Mutations in different genes encoding sarcomeric proteins are responsible for 50-60% of familial cases of hypertrophic cardiomyopathy (HCM); however, the genetic alterations causing the disease in ...one-third of patients are currently unknown. Here we describe a case with familial HCM of unknown cause. Whole-exome sequencing reveals a variant in the gene encoding the sarcomeric protein filamin C (p.A1539T) that segregates with the disease in this family. Sequencing of 92 HCM cases identifies seven additional variants segregating with the disease in eight families. Patients with FLNC mutations show marked sarcomeric abnormalities in cardiac muscle, and functional analysis reveals that expression of these FLNC variants resulted in the formation of large filamin C aggregates. Clinical studies indicate that FLNC-mutated patients have higher incidence of sudden cardiac death. On the basis of these findings, we conclude that mutations in the gene encoding the sarcomeric protein filamin C cause a new form of familial HMC.
Several common KCNQ1 gene polymorphisms have been associated with the risk of type 2 diabetes (T2DM) and diabetic nephropathy. This effect is explained by the role of the kcnq1 protein as a potassium ...channel that in the pancreatic beta-cells drives an electrical signal that facilitates glucose-stimulated insulin secretion. The KCNQ1 gene is also expressed in the kidney, and could thus be implicated in the risk of developing impaired renal function. To test this hypothesis, we genotyped six common KCNQ1 gene variants (three single nucleotide polymorphisms, rs2237892, rs2237895, and rs231362, and three intronic indels) in 681 healthy elderly individuals (>65 years old) from the Spanish Renastur cohort. None of the six variants was associated with T2DM (180 diabetics vs. 581 non-diabetics). The intron 12 insertion allele was associated with a reduced estimated glomerular filtration rate (eGFR<60, n = 90 vs. eGFR≥60, n = 591; II vs ID + DD genotypes, p = 0.031, OR = 2.06, 95%CI = 1.12–4.14). We also performed a next generation sequencing search of variants in the coding regions of the KCNQ1 gene in 100 individuals with the extreme eGFR values. We found two rare amino acid changes (p.K393N and p.P408A) and the 393 Asn variant was found only among diabetics (n = 4; p = 0.05). The two rare alleles were present in the two eGFR groups.
Our results suggest that a common KCNQ1 intron 12 indel polymorphism is a risk factor for impaired renal function independent of T2DM. If this association is confirmed by others, further research to determine the mechanism that drives this association would be warranted.
•KCNQ1 gene variants were associated with diabetes and diabetic nephropathy.•We determined five KCNQ1 polymorphisms in healthy elderly individuals.•None of the gene variants was significantly associated with diabetes in our cohort.•A common intron 12 indel was significantly associated with reduced renal filtration.•KCNQ1 gene variants might be independent predictors of renal function.
In this study we performed a next generation sequencing of 210 genes in 140 patients with cardiac failure requiring a heart transplantation. We identified a total of 48 candidate variants in 47 ...patients. Forty-three patients (90%) presented a single variant, and fourpatients (10%) were carriers of two variants. After refining the classification, we identified a pathogenic or likely pathogenic variant in 13 patients (10% of our cohort). In 34 additional cases (25%) the variants were classified as of unknown significance (VUS). In reference to the cause of cardiac failure in the 13 carriers of pathogenic variants, 5 were of dilated non-ischemic cause, 4 hypertrophic and 1 restrictive cardiomyopathy. In the ischemic cases (n = 3) no family history of cardiac disease was recorded, while nineof the non-ischemic had other relatives who were also diagnosed. In conclusion, the NGS of a cardiac transplanted cohort identified a definite or very likely genetic cause in 10% of the cases. Most of them had a family history of cardiac disease, and were thus previously studied as part of a routine screening by a genetic counselor. Pathogenic variants in cases without a family history of cardiac disease were mainly of ischemic origin.
The NF-kappaB pathway might play a role in the pathogenesis of renal disease and type 2 diabetes (T2DM). Our aim was to determine whether common polymorphisms in NF-kappaB genes were associated with ...impaired renal function and T2DM in a cohort of healthy elderly individuals. We studied 487 individuals, all Caucasian and aged 65–85 years. A total of 104 (21%) had impaired renal function (estimated glomerular filtration rate, eGFR < 60) and 146 (30%) were classified as diabetics. The genotypes of 4 common variants were determined through PCR-RFLP or fluorescent capillary electrophoresis.
The NFKB1 variants were significantly associated with T2DM: rs7667496 p = 0.01, OR = 1.68; and rs28362491 p = 0.02, OR = 1.67. They remained significantly associated in a multiple logistic regression with age, gender, hypertension, body mass index, and cholesterol. There was a trend toward the association of these variants with eGFR < 60. The two NFKB1 variants were in linkage disequilibrium (D′ = −0.86), and homozygous for the two non-risk alleles (rs7667496 CC + rs28362491 II), were significantly more common in the non-diabetics (p = 0.02).
In our cohort the NFKB1 variation was an independent risk factor for developing T2DM. Additional studies to confirm this association are of special interest, as well as studies to give a functional explanation to the genetic association.
•The nuclear-factor kappa-beta plays an important role in the pathogenesis of atherosclerosis and coronary artery disease (CAD).•Early-onset CAD was strongly associated with male sex and smoking in ...our population.•The NFKBIZ rs3217713 polymorphism was associated with early-onset CAD in our population.•Two common NFKB1 (-94 delATTG) and NFKBIA (rs8904) polymorphisms were not associated with CAD.•In our population, the NFKBIZ gene variation was an independent risk factor for developing early-onset CAD.
The nuclear-factor kappa-beta (NF-KB) is a driver of inflammation, and plays an important role in the pathogenesis of atherosclerosis and coronary artery disease (CAD). Early-onset CAD is defined as a coronary ischaemic episode at an age ≤55 years, and in our population was strongly associated with male sex and smoking. Our aim was to determine whether common variants in three NF-KB genes were associated with early-onset CAD. We studied 609 patients with early-onset CAD and 423 healthy controls, all male. Allele and genotype frequencies for the NFKB1 rs28362491 (-94 delATTG) and NFKBIA rs8904 were not significantly different between the two groups. For the NFKBIZ rs3217713, the deletion allele was significantly more frequent in the patients than in controls (0.27 vs. 0.22; p = 0.004). Deletion-carriers were more frequent in the patients (p < 0.001), with an OR = 1.48 (95%CI = 1.15–1.90). We performed a multiple logistic regression (linear generalized model) with smoking, hypercholesterolemia, type 2 diabetes, hypertension, and the rs3217713 deletion carriers remained significantly associated with early-onset CAD (p = 0.01).
In our population, the NFKBIZ variant was an independent risk factor for developing early-onset CAD.
Massive DNA sequencing, also known as next-generation sequencing, has revolutionized genetic diagnosis. This technology has reduced the effort and cost needed to analyze several genes simultaneously ...and has made genetic evaluation available to a larger number of patients. In hypertrophic cardiomyopathy, genetic analysis has increased from the 3 main genes implicated in the disease (MYH7, MYBPC3, TNNT2) to sequencing of more than 20 related genes. Despite the advantages of acquiring this additional information, many patients show variants of uncertain significance (mainly amino acid changes), which may also be present in at least 1 healthy control undergoing genome sequencing. This will be a dead-end situation unless the variant can be demonstrated to be associated with the disease in the patient's family. In the absence of clear evidence that these variants are truly pathogenic, they cannot be used for reliable genetic counselling in family members. Massive sequencing also enables identification of new candidate genes, but again, the problem of variants of uncertain significance limits the success of these assessments.
MYH7 mutations are found in ∼20% of hypertrophic cardiomyopathy (HCM) patients. Currently, mutational analysis is based on the sequencing of the coding exons and a few exon-flanking intronic ...nucleotides, resulting in omission of single-exon deletions and mutations in internal intronic, promoter, and 3′ UTR regions. We amplified and sequenced large MYH7 fragments in 60 HCM patients without previously identified sarcomere mutations. Lack of aberrant PCR fragments excluded single-exon deletions in the patients. Instead, we identified several new rare intronic variants. An intron 26 single nucleotide insertion (−5 insC) was predicted to affect pre-mRNA splicing, but allele frequencies did not differ between patients and controls ( n = 150). We found several rare promoter variants in the patients compared to controls, some of which were in binding sites for transcription factors and could thus affect gene expression. Only one rare 3′ UTR variant (c.*29T>C) found in the patients was absent among the controls. This nucleotide change would not affect the binding of known microRNAs. Therefore, MYH7 mutations outside the coding exon sequences would be rarely found among HCM patients. However, changes in the promoter region could be linked to the risk of developing HCM. Further research to define the functional effect of these variants on gene expression is necessary to confirm the role of the MYH7 promoter in cardiac hypertrophy.
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