Development and Validation of a New Molecular Diagnostic Assay for Detection of Myotonic Dystrophy Type 2.
BACKGROUND
Myotonic dystrophy (DM) is the most common adult form of muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia, and multiorgan involvement. Myotonic dystrophy type 2 (DM2) is caused by a [CCTG] expansion in the ZNF9/CNBP gene. The aim of this work was the validation of the new molecular diagnostic test Myotonic Dystrophy type 2 kit-FL.


RESULTS
A cohort of 126 individuals was analyzed. The results show that 126/126 patients were correctly identified using the new molecular assay. In particular, 74 were DM2 positive, 39 were DM2/DM1 negative and 13 DM2 negative/DM1 positive. Approximately 9.5% (7/74) of the DM2-positive samples had a single sizeable expansion and 85% (63/74) showed multiple bands or smears. Comparative fluorescence in situ hybridization (FISH) analyses, on muscle biopsies, revealed that the sensitivity and specificity were very high (>99%). Equivalent analytical performances were obtained using different DNA extraction methods. Among affected individuals 87.5% (28/32) had electrical myotonia, 69% (22/32) proximal weakness, 41% (13/32) cataracts, and about 37.5% (12/32) cardiac conduction defects. FISH analysis and clinical data were used to support the genetic analysis.
1 Research Laboratories-Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .|2 Service of Laboratory Medicine, IRCCS Policlinico San Donato , Milan, Italy .
Rea
R
Valaperta
1 Research Laboratories-Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .|2 Service of Laboratory Medicine, IRCCS Policlinico San Donato , Milan, Italy .
Fortunata
F
Lombardi
3 Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .
Rosanna
R
Cardani
4 Department of Biomedical Sciences for Health, University of Milan , IRCCS-Policlinico San Donato, Milan, Italy .
Barbara
B
Fossati
4 Department of Biomedical Sciences for Health, University of Milan , IRCCS-Policlinico San Donato, Milan, Italy .
Elisa
E
Brigonzi
4 Department of Biomedical Sciences for Health, University of Milan , IRCCS-Policlinico San Donato, Milan, Italy .
Ilaria
I
Merli
5 Neurorehabilitation Unit, University of Milan , NEMO Clinical Center (NeuroMuscular Omnicomprehensive), Fondazione Serena, Milan, Italy .
Valeria
V
Sansone
1 Research Laboratories-Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .
Giulia
G
Merletti
1 Research Laboratories-Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .
Edoardo
E
Spina
3 Laboratory of Muscle Histopathology and Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .|4 Department of Biomedical Sciences for Health, University of Milan , IRCCS-Policlinico San Donato, Milan, Italy .
Giovanni
G
Meola
1 Research Laboratories-Molecular Biology, IRCCS Policlinico San Donato , Milan, Italy .|2 Service of Laboratory Medicine, IRCCS Policlinico San Donato , Milan, Italy .
Elena
E
Costa
D000328:Adult; D000368:Aged; D015331:Cohort Studies; D042622:DNA Repeat Expansion; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000175:diagnosis* / Q000235:genetics* / Q000473:pathology; D011237:Predictive Value of Tests; D016601:RNA-Binding Proteins / Q000235:genetics*; D011933:Reagent Kits, Diagnostic
C433227:CNBP protein, human; D016601:RNA-Binding Proteins; D011933:Reagent Kits, Diagnostic