A P2RX2 exon-2 complex indel disrupts splicing and reduces P2X2 output: implications for DFNA41 and variable expressivity

Abstract

P2RX2 encodes the ATP-gated P2X2 receptor associated with autosomal dominant non-syndromic hearing loss 41 (DFNA41). DFNA41 is characterized by progressive sensorineural hearing loss and an increased susceptibility to acoustic trauma. However, the specific phenotypic consequences of truncating or splice-altering variants within this gene remain poorly understood. We evaluated a Han Chinese family using a targeted hearing-loss gene panel with segregation analysis. Splicing consequences of a complex indel in P2RX2 exon 2 (NM_174873: c.278_288delinsACGTGAAGCCCCC) were assessed using a pcMINI-C minigene assay, followed by RT-qPCR and Western blotting after expression of the reconstructed aberrant isoforms in heterologous cells. The proband had early-onset severe-to-profound sensorineural hearing loss and carried a heterozygous P2RX2 complex indel inherited from the father, together with a maternally inherited pathogenic GJB2 frameshift. Minigene assays revealed cryptic splice usage that generated two frameshifted isoforms with premature termination codons. Both mutant isoforms showed reduced steady-state mRNA and markedly reduced P2X2 protein output, consistent with decreased overall P2X2 expression. We functionally establish that this exon-2 complex indel disrupts splicing and markedly reduces P2X2 output. These findings support a mechanism of loss-of-function and haploinsufficiency. The pronounced intrafamilial variability—manifesting as profound early-onset hearing loss in the proband compared to a milder phenotype in the heterozygous father—underscores the variable expressivity and incomplete penetrance characteristic of P2RX2 -linked DFNA41. Although oligogenic modulation is a plausible conceptual framework, it requires cautious interpretation and independent future validation.