Mutations in the organic cation/carnitine transporter OCTN2 in primary carnitine deficiency.
Primary carnitine deficiency is an autosomal recessive disorder of fatty acid oxidation caused by defective carnitine transport. This disease presents early in life with hypoketotic hypoglycemia or later in life with skeletal myopathy or cardiomyopathy. The gene for this condition maps to 5q31.2-32 and OCTN2, an organic cation/carnitine transporter, also maps to the same chromosomal region. Here we test the causative role of OCTN2 in primary carnitine deficiency by searching for mutations in this gene in affected patients. Fibroblasts from patients with primary carnitine deficiency lacked mediated carnitine transport. Transfection of patient's fibroblasts with the OCTN2 cDNA partially restored carnitine transport. Sequencing of the OCTN2 gene revealed different mutations in two unrelated patients. The first patient was homozygous (and both parents heterozygous) for a single base pair substitution converting the codon for Arg-282 to a STOP codon (R282X). The second patient was a compound heterozygote for a paternal 1-bp insertion producing a STOP codon (Y401X) and a maternal 1-bp deletion that produced a frameshift creating a subsequent STOP codon (458X). These mutations decreased the levels of mature OCTN2 mRNA and resulted in nonfunctional transporters, confirming that defects in the organic cation/carnitine transporter OCTN2 are responsible for primary carnitine deficiency.
Division of Medical Genetics, Department of Pediatrics, Emory University, 2040 Ridgewood Drive, Atlanta, GA 30322, USA.
Y
Y
Wang
J
J
Ye
V
V
Ganapathy
N
N
Longo
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D002331:Carnitine / Q000172:deficiency* / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics*; D002460:Cell Line; D002874:Chromosome Mapping; D002895:Chromosomes, Human, Pair 5; D018388:Codon, Terminator; D005091:Exons; D005260:Female; D005347:Fibroblasts; D016368:Frameshift Mutation; D006580:Genetic Carrier Screening; D006720:Homozygote; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics*; D009679:Nuclear Family; D027701:Organic Cation Transport Proteins; D010375:Pedigree; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D000074058:Solute Carrier Family 22 Member 5; D014158:Transcription, Genetic; D014804:Vitamin B Deficiency / Q000235:genetics*
D002352:Carrier Proteins; D018388:Codon, Terminator; D008565:Membrane Proteins; D027701:Organic Cation Transport Proteins; D012333:RNA, Messenger; C492020:SLC22A5 protein, human; D000074058:Solute Carrier Family 22 Member 5; D002331:Carnitine