Characterization of molecular and cellular phenotypes associated with a heterozygous CNTNAP2 deletion using patient-derived hiPSC neural cells.

Neurodevelopmental disorders, such as autism spectrum disorders (ASD) and schizophrenia (SZ), are complex disorders with a high degree of heritability. Genetic studies have identified several candidate genes associated with these disorders, including contactin-associated protein-like 2 (CNTNAP2). Traditionally, in animal models or in vitro, the function of CNTNAP2 has been studied by genetic deletion or transcriptional knockdown, which reduce the expression of the entire gene; however, it remains unclear whether the mutations identified in clinical settings are sufficient to alter CNTNAP2 expression in human neurons. Here, using human induced pluripotent stem cells (hiPSCs) derived from two individuals with a large (289kb) and heterozygous deletion in CNTNAP2 (affecting exons 14-15) and discordant clinical outcomes, we have characterized CNTNAP2 expression patterns in hiPSC neural progenitor cells (NPCs), two independent populations of hiPSC-derived neurons and hiPSC-derived oligodendrocyte precursor cells (OPCs). First, we observed exon-specific changes in CNTNAP2 expression in both carriers; although the expression of exons 14-15 is significantly decreased, the expression of other exons is upregulated. Second, we observed significant differences in patterns of allele-specific expression in CNTNAP2 carriers that were consistent with clinical outcome. Third, we observed a robust neural migration phenotype that correlated with diagnosis and exon- and allele-specific CNTNAP2 expression patterns, but not with genotype. In all, our data highlight the importance of considering the nature, location and regulation of mutated alleles when attempting to connect GWAS studies to gene function.

Modeling schizophrenia using induced pluripotent stem cell-derived and fibroblast-induced neurons.

Although schizophrenia affects a number of brain regions and produces a range of clinical symptoms, we believe its origins lie at the level of single neurons and simple networks. Owing to this, as well as to its high degree of heritability, we hypothesize that schizophrenia is amenable to cell-based studies in vitro. Using induced pluripotent stem cell-derived neurons and/or fibroblast-induced neurons, a limitless quantity of live human neurons can now be generated from patient skin biopsies. We predict that cell-based studies will ultimately contribute to our understanding of the molecular and cellular underpinnings of this debilitating disorder.