Impact of delta-sarcoglycan gene polymorphism on the occurrence of coronary spastic angina in Japanese patients with hypertrophic cardiomyopathy

Genetic Loci and Novel Discrimination Measures Associated with Blood Pressure Variation in African Americans Living in Tallahassee

Sequencing of the human genome and decades of genetic association and linkage studies have dramatically improved our understanding of the etiology of many diseases. However, the multiple causes of complex diseases are still not well understood, in part because genetic and sociocultural risk factors are not typically investigated concurrently. Hypertension is a leading risk factor for cardiovascular disease and afflicts more African Americans than any other racially defined group in the US. Few genetic loci for hypertension have been replicated across populations, which may reflect population-specific differences in genetic variants and/or inattention to relevant sociocultural factors. Discrimination is a salient sociocultural risk factor for poor health and has been associated with hypertension. Here we use a biocultural approach to study blood pressure (BP) variation in African Americans living in Tallahassee, Florida by genotyping over 30,000 single nucleotide polymorphisms (SNPs) and capturing experiences of discrimination using novel measures of unfair treatment of self and others (n = 157). We perform a joint admixture and genetic association analysis for BP that prioritizes regions of the genome with African ancestry. We only report significant SNPs that were confirmed through our simulation analyses, which were performed to determine the false positive rate. We identify eight significant SNPs in five genes that were previously associated with cardiovascular diseases. When we include measures of unfair treatment and test for interactions between SNPs and unfair treatment, we identify a new class of genes involved in multiple phenotypes including psychosocial distress and mood disorders. Our results suggest that inclusion of culturally relevant stress measures, like unfair treatment in African Americans, may reveal new genes and biological pathways relevant to the etiology of hypertension, and may also improve our understanding of the complexity of gene-environment interactions that underlie complex diseases.

Dilated cardiomyopathy mutations in δ-sarcoglycan exert a dominant-negative effect on cardiac myocyte mechanical stability

Delta-sarcoglycan is a component of the sarcoglycan subcomplex within the dystrophin-glycoprotein complex located at the plasma membrane of muscle cells. While recessive mutations in δ-sarcoglycan cause limb girdle muscular dystrophy 2F, dominant mutations in δ-sarcoglycan have been linked to inherited dilated cardiomyopathy (DCM). The purpose of this study was to investigate functional cellular defects present in adult cardiac myocytes expressing mutant δ-sarcoglycans harboring the dominant inherited DCM mutations R71T or R97Q. This study demonstrates that DCM mutant δ-sarcoglycans can be stably expressed in adult rat cardiac myocytes and traffic similarly to wild-type δ-sarcoglycan to the plasma membrane, without perturbing assembly of the dystrophin-glycoprotein complex. However, expression of DCM mutant δ-sarcoglycan in adult rat cardiac myocytes is sufficient to alter cardiac myocyte plasma membrane stability in the presence of mechanical strain. Upon cyclical cell stretching, cardiac myocytes expressing mutant δ-sarcoglycan R97Q or R71T have increased cell-impermeant dye uptake and undergo contractures at greater frequencies than myocytes expressing normal δ-sarcoglycan. Additionally, the R71T mutation creates an ectopic N-linked glycosylation site that results in aberrant glycosylation of the extracellular domain of δ-sarcoglycan. Therefore, appropriate glycosylation of δ-sarcoglycan may also be necessary for proper δ-sarcoglycan function and overall dystrophin-glycoprotein complex function. These studies demonstrate that DCM mutations in δ-sarcoglycan can exert a dominant negative effect on dystrophin-glycoprotein complex function leading to myocardial mechanical instability that may underlie the pathogenesis of δ-sarcoglycan-associated DCM.

A Haplotype of Two Novel Polymorphisms in δ-Sarcoglycan Gene Increases Risk of Dilated Cardiomyopathy in Mongoloid Population

The role of genetic abnormality of δ-sarcoglycan (δ-SG) gene in dilated (DCM) and hypertrophied (HCM) cardiomyopathy patients is still unfolding. In this study we first defined the promoter region and then searched for polymorphisms/mutations among the promoter, 5'-untranslated region, and the encoding exons in δ-SG gene in 104 Chinese patients with DCM, 145 with HCM, and 790 normal controls. Two novel polymorphisms were found, an 11 base-pair (bp) deletion (c._-100~-110; -) in the promoter region and a missense polymorphism of A848G resulting in p.Q283R in the highly conserved C-terminus. The prevalence of homozygous genotype -/- of c._-100~-110 was slightly higher in DCM (14.42%) and HCM patients (14.48%), as compared with normal controls (11.01%). The prevalence of genotype of 848A/G was significantly higher in DCM (6.73%; OR = 9.43; p = 0.0002), but not in HCM patients (1.38%; OR = 1.37; p = 0.62), as compared with controls (0.76%). Haplotype -_G consisting c._-100~-110 and A848G was associated with increased risk of DCM (OR = 17.27; 95%CI = 3.19–93.56; p = 0.001) but not associated with HCM (OR = 1.90; 95%CI = 0.38–9.55; p = 0.44). Co-occurrence of the genotypes -/- of c._-100~-110 and 848A/G was found in 5 patients with DCM (4.81%; OR = 39.85; p = 0.0001), none of HCM patients, and only 1 of the controls (0.13%). Both polymorphisms were also found in the Japanese population, but not in the Africans and Caucasians. C._-100~-110 resulted in a decrease of δ-SG promoter activity to 64±3% of the control level (p<0.01). Both co-immunoprecipitation and in vitro protein pull-down assays demonstrated that δ-SG-283R interacts normally to β- and γ-SG, but significantly decreased localization of β/δ/γ-SG on the plasma membrane. In conclusion, haplotype -_G composed of c._-100~-110 and A848G confers higher susceptibility to DCM in the Mongoloid population.

The CC genotype of the delta-sarcoglycan gene polymorphism rs13170573 is associated with obstructive sleep apnea in the Chinese population

Obstructive sleep apnea (OSA) is a highly heterogeneous sleep disorder, and increasing evidence suggests that genetic factors play a role in the etiology of OSA. Airway muscle dysfunction might promote pharyngeal collapsibility, mutations or single nucleotide polymorphisms (SNPs) in the delta-sarcoglycan (SCGD) gene associated with muscle dysfunction. To evaluate if SCGD gene SNPs are associated with OSA, 101 individuals without OSA and 97 OSA patients were recruited randomly. The genotype distributions of SNPs (rs157350, rs7715464, rs32076, rs13170573 and rs1835919) in case and control populations were evaluated. The GG, GC and CC genotypes of rs13170573 in control and OSA groups were 51.5% and 37.1%, 36.6% and 35.1%, and 11.9% and 27.8%, respectively. Significantly fewer OSA patients possessed the GG genotype and significantly more possessed the CC genotype compared with controls. Further multivariate logistic regression analysis showed that the CC genotype was an independent risk factor for OSA, with an odds ratio (OR) of 2.17 (95% confidence interval [CI]: 1.19-6.01). Other factors, such as age ≥ 50 years, male gender, body mass index (BMI) ≥ 25 kg/m(2), low-density lipoprotein cholesterol (LDL-C) level ≥ 3.33 mg/dL, smoking and hypertension, were also independent risk factors for OSA in our multivariate logistic regression model.

A delta-sarcoglycan gene polymorphism as a risk factor for hypertrophic cardiomyopathy

BACKGROUND

The C allele of c.-94C>G polymorphism of the delta-sarcoglycan gene was associated as a risk factor for coronary spasm in Japanese patients with hypertrophic cardiomyopathy (HCM).

AIM

We evaluated whether the c.-94C>G polymorphism can be a risk factor for HCM in Mexican patients.

METHODS

The polymorphism was genotyped and the risk was estimated in 35 HCM patients and 145 healthy unrelated individuals. Data of this polymorphism reported in Mexican Amerindian populations were included.

RESULTS

The C allele frequency in HCM patients was higher with an odds ratio (OR) of 2.37, and the risk for the CC genotype increased to 5.0. The analysis with Mexican Amerindian populations showed that the C allele frequency was significantly higher in HCM patients with an OR of 2.96 and for CC genotype the risk increased to 7.60.

CONCLUSIONS

The C allele of the c.-94C>G polymorphism is a risk factor for HCM, which is increased by the Amerindian component and can play an important role in the etiology and progression of disease in Mexican patients.

δ-Sarcoglycan-deficient muscular dystrophy: from discovery to therapeutic approaches

Mutations in the δ-sarcoglycan gene cause limb-girdle muscular dystrophy 2F (LGMD2F), an autosomal recessive disease that causes progressive weakness and wasting of the proximal limb muscles and often has cardiac involvement. Here we review the clinical implications of LGMD2F and discuss the current understanding of the putative mechanisms underlying its pathogenesis. Preclinical research has benefited enormously from various animal models of δ-sarcoglycan deficiency, which have helped researchers to explore therapeutic approaches for both muscular dystrophy and cardiomyopathy.

Delta-sarcoglycan gene polymorphism frequency in Amerindian and Mestizo populations of Mexico

Mutations on the delta-sarcoglycan gene have been associated with the development of both hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy. Recently, the polymorphism c.-94C>G was associated with HCM in Japanese patients. The aim of our study was to evaluate the frequency of c.-94C>G polymorphism in Mexican-Amerindian and Mexican-Mestizo populations. We analyzed the frequency of this polymorphism in 165 Mexican-Amerindian individuals (23 Triquis, 25 Zapotecos, 24 Mayas, 41 Nahuas, and 52 Mixtecos) and 100 unrelated Mexican-Mestizos. Allele frequencies were similar in all Amerindian groups (0.33 Triquis, 0.54 Zapotecos, 0.54 Mayas, 0.46 Nahuas, and 0.49 Mixtecos). When compared with Mexican-Mestizos, only Triquis were different (p = 0.00742). However, when comparing the total sample of the Amerindian population with the Mestizos, the difference was not significant (p = 0.12225). Allele frequencies of Mexican populations were higher than in Asians and less than African and European populations (p < 0.05). These data show that the distribution of the C allele is higher in Mexican populations studied and consequently it is necessary to define if this may be associated with genetic susceptibility for HCM in the Mexican patients.