Familial dysbetalipoproteinemia in three patients with apoE 2*(Arg136-->Cys) gene variant

Apolipoprotein E (apoE) is a polymorphic protein which occurs in three common isoforms and more than 25 rare variants. Some of the rare apoE variants have been implicated in a dominant mode of inheritance of familial dysbetalipoproteinemia (FD). We have identified three unrelated apoE 2*(Arg136-->Cys) carriers with FD. This finding supports the notion that although apoE 2*(Arg136-->Cys) mutation is perhaps not sufficient to cause FD itself, the presence of other genetic and/or environmental factors can lead to the phenotypic expression of the disease in the carriers.     

Rare variant of apolipoprotein E (Arg136-->Cys) in a subject with normal lipid values

During the screening of apolipoprotein (apo) E gene polymorphism with PCR and subsequent restriction analysis, we have identified a female carrier with a mutant allele Arg136-->Cys. This proband had normal lipid parameters and no history of coronary artery disease (CAD). We did not confirm the previously described connection between apo E Arg136-->Cys mutation and elevated lipid levels. In the case of this mutation, other factors (environmental and/or genetic) are important for the development of lipid metabolism disorders.     

Variable expression of hypercholesterolemia in Apolipoprotein E2* (Arg136 --> Cys) heterozygotes

In the process of population screening for apo E gene polymorphism with the PCR and subsequent restriction analysis, we identified a female who demonstrated heterozygosity for an unusual restriction fragment caused by the loss of a CfoI restriction site. Sequence analysis of the apo E gene was performed and a carrier of the mutant allele with C --> T substitution at cDNA position 3817 was identified, which caused an Arg136 --> Cys change. The first-line relatives have been screened for this rare mutation with PCR and restriction analysis of PCR products. The complete lipoprotein parameters have been determined in the probands family. In the family, only one child had the same mutant allele as his mother had. The proband (7.49 mmol/l) with her siblings had hypercholesterolemia and a high body mass index (BMI 31.6 kg/m2). By contrast, her son had a normal lipid spectrum with normal BMI. We described the mutation apo E2* (Arg136 --> Cys) in a family with elevated lipid levels, but there was no confirmation of the connection between this mutation and type III hyperlipoproteinemia or hyperlipoproteinemia at all. In the case of this mutation, other factors (mainly genetic) are important for the development of lipid metabolism disorders.     

Characterization of apolipoprotein E genetic variations in Taiwanese: association with coronary heart disease and plasma lipid levels

Apolipoprotein E (apoE, protein; APOE, gene) is important in lipoprotein metabolism. Three isoforms, apoE2 (Cys112 Cys158), apoE3 (Cys112 Arg158), and apoE4 (Arg112 Arg158), are present in the general population. This report investigates the frequency distribution of apoE isoforms and the association of APOE genotypes with plasma lipid profile and coronary heart disease (CHD) in a population of Taiwan. ApoE isoforms were determined genetically by polymerase chain reaction and HhaI restriction enzyme digestion in control and coronary heart disease (CHD) patients. Plasma lipid and lipoprotein concentrations were also determined. The control group exhibited frequencies of 84.6% APOE3, 7.9% APOE4, 7.5% APOE2, 70.6% APOE3E3, 14.4% APOE3E4, 13.6% APOE2E3, and 1.4% APOE2E4. Comparable frequencies were observed in the CHD group. In both APOE2 carrier and APOE3E3 groups, the CHD patients expressed abnormal lipid profiles while the control group expressed normal lipid profiles. The APOE4 carriers, however, expressed abnormal lipid profiles in both normal control and CHD groups. Extremely high apoE levels in the hypertriglyceridemic group (TG > 400 mg/dL) seemed to be undesirable and were often observed in CHD patients.     

Characterization of five new mutants in the carboxyl-terminal domain of human apolipoprotein E: No cosegregation with severe hyperlipidemia

Assessment of the apolipoprotein E (apoE) phenotype by isoelectric focusing of both hyperlipidemic and normolipidemic individuals identified five new variants. All mutations were confined to the downstream part of the APOE gene by using denaturing gradient gel electrophoresis (DGGE). Sequence analysis revealed five new mutations causing unique amino acid substitutions in the carboxyl-terminal part of the protein containing the putative lipid-binding domain. Three hyperlipoproteinemic probands were carriers of the APOE*2(Val236→Glu) allele, the APOE*3(Cys112→Arg; Arg251→Gly) allele, or the APOE*1(Arg158→Cys; Leu252→Glu) allele. DGGE of the region encoding the receptor-binding domain was useful for haplotyping the mutations at codons 112 and 158. Family studies failed to demonstrate cosegregation between the new mutations and severe hyperlipoproteinemia, although a number of carriers for the APOE*3(Cys112→Arg; Arg251→Gly) allele and the APOE*1(Arg158→Cys; Leu252→Glu) allele expressed hypertriglyceridemia and/or hypercholesterolemia. Two other mutant alleles, APOE*4⁻ (Cys112→Arg; Arg274→His) and APOE*4⁺(Ser296→Arg), were found in normolipidemic probands. The lack of cosegregation of these new mutations with severe hyperlipoproteinemia suggests that these mutations do not exert a dominant effect on the functioning of apoE.     

Effect of arginine 172 on the binding of apolipoprotein E to the low density lipoprotein receptor

The region of apolipoprotein E (apoE) that interacts directly with the low density lipoprotein (LDL) receptor lies in the vicinity of residues 136-150, where lysine and arginine residues are crucial for full binding activity. However, defective binding of carboxyl-terminal truncations of apoE3 has suggested that residues in the vicinity of 170-183 are also important. To characterize and define the role of this region in LDL receptor binding, we created either mutants of apoE in which this region was deleted or in which arginine residues within this region were sequentially changed to alanine. Deletion of residues 167-185 reduced binding activity (15% of apoE3), and elimination of arginines at positions 167, 172, 178, and 180 revealed that only position 172 affected binding activity (2% of apoE3). Substitution of lysine for Arg(172) reduced binding activity to 6%, indicating a specific requirement for arginine at this position. The higher binding activity of the Delta167-185 mutant relative to the Arg(172) mutant (15% versus 2%) is explained by the fact that arginine residues at positions 189 and 191 are shifted in the deletion mutant into positions equivalent to 170 and 172 in the intact protein. Mutation of these residues and modeling the region around these residues suggested that the influence of Arg(172) on receptor binding activity may be determined by its orientation at a lipid surface. Thus, the association of apoE with phospholipids allows Arg(172) to interact directly with the LDL receptor or with other residues in apoE to promote its receptor-active conformation.     

Isolation of quinolone-resistant Escherichia coli found in major rivers in Korea

Twenty isolates resistant to seven quinolones were isolated from major rivers in Korea. All isolates had three mutations, Ser83-->Leu and Asp87-->Asn in GyrA and Ser80-->Ile or Ser80-->Arg in ParC and three isolates had an additional mutation Glu84-->Gly or Glu84-->Val in ParC. In addition, a clonal spread was not found in these isolates.     

青霉素G酰化酶β亚基Ser^579,Arg^580的定点突变研究

According to the comparison of amino acid sequence between PGA (Penicillin G Acylase) and PBPs (Penicillin Binding Protein), We suggest that No. 565-595 peptide fragment in beta-subunit of PGA may be a substrate-binding site of enzyme. Plasmid pTZGA was constructed by cloning the 2.6 kb PGA gene of pWGA into phagemid pTZ18U The technique of site-specific mutagenesis was used to study the role of residue No. 579 (Ser) and No. 580 (Arg) of PGA. Four kinds of mutants were obtained (Ser579-->Gly579, Arg580-->Gly580, Arg580-->Glu580, Arg580-->Lys580), both Glu580 and Gly580 mutants showed no activity of enzyme and Lys580 mutant remained 30% and Gly579 mutant kept 70% activity of wilde type. The same protein expression of four mutants according to the results of ELISA indicate that mutation does not affect the expression of PGA, but Arg580 residue may be essential for substrate-binding or catalysis of PGA.     

A second mutation associated with apparent beta-hexosaminidase A pseudodeficiency: identification and frequency estimation.

Deficient activity of beta-hexosaminidase A (Hex A), resulting from mutations in the HEXA gene, typically causes Tay-Sachs disease. However, healthy individuals lacking Hex A activity against synthetic substrates (i.e., individuals who are pseudodeficient) have been described. Recently, an apparently benign C739-to-T (Arg247Trp) mutation was found among individuals with Hex A levels indistinguishable from those of carriers of Tay-Sachs disease. This allele, when in compound heterozygosity with a second "disease-causing" allele, results in Hex A pseudodeficiency. We examined the HEXA gene of a healthy 42-year-old who was Hex A deficient but did not have the C739-to-T mutation. The HEXA exons were PCR amplified, and the products were analyzed for mutations by using restriction-enzyme digestion or single-strand gel electrophoresis. A G805-to-A (Gly269Ser) mutation associated with adult-onset GM2 gangliosidosis was found on one chromosome. A new mutation, C745-to-T (Arg249Trp), was identified on the second chromosome. This mutation was detected in an additional 4/63 (6%) non-Jewish and 0/218 Ashkenazi Jewish enzyme-defined carriers. Although the Arg249Trp change may result in a late-onset form of GM2 gangliosidosis, any phenotype must be very mild. This new mutation and the benign C739-to-T mutation together account for approximately 38% of non-Jewish enzyme-defined carriers. Because carriers of the C739-to-T and C745-to-T mutations cannot be differentiated from carriers of disease-causing alleles by using the classical biochemical screening approaches, DNA-based analyses for these mutations should be offered for non-Jewish enzyme-defined heterozygotes, before definitive counseling is provided.     

The achondroplasia mutation does not alter the dimerization energetics of the fibroblast growth factor receptor 3 transmembrane domain

The Gly380 --> Arg mutation in the TM domain of fibroblast growth factor receptor 3 (FGFR3) of the RTK family is linked to achondroplasia, the most common form of human dwarfism. The molecular mechanism of pathology induction is under debate, and two different mechanisms have been proposed to contribute to pathogenesis: (1) Arg380-mediated FGFR3 dimer stabilization and (2) slow downregulation of the activated mutant receptors. Here we show that the Gly380 --> Arg mutation does not alter the dimerization energetics of the FGFR3 transmembrane domain in detergent micelles or in lipid bilayers. This result indicates that pathogenesis in achondroplasia cannot be explained simply by a higher dimerization propensity of the mutant FGFR3 TM domain, thus highlighting the importance of the observed slow downregulation in phenotype induction.     

The functional characteristics of a human apolipoprotein E variant (cysteine at residue 142) may explain its association with dominant expression of type III hyperlipoproteinemia.

Type III hyperlipoproteinemia typically is associated with homozygosity for apolipoprotein (apo) E2(Arg158----Cys). Dominant expression of type III hyperlipoproteinemia associated with apoE phenotype E3/3 is caused by heterozygosity for a human apoE variant, apoE3(Cys112----Arg, Arg142----Cys). However, this apoE3 variant was not separable from the normal apoE3 in these patients' plasma because the two proteins have identical amino acid composition, charge, and molecular weight. Therefore, to determine the functional characteristics of this protein, we used recombinant DNA techniques to produce this apoE variant in bacteria. We also produced a non-naturally occurring variant, apoE(Arg142----Cys), that had only the cysteine substituted at residue 142. These two apoE variants were purified from cell lysates of the transfected Escherichia coli by ultracentrifugal flotation in the presence of phospholipid, by gel filtration chromatography, and by heparin-Sepharose chromatography. Both Cys142 apoE variants bound to lipoprotein receptors on human fibroblasts with only about 20% of normal binding activity. Therefore, cysteine at residue 142, not arginine at residue 112, is responsible for the decreased receptor binding activity of the variants. Cysteamine treatment and removal of the carboxyl-terminal domain had little effect on the binding activity, whereas both modulate the receptor binding activity of apoE2(Arg158----Cys). The mutation at residue 142 decreased the binding activity of apoE to both heparin and the monoclonal antibody 1D7 (this antibody inhibits receptor binding of apoE), whereas apoE2(Arg158----Cys), which is associated with recessive expression of type III hyperlipoproteinemia, binds normally to both. The Arg112, Cys142 variant predominantes 3:1 over normal apoE3 in the very low density lipoproteins of plasma from an affected subject, as assessed by differential reactivity with the antibody 1D7. The unique combination of functional properties of the Arg112, Cys142 variant provides a possible explanation for its association with dominant expression of type III hyperlipoproteinemia.     

Enzyme I of the phosphoenolpyruvate:sugar phosphotransferase system. In vitro intragenic complementation: the roles of Arg126 in phosphoryl transfer and the C-terminal domain in dimerization

Enzyme I mutants of the Salmonella typhimurium phosphoenolpyruvate:sugar phosphotransferase system (PTS), which show in vitro intragenic complementation, have been identified as Arg126Cys (strain SB1690 ptsI34), Gly356Ser (strain SB1681 ptsI16), and Arg375Cys (strain SB1476 ptsI17). The mutation Arg126Cys is in the N-terminal HPr-binding domain, and complements Gly356Ser and Arg375Cys enzyme I mutations located in the C-terminal phosphoenolpyruvate(PEP)-binding domain. Complementation results in the formation of unstable heterodimers. None of the mutations alters the K(m) for HPr, which is phosphorylated by enzyme I. Arg126 is a conserved residue; the Arg126Cys mutation gives a V(max) of 0.04% wild-type, establishing a role in phosphoryl transfer. The Gly356Ser and Arg375Cys mutations reduce enzyme I V(max) to 4 and 2%, respectively, and for both, the PEP K(m) is increased from 0.1 to 3 mM. It is concluded that this activity was from the monomer, rather than the dimer normally found in assays of wild-type. In the presence of Arg126Cys enzyme, V(max) for Gly356Ser and Arg375Cys enzymes I increased 6- and 2-fold, respectively; the K(m) for PEP decreased to <10 microM, but the K(m) became dependent upon the stability of the heterodimer in the assay. Gly356 is conserved in enzyme I and pyruvate phosphate dikinase, which is a homologue of enzyme I, and this residue is part of a conserved sequence in the subunit interaction site. Gly356Ser mutation impairs enzyme I dimerization. The mutation Arg375Cys also impairs dimerization, but the equivalent residue in pyruvate phosphate dikinase is not associated with the subunit interaction site. A 37 000 Da, C-terminal domain of enzyme I has been expressed and purified; it dimerizes and complements Gly356Ser and Arg375Cys enzymes I proving that the association/dissociation properties of enzyme I are a function of the C-terminal domain.     

Molecular characterization of genetic mutations in human lactate dehydrogenase (LDH) B (H) variant

Summary We have previously detected a single base substitution of G by A at the Arg codon CGC in exon 4 of the mutant lactate dehydrogenase (LDH) gene, an unstable LDH-B variant (case 1). Here, we use the polymerase chain reaction (PCR) to amplify genomic DNA of two cases (the original case 1 and a new patient, case 2). We were able to confirm that case 1 is homozygous for the mutation, causing a replacement of the conserved Arg by His at residue 173. The resulting LDH-B variant subunit is unstable in vivo. Whereas the mutation in exon 4 was not observed in case 2, a different single base substitution of A by C was detected at the Ser codon AGT in exon 3. This mutation causes a replacement of the conserved Ser by Arg at residue 131. Genomic analysis of the family of case 2 by mismatched PCR showed that the missense mutation was consistent with their biochemical phenotypes. The replacement results in a conformational change of the residues near the Ser, probably because the side chain of Arg is much more bulky than that of Ser. The change may affect the arrangement of the cofactor binding site and result in the loss of enzyme activity. The experimental observations are consistent with computer graphics analyses.     

Effects of mutations at Gly114 on the stability and refolding of haloarchaeal nucleoside diphosphate kinase in low salt solution

We have shown before that mutation of Gly114 to Arg enhances folding of hexameric nucleoside diphosphate kinase (HsNDK) from Halobacterium salinarum. In this study, we constructed three mutant forms, Gly114Lys (G114K), Gly114Ser (G114S) and Gly114Asp (G114D), to further clarify the role residue 114 plays in the stability and folding of HsNDK. While expression of G114D mutant resulted in inactive enzyme, other mutant HsNDKs were successfully expressed in active form. The G114K mutant, similar to Gly114Arg (G114R) mutant, refolded in 1 M NaCl after heat-denaturation, under which the wild-type HsNDK and G114S proteins showed no refolding.     

Physiological expression of macrophage apoE in the artery wall reduces atherosclerosis in severely hyperlipidemic mice

We have previously reported that the introduction of macrophage apoE into mice lacking both apoE and the LDL receptor (apoE(-)(/-)/LDLR(-)(/-)) through bone marrow transplantation (apoE(+)(/+)/LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-)) produces progressive accumulation of apoE in plasma without affecting lipid levels. This model provides a tool to study the effects of physiologically regulated amounts of macrophage apoE on atherogenesis in hyperlipidemic animals. Ten-week-old male apoE(-)(/-)/LDLR(-)(/-) mice were transplanted with either apoE(+)(/+)/LDLR(-)(/-) (n = 11) or apoE(-)(/-)/LDLR(-)(/-) (n = 14) marrow. Although there were no differences between the two groups in lipid levels at baseline or at 5 and 9 weeks after transplantation, apoE levels in the apoE(+)(/+)LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-) mice increased to 4 times the apoE levels of normal mice. This resulted in a 60% decrease in aortic atherosclerosis in the apoE(+)(/+)/LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-) compared with the apoE(-)(/-)/LDLR(-)(/-)-->apoE(-)(/-)/LDLR(-)(/-) controls, (15957 +/- 1907 vs. 40115 +/- 8302 micro m(2) +/- SEM, respectively). In a separate experiment, apoE(+)(/+)/LDLR(-)(/-) mice were transplanted with either apoE(+)(/+)/LDLR(-)(/-) or apoE(-)(/-)/LDLR(-)(/-) marrow and placed on a high-fat diet for 8 weeks. In the absence of macrophage apoE, lesion area was increased by 75% in the aortic sinus and by 56% in the distal aorta. These data show that physiologic levels of macrophage apoE in the vessel wall are anti-atherogenic in conditions of severe hyperlipidemia and can affect later stages of plaque development.     

Fibril formation by primate, rodent, and Dutch-hemorrhagic analogues of Alzheimer amyloid beta-protein.

Deposition of extraneuronal fibrils that assemble from the 39-43 residue beta/A4 amyloid protein is one of the earliest histopathological features of Alzheimer's disease. We have used negative-stain electron microscopy, Fourier-transform infrared (FT-IR) spectroscopy, and fiber X-ray diffraction to examine the structure and properties of synthetic peptides corresponding to residues 1-40 of the beta/A4 protein of primate [Pm(1-40); human and monkey], rodent [Ro(1-40); with Arg5-->Gly, Tyr10-->Phe, and His13-->Arg], and hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D) [Du(1-40); with Glu22-->Gln]. As controls, we examined a reverse primate sequence [Pm*(40-1)] and an extensively substituted primate peptide [C(1-40); with Glu3-->Arg, Arg5-->Glu, Asp7-->Val, His13-->Lys, Lys16-->His, Val18-->Asp, Phe19-->Ser, Phe20-->Tyr, Ser26-->Pro, Ala30-->Val, Ile31-->Ala, Met35-->norLeu, Gly38-->Ile, Val39-->Ala, and Val40-->Gly]. The assembly of these peptides was studied to understand the relationship between species-dependent amyloid formation and beta/A4 sequence and the effect of a naturally occurring point mutation of fibrillogenesis. The three N-terminal amino acid differences between Pm(1-40) and Ro(1-40) had virtually no effect on the morphology or organization of the fibrils formed by these peptides, indicating that the lack of amyloid deposits in rodent brain is not due directly to specific changes in its beta/A4 sequence. beta-Sheet and fibril formation, judged by FT-IR, was maximal within the pH range 5-8 for Pm(1-40), pH 5-10.5 for Du(1-40), and pH 2.5-8 for Ro(1-40).(ABSTRACT TRUNCATED AT 250 WORDS)     

Biophysical analysis of apolipoprotein E3 variants linked with development of type III hyperlipoproteinemia

Background

Apolipoprotein E (apoE) is a major protein of the lipoprotein transport system that plays important roles in lipid homeostasis and protection from atherosclerosis. ApoE is characterized by structural plasticity and thermodynamic instability and can undergo significant structural rearrangements as part of its biological function. Mutations in the 136–150 region of the N-terminal domain of apoE, reduce its low density lipoprotein (LDL) receptor binding capacity and have been linked with lipoprotein disorders, such as type III hyperlipoproteinemia (HLP) in humans. However, the LDL-receptor binding defects for these apoE variants do not correlate well with the severity of dyslipidemia, indicating that these variants may carry additional properties that contribute to their pathogenic potential.

Methodology/Principal Findings

In this study we examined whether three type III HLP predisposing apoE3 variants, namely R136S, R145C and K146E affect the biophysical properties of the protein. Circular dichroism (CD) spectroscopy revealed that these mutations do not significantly alter the secondary structure of the protein. Thermal and chemical unfolding analysis revealed small thermodynamic alterations in each variant compared to wild-type apoE3, as well as effects in the reversibility of the unfolding transition. All variants were able to remodel multillamelar 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) vesicles, but R136S and R145C had reduced kinetics. Dynamic light scattering analysis indicated that the variant R136S exists in a higher-order oligomerization state in solution. Finally, 1-anilinonaphthalene-8-sulfonic acid (ANS) binding suggested that the variant R145C exposes a larger amount of hydrophobic surface to the solvent.

Conclusions/Significance

Overall, our findings suggest that single amino acid changes in the functionally important region 136–150 of apoE3 can affect the molecule''s stability and conformation in solution and may underlie functional consequences. However, the magnitude and the non-concerted nature of these changes, make it unlikely that they constitute a distinct unifying mechanism leading to type III HLP pathogenesis.     

Contribution of cysteine 158, the glycosylation site threonine 194, the amino- and carboxy-terminal domains of apolipoprotein E in the binding to amyloid peptide beta (1-40).

Recent studies have shown that at physiological conditions (pH 7.6, 37 degrees C), the reactivity of recombinant apoE isoforms secreted by mammalian cells toward amyloid peptide beta (Abeta40) follows the order apoE2 > apoE3 > apoE4 for the apoE monomer and apoE2 > apoE3 for apoE dimer that is formed via that intramolecular disulfide bridges. Different Abeta binding properties have been reported for the plasma-derived apoE and commercially available apoE preparations that differ from the native apoE forms in the degree of their O-glycosylation. To define structural elements of apoE involved in the interaction with Abeta, we have introduced point mutations as well as amino- and carboxy-terminal deletions in the apoE structure. The mutant apoE forms were expressed transiently using the Semliki Forest Virus system, and the culture medium was utilized to study the reactivity of the mutated proteins with Abeta 40. This analysis showed that a mutation in the O-glycosylation site of apoE2 (Thr194-Ala) did not affect the SDS-stable binding of apoE to Abeta. In contrast, introduction of cysteine at position 158 of apoE4 (Arg112, Cys158) increased the SDS-stable binding of apoE to Abeta to the levels similar to those observed in apoE2. Similar analysis showed that apoE truncated at residues 259, 249, 239, and 229 retains the SDS-stable binding to Abeta40, whereas apoE truncated at residues 185 and 165 does not bind to Abeta. The deletion of aminoterminal residues 2-19 reduced the SDS-stable binding of apoE2 to Abeta and deletion of residues 2-81 abolished binding to Abeta. It is also noteworthy that the (Delta2-81) apoE mutant exists predominantly as a dimer, suggesting that removal of residues 2-81 promoted dimerization of apoE. These findings suggest that the amino- and carboxy-terminal residues of apoE are required for SDS-stable binding of apoE to Abeta and that the presence of at least one cysteine contributes to the efficient Abeta binding.     

Recurrent and founder mutations in the Netherlands

Background. Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is an inherited cardiac disease with reduced penetrance and a highly variable expression. Mutations in the gene encoding the plakophilin-2 gene (PKP2) are detected in about 50% of ARVC/D patients. The p.Arg79X mutation in PKP2 has been identified in Europe and North America and has been functionally characterised. We evaluated the prevalence of the p.Arg79X mutation in PKP2 in the Dutch population.Methods. Twelve index patients and 41 family members were evaluated in three university hospitals in the Netherlands. The diagnosis of ARVC/D was established according to the recently revised Task Force Criteria. Segregation of the p.Arg79X mutation was studied and haplotypes were reconstructed to determine whether the p.Arg79X mutation was a recurrent or a founder mutation.Results. The p.Arg79X mutation in PKP2 was identified in 12 index patients. Haplotype analysis revealed a shared haplotype among Dutch p.Arg79X mutation carriers, indicating a common founder. Six index patients (50%) had a first- or second-degree relative who had died of sudden cardiac death below 40 years of age. At age 60, only 60% of the mutation carriers had experienced any symptoms. There was no significant difference in symptom-free survival and event-free survival between men and women.Conclusion. We have identified the largest series of patients with the same desmosome gene mutation in ARVC/D reported to date. This p.Arg79X mutation in PKP2 is a founder mutation in the Dutch population. The phenotypes of PKP2 p.Arg79X mutation carriers illustrate the clinical variability and reduced penetrance often seen in ARVC/D. (Neth Heart J 2010;18:583–91.)     

Protective effect of apolipoprotein E2 on coronary artery disease in African Americans is mediated through lipoprotein cholesterol

We studied the relationship of apolipoprotein E (apoE) isoforms and coronary artery disease (CAD) in 224 African Americans and 326 Caucasians undergoing diagnostic coronary angiography. The presence of CAD was defined as >50% stenosis in at least one artery. ApoE allele frequencies were 0.12, 0.62, and 0.26 for epsilon 2, epsilon 3, and epsilon 4, respectively, in African Americans and 0.08, 0.78, and 0.14 for epsilon 2, epsilon 3, and epsilon 4, respectively, in Caucasians. Among African Americans, CAD was present in 9 of 34 epsilon 2 carriers (26%), significantly smaller (P < 0.05) in proportion compared with 39 of 82 epsilon 3 carriers and 43 of 92 epsilon 4 carriers (48% and 47%, respectively), suggesting a protective effect of the epsilon 2 allele. No such difference was seen in Caucasians. In African Americans but not Caucasians, LDL cholesterol was lower in epsilon 2 carriers than in epsilon 3 and epsilon 4 carriers (106 vs. 127 and 134 mg/dl, respectively; P < 0.005). After adjusting for lipid levels, the association between apoE2 and CAD was no longer significant. Thus, the protective effect of apoE2 seen in African Americans could be explained by a favorable lipid profile in epsilon 2 carriers, whereas in Caucasians, the absence of such a protective effect could be attributable to the lack of effect of apoE2 on the lipid profile.