NRXN1α+/- is associated with increased excitability in ASD iPSC-derived neurons

Background NRXN1 deletions are identified as one of major rare risk factors for autism spectrum disorder (ASD) and other neurodevelopmental disorders. ASD has 30% co-morbidity with epilepsy, and the latter is associated with excessive neuronal firing. NRXN1 encodes hundreds of presynaptic neuro-adhesion proteins categorized as NRXN1 alpha/beta/gamma. Previous studies on cultured cells show that the short NRXN1 beta primarily exerts excitation effect, whereas the long NRXN1 alpha which is more commonly deleted in patients involves in both excitation and inhibition. However, patient-derived models are essential for understanding functional consequences of NRXN1 alpha deletions in human neurons. We recently derived induced pluripotent stem cells (iPSCs) from five controls and three ASD patients carrying NRXN1 alpha(+/-) and showed increased calcium transients in patient neurons. Methods In this study we investigated the electrophysiological properties of iPSC-derived cortical neurons in control and ASD patients carrying NRXN1 alpha(+/-) using patch clamping. Whole genome RNA sequencing was carried out to further understand the potential underlying molecular mechanism. Results NRXN1 alpha(+/-) cortical neurons were shown to display larger sodium currents, higher AP amplitude and accelerated depolarization time. RNASeq analyses revealed transcriptomic changes with significant upregulation glutamatergic synapse and ion channels/transporter activity including voltage-gated potassium channels (GRIN1, GRIN3B, SLC17A6, CACNG3, CACNA1A, SHANK1), which are likely to couple with the increased excitability in NRXN1 alpha(+/-) cortical neurons. Conclusions Together with recent evidence of increased calcium transients, our results showed that human NRXN1 alpha(+/-) isoform deletions altered neuronal excitability and non-synaptic function, and NRXN1 alpha(+/-) patient iPSCs may be used as an ASD model for therapeutic development with calcium transients and excitability as readouts.

Automated summary

NRXN1α(+/-) patient-derived cortical neurons exhibit alterations in sodium currents, action potential characteristics, and transcriptomic changes related to upregulated glutamatergic synapse and ion channels/transporter activity. These changes are likely to contribute to the enhanced excitability observed in NRXN1α(+/-) cortical neurons, indicating potential therapeutic targets for ASD.