Verification of patient genotype and understanding of copy number variation is another essential step with hiPSC based studies. For example, characterization of hiPSCs from patients with 9p24.1 duplications/triplications, a copy number variant associated with psychotic disorders (Malhotra et al., 2011), revealed chromosomal instability during reprogramming in the form of extrachromosomal marker element rearrangement. Due to mosaicism in the patient derived fibroblasts, conversion to pluripotency serendipitously generated non-carrier isogenic controls (Tcw et al., 2017). Therefore, investigation in hiPSCs necessitates karyotyping to ensure absence of chromosomal abnormalities.
