Protein expression studies of desmoplakin mutations in cardiomyopathy patients reveal different molecular disease mechanisms

Abstract

Mutations in the gene for desmoplakin (DSP) may cause arrhythmogenic right ventricular cardiomyopathy (ARVC) and Carvajal syndrome (CS). Desmoplakin is part of all desmosomes, which are abundantly expressed in both myocardial and epidermal tissue and serve as intercellular mechanical junctions. This study aimed to investigate protein expression in myocardial and epidermal tissue of ARVC and CS patients carrying DSP mutations in order to elucidate potential molecular disease mechanisms. Genetic investigations identified three ARVC patients carrying different heterozygous DSP mutations in addition to a homozygous DSP mutation in a CS patient. The protein expression of DSP in mutation carriers was evaluated in biopsies from myocardial and epidermal tissue by immunohistochemistry. Keratinocyte cultures were established from skin biopsies of mutation carriers and characterized by reverse transcriptase polymerase chain reaction, western blotting, and protein mass spectrometry. The results showed that the mutation carriers had abnormal DSP expression in both myocardial and epidermal tissue. The investigations revealed that the disease mechanisms varied accordingly to the specific types of DSP mutation identified and included haploinsufficiency, dominant-negative effects, or a combination hereof. Furthermore, the results suggest that the keratinocytes cultured from patients are a valuable and easily accessible resource to elucidate the effects of desmosomal gene mutations in humans.

Mutated Desmoglein-2 Proteins are Incorporated into Desmosomes and Exhibit Dominant-Negative Effects in Arrhythmogenic Right Ventricular Cardiomyopathy

“…Within these digenic families only carriers of the DSP ‐p.Val30Met or the DSP ‐p.Asn593Ser variant in addition to the DSG2 ‐p.Arg46Gln mutation had ARVC. Recently, we investigated the DSP ‐p.Val30Met variant in keratinocytes of mutation carriers and demonstrated that the variant V30M DSP protein was expressed and incorporated in desmosomal protein complexes [Rasmussen et al, ]. This observation suggests that low‐frequent missense variants in desmosomal genes may possess modifying effects on desmosomal functions in presence of a pathogenic mutation.…”

Genetic susceptibility and pulmonary fibrosis

“…Specifically, variants in desmoplakin ( DSP ) and dipeptidyl peptidase 9 ( DPP9) are associated with fibrotic IIP [17**]. In addition, DSP expression in lung tissue varied with the number of copies of the most statistically significant common variant, rs2076295 [17**], and DSP and DPP9 have been shown in various organs (heart, skin, kidney) to be critical in epithelial integrity [53-55]. …”

Rare Variants in Cardiomyopathy Genes Associated With Stress-Induced Cardiomyopathy

“…The first was a non-synonymous coding change in DSP (rs148147581) that has a frequency of 0.06% in NHLBI GO-ESP (five recorded heterozygotes), a CADD score of 21, and a PhyloP of 0.64. DSP is noted to be expressed moderately in the heart (FPKM = 23), while cases of dilated left and right ventricular cardiomyopathy have been detailed in cases of human DSP mutants by Norgett et al 35 and Rasmussen et al, 36 respectively. This variant is located in the plectin repeat domain of the desmoplakin protein (with IPR001101 as the reference, this would occur at amino acid residue 2103).…”