Molecular and functional analysis of SLC25A20 mutations causing carnitine-acylcarnitine translocase deficiency

Vito Iacobazzi, Federica Invernizzi, Silvia Baratta, Roser Pons, Wendy Chung, Barbara Garavaglia, Carlo Dionisi-Vici, Antonia Ribes, Rossella Parini, Maria Dolores Huertas, Susana Roldan, Graziantonio Lauria, Ferdinando Palmieri, Franco Taroni

Research output: Contribution to journalArticlepeer-review

Abstract

The enzyme carnitine-acylcarnitine translocase (CACT) is involved in the transport of long-chain fatty acids into mitochondria. CACT deficiency is a life-threatening, recessively inherited disorder of lipid β-oxidation which manifests in early infancy with hypoketotic hypoglycemia, cardiomyopathy, liver failure, and muscle weakness. We report here the clinical, biochemical, and molecular features of six CACT-deficient patients from Italy, Spain, and North America who exhibited significant clinical heterogeneity. In five patients (Patients 1, 2, 4, 5, and 6) the disease manifested in the neonatal period, while the remaining patient (Patient 3), the younger sibling of an infant who had died with clinical suspicion of fatty acid oxidation defect, has been treated since birth and was clinically asymptomatic at 4.5 years of age. Patients 1 and 4 were deceased within 6 months from the onset of this study, while the remaining four are still alive at 8, 4.5, 3.5, and 2 years, respectively. Sequence analysis of the CACT gene (SLC25A20) disclosed five novel mutations and three previously reported mutations. Three patients were homozygous for the identified mutations. Two of the novel mutations (c.718 + 1G > C and c.843 + 4_843 + 50del) altered the donor splice site of introns 7 and 8, respectively. The 47-nt deletion in intron 8 caused both skipping of exon 8 only and skipping of exons 6-8. Four mutations {[c.159dupT;c.163delA] ([p.Gly54Trp;p.Thr55Ala]) c.397C > T (p.Arg133Trp), c.691G > C (p.Asp231His), and c.842C > T (p.Ala281Val)} resulted in amino acid substitutions affecting evolutionarily conserved regions of the protein. Interestingly, one of these exonic mutations (p.Ala281Val) was associated with a splicing defect also characterized by skipping of exons 6-8. The deleterious effect of the p.Arg133Trp substitution was demonstrated by measuring CACT activity upon expression of the normal and the mutant protein in E. coli and functional reconstitution into liposomes. Combined analysis of clinical, biochemical, and molecular data failed to indicate a correlation between the phenotype and the genotype.

Original languageEnglish
Pages (from-to)312-320
Number of pages9
JournalHuman Mutation
Volume24
Issue number4
DOIs
Publication statusPublished - 2004

Keywords

  • Cardiomyopathy
  • Fatty acids
  • Metabolic disease
  • Mitochondria
  • Mutation analysis
  • SLC25A20

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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