Phenotypic Diversity Caused by the Missense Mutation p.R127P (c.380G>C) Contributing to Significant Cardiac Mortality and Morbidity Associated With a Desmin Filament Assembly Defect.

BACKGROUND

Nonischemic cardiomyopathies are frequently caused by genetic mutations in about 100 different genes. The cardiomyopathy-associated gene encodes the intermediate filament protein desmin, which is important for the structural integrity of the cardiomyocytes.

METHODS

Using a next-generation sequencing approach, we performed cascade screening of a previously identified heterozygous missense mutation (c.380G>C, p.R127P) segregating in a large 6-generation Kuwaiti family, where several members died from sudden cardiac death or developed different cardiomyopathies, partially in combination with conduction disease and atrial fibrillation. -p.R127P affects a highly conserved position and is absent or super rare in different genetic human population databases. In silico predictions support the pathogenicity of -p.R127P. To investigate the detrimental impact of desmin-p.R127P, we performed cell transfection experiments using different cell lines and cardiomyocytes derived from induced pluripotent stem cells in combination with confocal microscopy.

RESULTS

These experiments demonstrated a severe desmin filament assembly defect leading to aberrant cytoplasmic desmin aggregates, even when co-expressed with wild-type desmin. Atomic force microscopy analysis supported the filament assembly defect of mutant recombinant desmin-p.R127P. To investigate the physicochemical impact of the amino acid at this position, we generated a set of 20 different variants and analyzed their filament formation in cell culture. Most of these variants disturbed the filament assembly comparable to p.R127P.

CONCLUSIONS

In summary, we present and characterize a likely pathogenic missense mutation -p.R127P, which causes high cardiac mortality and morbidity in the described family. Our study has relevance for the interpretation and classification of further variants and might be helpful for the genetic counseling of patients and their relatives in future cases.