mTOR Signaling Pathway Regulates the Release of Proinflammatory Molecule CCL5 Implicated in the Pathogenesis of Autism Spectrum Disorder.

Autism spectrum disorder (ASD) is a complex pervasive neurodevelopmental disorder and neuroinflammation may contribute to the pathogenesis of ASD. However, the exact mechanisms of abnormal release of proinflammatory mediators in ASD remain poorly understood. This study reports elevated plasma levels of the proinflammatory chemokine (C-C motif) ligand 5 (CCL5) in children with ASD, suggesting an aberrant inflammatory response appearing in the development of ASD. Mining of the expression data of brain or blood tissue from individuals with ASD reveals that mTOR signaling is aberrantly activated in ASD patients. Our in vitro study shows that suppression of mTOR reduces the gene expression and release of CCL5 from human microglia, supporting that CCL5 expression is regulated by mTOR activity. Furthermore, bacterial lipopolysaccharide (LPS)-induced CCL5 expression can be counteracted by siRNA against NF-κB, suggests a determining role of NF-κB in upregulating CCL5 expression. However, a direct regulatory relationship between the NF-κB element and the mTOR signaling pathway was not observed in rapamycin-treated cells. Our results show that the phosphorylated CREB can be induced to suppress CCL5 expression by outcompeting NF-κB in binding to CREB-binding protein (CREBBP) once the mTOR signaling pathway is inhibited. We propose that the activation of mTOR signaling in ASD may induce the suppression of phosphorylation of CREB, which in turn results in the increased binding of CREBBP to NF-κB, a competitor of phosphorylated CREB to drive expression of CCL5. Our study sheds new light on the inflammatory mechanisms of ASD and paves the way for the development of therapeutic strategy for ASD.

Leber's Hereditary Optic Neuropathy-Specific Heteroplasmic Mutation m.14495A>G Found in a Chinese Family.

PURPOSE: Leber's hereditary optic neuropathy (LHON) is a mitochondrial DNA (mtDNA)-associated, maternally inherited eye disease. Mutation heteroplasmy level is one of the leading causes to trigger LHON manifestation. In this study, we aimed to identify the causative mutation in a large Han Chinese family with LHON and explore the underlying pathogenic mechanism in this LHON family. METHODS: The whole-mtDNA sequence was amplified by long-range PCR. Mutations were subsequently identified by next-generation sequencing (NGS) and validated by Sanger sequencing. The heteroplasmy rates of those family members were determined by digital PCR (dPCR). Mitochondrial haplogroups were assigned based on mtDNA tree build 17. RESULTS: The m.14495A>G mutation was identified as causative due to its higher heteroplasmy level (>50%) in patients than in their unaffected relatives. All mutation carriers belong to M7b1a1 and are assigned to Asian mtDNA lineage. Interestingly, our result revealed that high mtDNA copy number in carrier might prevent LHON manifestation. CONCLUSIONS: This is the first report of m.14495A>G mutation in Asian individuals with LHON. Our study shows that dPCR technology can provide more reliable results in mutation heteroplasmy assay and determination of the cellular mtDNA content, making it a potentially promising tool for clinical precise diagnosis of LHON. Furthermore, our results also add evidence to the opinion that higher mtDNA content may protect mutation carriers from LHON. TRANSLATIONAL RELEVANCE: dPCR can be used for the assessment of LHON disease, and a new genetic-based diagnostic strategy has been proposed for LHON patients with the m.14495A>G mutation.