Skipping of Exon 14 and Possible Instability of Both the mRNA and the Resultant Truncated Protein Underlie a Common Cholesteryl Ester Transfer Protein Deficiency in Japan

Abstract

Among the Japanese population, a G-to-A mutation at the beginning of intron 14 of the human cholesteryl ester transfer protein (CETP) gene is a frequent cause of CETP deficiency characterized by markedly increased HDL cholesterol. The resulting abnormalities responsible for null CETP deficiency were studied in detail. The CETP mRNA transcripts amplified by polymerase chain reaction from the monocyte-derived macrophages of two homozygous patients were both found to be normal except for the whole deletion of exon 14. The deletion causes a shift of reading frame and introduces a premature termination codon downstream. Examination of the macrophage RNA from heterozygotes suggested the increased instability of the abnormal mRNA in the cytoplasm, because the amount of the aberrant transcript was nearly one third that of a normal transcript in the cytoplasm, while they were equal in the nucleus. Although this indicated the synthesis of a mutant CETP that lacks about 15% at its carboxy terminus, immunoblot analysis demonstrated that the abnormal CETP was virtually absent in both the media and cell lysates of transfected COS-1 cells, which massively expressed the mutant CETP mRNA. These results elucidate the primary abnormality due to the common CETP splicing mutation to be the exon skipping of mRNA, which decreases the level of mRNA and produces a truncated protein that should be rapidly degraded intracellularly.

Severity of cardiovascular disease in postmenopausal women: associations with common estrogen receptor α polymorphic variants

“…There are several studies in the literature supporting the functional importance of the ERa polymorphisms, studied in the present study. It has been speculated that this intronic site, which is situated at a distance between 397 and 351 nucleotides from exon 2, might result in alternative splicing, thus modifying the gene's function as has been reported for other genes (52,53). It is also possible that this site might be the locus of attachment of a transcription factor, B-myb, which is nullified when nucleotide T is present, thus affecting the speed of transcription of the receptor gene (54,55).…”

Novel mutations of cholesteryl ester transfer protein (CETP) gene in Japanese hyperalphalipoproteinemic subjects

“…The Int 14+1G>A mutation is also known to cause exon skipping leading to a premature stop co-don, and the amounts of its aberrant mRNA in cell are about 1/3 of that of wild type [18]. The extended 3' UTR length by the premature stop codon is longer, and the mRNA is more degraded [19].…”

Association between Estrogen Receptor .ALPHA. (ESR1) Gene Polymorphisms and Severe Preeclampsia

“…An intronic polymorphism could exert phenotypic effects through several mechanisms. It may enhance or reduce gene transcription, and it may also affect the splicing of RNA, producing alternatively spliced mRNA variants with resultant significant changes in gene function (25)(26)(27). In addition, an intronic polymorphism may also be linked to another, truly functional sequence variant and may therefore be a genetic marker of another polymorphism.…”