Lamin A/C cardiomyopathy: young onset, high penetrance, and frequent need for heart transplantation.

Aims: Lamin A/C (LMNA) mutations cause familial dilated cardiomyopathy (DCM) with frequent conduction blocks and arrhythmias. We explored the prevalence, cardiac penetrance, and expressivity of LMNA mutations among familial DCM in Norway. Furthermore, we explored the risk factors and the outcomes in LMNA patients. Methods and results: During 2003-15, genetic testing was performed in patients referred for familial DCM. LMNA genotype-positive subjects were examined by electrocardiography, Holter monitoring, cardiac magnetic resonance imaging, and echocardiography. A positive cardiac phenotype was defined as the presence of atrioventricular (AV) block, atrial fibrillation/flutter (AF), ventricular tachycardia (VT), and/or echocardiographic DCM. Heart transplantation was recorded and compared with non-ischaemic DCM of other origin. Of 561 unrelated familial DCM probands, 35 (6.2%) had an LMNA mutation. Family screening diagnosed an additional 93 LMNA genotype-positive family members. We clinically followed up 79 LMNA genotype-positive [age 42 ± 16 years, ejection fraction (EF) 45 ± 13%], including 44 (56%) with VT. Asymptomatic LMNA genotype-positive family members (age 31 ± 15 years) had a 9% annual incidence of a newly documented cardiac phenotype and 61% (19/31) of cardiac penetrance during 4.4 ± 2.9 years of follow-up. Ten (32%) had AV block, 7 (23%) AF, and 12 (39%) non-sustained VT. Heart transplantation was performed in 15 of 79 (19%) LMNA patients during 7.8 ± 6.3 years of follow-up. Conclusion: LMNA mutation prevalence was 6.2% of familial DCM in Norway. Cardiac penetrance was high in young asymptomatic LMNA genotype-positive family members with frequent AV block and VT, highlighting the importance of early family screening and cardiological follow-up. Nearly 20% of the LMNA patients required heart transplantation.

Novel mutation in the SLC12A3 gene in a Sri Lankan family with Gitelman syndrome & coexistent diabetes: a case report.

BACKGROUND: Gitelman syndrome (GS) is a rare autosomal recessively inherited salt-wasting tubulopathy associated with mutations in the SLC12A3 gene, which encodes for NaCl cotransporter (NCC) in the kidney. CASE PRESENTATION: In this report, we describe two siblings from a Sri Lankan non-consanguineous family presenting with hypokalaemia associated with renal potassium wasting, hypomagnesemia, hypocalciuria and hypereninemic hyperaldosteronism with normal blood pressure. Genetic testing showed that both were homozygotes for a novel missense mutation in exon 10 of the SLC12A3 gene [NM_000339.2, c.1276A > T; p.N426Y], which has not previously been reported in the literature in association with GS. Their mother was a heterozygous carrier for the same mutation. The father was not alive at the time of testing. This novel mutation extends the spectrum of known SLC12A3 gene mutations and further supports the allelic heterogeneity of GS. Interestingly both siblings had young onset Diabetes with strong family history. CONCLUSION: These findings have implications in providing appropriate genetic counseling to the family with regard to the risk associated with inbreeding, the detection of carrier/presymptomatic relatives. It further expands the known spectrum of genotypic and phenotypic characteristics of Gitelman syndrome.

[Weight loss pills purchased on the internet as the cause of ventricular fibrillation]. / Slankepiller købt på internettet som årsag til ventrikelflimren.

We present a case regarding a 25-year-old woman who had been taking unauthorized weight loss pills prior to a sudden cardiac arrest from which she was resuscitated by paramedics. Her initial electrocardiogram revealed a prolonged corrected QT-interval (QTc). During admission she developed torsades de pointes and was treated with magnesium sulphate and temporary pacing. An electrophysiological study, a coronary angiogram and genetic testing for long QT syndrome all revealed normal results. After cessation of the pills the QTc normalized, and two weeks later she was discharged.

Description of a large family with autosomal dominant hypercholesterolemia associated with the APOE p.Leu167del mutation.

Apolipoprotein (apo) E mutants are associated with type III hyperlipoproteinemia characterized by high cholesterol and triglycerides levels. Autosomal dominant hypercholesterolemia (ADH), due to the mutations in the LDLR, APOB, or PCSK9 genes, is characterized by an isolated elevation of cholesterol due to the high levels of low-density lipoproteins (LDLs). We now report an exceptionally large family including 14 members with ADH. Through genome-wide mapping, analysis of regional/functional candidate genes, and whole exome sequencing, we identified a mutation in the APOE gene, c.500_502delTCC/p.Leu167del, previously reported associated with sea-blue histiocytosis and familial combined hyperlipidemia. We confirmed the involvement of the APOE p.Leu167del in ADH, with (1) a predicted destabilization of an alpha-helix in the binding domain, (2) a decreased apo E level in LDLs, and (3) a decreased catabolism of LDLs. Our results show that mutations in the APOE gene can be associated with bona fide ADH.

The prevalence of mutations in KCNQ1, KCNH2, and SCN5A in an unselected national cohort of young sudden unexplained death cases.

INTRODUCTION: Sudden unexplained death account for one-third of all sudden natural deaths in the young (1-35 years). Hitherto, the prevalence of genopositive cases has primarily been based on deceased persons referred for postmortem genetic testing. These deaths potentially may represent the worst of cases, thus possibly overestimating the prevalence of potentially disease causing mutations in the 3 major long-QT syndrome (LQTS) genes in the general population. We therefore wanted to investigate the prevalence of mutations in an unselected population of sudden unexplained deaths in a nationwide setting. METHODS: DNA for genetic testing was available for 44 cases of sudden unexplained death in Denmark in the period 2000-2006 (equaling 33% of all cases of sudden unexplained death in the age group). KCNQ1, KCNH2, and SCN5A were sequenced and in vitro electrophysiological studies were performed on novel mutations. RESULTS: In total, 5 of 44 cases (11%) carried a mutation in 1 of the 3 genes corresponding to 11% of all investigated cases (R190W KCNQ1, F29L KCNH2 (2 cases), P297S KCNH2 and P1177L SCN5A). P1177L SCN5A has not been reported before. In vitro electrophysiological studies of P1177L SCN5A revealed an increased sustained current suggesting a LQTS phenotype. CONCLUSION: In a nationwide setting, the genetic investigation of an unselected population of sudden unexplained death cases aged 1-35 years finds a lower than expected number of mutations compared to referred populations previously reported. We therefore conclude that the prevalence of mutations in the 3 major LQTS associated genes may not be as abundant as previously estimated.

Pregnancy outcomes in familial hypercholesterolemia: a registry-based study.

BACKGROUND: Women with familial hypercholesterolemia (FH) are prone to early cardiovascular disease and death. It is unknown whether FH adversely affects pregnant women and birth outcomes. We determined whether heterozygous FH women are at higher risk of premature birth (<37 gestational weeks), delivering children with low birth weight (<2500 g) and/or with congenital malformations compared to women in general. METHODS AND RESULTS: We linked information from the Medical Genetics Laboratory with that of the Medical Birth Registry of Norway. We included 1869 FH women (≥ 14 years) from the Medical Genetics Laboratory and about 2 million (general population) from the Medical Birth Registry of Norway during the period 1967 to 2006. The registry match resulted in analysis of 2319 births of 1093 women with heterozygous FH. The mean (SD) prepregnancy total cholesterol concentration was 9.59 (2.06) mmol/L (370 [80 mg/dL]), whereas the concentration of total cholesterol was not available during pregnancy. The frequencies of prematurity, low birth weight, and congenital malformations for the 40-year period in the FH population were 6.8, 5.0, and 3.3, respectively. The corresponding values for the general population were 6.2, 5.2, and 3.2. The corresponding odds ratios were 1.11 (95 confidence interval 0.94-1.31; P=0.23), 0.96 (0.79-1.15; P=0.64), and 1.09 (0.87-1.37; P=0.45). CONCLUSIONS: Women with FH do not appear to have a higher risk of preterm delivery or of having infants with low birth weight or congenital malformations than women in general, but, although this is unlikely, some undetected bias may obscure the real differences.

Nonsense-mediated decay of human LDL receptor mRNA.

OBJECTIVE: The objective of this project was to determine whether nonsense mutation in the low density lipoprotein receptor (LDLR) induces nonsense-mediated mRNA decay (NMD). MATERIAL AND METHODS: Four known nonsense mutations (W23X, S78X, E207X and W541X) in the LDLR gene, which are found in Norwegian familial hypercholesterolaemia (FH) patients, were investigated. Epstein-Barr virus (EBV) transformed lymphocytes from patients heterozygous for these mutations in the LDLR gene were analysed. Flow cytometric analysis was used to determine the amount and function of the cell surface LDLRs. The expression of LDLR mRNA in lymphocytes was quantified by real-time polymerase chain reaction (PCR). The presence of NMD was tested using the inhibitors gentamicin, emetine or cycloheximide. RESULTS: Cells from heterozygous FH patients with nonsense mutations in the LDLR gene contained significantly less LDLR protein (p<0.05). In addition, flow cytometric analysis revealed that these patients had a reduced LDL-uptake compared to controls (p<0.005). Cells from heterozygous FH patients with nonsense mutations W23X, S78X or W541X in the LDLR gene showed significantly decreased levels of LDLR mRNA (p<0.005). LDLR mRNA was reduced in the mutant lymphocyte S78X prior to treatment with pharmacological inhibitors, and after treatment the level of LDLR mRNA increased to the same level as that of normal cells. CONCLUSION: In the present study, NMD was confirmed in the LDLR gene. Translation inhibitors showed reduced NMD caused by nonsense mutated LDLR transcripts. Knowledge of NMD might have an important impact in clinical medicine as genetic intervention develops.

Model system for phenotypic characterization of sequence variations in the LDL receptor gene.

BACKGROUND: Sequence variations in the LDL receptor (LDLR) gene cause defects of LDLR protein production and function through different molecular mechanisms. Here we describe a cell model system for the phenotypic characterization of sequence variations in the LDLR gene. Well-known sequence variations belonging to LDLR classes 2 to 5 (p.G565V, p.I161D, p.Y828C, and p.V429M) were studied in CHO and HepG2 cells. METHODS: Expression of LDLR protein on the cell surface was detected by use of fluorescence-conjugated antibodies against the LDLR and the LDLR activity was measured by incubating the cells with fluorescently labeled and radiolabeled LDL. The intracellular locations of the LDLR mutants and wild-type were also investigated. RESULTS: The class 2A p.G565V sequence variant exhibited an intracellular distribution of LDLR with no active receptors on the cell surface. Both the class 3 p.I161D and class 4 p.Y828C sequence variants gave surface staining but had a reduced ability to bind or internalize LDL, respectively. By determining the intracellular locations of the receptors we were able to visualize the accumulation of the class 5 p.V429M sequence variant in endosomes by means of a specific marker, as well as confirming that the class 4 p.Y828C variant was not localized in clathrin-coated pits. Flow cytometry allowed us quantitatively to determine the amount and activity of receptors. To confirm the results of binding and cell association of fluorescently labeled LDL analyzed by flow cytometry, assays using 125I-labeled LDL were performed. In addition to a useful and valid alternative to radiolabeled LDL, the unique properties of fluorescently labeled LDL allowed a variety of detection technologies to be used. CONCLUSIONS: This new approach enables phenotypic characterization of sequence variations in the LDLR gene. The assays developed may be valuable for confirming the pathogenicity of novel missense sequence variations found throughout the LDLR gene.