Screening for Mitochondrial tRNA Mutations in 318 Patients with Dilated Cardiomyopathy

Objectives: Dilated cardiomyopathy (DCM) is a complex cardiovascular disease with unknown etiology. Although nuclear genes play active roles in DCM, mitochondrial dysfunction was believed to be involved in the pathogenesis of DCM. The objective of this study is to analysis the association between mitochondrial tRNA (mt-tRNA) mutations and DCM. Material and Methods: We performed a mutational analysis of mt-tRNA genes in a cohort of 318 patients with DCM and 200 age- and gender-matched control subjects. To further assess their pathogenicity, phylogenetic analysis and mitochondrial functions including mtDNA copy number, ATP and ROS were analyzed. Results: 7 possible pathogenic mutations: MT-TL1 3302A>G, MT-TI 4295A>G, MT-TM 4435A>G, MT-TA 5655T>C, MT-TH 12201T>C, MT-TE 14692A>G and MT-TT 15927G>A were identified in DCM group but absent in controls. These mutations occurred at extremely conserved nucleotides of corresponding tRNAs, and led to the failure in tRNAs metabolism. Moreover, a significant reduction in ATP and mtDNA copy number, whereas a markedly increased in ROS level were observed in polymononuclear leukocytes (PMNs) derived from the DCM patients carrying these mt-tRNA mutations, suggesting that these mutations may cause mitochondrial dysfunction that was responsible for DCM. Conclusions: Our data indicated that mt-tRNA mutations may be the molecular basis for DCM, which shaded novel insight into the pathophysiology of DCM that was manifestated by mitochondrial dysfunction.

Identification of CHEK2 germline mutations in BRCA1/2 and PALB2 negative breast and ovarian cancer patients

Introduction: The CHEK2 gene is known to be an important signal transducer involved in DNA repair, apoptosis, or cell cycle arrest in response to DNA damage. The mutations in this gene have been associated with a wide range of cancers, both sporadic and hereditary. Germline CHEK2 mutations are linked to an increased risk of breast cancer. Therefore, the aim of this study was to identify the prevalence of CHEK2 variants in BRCA1/2 and PALB2 negative early-onset patients with breast cancer and/or ovarian cancer in a Turkish population for the first time. Methods: The study included 95 patients with BRCA1/2 and PALB2 negative early-onset breast cancer and/or ovarian cancer and also 60 unaffected women. All the intron/exon boundaries and coding exons of CHEK2 were subjected to mutational analysis by heteroduplex analysis and DNA sequencing. Results: A total of 16 CHEK2 variants were found in breast cancer patients within the Turkish population. CHEK2 c.1100delC mutation studied in the CHEK2 gene most frequently was not detected in our study. The prevalence of variants of uncertain significance in CHEK2 was found to be 7.3% (n= 7) in BRCA1/2 and PALB2 mutation negative Turkish patients with early-onset breast and/or ovarian cancer. Discussion/Conclusion: The present study may shed light on alternative variations that could be significant for understanding the prevalence and clinical suitability of the CHEK2 gene.

Family history of breast cancer is associated with elevated risk of prostate cancer: evidence for shared genetic risks

Introduction: Although breast and prostate cancers arise in different organs and are more frequent in the opposite sex, multiple studies have reported an association between their family history. Analysis of single nucleotide polymorphism data, based on distant relatives, has revealed a small positive genetic correlation between these cancers explained by common variants. The estimate of genetic correlation based on close relatives reveals the extent to which shared genetic risks are explained by both common and rare variants. This estimate is unknown for breast and prostate cancer. Method: We estimated the relative risks, heritability, and genetic correlation of breast cancer and prostate cancer, based on the Minnesota Breast and Prostate Cancer Study, a family study of 141 families ascertained for breast cancer. Results: Heritability of breast cancer was 0.34 (95% credible interval: 0.23-0.49) and 0.65 (95% credible interval: 0.36-0.97) for prostate cancer, and the genetic correlation was 0.23. In terms of odds ratios, these values correspond to a 1.3 times higher odds of breast cancer among probands, given that the brother has prostate cancer. Conclusion: This study shows the inherent relation between prostate cancer and breast cancer; an incident of one in a family increases the risk of developing the other. The large difference between estimates of genetic correlation from distant and close relatives, if replicated, suggests that rare variants contribute to the shared genetic risk of breast and prostate cancer. However, the difference could steam from genotype-by-family effects shared between the two types of cancers.

Association of PNPLA3 I148M with liver disease biomarkers in Latinos

Introduction. Liver disease accounts for approximately 2 million deaths per year worldwide. The majority of liver diseases are due to complications of cirrhosis, viral hepatitis, and hepatocellular carcinoma. Increased levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) may indicate liver disease. Moreover, there are additional noninvasive liver fibrosis indices that help to estimate liver damage, including AST to ALT ratio, AST to platelet ratio index (APRI), fibrosis-4 (FIB-4) score, and nonalcoholic fatty liver disease (NAFLD) fibrosis score. The aims of the present study were to (1) perform an association analysis of the patatin-like phospholipase domain containing 3 (PNPLA3) I148M (rs738409) variant with ALT, AST, and various liver fibrosis indices, and (2) determine whether there are gender related-differences in these associations. Methods. We obtained demographic, anthropometric, and metabolic phenotypes from Latino adult participants (n = 503, 64% female, 36.4 ± 0.5 years) from the Arizona Insulin Resistance (AIR) registry. SNP genotyping of I148M was performed using the TaqMan allelic discrimination assay. We used linear regression for the association analyses of the genotypes with ALT, AST, and the various liver fibrosis indices. We included genotype, age, body mass index (BMI), and alcohol status in the linear regression model. Results. The variant I148M was in Hardy-Weinberg equilibrium, with genotype distribution: non-risk CC = 118, heterozygous CG = 246, and risk GG = 139. The G allele was significantly associated with increased ALT and AST levels (p = 7.8 x 10-7 and p = 9.7 x 10-6, respectively). Moreover, we showed that the G allele was significantly associated with higher APRI (p = 3.7 x 10-7) and FIB-4 score (p = 4.1 x 10-3). When we analyzed the data by gender, we observed similar significant trends for ALT, AST, and APRI (all, p < 0.01). In females, the G allele was significantly associated with increased FIB-4 score (p = 6.9 x 10-3), which was not observed in the males (p > 0.05). There was no association of the I148M variant with AST/ALT ratio nor NAFLD risk score, whether analyzed in all adults or by gender. Discussion/Conclusion. Our findings provide additional evidence of an association of PNPLA3 I148M with several liver disease biomarkers in male and female Latinos residing in the Southwest of the United States.

Exome-Wide Pan-Cancer Analysis of Germline Variants in 8,719 Individuals Finds Little Evidence of Rare Variant Associations

<b><i>Background:</i></b> Many cancer types show considerable heritability, and extensive research has been done to identify germline susceptibility variants. Linkage studies have discovered many rare high-risk variants, and genome-wide association studies (GWAS) have discovered many common low-risk variants. However, it is believed that a considerable proportion of the heritability of cancer remains unexplained by known susceptibility variants. The “rare variant hypothesis” proposes that much of the missing heritability lies in rare variants that cannot reliably be detected by linkage analysis or GWAS. Until recently, high sequencing costs have precluded extensive surveys of rare variants, but technological advances have now made it possible to analyze rare variants on a much greater scale. <b><i>Objectives:</i></b> In this study, we investigated associations between rare variants and 14 cancer types. <b><i>Methods:</i></b> We ran association tests using whole-exome sequencing data from The Cancer Genome Atlas (TCGA) and validated the findings using data from the Pan-Cancer Analysis of Whole Genomes Consortium (PCAWG). <b><i>Results:</i></b> We identified four significant associations in TCGA, only one of which was replicated in PCAWG (BRCA1 and ovarian cancer). <b><i>Conclusions:</i></b> Our results provide little evidence in favor of the rare variant hypothesis. Much larger sample sizes may be needed to detect undiscovered rare cancer variants.

Meta-Analysis of Joint Test of SNP and SNP-Environment Interaction with Heterogeneity

Many complex diseases are caused by single nucleotide polymorphisms (SNPs), environmental factors, and the interaction between SNPs and environment. Joint tests of the SNP and SNP-environment interaction effects (JMA) and meta-regression (MR) are commonly used to evaluate these SNP-environment interactions. However, these two methods do not consider genetic heterogeneity. We previously presented a random-effect MR, which provided higher power than the MR in datasets with high heterogeneity. However, this method requires group-level data, which sometimes are not available. Given this, we designed this study to evaluate the introduction of the random effects of SNP and SNP-environment interaction into the JMA, and then extended this to the random effect model. Likelihood ratio statistic is applied to test the JMA and the new method we proposed in this paper. We evaluated the null distributions of these tests, and the powers for this method. This method was verified by simulation and was shown to provide similar powers to the random effect meta-regression method (RMR). However, this method only requires study-level data which relaxed the condition of the RMR. Our study suggests that this method is more suitable for finding the association between SNP and diseases in the absence of group-level data.

PhosSNPs-Regulated Gene Network and Pathway Significant for Rheumatoid Arthritis

<b><i>Objectives:</i></b> Peripheral blood mononuclear cells (PBMCs) are critical for immunity and participate in multiple human diseases, including rheumatoid arthritis (RA). PhosSNPs are nonsynonymous SNPs influencing protein phosphorylation, thus probably modulate cell signaling and gene expression. We aimed to identify phosSNPs-regulated gene network/pathway potentially significant for RA. <b><i>Methods:</i></b> We collected genome-wide phosSNP genotyping data and transcriptome-wide mRNA expression data from PBMCs of a Chinese sample. We discovered and verified with public datasets differentially expressed genes (DEGs) associated with RA, and replicated RA-associated SNPs in our study sample. We performed a targeted expression quantitative trait locus (eQTL) study on significant phosSNPs and DEGs. <b><i>Results:</i></b> We identified 29 nominally significant eQTL phosSNPs and 83 target genes, and constructed comprehensive regulatory/interaction networks, highlighting the vital effects of two eQTL phosSNPs (rs371513 and rs4824675, FDR &#x3c;0.05) and four critical node genes (HSPA4, NDUFA2, MRPL15, and ATP5O). Besides, two node/key genes NDUFA2 and ATP5O, regulated by rs371513, were significantly enriched in mitochondrial oxidative phosphorylation pathway. Besides, four pairs of eQTL effects were replicated independently in whole blood and/or transformed fibroblasts. <b><i>Conclusions:</i></b> The findings delineated a potential role of protein phosphorylation and genetic variations in RA and warranted the significant roles of phosSNPs in regulating RA-associated genes expression in PBMCs. The results pointed out the relevance and significance of oxidative phosphorylation pathway to RA.

Putative Digenic GJB2/MYO7A Inheritance of Hearing Loss Detected in a Patient with 48,XXYY Klinefelter Syndrome

<b><i>Objectives:</i></b> Nonsyndromic hearing loss (NSHL) is the most frequent type of hereditary hearing impairment. Here, we explored the underlying genetic cause of NSHL in a three-generation family using whole-exome sequencing. The proband had concomitant NSHL and rare 48,XXYY Klinefelter syndrome. <b><i>Material and Methods:</i></b> Genomic DNA was extracted from the peripheral blood of the proband and their family members. Sanger sequencing and pedigree verification were performed on the pathogenic variants filtered by whole-exome sequencing. The function of the variants was analyzed using bioinformatics software. <b><i>Results:</i></b> The proband was digenic heterozygous for p.V37I in the <i>GJB2</i> gene and p.L347I in the <i>MYO7A</i> gene. The proband’s mother had normal hearing and did not have any variant. The proband’s father and uncle both had NSHL and were compound for the <i>GJB2</i> p.V37I and <i>MYO7A</i> p.L347I variants, thus indicating a possible <i>GJB2/MYO7A</i> digenic inheritance of NSHL. 48,XXYY Klinefelter syndrome was discovered in the proband after the karyotype analysis, while his parents both had normal karyotypes. <b><i>Conclusions:</i></b> Our findings reported a putative <i>GJB2/MYO7A</i> digenic inheritance form of hearing loss, expanding the genotype and phenotype spectrum of NSHL. In addition, this is the first report of concomitant NSHL and 48,XXYY syndrome.

Molecular Characterization of Glucose-6-Phosphate Dehydrogenase Deficiency in the Shenzhen Population

<b><i>Background:</i></b> Glucose-6-phosphate dehydrogenase (G6PD) deficiency is caused by one or more mutations in the G6PD gene on chromosome X. This study aimed to characterize the G6PD gene variant distribution in Shenzhen of Guangdong province. <b><i>Methods:</i></b> A total of 33,562 individuals were selected at the hospital for retrospective analysis, of which 1,213 cases with enzymatic activity-confirmed G6PD deficiency were screened for G6PD gene variants. Amplification refractory mutation system PCR was first used to screen the 6 dominant mutants in the Chinese population (c.1376G&#x3e;T, c.1388G&#x3e;A, c.95A&#x3e;G, c.1024C&#x3e;T, c.392G&#x3e;T, and c.871G&#x3e;A). If the 6 hotspot variants were not found, next-generation sequencing was then performed. Finally, Sanger sequencing was used to verify all the mutations. <b><i>Results:</i></b> The incidence of G6PD deficiency in this study was 3.54%. A total of 26 kinds of mutants were found in the coding region, except for c.-8-624T&#x3e;C, which was in the noncoding region. c.1376G&#x3e;T and c.1388G&#x3e;A, both located in exon 12, were the top 2 mutants, accounting for 68.43% of all individuals. The 6 hotspot mutations had a cumulative proportion of 94.02%. <b><i>Conclusions:</i></b> This study provided detailed characteristics of G6PD gene variants in Shenzhen, and the results would be valuable to enrich the knowledge of G6PD deficiency.

Voltage-Gated Sodium Channel β1 Gene: An Overview

<b><i>Background:</i></b> Voltage-gated sodium channels are protein complexes composed of 2 subunits, namely, pore-forming α- and regulatory β-subunits. A β-subunit consists of 5 proteins encoded by 4 genes (i.e., <i>SCN1B–SCN4B</i>). <b><i>Summary:</i></b> β₁-Subunits regulate sodium ion channel functions, including gating properties, subcellular localization, and kinetics. <b><i>Key Message:</i></b> Sodium channel β₁- and its variant β_1B-subunits are encoded by <i>SCN1B</i>. These variants are associated with many human diseases, such as epilepsy, Brugada syndrome, Dravet syndrome, and cancers. On the basis of previous research, we aimed to provide an overview of the structure, expression, and involvement of <i>SCN1B</i> in physiological processes and focused on its role in diseases.