Novel PNKP mutations associated with reduced DNA single-strand break repair and severe microcephaly, seizures, and developmental delay
Background: Microcephaly with early-onset seizures (MCSZ) is a neurodevelopmental disorder caused by pathogenic variants in the DNA strand break repair protein, polynucleotide kinase 3′-phosphatase (PNKP).
Methods: We have used whole genome sequencing and Sanger sequencing to identify disease-causing variants, followed by a minigene assay, Western blotting, alkaline comet assay, γH2AX, and ADP-ribose immunofluorescence.
Results: Here, we describe a patient with compound heterozygous variants in PNKP, including a missense variant in the DNA phosphatase domain (T323M) and a novel splice acceptor site variant within the DNA kinase domain that we show leads to exon skipping. We show that primary fibroblasts derived from the patient exhibit greatly reduced levels of PNKP protein and reduced rates of DNA single-strand break repair, confirming that the mutated PNKP alleles are dysfunctional.
Conclusion: The data presented show that the detected compound heterozygous variants result in reduced levels of PNKP protein, which affect the repair of both oxidative and TOP1-induced single-strand breaks, and most likely causes MCSZ in this patient.
Funding
Mechanisms of DNA Single-Strand Break-Induced Genetic Disease and Opportunities for Therapeutic Intervention : MRC-MEDICAL RESEARCH COUNCIL | MR/W024128/1
History
Publication status
- Published
File Version
- Published version
Journal
Molecular Genetics and Genomic MedicineISSN
2324-9269Publisher
WileyPublisher URL
External DOI
Issue
1Volume
12Article number
e2295Department affiliated with
- Sussex Centre for Genome Damage Stability Publications
Institution
University of SussexFull text available
- Yes
Peer reviewed?
- Yes