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Mol Autism. 2015 May 13;6:25. doi: 10.1186/s13229-015-0014-3. eCollection 2015.

The female protective effect in autism spectrum disorder is not mediated by a single genetic locus.

Author information

1
Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520 USA.
2
Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520 USA ; Department of Psychiatry, University of California, San Francisco, 401 Parnassus Avenue, San Francisco, CA 94143 USA.
3
Department of Genetics, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520 USA ; Center for Bioinformatics, State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, No.5 Yiheyuan Road, Haidian District, Beijing, 100871 People's Republic of China.
4
Department of Psychiatry, Washington University, 660 South Euclid Avenue, St Louis, MO 63110 USA ; Department of Genetics, Washington University, 4566 Scott Ave, St Louis, MO 63110 USA.
5
Department of Psychiatry, Washington University, 660 South Euclid Avenue, St Louis, MO 63110 USA.

Abstract

BACKGROUND:

A 4:1 male to female sex bias has consistently been observed in autism spectrum disorder (ASD). Epidemiological and genetic studies suggest a female protective effect (FPE) may account for part of this bias; however, the mechanism of such protection is unknown. Quantitative assessment of ASD symptoms using the Social Responsiveness Scale (SRS) shows a bimodal distribution unique to females in multiplex families. This leads to the hypothesis that a single, common genetic locus on chromosome X might mediate the FPE and produce the ASD sex bias. Such a locus would represent a major therapeutic target and is likely to have been missed by conventional genome-wide association study (GWAS) analysis.

METHODS:

To explore this possibility, we performed an association study in affected versus unaffected females, considering three tiers of single nucleotide polymorphisms (SNPs) as follows: 1) regions of chromosome X that escape X-inactivation, 2) all of chromosome X, and 3) genome-wide.

RESULTS:

No evidence of a SNP meeting the criteria for a single FPE locus was observed, despite the analysis being well powered to detect this effect.

CONCLUSIONS:

The results do not support the hypothesis that the FPE is mediated by a single genetic locus; however, this does not exclude the possibility of multiple genetic loci playing a role in the FPE.

KEYWORDS:

Autism spectrum disorder; Female protective effect; GWAS; Sex bias

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