title: PYGM expression analysis in white blood cells: a complementary tool for diagnosing McArdle disease?
abstract: McArdle disease is caused by an inherited deficiency of the enzyme myophosphorylase, resulting in exercise intolerance from childhood and acute crises of early fatigue and contractures. In severe cases, these manifestations can be accompanied by rhabdomyolysis, myoglobinuria, and fatal renal failure. Diagnosis of McArdle disease is based on clinical diagnostic tests, together with an absence of myophosphorylase activity in skeletal muscle biopsies and genetic analysis of the myophosphorylase-encoding gene, PYGM. The recently reported association between myophosphorylase and Rac1 GTPase in a T lymphocyte cell line prompted us to study myophosphorylase expression in white blood cells (WBCs) from 20 healthy donors and 30 McArdle patients by flow cytometry using a fluorescent-labeled PYGM antibody. We found that T lymphocytes expressed myophosphorylase in healthy donors, but expression was significantly lower in McArdle patients (p<0.001). PYGM mRNA levels were also lower in white blood cells from McArdle patients. Nevertheless, in 13% of patients (who were either heterozygotes or homozygotes for the most common PYGM pathogenic mutation among Caucasians (p.R50X)), the percentage of myophosphorylase-positive white blood cells was not different compared with the control group. Our findings suggest that analysis of myophosphorylase expression in white blood cells might be a useful, less-invasive, complementary test for diagnosing McArdle disease.
authors.affiliation: Mitochondrial Pathology and Neuromuscular Disorders laboratory, Vall d'Hebron Research Institute, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Spain.
authors.forename: Noemí
authors.initials: N
authors.lastname: de Luna
authors.affiliation: Mitochondrial Pathology and Neuromuscular Disorders laboratory, Vall d'Hebron Research Institute, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Spain.
authors.forename: Astrid
authors.initials: A
authors.lastname: Brull
authors.affiliation: Universidad Europea and Instituto de Investigación 'i+12', Madrid, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Lucia
authors.affiliation: Universidad Pablo de Olavide, Seville, Spain.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Santalla
authors.affiliation: Facultad de Ciencias de la Salud y del Deporte, Universidad de Zaragoza, Huesca, Spain.
authors.forename: Nuria
authors.initials: N
authors.lastname: Garatachea
authors.affiliation: Mitochondrial Pathology and Neuromuscular Disorders laboratory, Vall d'Hebron Research Institute, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Spain.
authors.forename: Ramon
authors.initials: R
authors.lastname: Martí
authors.affiliation: Mitochondrial Pathology and Neuromuscular Disorders laboratory, Vall d'Hebron Research Institute, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Spain. Electronic address: toniandreu.bcn@gmail.com.
authors.forename: Antoni L
authors.initials: AL
authors.lastname: Andreu
authors.affiliation: Mitochondrial Pathology and Neuromuscular Disorders laboratory, Vall d'Hebron Research Institute, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Spain. Electronic address: tomas.pinos@vhir.org.
authors.forename: Tomàs
authors.initials: T
authors.lastname: Pinós
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D002648:Child; D015331:Cohort Studies; D005260:Female; D005434:Flow Cytometry; D060005:Genotyping Techniques; D024982:Glycogen Phosphorylase, Muscle Form / Q000097:blood* / Q000235:genetics; D006012:Glycogen Storage Disease Type V / Q000097:blood* / Q000175:diagnosis / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D007962:Leukocytes / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000201:enzymology; D009154:Mutation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000201:enzymology; D055815:Young Adult
chemical_list: D015415:Biomarkers; D012333:RNA, Messenger; D024982:Glycogen Phosphorylase, Muscle Form
keywords: Diagnosis; Flow cytometry; McArdle disease; Myophosphorylase; White blood cells