Novel missense mutations in exon 15 of desmoglein-2: role of the intracellular cadherin segment in arrhythmogenic right ventricular cardiomyopathy?
BACKGROUND
The diagnosis of arrhythmogenic right ventricular cardiomyopathy can be challenging. Disease-causing mutations in desmosomal genes have been identified. A novel diagnostic feature, loss of immunoreactivity for plakoglobin from the intercalated disks, recently was proposed.


OBJECTIVE
The purpose of this study was to identify two novel mutations in the intracellular cadherin segment of desmoglein-2 (G812S and C813R in exon 15). Co-segregation of the G812S mutation with disease expression was established in a large Caucasian family. Endomyocardial biopsies of two individuals showed reduced plakoglobin signal at the intercalated disk.


METHODS
To understand the pathologic changes occurring in the diseased myocardium, functional studies on three mutations in exon 15 of desmoglein-2 (G812C, G812S, C813R) were performed.


RESULTS
Localization studies failed to detect any differences in targeting or stability of the mutant proteins, suggesting that they act via a dominant negative mechanism. Binding assays were performed to probe for altered binding affinities toward other desmosomal proteins, such as plakoglobin and plakophilin-2. Although no differences were observed for the mutated proteins in comparison to wild-type desmoglein-2, binding to plakophilin-2 depended on the expression system (i.e., bacterial vs mammalian protein expression). In addition, abnormal migration of the C813R mutant protein was observed in gel electrophoresis.


CONCLUSIONS
Loss of plakoglobin immunoreactivity from the intercalated disks appears to be the endpoint of complex pathologic changes, and our functional data suggest that yet unknown posttranslational modifications of desmoglein-2 might be involved.
Gehmlich
Katja
K
Institute of Cardiovascular Science, University College London, United Kingdom. katja.gehmlich@cardiov.ox.ac.uk
Asimaki
Angeliki
A
Cahill
Thomas J
TJ
Ehler
Elisabeth
E
Syrris
Petros
P
Zachara
Elisabetta
E
Re
Federica
F
Avella
Andrea
A
Monserrat
Lorenzo
L
Saffitz
Jeffrey E
JE
McKenna
William J
WJ
D000293:Adolescent; D000328:Adult; D000368:Aged; D019571:Arrhythmogenic Right Ventricular Dysplasia / Q000235:genetics* / Q000473:pathology / Q000503:physiopathology; D001707:Biopsy, Needle; D015820:Cadherins / Q000235:genetics* / Q000378:metabolism; D051301:Desmoglein 2 / Q000235:genetics* / Q000378:metabolism; D004699:Endocardium / Q000378:metabolism / Q000473:pathology; D005260:Female; D005838:Genotype; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D020125:Mutation, Missense; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D010375:Pedigree; D051191:Plakophilins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D055815:Young Adult; D051185:gamma Catenin / Q000276:immunology / Q000378:metabolism
D015820:Cadherins; D051301:Desmoglein 2; D051191:Plakophilins; D051185:gamma Catenin