Real-time quantitative polymerase chain reaction. A new method that detects both the peripheral myelin protein 22 duplication in Charcot-Marie-Tooth type 1A disease and the peripheral myelin protein 22 deletion in hereditary neuropathy with liability to pressure palsies.
In Charcot-Marie-Tooth type 1A disease (CMTIA), heterozygosity for the peripheral myelin protein 22 (PMP22) duplication increases the gene dose from two to three, whereas, in hereditary neuropathy with liability to pressure palsies (HNPP), heterozygosity for the PMP22 deletion reduces the gene dose from two to one. Thirty-eight Norwegian patients with CMT1, 4 patients with HNPP, 15 asymptomatic family members, and 45 normal controls were studied using the ABI 7700 sequence detection system and the TaqMan method of real-time quantitative polymerase chain reaction (PCR). Using a comparative threshold cycle (Ct) method and albumin as reference gene, the gene copy number by PMP22 gene duplication or deletion on chromosome 17p11.2-12 was quantified. The PMP22 duplication ratio ranged from 1.50 to 2.21, the PMP22 deletion ratio ranged from 0.44 to 0.55, and the PMP22 ratio in normals ranged from 0.82 to 1.27. All samples were run in triplicate, with a mean standard deviation of 0.07 (range 0.01-0.17). Thirty-four of thirty-eight CMT1 patients (89.6%) had the PMP22 duplication and the four HNPP patients had the PMP22 deletion. This was not found in any of the asymptomatic family members or the controls. Real-time quantitative PCR is a sensitive, specific, and reproducible method for diagnosing PMP22 duplication and deletion. The method is fast, allowing 13 patients to be diagnosed in 2 h. It involves no radioisotopes and requires no post-PCR handling. In our opinion, real-time quantitative PCR is the first method of choice in diagnosing PMP22 duplication and deletion.
Aarskog
N K
NK
Department of Neurology, Haukeland University Hospital, University of Bergen, Norway. Nina.Aarskog@Haukeland.no
Vedeler
C A
CA
D002607:Charcot-Marie-Tooth Disease / Q000175:diagnosis / Q000235:genetics*; D002874:Chromosome Mapping; D002886:Chromosomes, Human, Pair 17; D017353:Gene Deletion; D020440:Gene Duplication; D009477:Hereditary Sensory and Autonomic Neuropathies / Q000175:diagnosis / Q000235:genetics*; D006801:Humans; D009185:Myelin Proteins / Q000235:genetics*; D009664:Norway; D016133:Polymerase Chain Reaction / Q000379:methods; D012016:Reference Values; D012709:Serum Albumin / Q000235:genetics; D044465:White People / Q000235:genetics
D009185:Myelin Proteins; C073687:PMP22 protein, human; D012709:Serum Albumin