Identification of mis sense mutations and haplotyping of carnitine palmitoyltransferase II gene

Carnitine palmitoyltransferase II (CPTII) deficiency manifests as various clinical phenotypes: a relatively mild form with muscular symptoms and a severe phenotype presenting with hepatocardiomuscular manifestations. We have investigated three Japanese patients with CPT II deficiency. Molecular analysis revealed two novel missense mutations, a glutamate (174)-to-lyine substitution (E174K) and a phenylalanine (383)-to-tyrosine substitution (F383Y) in the CPTII cDNA. Transfection experiments demonstrated that the two mutations reduced CPTII catalytic activity. Case 1 (muscular form) was homozygous for the E174K mutation, whereas case 2 (hepatic form) was homozygous for the F383Y mutation. Interestingly, case 3, who was a compound hétérozygote for E174K and F383Y, exhibited hepatic symptoms. We also identified a polymorphism in the CPTII gene, a phenylalanine (352)-to-cysteine substitution (F352C). According to an expression analysis, this mutation did not alter CPTII activity. It was present in 21 out of 100 normal alleles in the Japanese population, but was not observed among Caucasians. Genotyping with this polymorphism and the p/eviously reported polymorphisms V368I and M647V allowed normal alleles to be classified into five naplotypes. In all three families, the E174K mutation resided only on F1V1M1 allele, while the F383Y mutation was observed on F2V2M1 allele, suggesting a single origin of each mutation.