty. The epigenetic component of this is about blood cell type measurement, and is not fundamentally different to other blood measurements one could do. For all these reasons I am skeptical about this result.”

Prof. Gil McVean, Professor of Statistical Genetics, University of Oxford, said:

“The key issue here is that the authors have searched through the entire genome to identify some difference between discordant twins.  Given the number of tests, it is likely that some regions will show up as differentiated by chance.  Without validation of the result in an independent data set it is not really possible to know whether there is any substance in this claim.”

Prof. Johnjoe McFadden, Professor of Molecular Genetics, University of Surrey, said:

“Studies that associate biomarkers with particular traits are notoriously prone to false positive results due to the tendency of these studies to find spurious associations that are down to sheer chance. The key test is whether the associations are found in a completely independent study population. From the abstract this confirmatory test does not appear to have been performed in this study. Without it, the results should be considered to be suggestive and preliminary but in need of verification before any firm conclusions can be drawn.”

Prof. Darren Griffin, Professor of Genetics, University of Kent, said:

“With only a research summary (abstract) to work with it is difficult to give a full appraisal of the research.  Nonetheless, to claim a 70% predictive value of something as complex as homosexuality is bold indeed.  I wait with baited breath for a full peer-reviewed article.  While there is strong evidence in general for a biological basis for homosexuality my personal impression has always been one of a multiple contributory factors, including life experiences. My gut feeling it that, as the complete story unfolds, the association may not be quite as simple as the summary (abstract) and press release suggest. The important thing to note however is the mounting evidence that homosexuality is a perfectly normal trait segregating in human populations.”

Dr Eric Miska, Herchel Smith Chair of Molecular Genetics, The Gurdon Institute and Department of Genetics, University of Cambridge, said:

“Epigenetic marks are the consequence of complex interactions between the genetics, development and environment of an individual. Epigenetics is still a young science and although there is great potential very little is known about the mechanisms that shape the epigenetic landscapes of an individual. Simple correlations – if significant – of epigenetic marks of an individual with anything from favourite football player to disease risk does not imply a causal relationship or understanding.”

Prof. Tim Spector, Professor of Genetic Epidemiology, King’s College London, said:

“It has always been a mystery why identical twins who share all their genes can vary in homosexuality. Epigenetic differences are one obvious reason and this study provides evidence for this. However the small study needs replicating before any talk of prediction is realistic.”

Abstract title: ‘PgmNr 95: A novel predictive model of sexual orientation using epigenetic markers’ by T. C. Ngun et al. presented at the American Society of Human Genetics 2015 Annual Meeting. It is unpublished work.

Declared interests

Prof. Gil McVean, Dr Eric Miska and Prof. Tim Spector declare that they have no interests.

None others received