Background: The half of hyperalphalipoproteinemia (HALP) in Japan is caused by CETP gene mutations. Other than two prevalent mutations (D442G and Intron 14 splicing donor site +1G>A), some rare CETP mutations are found in Japanese HALP subjects.
Methods: CETP gene analysis of genomic DNA from subjects was performed by restriction fragment length polymorphism (RFLP) and sequencing analysis. Mutations which were suspected to cause a splicing defect or a protein secretion defect were investigated in COS-1 cells transfected with a CETP minigene construct or a cDNA expression vector.
Results: Each of three subjects was identified as a carrier of CETP gene mutation of a compound heterozygote of c.653_654delGGinsAAAC and Intron 14 splicing donor site +1G>A, a heterozygote of c.658G>A or a homozygote of L261R. The c.658G>A mutation was located at the last nucleotide of exon 7, and it was confirmed to cause splicing abnormality revealed by the CETP minigene analysis. The L261R CETP was not secreted to conditioned media of the cells.
Conclusions: Three novel CETP gene mutations are responsible for HALP by CETP deficiency. It is predicted that there are more rare CETP gene mutations in Japanese, and these multiple rare mutations alone or a combination with each of prevalent mutations is responsible for mild-to-moderate or marked HALP, respectively.
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