Rapid, Cost-effective Gene Mutation Screening for Carnitine Palmitoyltransferase II Deficiency Using Whole Blood on Filter Paper

Carnitine palmitoyltransferase II (CPT II; EC 2.3.1.21), an enzyme associated with the inner mitochondrial membrane, is important in the transport of long-chain fatty acids from the cytosol into the mitochondrial matrix for β-oxidation (1). CPT II deficiency presents as three distinct clinical phenotypes: adult myopathic (MIM 255110), lethal neonatal (MIM 600649), and a severe infantile phenotype (2). The adult form is the most common lipid myopathy in humans and is characterized by muscle pain, stiffness, and myoglobinuria triggered by exercise, fasting, anesthesia, or other metabolic stressors (3). CPT II is a homotetramer (4) encoded by a gene (MIM 600650) on chromosome 1p32 (5) that spans 20 kb and contains five exons ranging in length from 81 to 1305 bp (6). At least 15 mutations in CPT2 are associated with the adult and infantile disorders (7)(8)(9). CPT II deficiency is an autosomal recessive disorder (3)(9); however, recent biochemical and molecular evidence suggests the existence of manifesting carriers, predicting that the prevalence of the disease may be even higher than previously believed (9). Screening for mutations in CPT2 has been performed using DNA isolated from biopsied muscle tissue (9), venous blood (10), lymphoblasts (11), or fibroblasts (8). Isolation of DNA from these specimens is time-consuming, and mutation screening generally has been performed using restriction fragment length polymorphisms (12) or allele-specific oligonucleotide (ASO) detection (9), requiring portions of several days for completion (9). Large-scale screening has not been performed to determine the carrier frequency of the common mutations in the general population. Although the methods for DNA isolation, PCR amplification, and ASO analysis developed previously by our laboratory are effective for detecting known mutations in the CPT2 gene (9), they were too costly and laborious for application to large family studies or population screening. We proposed …