Gene correction of reversed Kostmann disease phenotype in patient-specific induced pluripotent stem cells.

Severe congenital neutropenia (SCN, Kostmann disease) is a heritable disorder characterized by a granulocytic maturation arrest. Biallelic mutations in () are frequently detected in affected individuals, including those of the original pedigree described by Kostmann in 1956. To date, no faithful animal model has been established to study SCN mediated by HAX1 deficiency. Here we demonstrate defective neutrophilic differentiation and compensatory monocyte overproduction from patient-derived induced pluripotent stem cells (iPSCs) carrying the homozygous nonsense mutation. Targeted correction of the mutation using the CRISPR-Cas9 system and homologous recombination rescued neutrophil differentiation and reestablished an and -centered transcription network in immature myeloid progenitors, which is involved in the regulation of apoptosis, apoptotic mitochondrial changes, and myeloid differentiation. These findings made in isogenic iPSC-derived myeloid cells highlight the complex transcriptional changes underlying Kostmann disease. Thus, we show that patient-derived -iPSCs recapitulate the Kostmann disease phenotype in vitro and confirm mutations as the disease-causing monogenic lesion. Finally, our study paves the way for nonvirus-based gene therapy approaches in SCN.