University of Sussex
Molec Gen Gen Med - 2023 - Thuresson - Novel PNKP mutations associated with reduced DNA single‐strand break repair and.pdf (2.64 MB)

Novel PNKP mutations associated with reduced DNA single-strand break repair and severe microcephaly, seizures, and developmental delay

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posted on 2024-02-08, 13:59 authored by Ann-Charlotte Thuresson, Jan Brazina, Talia Akram, Julia Albrecht, Niklas Dahl, Cecilia Soussi Zander, Keith CaldecottKeith Caldecott

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.


Mechanisms of DNA Single-Strand Break-Induced Genetic Disease and Opportunities for Therapeutic Intervention : MRC-MEDICAL RESEARCH COUNCIL | MR/W024128/1


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Molecular Genetics and Genomic Medicine









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  • Sussex Centre for Genome Damage Stability Publications


University of Sussex

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