A third of LGMD2A biopsies have normal calpain 3 proteolytic activity as determined by an in vitro assay.
Limb-girdle muscular dystrophy type 2A (LGMD2A) is an autosomal recessive muscular disorder caused by mutations in the gene coding for calpain 3, a calcium-dependent protease. We developed an in vitro assay that can detect the proteolytic activity of calpain 3 in a muscle sample. This assay is based on the use of an inactive calpain 3 as a substrate for active calpain 3 molecules. A total of 79 human biopsies have been analysed using an unbiased single blind method. Results were confronted with the molecular diagnosis for confirmation. Proteolytic activity was either reduced or absent in 68% of LGMD2A biopsies. In the remaining 32%, normal proteolytic activity was found despite the presence of calpain 3 mutation(s), suggesting that other calpain 3 properties might be impaired to give rise to the LGMD2A phenotype. Our assay is easily adaptable to routine and appears to be more sensitive than common analysis by immunodetection.
Milic
Astrid
A
Laboratory of Clinical Neurogenetics and Muscular Disorders, Zagreb University School of Medicine, Croatian Institute for Brain Research, Salata 12, 10000 Zagreb, Croatia.
Daniele
Nathalie
N
Lochmüller
Hanns
H
Mora
Marina
M
Comi
Giacomo P
GP
Moggio
Maurizio
M
Noulet
Fanny
F
Walter
Maggie C
MC
Morandi
Lucia
L
Poupiot
Jérôme
J
Roudaut
Carinne
C
Bittner
Reginald E
RE
Bartoli
Marc
M
Richard
Isabelle
I
D000818:Animals; D015153:Blotting, Western; D002154:Calpain / Q000378:metabolism*; D004195:Disease Models, Animal; D004591:Electrophoresis, Polyacrylamide Gel; D006579:Heterozygote; D006801:Humans; D051379:Mice; D009124:Muscle Proteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000201:enzymology*; D049288:Muscular Dystrophies, Limb-Girdle / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D041681:NIH 3T3 Cells; D010641:Phenotype; D015203:Reproducibility of Results; D014015:Tissue Banks; D014162:Transfection
D009124:Muscle Proteins; C105884:CAPN3 protein, human; D002154:Calpain