Autism spectrum disorders (ASD) are lifelong heterogeneous set of neurodevelopmental conditions with strikingly profound male prevalence. Differences in sex biology and hormones are thought to play key roles in ASD prevalence and outcome, but the underlying molecular mechanisms responsible for ASD sex-differential risk are not well understood. Two recent studies reported a significant association between shortened telomere length (TL) and autistic children. However, the role of gender bias has been overlooked. Here, we carefully examined the status of average TL among non-syndromic male and female children with autism, and we also took a close look at the data from earlier reports. A total of 58 children were recruited for this project, including 24 apparently non-syndromic autistic children (14 males and 10 females), their healthy siblings (n = 10), and 24 sex-, age, and location-matched healthy controls. Relative TLs (RTL) were assessed by the monochrom multiplex quantitative polymerase chain reaction (MMQPCR) technique, using genomic DNA extracted from saliva samples. Data analysis showed that gender and age had strong impacts on average RTLs among the study groups. In a sex stratified manner, autistic male children had significantly shorter average RTL than their female counterparts. Only male children with autism showed a homogeneous pattern of shorter RTLs compared with their respective healthy controls. Our findings are indicative of a sexually dimorphic pattern of TL in childhood autism. The data presented here have important implications for the role of telomere biology in the molecular mechanisms responsible for ASD male bias prevalence and etiology.

doi: medRxiv preprint NOTE: This preprint reports new research that has not been certified by peer review and should not be used to guide clinical practice.

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The underlying molecular mechanisms responsible for the etiology of autism and its sex-biased prevalence remain largely elusive. Abnormally shortened telomeres have recently been associated with autism. We have previously shown that children with non-syndromic autism exhibit a sexually dimorphic pattern of relative telomere length (RTL). Only male children with autism have significantly shorter RTLs than the healthy controls and paired siblings. Autistic females have substantially longer RTLs than autistic males. Aberrantly high levels of oxidative stress plays a fundamental role in the pathophysiology of autism, and telomeres are thought to be susceptible to oxidative damage due to their high guanine-repeat content. Employing a quantitative PCR (qPCR)-based method, telomeric oxidized base lesions were measured using genomic DNA extracted from saliva samples, and levels of telomeric RNA transcripts know as TERRA were evaluated using reverse transcriptase qPCR technique. Our data show that the autistic children exhibit substantially higher levels of oxidative base lesions at their telomeres than the healthy controls and paired siblings. Intriguingly, despite having significantly longer RTLs, female children with autism have even higher levels of telomeric oxidized bases than their male counterparts. Furthermore, despite having significantly shorter RTLs, the male children with autism exhibit lower levels of TERRA expression from the short arms of chromosomes 17 and X/P compared to their individually-matched healthy controls. These findings open a fresh angle into autism. Abnormal TL and high levels of telomeric oxidized bases may serve as biomarkers for childhood autism.