Haploinsufficiency of A20 with a novel mutation of deletion of exons 2–3 of TNFAIP3

Abstract

Objectives Haploinsufficiency of A20 (HA20) due to loss-of-function mutations of TNFAIP3 leads to an autoinflammatory disease. These mutations produce a premature termination codon in most cases of HA20. However, exon deletion has not been reported. Methods Genomic DNA was extracted from the peripheral blood of the patient clinically suspected of HA20. We examined autoinflammatory disease-causing genes and performed a multiplex ligation-dependent probe amplification (MLPA) assay for copy number analysis. Next, to determine the disconnection point, genomic DNA was amplified with long-range PCR and sequenced. Finally, western blotting was carried out to measure A20 protein expression in mitogen phytohaemagglutinin (PHA)-induced T-cell blasts from the patient and a healthy volunteer. Results Targeted next-generation sequencing found no pathogenic mutation, but copy number variation (CNV) analysis suggested a heterozygous deletion of exons 2–3. The MLPA assay and long-range PCR confirmed the mutation. Western blotting analysis indicated a marked decrease in expression of A20 protein from the patient compared to a normal control. The results showed that this deletion was a pathogenic mutation. Conclusion This study demonstrates a novel mutation resulting in a deletion of exons 2–3 of TNFAIP3. MLPA analysis is a useful initial screening method for HA20 patients.