ABCMdb

PMID: 19765707

Cameron J, Ranheim T, Halvorsen B, Kulseth MA, Leren TP, Berge KE
Tangier disease caused by compound heterozygosity for ABCA1 mutations R282X and Y1532C.
Atherosclerosis. 2010 Mar;209(1):163-6. Epub 2009 Aug 29., [PubMed]

Sentences

No. Mutations Sentence Comment

0 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys Atherosclerosis 209 (2010) -166 Contents lists available at ScienceDirect Atherosclerosis journal homepage: www.elsevier.com/locate/atherosclerosis Tangier disease caused by compound heterozygosity for ABCA1 mutations R282X and Y1532C Jamie Camerona , Trine Ranheima , Bente Halvorsenb,c , Mari Ann Kulsetha , Trond P. Lerena , Knut Erik Bergea,* a Medical Genetics Laboratory, Department of Medical Genetics, Rikshospitalet, Oslo University Hospital, NO-0027 Oslo, Norway b Research Institute of Internal Medicine, Rikshospitalet, Oslo University Hospital, Norway c University of Oslo, Norway a r t i c l e i n f o Article history: Received 10 July 2009 Received in revised form 18 August 2009 Accepted 19 August 2009 Available online 29 August 2009 Keywords: ABCA1 gene Cholesterol efflux HDL cholesterol Mutation Tangier disease a b s t r a c t Background: Inherited low levels of high density lipoprotein (HDL) cholesterol may be due to mutations in the genes encoding the ATP-binding cassette transporter A1 (ABCA1), apolipoprotein (apo) A-I or lecithin:cholesterol acyltransferase (LCAT). Login to comment 5 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys Results: The proband was a compound heterozygote for ABCA1 mutations R282X (c.844 C>T) and Y1532C (c.4595 A>G). Login to comment 7 ABCA1 p.Tyr1532Cys Cholesterol efflux was reduced in fibroblasts from the proband, as was cholesterol efflux from HEK293 cells transfected with an human (h) ABCA1 expression plasmid harboring the Y1532C mutation. Login to comment 8 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys Confocal microscopy of HeLa cells transfected with the Y1532C-hABCA1 plasmid revealed that the Y1532C mutation inhibits ABCA1 from reaching the cellular membrane. Login to comment 9 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys Conclusion: Compound heterozygosity for the nonsense mutation R282X and the missense mutation Y1532C in the ABCA1 gene causes Tangier disease. Login to comment 10 ABCA1 p.Arg282* R282X has a detrimental effect on the function of ABCA1 since a premature stop codon is introduced. Login to comment 11 ABCA1 p.Tyr1532Cys Mutation Y1532C disrupts the normal function of ABCA1 as determined by in vitro analyses. Login to comment 64 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys However, DNA sequencing of the ABCA1 gene suggested that the proband was a compound heterozygote for the nonsense mutation R282X (c.844 C>T) in exon 9 and the missense mutation Y1532C (c.4595 A>G) in exon 34. Login to comment 65 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys R282X has previously been reported by Altilia et al. [19] as a cause of defective function of ABCA1, while Y1532C is a novel mutation. Login to comment 66 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys However, DNA sequencing of the ABCA1 gene suggested that the proband was a compound heterozygote for the nonsense mutation R282X (c.844 C>T) in exon 9 and the missense mutation Y1532C (c.4595 A>G) in exon 34. Login to comment 67 ABCA1 p.Arg282* ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys R282X has previously been reported by Altilia et al. [19] as a cause of defective function of ABCA1, while Y1532C is a novel mutation. Login to comment 69 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys With respect to the genotypes, the proband`s mother and brother were both heterozygous for mutation R282X, while his father and daughter were heterozygous for mutation Y1532C. Login to comment 82 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys Together with the finding that none of 100 healthy unrelated individuals with levels of total serum cholesterol ࣘ6.5 mmol/l, HDL cholesterol between 1.2 and 1.8 mmol/l and triglycerides ࣘ3.0 mmol/l were found to be heterozygous for R282X or Y1532C in the ABCA1 gene, our findings suggest that the proband had Tangier disease. Login to comment 84 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys Together with the finding that none of 100 healthy unrelated individuals with levels of total serum cholesterol ≤6.5 mmol/l, HDL cholesterol between 1.2 and 1.8 mmol/l and triglycerides ≤3.0 mmol/l were found to be heterozygous for R282X or Y1532C in the ABCA1 gene, our findings suggest that the proband had Tangier disease. Login to comment 87 ABCA1 p.Arg282* Mutation R282X has recently been described in a Tangier disease patient, who was also heterozygous for mutation IVS2+5G>C [19]. Login to comment 88 ABCA1 p.Arg282* R282X introduces a premature stop codon in the predicted large 1st extracellular loop of ABCA1. Login to comment 89 ABCA1 p.Arg282* ABCA1 p.Arg282* Mutation R282X has recently been described in a Tangier disease patient, who was also heterozygous for mutation IVS2+5G>C [19]. Login to comment 90 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys R282X introduces a premature stop codon in the predicted large 1st extracellular loop of ABCA1. Login to comment 91 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys mRNA analyses of fibroblasts failed to detect a transcript from the allele harboring mutation R282X, which the authors attributed to nonsense-mediated mRNA Fig. 3. Login to comment 92 ABCA1 p.Tyr1532Cys Reduced cholesterol efflux from HEK293 cells transfected with Y1532C-hABCA1-FLAG plasmid. Login to comment 93 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys HEK293 cells were transiently transfected with plasmids encoding WT-hABCA1-FLAG, Y1532C-hABCA1-FLAG or an empty plasmid. Login to comment 95 ABCA1 p.Tyr1532Cys The differences in cholesterol efflux between HEK293 cells transfected with the WT-hABCA1-FLAG plasmid and the Y1532C hABCA1-FLAG plasmid or an empty plasmid were significant different (p < 0.05 (*)). Login to comment 96 ABCA1 p.Arg282* Thus, R282X should be considered to be a pathogenic mutation. Login to comment 97 ABCA1 p.Tyr1532Cys However, some uncertainty may exist regarding the pathogenicity of the Y1532C mutation even though it was predicted to be probably damaging by the use of the web-based software package PolyPhen (http://genetics.bwh.harvard.edu/pph). Login to comment 98 ABCA1 p.Arg282* ABCA1 p.Arg282* Thus, R282X should be considered to be a pathogenic mutation. Login to comment 99 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys However, some uncertainty may exist regarding the pathogenicity of the Y1532C mutation even though it was predicted to be probably damaging by the use of the web-based software package PolyPhen (http://genetics.bwh.harvard.edu/pph). Login to comment 100 ABCA1 p.Arg282* It cannot be excluded that this mutation could be a normal genetic variant and that Tangier disease in the proband was caused by mutation R282X and an unidentified mutation in the ABCA1 gene. Login to comment 101 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys To establish whether the Y1532C mutation affected the function of ABCA1, we set out to perform a series of in vitro experiments. Login to comment 102 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys Cholesterol efflux in HEK293 cells To further elucidate the role of mutation Y1532C on ABCA1-mediated cholesterol efflux, an ABCA1-containing plasmid harboring this mutation (Y1532C-hABCA1-FLAG) was transiently transfected into HEK293 cells. Login to comment 103 ABCA1 p.Tyr1532Cys Studies of mutation Y1532C in the ABCA1 gene 3.2.1. Login to comment 104 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys Cholesterol efflux in HEK293 cells To further elucidate the role of mutation Y1532C on ABCA1-mediated cholesterol efflux, an ABCA1-containing plasmid harboring this mutation (Y1532C-hABCA1-FLAG) was transiently transfected into HEK293 cells. Login to comment 105 ABCA1 p.Tyr1532Cys The apoA-I induced cholesterol efflux in HEK293 cells transfected with the Y1532C-hABCA1-FLAG Fig. 4. Login to comment 106 ABCA1 p.Tyr1532Cys Y1532C-hABCA1-FLAG is predominantly located intracellularly. Login to comment 107 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys The apoA-I induced cholesterol efflux in HEK293 cells transfected with the Y1532C-hABCA1-FLAG Fig. 4. Login to comment 108 ABCA1 p.Tyr1532Cys Y1532C-hABCA1-FLAG is predominantly located intracellularly. Login to comment 109 ABCA1 p.Tyr1532Cys Confocal microscopy of permeabilized HeLa cells transiently transfected with WT-hABCA1-FLAG or Y1532C-hABCA1-FLAG plasmids. Login to comment 111 ABCA1 p.Tyr1532Cys Thus, mutation Y1532C causes reduced cholesterol efflux. Login to comment 113 ABCA1 p.Tyr1532Cys Thus, mutation Y1532C causes reduced cholesterol efflux. Login to comment 114 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys To study whether the mutant Y1532C-ABCA1 is inserted into the cell membrane, HeLa cells were transiently transfected with WT-hABCA1-FLAG or Y1532C-hABCA1-FLAG plasmids. Login to comment 115 ABCA1 p.Tyr1532Cys HeLa cells transfected with WT-hABCA1-FLAG showed a membrane-associated localization of ABCA1, while cells transfected with Y1532C-hABCA1-FLAG predominantly showed an intracellular localization of ABCA1 (Fig. 4). Login to comment 116 ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys ABCA1 p.Tyr1532Cys To study whether the mutant Y1532C-ABCA1 is inserted into the cell membrane, HeLa cells were transiently transfected with WT-hABCA1-FLAG or Y1532C-hABCA1-FLAG plasmids. Login to comment 117 ABCA1 p.Tyr1532Cys HeLa cells transfected with WT-hABCA1-FLAG showed a membrane-associated localization of ABCA1, while cells transfected with Y1532C-hABCA1-FLAG predominantly showed an intracellular localization of ABCA1 (Fig. 4). Login to comment 118 ABCA1 p.Tyr1532Cys Thus, the failure of Y1532C-ABCA1 to promote cholesterol efflux appears to be caused by disrupted transport of the mutant protein to the cell surface. Login to comment 119 ABCA1 p.Cys1477Arg ABCA1 p.Ser1506Leu Mutations C1477R and S1506L affecting residues in this loop, have been found to have no effect on the transport of ABCA1 [21], but the mutant proteins encoded by the two mutant alleles interacted much weaker with apoA-I than normal. Login to comment 120 ABCA1 p.Cys1477Arg Singaraja et al. [22] also showed C1477R-ABCA1 to be present at the cell surface to a similar degree as WT-ABCA1. Login to comment 121 ABCA1 p.Cys1477Arg ABCA1 p.Ser1506Leu ABCA1 p.Ser1506Leu Mutations C1477R and S1506L affecting residues in this loop, have been found to have no effect on the transport of ABCA1 [21], but the mutant proteins encoded by the two mutant alleles interacted much weaker with apoA-I than normal. Login to comment 122 ABCA1 p.Cys1477Arg ABCA1 p.Leu1379Phe Singaraja et al. [22] also showed C1477R-ABCA1 to be present at the cell surface to a similar degree as WT-ABCA1. Login to comment 123 ABCA1 p.Ser1506Leu On the other hand, significantly lower amounts of S1506L-ABCA1 were found at the cell surface. Login to comment 124 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys ABCA1 p.Leu1379Phe Albrecht et al. [23] showed that mutation L1379F, which is also predicted to be in the 4th extracellular loop, was present at reduced levels at the cell surface. Login to comment 126 ABCA1 p.Arg282* ABCA1 p.Tyr1532Cys In conclusion, we have identified the first patient with Tangier disease of Norwegian origin, due to compound heterozygosity for the previously described ABCA1 mutation R282X [19], and the novel ABCA1 mutation Y1532C. Login to comment