ABCMdb

PMID: 21575609

Sorrenson B, Suetani RJ, Bickley VM, George PM, Williams MJ, Scott RS, McCormick SP
An ABCA1 truncation shows no dominant negative effect in a familial hypoalphalipoproteinemia pedigree with three ABCA1 mutations.
Biochem Biophys Res Commun. 2011 Jun 10;409(3):400-5. Epub 2011 May 7., [PubMed]

Sentences

No. Mutations Sentence Comment

2 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met Following the finding of three different ABCA1 mutations, p.C978fsX988, p.T1512M and p.N1800H in a subject with hypoalphalipoproteinemia, we aimed to establish whether the p.C978fsX988 truncation exerted a dominant negative effect on the full-length ABCA1 alleles within family members as has been reported for other ABCA1 truncations. Login to comment 6 ABCA1 p.Asn1800His There was no evidence of a dominant negative effect on wildtype or p.N1800H protein levels. Login to comment 17 ABCA1 p.Asn1800His The majority of the 154 mutations identified in ABCA1 (see http://www.hgmd.cf.ac.uk/ac/gene.php?gene=ABCA1) are missense mutations associated with isolated cases of Tangier disease or FHA, with some exceptions such as the common p.N1800H mutation [6]. Login to comment 20 ABCA1 p.Arg1851* Expression and functional analysis of truncated ABCA1 mutants in isolation is limited to the ABCA1 p.R1851X truncation [9,10]. Login to comment 29 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met In this study, we characterised a pedigree with three different ABCA1 mutations; p.N1800H, p.C978fsX988 and p.T1512M. Login to comment 30 ABCA1 p.Asn1800His ABCA1 p.Asn1800His ABCA1 p.Thr1512Met The p.N1800H is a common ABCA1 mutation known to impair function [1,6,11,12]. Login to comment 31 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met The p.C978fsX988 and p.T1512M mutations were recently reported but were not characterised with respect to segregation, expression or function in the case of the p.C978fsX988 mutation [13]. Login to comment 32 ABCA1 p.Thr1512Met ABCA1 p.Thr1512Met Here we show that the p.C978fsX988 and p.T1512M mutations are on the same allele and that the p.C978fsX988 protein is dysfunctional. Login to comment 33 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met This situation gave us the unique opportunity to test the effect of a short ABCA1 truncation on the expression and function of both the wildtype and the p.N1800H ABCA1 alleles. Login to comment 34 ABCA1 p.Asn1800His This situation gave us the unique opportunity to test the effect of a short ABCA1 truncation on the expression and function of both the wildtype and the p.N1800H ABCA1 alleles. Login to comment 72 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met The T1512 primer was used to amplify the wildtype and p.N1800H alleles and the M1512 primer to amplify the p.C978fsX988/p.T1512M allele. Login to comment 73 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met The T1512 primer was used to amplify the wild-type and p.N1800H alleles and the M1512 primer to amplify the p.C978fsX988/p.T1512M allele. Login to comment 84 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met Sequencing showed the proband (I:1) was heterozygote for three mutations; p.C978fsX988 (c.2934delT), p.T1512M (c.4535C > T) and p.N1800H (c.5398A > C). Login to comment 85 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met Sequencing showed the proband (I:1) was heterozygote for three mutations; p.C978fsX988 (c.2934delT), p.T1512M (c.4535C > T) and p.N1800H (c.5398A > C). Login to comment 87 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met ABCA1 p.Thr1512Met The daughter (II:2) was heterozygous for the N1800H mutation and the son (II:1) heterozygous for the p.C978fsX988 and p.T1512M mutations making it apparent that the p.C978fsX988 and p.T1512M mutations were on the same allele. Login to comment 88 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met ABCA1 p.Thr1512Met The daughter (II:2) was heterozygous for the N1800H mutation and the son (II:1) heterozygous for the p.C978fsX988 and p.T1512M mutations making it apparent that the p.C978fsX988 and p.T1512M mutations were on the same allele. Login to comment 101 ABCA1 p.Asn1800His No significant difference in stimulated mRNA levels was seen between wildtype and the two p.N1800H heterozygotes (I:2 and II:2). Login to comment 102 ABCA1 p.Asn1800His No significant difference in stimulated mRNA levels was seen between wildtype and the two p.N1800H heterozygotes (I:2 and II:2). Login to comment 103 ABCA1 p.Asn1800His Allele-specific quantification of p.C978fsX988 mRNA in the two heterozygotes (Fig. 4B) showed it to be present at negligible levels compared to their p.N1800H (subject I:1) or wildtype allele (subject II:1). Login to comment 104 ABCA1 p.Asn1800His ABCA1 p.Asn1800His ABCA1 p.Asn1800His ABCA1 p.Asn1800His The level of p.N1800H and wildtype mRNA in these two subjects was approximately 50% that of the combined p.N1800H and wildtype mRNA levels in p.N1800H heterozygotes (I:2 and II:2). Login to comment 105 ABCA1 p.Asn1800His ABCA1 p.Asn1800His ABCA1 p.Asn1800His The level of p.N1800H and wildtype mRNA in these two subjects was approximately 50% that of the combined p.N1800H and wildtype mRNA levels in p.N1800H heterozygotes (I:2 and II:2). Login to comment 106 ABCA1 p.Asn1800His Protein levels in the subjects heterozygous for the p.N1800H allele were not significantly different to wildtype. Login to comment 107 ABCA1 p.Asn1800His Protein levels in the subjects heterozygous for the p.N1800H allele were not significantly different to wildtype. Login to comment 108 ABCA1 p.Asn1800His Discussion In this study we describe and characterise a FHA pedigree harbouring three different ABCA1 mutations; p.C978fsX988, p.T 1512M and p.N1800H [12,13]. Login to comment 109 ABCA1 p.Asn1800His ABCA1 p.Asn1800His ABCA1 p.Thr1512Met The proband, a compound heterozygote for the p.C978fsX988, p.T1512M and p.N1800H mutations, exhibited a low HDL-C level (0.23 mmol/L) but showed no signs of Tangier disease. Login to comment 110 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met ABCA1 p.Thr1512Met ABCA1 p.Thr1512Met Segregation of alleles within the family showed the p.C978fsX988 and p.T1512M mutations to be on the same allele making the p.T1512M mutation effectively redundant. Login to comment 111 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met ABCA1 p.Thr1512Met As few studies have characterised the effect of truncated ABCA1 alleles [9,10,17], this family gave us a unique opportunity to test the effect of a short truncated allele on both the full-length wildtype and p.N1800H alleles. Login to comment 112 ABCA1 p.Asn1800His As few studies have characterised the effect of truncated ABCA1 alleles [9,10,17], this family gave us a unique opportunity to test the effect of a short truncated allele on both the full-length wildtype and p.N1800H alleles. Login to comment 113 ABCA1 p.Asn1800His With respect to function, efflux studies in fibroblasts from all family members showed both the p.N1800H and p.C978fsX988 mutants to have impaired function as heterozygote carriers had significantly reduced cholesterol efflux compared to wildtype. Login to comment 114 ABCA1 p.Asn1800His With respect to function, efflux studies in fibroblasts from all family members showed both the p.N1800H and p.C978fsX988 mutants to have impaired function as heterozygote carriers had significantly reduced cholesterol efflux compared to wildtype. Login to comment 115 ABCA1 p.Asn1800His The level of stimulated efflux correlated with the HDL-C levels seen in the individuals apart from the two p.N1800H heterozygotes, I:2 and II:2, who had similar efflux levels but different HDL-C levels (0.87 versus 1.33 mmol/L) respectively. Login to comment 116 ABCA1 p.Asn1800His The level of stimulated efflux correlated with the HDL-C levels seen in the individuals apart from the two p.N1800H heterozygotes, I:2 and II:2, who had similar efflux levels but different HDL-C levels (0.87 versus 1.33 mmol/L) respectively. Login to comment 117 ABCA1 p.Asn1800His Prior studies of the p.N1800H mutant in isolation have shown it to impair efflux capacity [6,11]. Login to comment 118 ABCA1 p.Asn1800His Prior studies of the p.N1800H mutant in isolation have shown it to impair efflux capacity [6,11]. Login to comment 121 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met The p.C978fsX988/ p.T1512M and p.N1800H alleles are represented by grey and black shading respectively. Login to comment 122 ABCA1 p.Asn1800His ABCA1 p.Thr1512Met The p.C978fsX988/ p.T1512M and p.N1800H alleles are represented by grey and black shading respectively. Login to comment 144 ABCA1 p.Asn1800His Treatment of fibroblasts from both p.C978fsX988 carriers with cycloheximide caused an increase in mRNA levels that was not apparent in a p.N1800H heterozygote, providing evidence for nonsense-mediated decay of the p.C978fsX988 transcript. Login to comment 145 ABCA1 p.Asn1800His Treatment of fibroblasts from both p.C978fsX988 carriers with cycloheximide caused an increase in mRNA levels that was not apparent in a p.N1800H heterozygote, providing evidence for nonsense-mediated decay of the p.C978fsX988 transcript. Login to comment 147 ABCA1 p.Asn1800His Protein analysis of fibroblasts showed p.C978fsX988 heterozygotes had ABCA1 protein levels 50% that of the p.N1800H heterozygotes, precluding a dominant negative effect for the p.C978fsX988 truncation. Login to comment 148 ABCA1 p.Asn1800His Protein analysis of fibroblasts showed p.C978fsX988 heterozygotes had ABCA1 protein levels 50% that of the p.N1800H heterozygotes, precluding a dominant negative effect for the p.C978fsX988 truncation. Login to comment 149 ABCA1 p.Arg909* This contrasts to a previous report showing full-length ABCA1 protein levels well below the expected 50% in fibroblasts harbouring ABCA1 truncations, including the p.R909X truncation which is shorter than p.C978fsX988 [9]. Login to comment 150 ABCA1 p.Arg909* This contrasts to a previous report showing full-length ABCA1 protein levels well below the expected 50% in fibroblasts harbouring ABCA1 truncations, including the p.R909X truncation which is shorter than p.C978fsX988 [9]. Login to comment