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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

ABSTRACT 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_502del TCC/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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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.