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Assortative Mating in Autism Spectrum Disorder
Assortative mating is a non-random mating system in which individuals with similar genotypes and/or phenotypes mate with one another more frequently than would be expected in a random mating system. Autism Spectrum Disorder (ASD) is considered to be a heritable neurodevelopmental disorder and when investigating the genetic components of ASD, random mating is assumed, although this may not necessarily be the case. The prevalence of ASD has increased from 4 in 1000 in the early nineties to a more recent estimate of 1 in 68 children aged 8 in the US. This increase in prevalence is due to many factors such as increased awareness and diagnoses but it has been hypothesised that some of this increase in prevalence is due to assortative mating.
Objectives:
Assortative mating can be explored through both phenotypic and genotypic data, although it has never been investigated through genotypic measures in ASD. The objectives here are to investigate evidence of genetic assortative mating between ASD parents.
Methods:
We investigated whether or not there is evidence of excess of genotypically similar mating pairs using genome-wide Single Nucleotide Polymorphisms (SNP) data on trio families (Autism Genome Project (AGP) data (1,650 family trios) and Simons Simplex Collection (SSC) data (1,962 family trios)). Determining whether an excess in genetic similarity was present or not was explored through kinship coefficients and spousal correlation between the principle components in both the AGP and SSC datasets.
Results:
We found evidence of assortative mating in the AGP data using both methods. There was no significant evidence of assortative mating using the kinship coefficients in the SSC data. Although, there was significant evidence when investigating assortative mating using correlation between the principle components in the SSC dataset.
Conclusions:
Although both the AGP and the SSC show evidence of assortative mating when exploring the correlation of the principle components, the AGP shows further evidence of assortative mating when investigating genetic similarity of parents of ASD offspring using kinship coefficients. Therefore, this stronger evidence of assortative mating in the AGP (contains mulitplex and simplex families) compared to the SSC (strictly contains simplex families) reflects the differences that have previously been observed between multiplex ASD families and simplex ASD families (Klei et al. 2012, Chaste et al. 2012).