Cortical organoid models to study autism-associated 16p.11.2.CNV

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SUMMARY The 16p11.2 Copy Number Variant (CNV) containing 29 genes represents one of the strongest risk factors for neurodevelopmental disorders. It is the most common among all rare CNVs implicated in Autism Spectrum Disorder (ASD). Both, deletions (DEL) and duplications (DUP) of this locus are strongly associated with ASD, whereas DEL are also associated with intellectual disability, and DUP are also associated with schizophrenia. The 16p11.2 CNV dosage has “mirror” effect on the brain volume and body mass index (BMI) in human carriers diagnosed with ASD. Macrocephaly and high BMI are observed in the DEL carriers, and microcephaly and low BMI are observed in the duplication carriers. Surprisingly, 16p11.2 DEL and DUP mouse models have brain and body size phenotypes opposite to human carriers. Despite the importance of this CNV, the detailed molecular mechanisms that are disrupted during early brain development remain unknown. We recently generated induced pluripotent stem cells (iPSCs) and cerebral organoids from fibroblasts of 16p11.2 DEL and DUP patients with extreme head size phenotypes. Cerebral organoids recapitulated patients’ brain size phenotypes. Excess neuron number and depletion of neuroprogenitors was observed in DEL, with a “mirror” phenotypes in DUP. In addition, neuron migration and synaptic defects were identified, implicating Rho/Wnt signaling. The central hypothesis of this proposal is that that 16p11.2 CNV dosage (DEL or DUP) impacts brain development by altering the ratio of different neuronal (sub)types and by perturbing their electrophysiological properties. To test this hypothesis, we will: (1) Investigate how 16p11.2 CNV impacts cell type populations and chromatin accessibility at the single cell resolution; (2) Investigate how 16p11.2 CNV affects synaptic transmission and oscillatory network activity in organoids using whole-cell patch-clamp and multielectrode array (MEA) recordings; Investigate involvement of Rho/Wnt and other signaling pathways by rescuing molecular and cellular phenotypes of DEL and DUP organoids. Our study has a potential to uncover new mechanisms behind 16p11.2 CNV in autism.