Identification of a High-Frequency Somatic NLRC4 Mutation as a Cause of Autoinflammation by Pluripotent Cell-Based Phenotype Dissection.

TLDR: To elucidate the genetic background of a patient with neonatal‐onset multisystem inflammatory disease (NOMID) with no NLRP3 mutation, a deletion study is conducted.

Abstract: Objective To elucidate the genetic background of a patient with neonatal-onset multisystem inflammatory disease (NOMID) who does not carry any NLRP3 mutation Methods A Japanese male diagnosed as NOMID was recruited The patient had no NLRP3 mutation even as low frequency mosaicism We performed whole exome sequencing (WES) of the patient and his parents Induced pluripotent stem cells (iPSCs) were established from the fibroblasts of the patient iPSCs were then differentiated into monocytic lineage to evaluate the cytokine profile Results We established multiple iPSC clones from an NOMID patient and incidentally found that the phenotype of monocytes from iPSC clones were heterogeneous, and could be grouped into “diseased” and “normal” phenotype Because each iPSC clone was derived from a single somatic cell, we hypothesized the patient had somatic mosaicism of an IL-1β-related gene WES of both representative iPSC clones and patient's blood identified a novel heterozygous NLRC4 mutation, pT177A (c529A>G), as a specific mutation in “diseased” iPSC clones Knockout of the NLRC4 gene using CRISPR/Cas9 system in a mutant iPSC clone abrogated the pathogenic phenotype Conclusion We concluded the patient as having somatic mosaicism of a novel NLRC4 mutation To our knowledge, this is the first case showing somatic NLRC4 mutation causes autoinflammatory symptoms compatible to NOMID The present study demonstrates the significance of prospective genetic screening combined with iPSC-based phenotypic dissection for individualized diagnoses This article is protected by copyright All rights reserved