Three novel mutations in the carnitine-acylcarnitine translocase (CACT) gene in patients with CACT deficiency and in healthy individuals

Carnitine-acylcarnitine translocase (CACT) and carnitine palmitoyltransferase II (CPT2) are key enzymes for transporting long-chain fatty acids into mitochondria. Deficiencies of these enzymes, which are clinically characterized by life-threatening non-ketotic hypoglycemia and rhabdomyolysis, cannot be distinguished by acylcarnitine analysis performed using tandem mass spectrometry. We had previously reported the CPT2 genetic structure and its role in CPT2 deficiency. Here, we analyzed the CACT gene in 2 patients diagnosed clinically with CACT deficiency, 18 patients with non-traumatic rhabdomyolysis and 58 healthy individuals, all of whom were confirmed to have normal CPT2 genotypes. To facilitate CACT genotyping, we used heat-denaturing high-performance liquid chromatography (DHPLC), which helped identify five distinct patterns. The abnormal heteroduplex fragments were subjected to CACT-specific DNA sequencing. We found that one patient with CACT deficiency, Case 1, carried c.576G>A and c.199-10t>g mutations, whereas Case 2 was heterozygous for c.106-2a>t and c.576G>A. We also found that one patient with non-traumatic rhabdomyolysis and one healthy individual were heterozygous for c.804delG and the synonymous mutation c.516T>C, respectively. In summary, c.576G>A, c.106-2a>t and c.516T>C are novel CACT gene mutations. Among the five mutations identified, three were responsible for CACT deficiency. We have also demonstrated the successful screening of CACT mutations by DHPLC.