Biallelic genome engineering to create isogenic induced pluripotent stem cells modeling Huntington's disease.

We developed Huntington's disease (HD)-modeling induced pluripotent stem cells (iPSCs) by genome engineering of iPSCs from healthy donors. For this, we established a homologous-recombination-based biallelic substitution technique called the allele-specific universal knock-in system (asUKiS). asUKiS allows for scarless and allele-by-allele substitution of the entire region encompassing not only the polyQ repeat but also the associated genetic modifiers surrounding the repeat region, allowing us to generate five iPSC lines with identical genetic modifiers on both alleles, differing only in polyQ repeat numbers. All cell lines were validated by allele-specific genotyping to confirm the precise engineering of both alleles. Even for modeling autosomal dominant diseases, our approach of employing biallelic modification offers the distinct advantage of enabling investigation of the effects of specific genomic mutations with minimal interference from genetic background noise.