Protein redistribution in buccal cells as a prognostic marker for arrhythmogenic cardiomyopathy in paediatric patients

Abstract Background Mutations in genes encoding desmosomal proteins [plakoglobin (JUP), desmoplakin (DSP), plakophilin-2 (PKP2), desmoglein-2 (DSG2) and desmocollin-2 (DSC2)] cause complex genetic heart muscle disorders collectively described as arrhythmogenic cardiomyopathies (ACM). Diagnosis and risk stratification, particularly in the paediatric population, remain challenging owing to heterogeneous phenotypic manifestations and reduced genetic penetrance. Immunohistochemical analysis of heart muscle samples has shown that several junctional and signalling molecules are redistributed in patients with ACM, offering diagnostic information. However, the use of this approach in living patients was limited by need for heart samples. Recent studies in adults with ACM showed that the same set of proteins re-localised in the ACM heart also do so in the buccal epithelium. Purpose Given the ease of analysing serial cheek smears, we sought to establish how protein redistribution in buccal cells relates to disease onset and progression in children bearing desmosomal gene mutations. Methods Serial cheek smears from children with desmosomal variants were subjected to immunocytochemistry and confocal microscopy to study the distribution of JUP, DSP and PKP-1 as well as the major gap junction protein connexin43 (Cx43; GJA1) and the major subunit of the NFκB inflammatory pathway; RelA. Results 37 patients Conclusion These data indicate that shifts in junctional/signalling proteins precede the onset of clinical disease. Indeed, in the majority of pre-clinical children, Cx43 and RelA seem to be redistributed first, suggesting that onset of abnormalities in electrical conductivity and inflammatory pathways occur first in the natural disease progression, in agreement with previous clinical observations. Moreover, the data suggest that additional proteins are shifted as the disease progresses. Although further verification is required, this study suggests that analysis of buccal smears may be used as a prognostic/risk stratification test in children with desmosomal variants.