PHOX2B defects alter protein folding, cell-cycle, and mitochondrial pathways in an in vitro model of CCHS

Abstract Background Congenital Central Hypoventilation Syndrome (CCHS) is a rare autosomal dominant disorder caused by heterozygous mutations in the PHOX2B gene, leading to impaired ventilatory responses to hypoxia and hypercapnia. No pharmacological therapy exists, and patients rely on ventilatory support, tracheostomy, or diaphragmatic pacing. Most mutations are polyalanine expansions in exon 3, which mislocalize PHOX2B to the cytoplasm, disrupting the regulation of its transcriptional targets. Previous studies showed that geldanamycin and its derivative 17-AAG can partially rescue both the localization and the function of polyalanine expansion mutant PHOX2B. Nonetheless, downstream molecular effects of these mutations remain poorly understood. Methods The transcriptomic approach was applied to cells transiently expressing wild-type PHOX2B or the mutant carrying the most severe polyalanine expansion, to investigate the cellular consequences of whole transcripts deregulation caused by the PHOX2B mutation with or without 17-AAG treatments. Results Bioinformatic analysis allowed us to confirm the involvement of pathways already observed in polyalanine pathogenesis, such as protein folding and transcriptional repression, and to identify oxidative stress, mitochondrial dysfunction, and altered cell-cycle regulation as novel components of the PHOX2B+13Ala pathogenesis. Conclusions The RNA-sequencing approach recapitulates the molecular pathogenesis of PHOX2B polyalanine expansion mutations in CCHS and in vitro functional validations, thus confirming the suitability of this cellular model to study the molecular pathogenesis of the disease.