KCNQ1 p.D446E Variant as a Risk Allele for Arrhythmogenic Phenotypes: Electrophysiological Characterization Reveals a Complex Phenotype Affecting the Slow Delayed Rectifier Potassium Current (IKs) Voltage Dependence by Causing a Hyperpolarizing Shift and a Lack of Response to Protein Kinase A Activation.

Genetic testing is crucial in inherited arrhythmogenic channelopathies; however, the clinical interpretation of genetic variants remains challenging. Incomplete penetrance, oligogenic, polygenic or multifactorial forms of channelopathies further complicate variant interpretation. We identified the KCNQ1/p.D446E variant in 2/63 patients with long QT syndrome, 30-fold more frequent than in public databases. We thus characterized the biophysical phenotypes of wildtype and mutant IKs co-expressing these alleles with the ß-subunit minK in HEK293 cells. KCNQ1 p.446E homozygosity significantly shifted IKs voltage dependence to hyperpolarizing potentials in basal conditions (gain of function) but failed to shift voltage dependence to hyperpolarizing potentials (loss of function) in the presence of 8Br-cAMP, a protein kinase A activator. Basal IKs activation kinetics did not differ among genotypes, but in response to 8Br-cAMP, IKs 446 E/E (homozygous) activation kinetics were slower at the most positive potentials. Protein modeling predicted a slower transition of the 446E Kv7.1 tetrameric channel to the stabilized open state. In conclusion, biophysical and modelling evidence shows that the KCNQ1 p.D446E variant has complex functional consequences including both gain and loss of function, suggesting a contribution to the pathogenesis of arrhythmogenic phenotypes as a functional risk allele.

Enzymatic-assisted polymerization of the lignin obtained from a macroalgae consortium, using an extracellular laccase-like enzyme (Tg-laccase) from Tetraselmis gracilis.

In the past decade, Mexican coasts have received an enormous influx of macroalgae species, producing serious environmental and public health concerns. Here, we developed a green methodology to generate a new polymer from the lignin contained in the macroalgae. The methodology consists in lignin extraction-by-boiling and its subsequent polymerization with a laccase-like enzyme from the green algae Tetraselmis gracilis (Tg-laccase). Mass spectrometry revealed the presence of guaiacyl (G), p-hydroxyphenyl (H), and sinapyl alcohol as the main monolignols in the lignin from Sargassum sp. On the other hand, MALDI-TOF spectra shows an increase in the size of the lignin chain after enzymatic polymerization process with Tg-laccase. Besides, the characterization of the novel polymer -using 1H NMR, FTIR, SEC-FPLC, and UV/Vis- allowed establishing that during the polymerization process there is a decrease in the number of phenolic groups as well as loss of aromatic protons, which allowed proposing a polimerizacion mechanism. This methodology could be promising in the development of a new lignin-based polymer and would open a new direction for the environmental management of the macroalgae on the Mexican beaches.

Demographic history and biologically relevant genetic variation of Native Mexicans inferred from whole-genome sequencing.

Understanding the genetic structure of Native American populations is important to clarify their diversity, demographic history, and to identify genetic factors relevant for biomedical traits. Here, we show a demographic history reconstruction from 12 Native American whole genomes belonging to six distinct ethnic groups representing the three main described genetic clusters of Mexico (Northern, Southern, and Maya). Effective population size estimates of all Native American groups remained below 2,000 individuals for up to 10,000 years ago. The proportion of missense variants predicted as damaging is higher for undescribed (~ 30%) than for previously reported variants (~ 15%). Several variants previously associated with biological traits are highly frequent in the Native American genomes. These findings suggest that the demographic and adaptive processes that occurred in these groups shaped their genetic architecture and could have implications in biological processes of the Native Americans and Mestizos of today.

Compound heterozygous KCNQ1 mutations (A300T/P535T) in a child with sudden unexplained death: Insights into possible molecular mechanisms based on protein modeling.

Sudden death in a child is a devastating event with important medical implications for surviving relatives. Because it may be the first manifestation of unknown inherited cardiac disease, molecular autopsy can be helpful to determine the cause of death and identify at risk family members. The aim of the study was to perform a molecular autopsy in a seven year-old girl with sudden unexplained death, to find evidence supporting the possible pathogenicity of mutations identified in inherited cardiac disease genes, and to clinically and genetically assess first-degree relatives. DNA from the index case was extracted from umbilical cord cells stored at birth, and DNA of first-degree relatives from blood samples. Targeted sequencing was performed using a Haloplex design including 81 cardiogenes. Possible functional consequences of the mutations were analyzed using protein modeling and structural mobility analyses. The child was compound heterozygous for KCNQ1 variants p.Ala300Thr and p.Pro535Thr. Ala300Thr is known to cause long QT syndrome in the homozygous state, while Pro535Thr is novel and of unknown clinical significance. The father and sibling were Ala300Thr heterozygous, and had normal QTc intervals at rest and during exercise. The asymptomatic mother was heterozygous for Pro535Thr, and showed borderline QTc at rest, but prolonged QTc during exercise. Protein modeling predicted that Ala300Thr alters the mobility profile of the Kv7.1 tetramer and Thr535 disrupts a calmodulin-binding site, probably causing co-assembly or trafficking defects of the mutant monomer. Altogether, the evidence strongly suggests that this child was affected with a recessive form of Romano Ward syndrome.

Dietary fat and carbohydrate modulate the effect of the ATP-binding cassette A1 (ABCA1) R230C variant on metabolic risk parameters in premenopausal women from the Genetics of Atherosclerotic Disease (GEA) Study.

BACKGROUND: Although the R230C-ATP-binding cassette A1 (ABCA1) variant has been consistently associated with HDL-C levels, its association with diabetes and other metabolic parameters is unclear. Estrogen and dietary factors are known to regulate ABCA1 expression in different tissues. Thus, we aimed to explore whether gender, menopausal status and macronutrient proportions of diet modulate the effect of this variant on various metabolic parameters. METHODS: One thousand five hundred ninety-eight controls from the GEA study were included (787 men, 363 premenopausal women and 448 menopausal women), previously assessed for anthropometric and biochemical measurements and visceral to subcutaneous abdominal fat (VAT/SAT) ratio on computed tomography. Taqman assays were performed for genotyping. Diet macronutrient proportions were assessed using a food frequency questionnaire validated for the Mexican population. Multivariate regression models were constructed to assess the interaction between the proportion of dietary macronutrients and the R230C polymorphism on metabolic parameters. RESULTS: All significant interactions were observed in premenopausal women. Those carrying the risk allele and consuming higher carbohydrate/lower fat diets showed an unfavorable metabolic pattern [lower HDL-C and adiponectin levels, higher VAT/SAT ratio, homeostasis model assessment for insulin resistance (HOMA-IR) and higher gamma-glutamyl transpeptidase (GGT) and alkaline phosphatase (ALP) levels]. Conversely, premenopausal women carrying the risk allele and consuming lower carbohydrate/higher fat diets showed a more favorable metabolic pattern (higher HDL-C and adiponectin levels, and lower VAT/SAT ratio, HOMA-IR, GGT and ALP levels). CONCLUSION: This is the first study reporting a gender-specific interaction between ABCA1/R230C variant and dietary carbohydrate and fat percentages affecting VAT/SAT ratio, GGT, ALP, adiponectin levels and HOMA index. Our study confirmed the previously reported gender-specific ABCA1-diet interaction affecting HDL-C levels observed in an independent study. Our results show how gene-environment interactions may help further understand how certain gene variants confer metabolic risk, and may provide information useful to design diet intervention studies.

Premature and severe cardiovascular disease in a Mexican male with markedly low high-density-lipoprotein-cholesterol levels and a mutation in the lecithin:cholesterol acyltransferase gene: a family study.

Epidemiological and clinical studies have shown that a low plasma high­density lipoprotein cholesterol (HDL-C) level is a strong predictor of cardiovascular disease (CVD). Lecithin:cholesterol acyltransferase (LCAT) is a key enzyme in the formation, maturation and function of HDL. Therefore impaired LCAT function may enhance atherosclerosis because of defective cholesterol transport. In this study, we examined a 34-year old LCAT­deficient patient and eight first-degree family members. There was a strong family history for CVD and type 2 diabetes mellitus (DM2). The proband was found homozygous for a previously reported LCAT gene mutation (Thr37Met). A sister and two sons of the proband were heterozygous for the same mutation. The proband had DM2 and showed severe multivessel coronary artery disease, corneal opacification and extremely low HDL-C levels. Large HDL particles were absent while small HDL particles were increased. The HDL of the patient had a reduced ability to promote cell cholesterol efflux, and the low­density lipoproteins (LDL) were more susceptible to oxidation. Among his family members, two heterozygotes and one non-carrier had early carotid or coronary atherosclerosis. In conclusion, as the increased LDL oxidability and structural and functional abnormalities of HDL particles have been reported in patients with obesity and diabetes, the results suggested that the adverse coronary risk profile, and not being LCAT deficient, may be responsible for the CVD found in our proband, and for the early atherosclerosis observed in the two heterozygotes and in the wild­type family members.

The ABCA1 gene R230C variant is associated with decreased risk of premature coronary artery disease: the genetics of atherosclerotic disease (GEA) study.

BACKGROUND: ABCA1 genetic variation is known to play a role in HDL-C levels and various studies have also implicated ABCA1 variation in cardiovascular risk. The functional ABCA1/R230C variant is frequent in the Mexican population and has been consistently associated with low HDL-C concentrations. Although it has been associated with other cardiovascular risk factors such as obesity and type 2 diabetes mellitus, it is not known whether it is associated with coronary artery disease (CAD). AIM: The purpose of the study was to analyze whether the ABCA1/R230C variant is associated with premature CAD in a case-control association study (GEA or Genetics of Atherosclerotic Disease), and to explore whether BMI modulates the effect of the C230 allele on other metabolic traits using a population-based design. RESULTS: The C230 allele was significantly associated with both lower HDL-C levels and a lower risk of premature CAD as compared to controls (OR = 0.566; P(add) = 1.499×10(-5)). In addition, BMI modulated the effect of R230C on body fat distribution, as the correlation between BMI and visceral to subcutaneous adipose tissue (a metric of the propensity to store fat viscerally as compared to subcutaneously) was negative in RR homozygous individuals, but positive in premenopausal women bearing the C230 allele, with a statistically significant interaction (P = 0.005). BMI-R230C interaction was also significant for triglyceride levels in women regardless of their menopausal status (P = 0.036). CONCLUSION: This is the first study assessing the effect of the R230C/ABCA1 variant in remature CAD. C230 was associated with both decreased HDL-C levels and a lower risk of premature CAD, and gender-specific BMI-R230C interactions were observed for different metabolic traits. These interactions may help explain inconsistencies in associations, and underscore the need to further analyze interactions of this functional and frequent variant with diet, exercise and other environmental factors.