Using genetics to uncover cellular phenotypes underlying Dup15q syndrome

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Duplications of chromosome 15q11-q13 are one of the most common chromosomal anomalies associated with autism. In addition to the social, speech/language, and repetitive behavior deficits associated with autism, individuals with duplications of chromosome 15q (Dup15q) also suffer from features that are frequently co-morbid with idiopathic autism--developmental delay, motor skills delay, and seizures. Dup15q syndrome is a fully- penetrant disorder caused by the presence of one or two extra copies of a region spanning ~15-20 genes, but the specific gene(s) responsible are not clear. Based on human genetic studies and mouse models, we hypothesize that increased expression of UBE3A plus at least one other gene leads to the phenotypic manifestations of Dup15q syndrome. To test this hypothesis, we will use CRISPR and LoxP technologies to genetically correct human induced pluripotent stem cells (iPSCs) derived from individuals with Dup15q syndrome. We will then perform detailed electrophysiological characterization of neurons generated from these isogenic Dup15q/control iPSC pairs to identify cellular phenotypes associated with Dup15q syndrome. Preliminary data suggests that Dup15q iPSC-derived neurons are hyperexcitable and have deficits in synaptic plasticity and homeostatic synaptic scaling. Finally, we will use CRISPR inhibition and antisense oligonucleotide technologies to reduce expression of genes in the duplicated region individually or in combination to determine their contribution to the cellular pathophysiology in human Dup15q neurons. Successful completion of these experiments will identify cellular phenotypes underlying Dup15q syndrome as well as the genes contributing to them. The information garnered here will create cellular resources for drug discovery, inform construction of better mouse models for Dup15q syndrome, and identify neuronal pathophysiology that may contribute to syndromic and idiopathic forms of autism.