Functional Alteration in Gating Behavior of IP3R Channel Mediating Calcium Signaling As Common Biomarker in Autism Spectrum Disorder

Background: Current clinical measures used in diagnosing Autism Spectrum Disorder (ASD) have been adapted to screen core characteristics that range widely in severity. However, even at its most refined, ASD remains a group of developmental disorders that is defined by behavioral qualities, not by its pathogenesis. Studies on the genetic architecture of ASD and related neurological disorders have brought light to the central role of calcium channelopathies and its effects on calcium signaling pathways rationally implicated in diverse aspects of ASD pathogenesis.

Objectives: We propose that depressed function in IP3R mediated calcium release channels in the ER may be a reliable diagnostic biological marker for monogenic and ‘sporadic’ forms of ASD.

Methods: Functional components of calcium signaling were dissected in ASD and a super-resolution STORM system was used to obtain molecular-resolution optical patch clamp analysis on monogenic ASD models. Fibroblasts derived from skin biopsies of healthy, unaffected inviduals, and patients with rare monogenic forms or ‘sporadic’ autism were cultured and monitored for agonist-evoked calcium signals using a high throughput FLIPR assay. Human induced pluripotent stem cells (hiPSCs) were generated from primary fibroblasts using the Thermo-Fisher Sendai virus protocol. hiPSCs were differentiated into neuronal progenitors, and measured with UV-activated caged iP3.

Results: Local IP3-mediated calcium signaling was decreased in fibroblasts derived from patients with monogenic forms of ASD when compared to those derived from healthy, control patients. Likewise, IP3-mediated calcium signaling was repeatedly decreased in fibroblasts derived from patients with monogenic or ‘sporadic’ forms of ASD when compared to healthy, control patients. iPSC- derived neuronal precursors from patient fibroblasts also share this signaling defect.

Conclusions: Our results strongly implicate deregulated calcium signaling in the pathogenesis of ASD and supports iP3-mediated calcium signaling as a diagnostic biological marker for ASD. Furthermore, a high-throughput FLIPR assay may be used as a highly reproducible diagnostic that is able to capture differences in IP3-mediated calcium signaling.