Modeling non-syndromic autism and the impact of TRPC6 disruption in human neurons

Abstract

An increasing number of genetic variants have been implicated in autism spectrum disorders (ASD), and the functional study of such variants will be critical for the elucidation of autism pathophysiology. Here, we report a de novo balanced translocation disruption of TRPC6, a cation channel, in a non-syndromic autistic individual. Using multiple models, such as dental pulp cells, iPSC-derived neuronal cells and mouse models, we demonstrate that TRPC6 reduction or haploinsufficiency leads to altered neuronal development, morphology, and function. The observed neuronal phenotypes could then be rescued by TRPC6 complementation and by treatment with IGF1 or hyperforin, a TRPC6-specific agonist, suggesting that ASD individuals with alterations in this pathway might benefit from these drugs. We also demonstrate that MeCP2 levels affect TRPC6 expression. Mutations in MeCP2 cause Rett syndrome, revealing common pathways among ASDs. Genetic sequencing of TRPC6 in 1041 ASD individuals and 2872 controls revealed significantly more nonsynonymous mutations in the ASD population, and identified loss-of-function mutations with incomplete penetrance in two patients. Taken together, these findings suggest that TRPC6 is a novel predisposing gene for ASD that may act in a multiple-hit model. This is the first study to use iPSC-derived human neurons to model non-syndromic ASD and illustrate the potential of modeling genetically complex sporadic diseases using such cells.

Modeling Williams syndrome with induced pluripotent stem cells

“…23,25,29,30 Although the findings of the differences in the number of dendritic segments, branching points and trees did not agree between the iPSC model and postmortem tissue, we did observed a similar trend for WS iPSC-derived neurons to have a higher number of dendritic segments and branching points, as observed in WS postmortem brains. It is possible that iPSC-derived neurons lack the dynamics from environmental inputs, and deficiencies in dendritic segments and branching points may occur later in development, resulting in the only partial dendritic changes observed in postmortem specimens.…”

“…21 Such advancement has opened up new possibilities that could greatly benefit the medical research, including therapeutic applications and disease modeling. [22][23][24][25][26] First, unlike primary patient cells, which are limited in quantity, iPSCs provide infinite storable source for studies requiring large amount of cells such as highthroughput drug screening. Second, human iPSCderived cells are more physiologically relevant than animal models and available transformed cell lines.…”

“…As demonstrated in our previously published studies, 23,25 iPSCs could be used to investigate the functional consequences of MECP2 mutation (Rett syndrome) and TRPC6 disruption (non-syndromic autism) on neurons derived from those patients. iPSC-derived neurons from both diseases shared common phenotypes including altered calcium influx, morphological alterations and significant reduction in glutamatergic synapses.…”

The Use of Induced Pluripotent Stem Cell Technology to Advance Autism Research and Treatment

“…As a proof-of-principle, our laboratory recently generated an iPSCs model of nonsyndromic autism to investigate cellular and molecular phenotypes [116]. The proband presented with classical autism, delayed motor skills development, and poor social responsiveness.…”

Discovery of Rare Mutations in Autism: Elucidating Neurodevelopmental Mechanisms

“…In another study, disruption of calcium signaling, changes in gene expression, and decreased neurite growth were observed in iPSC-derived neurons from a nonsyndromic patient with autism with a translocation disrupting the cation channel gene TRPC6. Some of the defective phenotypes could be reversed by treatment with insulin-like growth factor-1 or a TRPC6 agonist, hyperforin [196]. The use of iPSC-derived neurons to connect gene variants to autism-related cellular phenotypes provides a new path to identifying and screening potential therapeutics for autism.…”