Proteins of the mTOR pathway dysregulated in animal models of Autism Spectrum Disorder:A systematic review, meta-analysis, and molecular follow-up

Background: Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition including social, communicative, and behavioural difficulties. It is thought to arise from both genetic and environmental factors leading to extremely heterogeneous clinical manifestations in patients [1, 2]. Scientific efforts focus on elucidating the molecular mechanisms of ASD, with a recent emphasis on the mammalian Target of Rapamycin (mTOR) pathway. This pathway, a crucial intracellular signalling cascade, intricately regulates fundamental cellular processes including growth, proliferation, and synaptic plasticity. Dysregulations in the mTOR pathway are considered in the pathophysiology of ASD and consequently, it is important to study this pathway in the context of this disease [3, 4]. Using a systematic review and meta-analysis, we analysed and compiled findings from all eligible studies on genetic, environmental, and idiopathic animal models for ASD pathology to assess consistencies in alterations in mTOR pathway activity. Based on the outcomes of this systematic review and meta-analysis, we analysed relevant mTOR pathway proteins in three different gene knockout mouse models of synaptic dysfunction relevant to ASD (namely Shank3, Neurexin1 and Cntnap2).<br/><br/>Methods: The systematic review and meta-analysis were performed according to the PRISMA guidelines. Accordingly, a comprehensive search in PubMed and Web of Science was conducted and 169 studies have been included in the final analysis, thereof 156 in the meta-analysis. Meta-analyses have been performed on all proteins of the mTOR pathway by using random-effects meta-analysis models. Subgroup analyses have been performed for species, sex, age, induction and brain region when at least 10 comparisons were available for the subgroup.<br/><br/>Brain protein assessments in the three gene knockout mouse lines consisted of Western Blot analyses for mTOR, (p-)S6 and LC3 using dissected tissue from the somatosensory cortex (SSC) and the thalamus from six weeks and twelve weeks old homozygous (KO) and wild type (WT) mice of all three mouse lines (n= 12 or 13 in each group).<br/><br/>Results: Meta-analyses have shown that several relevant proteins from the mTOR pathway are significantly up- or downregulated in a number of genetic and environmentally-induced animal models for ASD. Our own Western blot analysis showed no significant differences in any of the measured proteins in the Cntnap2 and Neurexin1 mouse brain tissues, nor in the thalamus of Shank3 mice. However, in the SSC of the Shank3 KO mice, (p)-S6, LC3 and mTOR were significantly elevated at 12 weeks of age.<br/><br/>Conclusion: Both the systematic review with meta-analyses and our own Western Blot analyses showed that several relevant proteins from the mTOR pathway are consistently dysregulated in a variety of genetic and environmental animal models for ASD pathology. Therefore the pathway might play an important role in further understanding the molecular underpinnings of the diverse disease aetiology, and may provide biological means to stratify and treat autistic people when in need.