Autism and Increased Paternal Age
With today’s population living longer, there is a trend in many modern societies to delay parenthood until the prospective parents have completed their education and established their careers. This has resulted in an increase in children born to parents of advanced age, which has been linked to several disorders of brain development including mental retardation, schizophrenia, and autism. The underlying mechanisms for this relationship are believed to be complex and likely differ between maternal and paternal age effects. Maternal age has been associated with an increase in genetic disorders such as Down syndrome caused by duplication of chromosome 21. All of a female’s oocytes are present at birth, wherefore oocytes in older women have increased time to undergo genetic rearrangements and duplications. This is not true for fathers whose spermatocytes are continuously produced throughout life. Suggested mechanisms for an effect of advanced paternal age on autism and other disorders include de novo (new) mutations in older fathers’ DNA and multiple epigenetic mechanisms including changes in DNA methylation, histone modifications, and noncoding RNAs. Evidence for genetic and epigenetic mechanisms is reviewed herein and important areas for future research are highlighted.
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