Deletion polymorphism 5' to the human apolipoprotein AI (apo AI) gene

Genetic markers in the apo AI-CIII-AIV gene cluster for combined hyperlipidemia, hypertriglyceridemia, and predisposition to atherosclerosis

The aim of the present study was to search for genetic determinants of combined hyperlipidemia and hypertriglyceridemia, and to evaluate whether such determinants might be associated with predisposition to atherosclerosis. Four DNA polymorphisms in the apo AI-CIII-AIV gene cluster (G to A mutation at position -75 basepairs in the apo AI promoter, XmnI, PstI and SstI) were studied in relation to combined hyperlipidemia, hypertriglyceridemia, lipoprotein levels, atherosclerosis and age in 221 Danish men. The frequency of the rare allele of the XmnI polymorphism, the X+ allele, was higher in individuals below 55 years of age with combined hyperlipidemia than in individuals with normal lipid levels (0.31 vs. 0.14; P = 0.05). The rare allele of the SstI polymorphism, the S+ allele, was more frequent in hypertriglyceridemic individuals compared with normotriglyceridemic individuals (0.16 vs. 0.09; P < 0.05) and on analysis of variance the combined S-S+ and S+S+ genotypes were also associated with the highest triglyceride levels. Furthermore, the frequency of the S+ allele decreased significantly as a function of age in nonatherosclerotic subjects (from 0.15 to 0.10 to 0.02 in 48-, 63- and 85-year-olds, respectively; 48- versus 85-year-olds, P = 0.03). These results suggest that genetic variation in the apo AI-CIII-AIV gene complex is associated with combined hyperlipidemia and hypertriglyceridemia and may have an impact on longevity and/or predisposition to atherosclerosis.

Characterization of genetic markers in the 5'flanking region of the apo A1 gene

Genetic variation of apo A1/C3/A4 is associated with hyperlipidaemia and coronary heart disease. We report the polymerase chain reaction (PCR) conditions for determining three polymorphic sites in the 5'flanking region of apoA1 using DNA prepared from small aliquots of whole blood. These polymorphisms identify six haplotypes that will be of value in genetic studies.

Apolipoprotein A-I deficiency due to a codon 84 nonsense mutation of the apolipoprotein A-I gene

The molecular genetic defect of a female patient with apolipoprotein A-I (apoA-I) deficiency and premature atherosclerosis was examined. Her parents were first cousins. Her plasma density fraction from 1.063 to 1.21 g/ml contained no apoA-I on SDS/PAGE and no measurable high density lipoprotein cholesterol. Southern blot hybridization showed no gross abnormality to be present in the patient's apoA-I gene and homozygosity for a haplotype of restriction fragment length polymorphisms in the apoA-I gene region. Sequencing after amplification by PCR revealed a codon 84 nonsense mutation (CAG----TAG, Gln----stop) of exon 4 and a codon 67 missense mutation (GCC----ACC, Ala----Thr) of exon 3 in the patient's apoA-I gene. The data from dot-blot hybridization with allele-specific oligonucleotide probes indicated that she was homozygous for the apoA-I gene with regard to the two mutations. The codon 37 missense mutation was also detected in the apoA-I gene of 6 out of 60 controls, who all had normal levels of apoA-I and high density lipoprotein cholesterol, suggesting that the missense mutation is polymorphic and not associated with apoA-I deficiency. These findings indicate that homozygosity for the apoA-I gene with codon 84 nonsense mutation causes the deficiency of apoA-I and of high density lipoprotein cholesterol in the patient.

Isolation of region-specific and polymorphic markers from chromosome 17 by restricted Alu polymerase chain reaction

We demonstrate that the digestion of template DNAs with restriction endonucleases prior to Alu polymerase chain reaction ("restricted Alu-PCR") reduces the complexity of the Alu-primed amplification patterns of human DNA in somatic cell hybrids and allows a direct informative comparison of these patterns. A comparison of restricted Alu-PCR patterns of a monochromosomal hybrid retaining a human chromosome 17 (MH22-6) and a hybrid retaining a human chromosome 17 deleted for band p11.2 (DH110-D1) revealed four Alu-PCR products that were present in the former but absent in the latter hybrid. Hybridization of these fragments to the total Alu-PCR amplification products of the two hybrids confirmed their absence in DH110-D1 amplification products. Hybridization to a panel of somatic cell hybrids indicated that two of these fragments were deleted in the hybrid DH110-D1 and mapped to 17p11.2, as expected. However, two additional fragments were not deleted in the hybrid DH110-D1 and mapped to other regions of chromosome 17. An insertion-deletion polymorphism was associated with one of the latter fragments, which may be the mechanism for the lack of its amplification in the hybrid DH110-D1. Restricted Alu-PCR should enhance the applications of Alu-PCR and provides a new method for the identification of chromosome-specific polymorphic markers.

The polydeoxyadenylate tract of Alu repetitive elements is polymorphic in the human genome

To identify DNA polymorphisms that are abundant in the human genome and are detectable by polymerase chain reaction amplification of genomic DNA, we tested the hypothesis that the polydeoxyadenylate tract of the Alu family of repetitive elements is polymorphic among human chromosomes. We analyzed the 3' ends of three specific Alu sequences and found that two (in the adenosine deaminase gene and the beta-globin pseudogene) were polymorphic. This novel class of polymorphisms, termed AluVpA [Alu variable poly(A)] may represent one of the most useful and informative group of DNA markers in the human genome.

Apolipoprotein genetic variation in the assessment of atherosclerosis susceptibility

Apolipoproteins are the protein constituents of lipoproteins, the particles that transport cholesterol and triglycerides in the plasma. Numerous epidemiologic studies have associated variations in plasma levels of lipoproteins and apolipoproteins with the development of atherosclerosis. Furthermore, genetic variations in lipoproteins and apolipoproteins have been associated with disorders of lipid metabolism. Recent advances in biochemical and molecular genetic methods have resulted in an increased understanding of interindividual variations in lipoprotein metabolism and of their relationship to atherosclerosis and the dyslipoproteinemias. In particular, certain DNA restriction fragment length polymorphisms of the apolipoprotein genes have, in the last few years, been associated with atherosclerotic diseases and dyslipoproteinemias. We believe that genetic markers, when used in conjunction with traditional clinical and biochemical determinations, may one day be useful in predicting atherosclerosis susceptibility in the general population.