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1.  IDH1 p.R132 mutations may not be actively involved in the carcinogenesis of hepatocellular carcinoma 
Recent studies have identified prevalent isocitrate dehydrogenase 1 (IDH1) codon 132 mutations (p.R132) in gliomas and acute myeloid leukemia (AML). The IDH1 mutations lead to a loss of its normal enzymatic activity and acquisition of neomorphic activity in production of α-ketoglutarate (α-KG) and 2-hydroxyglutarate (2-HG), which finally cause alterations of multiple gene expression of tumorigenesis-associated α-KG-dependent enzymes. The aim of this study was to determine whether IDH1 p.R132 mutations are involved in the carcinogenesis of hepatocellular carcinoma.
A total of 87 Han Chinese patients with primary hepatocellular carcinoma (HCC) were analyzed by direct DNA sequencing for IDH1 p.R132 mutations. The expression levels of multiple α-KG-dependent enzymes and associated genes were quantified in HepG2 cells overexpressing IDH1 p.R132 mutants by Western blotting and real-time PCR.
None of 87 Han Chinese patients with HCC harbored any IDH1 p.R132 mutations. The protein levels of HIF-1α and histone methylation marker (H3K4me3 and H3K79me2) were determined in HepG2 cells overexpressing IDH1 p.R132 mutants, but we discerned no difference. Measurement of mRNA expression levels of VEGF, GLUT1, and HOXA genes also showed no significant difference between cells overexpressing IDH1 wild-type and p.R132 mutants.
Our negative results, together with some previous reports of the absence of IDH1 p.R132 mutations in HCC tissues, suggests that IDH1 p.R132 mutations are not actively involved in the development of HCC.
PMCID: PMC3930585  PMID: 24531386
Carcinoma; Hepatocellular; Mutation – genetics; Carcinogenesis; Histones
2.  One-Carbon Metabolism Pathway Gene Variants and Risk of Clear Cell Renal Cell Carcinoma in a Chinese Population 
PLoS ONE  2013;8(11):e81129.
One-carbon metabolism is the basement of nucleotide synthesis and the methylation of DNA linked to cancer risk. Variations in one-carbon metabolism genes are reported to affect the risk of many cancers, including renal cancer, but little knowledge about this mechanism is known in Chinese population.
Each subject donated 5 mL venous blood after signing the agreement. The study was approved by the Institutional Review Board of the Nanjing Medical University, Nanjing, China. 18 SNPs in six one-carbon metabolism-related genes (CBS, MTHFR, MTR, MTRR, SHMT1, and TYMS) were genotyped in 859 clear cell renal cell carcinoma (ccRCC) patients and 1005 cancer-free controls by the Snapshot.
Strong associations with ccRCC risk were observed for rs706209 (P = 0.006) in CBS and rs9332 (P = 0.027) in MTRR. Compared with those carrying none variant allele, individuals carrying one or more variant alleles in these two genes had a statistically significantly decreased risk of ccRCC [P = 0.001, adjusted odds ratio (OR) = 0.73, 95% confidence interval (CI) = 0.06–0.90]. In addition, patients carrying one or more variant alleles were more likely to develop localized stage disease (P = 0.002, adjusted OR = 1.37, 95%CI = 1.11–1.69) and well-differentiated ccRCC (P<0.001, adjusted OR = 1.42, 95%CI = 0.87–1.68). In the subgroup analysis, individuals carrying none variant allele in older group (P = 0.007, adjusted OR = 0.67, 95%CI = 0.49–0.91), male group (P = 0.007, adjusted OR = 0.71, 95%CI = 0.55–0.92), never smoking group (P = 0.002, adjusted OR = 0.68, 95%CI = 0.53–0.88) and never drinking group (P<0.001, adjusted OR = 0.68, 95%CI = 0.53–0.88) had an increased ccRCC risk.
Our results suggest that the polymorphisms of the one-carbon metabolism-related genes are associated with ccRCC risk in Chinese population. Future population-based prospective studies are required to confirm the results.
PMCID: PMC3837692  PMID: 24278388
3.  BRG1 Is Required for Formation of Senescence-Associated Heterochromatin Foci Induced by Oncogenic RAS or BRCA1 Loss 
Molecular and Cellular Biology  2013;33(9):1819-1829.
Cellular senescence is an important tumor suppression mechanism. We have previously reported that both oncogene-induced dissociation of BRCA1 from chromatin and BRCA1 knockdown itself drive senescence by promoting formation of senescence-associated heterochromatin foci (SAHF). However, the molecular mechanism by which BRCA1 regulates SAHF formation and senescence is unclear. BRG1 is a chromatin-remodeling factor that interacts with BRCA1 and pRB. Here we show that BRG1 is required for SAHF formation and senescence induced by oncogenic RAS or BRCA1 loss. The interaction between BRG1 and BRCA1 is disrupted during senescence. This correlates with an increased level of chromatin-associated BRG1 in senescent cells. BRG1 knockdown suppresses the formation of SAHF and senescence, while it has no effect on BRCA1 chromatin dissociation induced by oncogenic RAS, indicating that BRG1 functions downstream of BRCA1 chromatin dissociation. Furthermore, BRG1 knockdown inhibits SAHF formation and senescence induced by BRCA1 knockdown. Conversely, BRG1 overexpression drives SAHF formation and senescence in a DNA damage-independent manner. This effect depends upon BRG1's chromatin-remodeling activity as well as the interaction between BRG1 and pRB. Indeed, the interaction between BRG1 and pRB is enhanced during senescence. Chromatin immunoprecipitation analysis revealed that BRG1's association with the human CDKN2A and CDKN1A gene promoters was enhanced during senescence induced by oncogenic RAS or BRCA1 knockdown. Consistently, knockdown of pRB, p21CIP1, and p16INK4a, but not p53, suppressed SAHF formation induced by BRG1. Together, these studies reveal the molecular underpinning by which BRG1 acts downstream of BRCA1 to promote SAHF formation and senescence.
PMCID: PMC3624184  PMID: 23438604
4.  Mitochondrial DNA mutation m.10680G > A is associated with Leber hereditary optic neuropathy in Chinese patients 
Leber hereditary optic neuropathy (LHON) is a mitochondrial disorder with gender biased and incomplete penetrance. The majority of LHON patients are caused by one of the three primary mutations (m.3460G > A, m.11778G > A and m.14484T > C). Rare pathogenic mutations have been occasionally reported in LHON patients.
We screened mutation m.10680G > A in the MT-ND4L gene in 774 Chinese patients with clinical features of LHON but lacked the three primary mutations by using allele specific PCR (AS-PCR). Patients with m.10680G > A were further determined entire mtDNA genome sequence.
The optimal AS-PCR could detect as low as 10% heteroplasmy of mutation m.10680G > A. Two patients (Le1263 and Le1330) were identified to harbor m.10680G > A. Analysis of the complete mtDNA sequences of the probands suggested that they belonged to haplogroups B4a1 and D6a1. There was no other potentially pathogenic mutation, except for a few private yet reported variants in the MT-ND1 and MT-ND5 genes, in the two lineages. A search in reported mtDNA genome data set (n = 9277; excluding Chinese LHON patients) identified no individual with m.10680G > A. Frequency of m.10680G > A in Chinese LHON patients analyzed in this study and our previous studies (3/784) was significantly higher than that of the general populations (0/9277) (P = 0.0005).
Taken together, we speculated that m.10680G > A may be a rare pathogenic mutation for LHON in Chinese. This mutation should be included in future clinical diagnosis.
PMCID: PMC3372436  PMID: 22400981
LHON; mtDNA; m.10680G > A; Chinese; Rare primary mutation
5.  Inland post-glacial dispersal in East Asia revealed by mitochondrial haplogroup M9a'b 
BMC Biology  2011;9:2.
Archaeological studies have revealed a series of cultural changes around the Last Glacial Maximum in East Asia; whether these changes left any signatures in the gene pool of East Asians remains poorly indicated. To achieve deeper insights into the demographic history of modern humans in East Asia around the Last Glacial Maximum, we extensively analyzed mitochondrial DNA haplogroup M9a'b, a specific haplogroup that was suggested to have some potential for tracing the migration around the Last Glacial Maximum in East Eurasia.
A total of 837 M9a'b mitochondrial DNAs (583 from the literature, while the remaining 254 were newly collected in this study) pinpointed from over 28,000 subjects residing across East Eurasia were studied here. Fifty-nine representative samples were further selected for total mitochondrial DNA sequencing so we could better understand the phylogeny within M9a'b. Based on the updated phylogeny, an extensive phylogeographic analysis was carried out to reveal the differentiation of haplogroup M9a'b and to reconstruct the dispersal histories.
Our results indicated that southern China and/or Southeast Asia likely served as the source of some post-Last Glacial Maximum dispersal(s). The detailed dissection of haplogroup M9a'b revealed the existence of an inland dispersal in mainland East Asia during the post-glacial period. It was this dispersal that expanded not only to western China but also to northeast India and the south Himalaya region. A similar phylogeographic distribution pattern was also observed for haplogroup F1c, thus substantiating our proposition. This inland post-glacial dispersal was in agreement with the spread of the Mesolithic culture originating in South China and northern Vietnam.
PMCID: PMC3027199  PMID: 21219640
6.  Common promoter variants of the NDUFV2 gene do not confer susceptibility to schizophrenia in Han Chinese 
The NADH-ubiquinone oxidoreductase flavoprotein gene (NDUFV2), which encodes a 24 kD mitochondrial complex I subunit, has been reported to be positively associated with schizophrenia and bipolar disorder in different populations.
We genotyped the promoter variants of this gene (rs6506640 and rs1156044) by direct sequencing in 529 unrelated Han Chinese schizophrenia patients and 505 matched controls. Fisher's Exact test was performed to assess whether these two reported single nucleotide polymorphisms (SNPs) confer susceptibility to schizophrenia in Chinese.
Allele, genotype and haplotype comparison between the case and control groups showed no statistical significance, suggesting no association between the NDUFV2 gene promoter variants and schizophrenia in Han Chinese.
The role of NDUFV2 played in schizophrenia needs to be further studied. Different racial background and/or population substructure might account for the inconsistent results between studies.
PMCID: PMC3022841  PMID: 21190551
7.  Mitochondrial DNA Sequence Variation and Haplogroup Distribution in Chinese Patients with LHON and m.14484T>C 
PLoS ONE  2010;5(10):e13426.
Leber hereditary optic neuropathy (LHON, MIM 535000) is one of the most common mitochondrial genetic disorders caused by three primary mtDNA mutations (m.3460G>A, m.11778G>A and m. 14484T>C). The clinical expression of LHON is affected by many additional factors, e.g. mtDNA background, nuclear genes, and environmental factors. Hitherto, there is no comprehensive study of Chinese LHON patients with m.14484T>C.
Methodology/Principal Findings
In this study, we analyzed the mtDNA sequence variations and haplogroup distribution pattern of the largest number of Chinese LHON patients with m.14484T>C to date. We first determined the complete mtDNA sequences in eleven LHON probands with m.14484T>C, to discern the potentially pathogenic mutations that co-segregate with m.14484T>C. We then dissected the matrilineal structure of 52 patients with m.14484T>C (including 14 from unrelated families and 38 sporadic cases) and compared it with the reported Han Chinese from general populations. Complete mtDNA sequencing showed that the eleven matrilines belonged to nine haplogroups including Y2, C4a, M8a, M10a1a, G1a1, G2a1, G2b2, D5a2a1, and D5c. We did not identify putatively pathogenic mutation that was co-segregated with m.14484T>C in these lineages based on the evolutionary analysis. Compared with the reported Han Chinese from general populations, the LHON patients with m.14484T>C had significantly higher frequency of haplogroups C, G, M10, and Y, but a lower frequency of haplogroup F. Intriguingly, we also observed a lower prevalence of F lineages in LHON subjects with m.11778G>A in our previous study, suggesting that this haplogroup may enact similar role during the onset of LHON in the presence of m.14484T>C or m.11778G>A.
Our current study provided a comprehensive profile regarding the mtDNA variation and background of Chinese patients with LHON and m.14484T>C. Matrilineal background might affect the expression of LHON in Chinese patients with m.14484T>C.
PMCID: PMC2956641  PMID: 20976138
8.  Mitochondrial DNA haplogroup distribution in Chaoshanese with and without myopia 
Molecular Vision  2010;16:303-309.
Mitochondrial DNA (mtDNA) haplogroups affect the clinical expression of Leber hereditary optic neuropathy, age-related macular degeneration, and other diseases. The objective of this study is to investigate whether an mtDNA background is associated with myopia.
Blood DNA was obtained from 192 college students, including 96 individuals with moderate-to-high myopia and 96 controls without myopia. All the subjects were from a well-known isolated population living in the Chaoshan area of east Guangdong Province and speaking one of the four major dialects in southern China. The mtDNA haplogroups in the 192 subjects were determined by sequencing the mtDNA control region and partial coding regions as well as by analysis of restriction fragment length polymorphisms. Each mtDNA was classified according to the updated version of the Eastern Asian haplogroup system.
Sixteen mtDNA haplogroups were recognized in the 192 subjects. The overall matrilineal structures of the samples with and without myopia were similar and had genetic imprints showing their ethno-origin. There was no statistical difference in frequencies of haplogroup distribution between subjects with and without myopia (χ2 test, p=0.556).
We failed to identify clues that suggest an involvement of mtDNA background in the predisposition to myopia.
PMCID: PMC2830021  PMID: 20208987
9.  Sequence Characterization of the MC1R Gene in Yak (Poephagus grunniens) Breeds with Different Coat Colors 
Melanocortin 1 receptor (MC1R) gene plays a key role in determining coat color in several species, including the cattle. However, up to now there is no report regarding the MC1R gene and the potential association of its mutations with coat colors in yak (Poephagus grunniens). In this study, we sequenced the encoding region of the MC1R gene in three yak breeds with completely white (Tianzhu breed) or black coat color (Jiulong and Maiwa breeds). The predicted coding region of the yak MC1R gene resulted of 954 bp, the same to that of the wild-type cattle sequence, with >99% identity. None of the mutation events reported in cattle was found. Comparing the yak obtained sequences, five nucleotide substitutions were detected, which defined three haplotypes (EY1, EY2, and EY3). Of the five mutations, two, characterizing the EY1 haplotype, were nonsynonymous substitutions (c.340C>A and c.871G>A) causing amino acid changes located in the first extracellular loop (p.Q114K) and in the seventh transmembrane region (p.A291T). In silico prediction might indicate a functional effect of the latter substitution. However, all three haplotypes were present in the three yak breeds with relatively consistent frequency distribution, despite of their distinguished coat colors, which suggested that there was no across-breed association between haplotypes or genotypes and black/white phenotypes, at least in the investigated breeds. Other genes may be involved in affecting coat color in the analyzed yaks.
PMCID: PMC2704008  PMID: 19584942
10.  Identification and association of the single nucleotide polymorphisms in calpain3 (CAPN3) gene with carcass traits in chickens 
BMC Genetics  2009;10:10.
The aim of this study is to screen single nucleotide polymorphisms (SNP) of chicken Calpain3 (CAPN3) gene and to analyze the potential association between CAPN3 gene polymorphisms and carcass traits in chickens. We screened CAPN3 single nucleotide polymorphisms (SNP) in 307 meat-type quality chicken from 5 commercial pure lines (S01, S02, S03, S05, and D99) and 4 native breeds from Guangdong Province (Huiyang Huxu chicken and Qingyuan Ma chicken) and Sichuan Province (Caoke chicken and Shandi Black-bone chicken), China.
Two SNPs (11818T>A and 12814T>G) were detected by single strand conformation polymorphism (SSCP) method and were verified by DNA sequencing. Association analysis showed that the 12814T>G genotypes were significantly associated with body weight (BW), carcass weight (CW), breast muscle weight (BMW), and leg muscle weight (LMW). Haplotypes constructed on the two SNPs (H1, TG; H2, TT; H3, AG; and H4, AT) were associated with BW, CW (P < 0.05), eviscerated percentage (EP), semi-eviscerated percentage (SEP), breast muscle percentage (BMP), and leg muscle percentage (LMP) (P < 0.01). Diplotype H1H2 was dominant for BW, CW, and LMP, and H2H2 was dominant for EP, SEP, and BMP.
We speculated that the CAPN3 gene was a major gene affecting chicken muscle growth and carcass traits or it was linked with the major gene(s). Diplotypes H1H2 and H2H2 might be advantageous for carcass traits.
PMCID: PMC2656522  PMID: 19265533
11.  A homogenous nature of native Chinese duck matrilineal pool 
China, with around 30 unique breeds, has a diverse duck genetic pool. Currently, there is no systematic report which investigates the genetic diversity, phylogenetic relationship, and matrilineal genetic structure of these domestic breeds and wild mallards (Anas platyrhynchos).
In this study, we sequenced the mitochondrial DNA (mtDNA) control region segments in 278 domestic ducks (Anas platyrhynchos domestica) from 19 indigenous breeds/populations and 70 wild mallard samples and analyzed them together with the 101 control region sequences from published sources. Fifty-two samples were then sequenced for a cytochrome b (Cyt b) gene fragment to solidify the pattern emerged from the control region sequences. All domestic duck and wild mallard haplotypes were essentially indistinguishable and were clustered together in the phylogenetic tree. There was no geographic differentiation and breed/population-specific distribution of duck lineages.
Our results showed that unlike other domesticated farm animals in China such as chicken, cattle, goat, and yak with multiple matrilineal components, the matrilineal pool of Chinese ducks was homogenous.
PMCID: PMC2586638  PMID: 18957137
12.  Distilling Artificial Recombinants from Large Sets of Complete mtDNA Genomes 
PLoS ONE  2008;3(8):e3016.
Large-scale genome sequencing poses enormous problems to the logistics of laboratory work and data handling. When numerous fragments of different genomes are PCR amplified and sequenced in a laboratory, there is a high immanent risk of sample confusion. For genetic markers, such as mitochondrial DNA (mtDNA), which are free of natural recombination, single instances of sample mix-up involving different branches of the mtDNA phylogeny would give rise to reticulate patterns and should therefore be detectable.
Methodology/Principal Findings
We have developed a strategy for comparing new complete mtDNA genomes, one by one, to a current skeleton of the worldwide mtDNA phylogeny. The mutations distinguishing the reference sequence from a putative recombinant sequence can then be allocated to two or more different branches of this phylogenetic skeleton. Thus, one would search for two (or three) near-matches in the total mtDNA database that together best explain the variation seen in the recombinants. The evolutionary pathway from the mtDNA tree connecting this pair together with the recombinant then generate a grid-like median network, from which one can read off the exchanged segments.
We have applied this procedure to a large collection of complete human mtDNA sequences, where several recombinants could be distilled by our method. All these recombinant sequences were subsequently corrected by de novo experiments – fully concordant with the predictions from our data-analytical approach.
PMCID: PMC2515346  PMID: 18714389
13.  Population phylogenomic analysis of mitochondrial DNA in wild boars and domestic pigs revealed multiple domestication events in East Asia 
Genome Biology  2007;8(11):R245.
A fine-grained mitochondrial DNA phylogenomic analysis was conducted in domestic pigs and wild boars, revealing that pig domestication in East Asia occurred in the Mekong and the middle and downstream regions of the Yangtze river.
Previously reported evidence indicates that pigs were independently domesticated in multiple places throughout the world. However, a detailed picture of the origin and dispersal of domestic pigs in East Asia has not yet been reported.
Population phylogenomic analysis was conducted in domestic pigs and wild boars by screening the haplogroup-specific mutation motifs inferred from a phylogenetic tree of pig complete mitochondrial DNA (mtDNA) sequences. All domestic pigs are clustered into single clade D (which contains subclades D1, D2, D3, and D4), with wild boars from East Asia being interspersed. Three haplogroups within D1 are dominant in the Mekong region (D1a2 and D1b) and the middle and downstream regions of the Yangtze River (D1a1a), and may represent independent founders of domestic pigs. None of the domestic pig samples from North East Asia, the Yellow River region, and the upstream region of the Yangtze River share the same haplogroup status with the local wild boars. The limited regional distributions of haplogroups D1 (including its subhaplogroups), D2, D3, and D4 in domestic pigs suggest at least two different in situ domestication events.
The use of fine-grained mtDNA phylogenomic analysis of wild boars and domestic pigs is a powerful tool with which to discern the origin of domestic pigs. Our findings show that pig domestication in East Asia mainly occurred in the Mekong region and the middle and downstream regions of the Yangtze River.
PMCID: PMC2258183  PMID: 18021448
14.  External Contamination in Single Cell mtDNA Analysis 
PLoS ONE  2007;2(8):e681.
Mitochondrial DNA (mtDNA) variation in single hematopoietic cells, muscle fibers, oocytes, and from tiny amount of tumor tissues and degraded clinical specimens has been reported in many medical publications. External DNA contamination, notoriously difficult to avoid, threatens the integrity of such studies.
Methodology/Principal Findings
Employing a phylogenetic approach, we analyzed the geographic origins of mtDNA sequence anomalies observed during multiple studies of mtDNA sequence variation in a total of 7094 single hematopoietic cells. 40 events with irregular mtDNA patterns were detected: eight instances (from seven different haplotypes) could be traced to laboratory personnel; six cases were caused by sample cross-contamination. The sources of the remaining events could not be identified, and the anomalous sequence variation referred to matrilines from East Asia, Africa, or West Eurasia, respectively. These mtDNA sequence anomalies could be best explained by contamination.
Using the known world mtDNA phylogeny, we could distinguish the geographic origin of the anomalous mtDNA types, providing some useful information regarding the source of contamination. Our data suggest that routine mtDNA sequence analysis of laboratory personnel is insufficient to identify and eliminate all contaminants. A rate of 0.6% of external contamination in this study, while low, is not negligible: Unrecognized contaminants will be mistaken as evidence of remarkable somatic mutations associated with the development of cancer and other diseases. The effective contamination rate can increase by a factor of more than an order of magnitude in some studies that did not institute high standards. Our results are of particular relevance to mtDNA research in medicine, and such an approach should be adopted to maintain and improve quality control in single-cell analyses.
PMCID: PMC1930155  PMID: 17668059
15.  Immunolocalization and Expression of Vascular Endothelial Growth Factor Receptors (VEGFRs) and Neuropilins (NRPs) on Keratinocytes in Human Epidermis 
Molecular Medicine  2006;12(7-8):127-136.
Vascular endothelial growth factor (VEGF) plays an important role in normal and pathological angiogenesis. VEGF receptors (VEGFRs, including VEGFR-1, VEGFR-2, and VEGFR-3) and neuropilins (NRPs, including NRP-1 and NRP-2) are high-affinity receptors for VEGF and are typically considered to be specific for endothelial cells. Here we showed expression of VEGFRs and NRPs on cultured epidermal keratinocytes at both mRNA and protein levels. We further localized these receptors by immunofluorescence (IF) staining in the epidermis of surgical skin specimens. We found positive staining for VEGFRs and NRPs in all layers of the epidermis except for the stratum corneum. VEGFR-1 and VEGFR-2 are primarily expressed on the cytoplasmic membrane of basal cells and the adjacent spinosum keratinocytes. All layers of the epidermis except for the horny cell layer demonstrated a uniform pattern of VEGFR-3, NRP-1, and NRP-2. Sections staining for NRP-1 and NRP-2 also showed diffuse intense fluorescence and were localized to the cell membrane and cytoplasm of keratinocytes. In another panel of experiments, keratinocytes were treated with different concentrations of VEGF, with or without VEGFR-2 neutralizing antibody in culture. VEGF enhanced the proliferation and migration of keratinocytes, and these effects were partially inhibited by pretreatment with VEGFR-2 neutralizing antibody. Adhesion of keratinocytes to type IV collagen–coated culture plates was decreased by VEGF treatment, but this reduction could be completely reversed by pretreatment with VEGFR-2 neutralizing antibody. Taken together, our results suggest that the expression of VEGFRs and NRPs on keratinocytes may constitute important regulators for its activity and may possibly be responsible for the autocrine signaling in the epidermis.
PMCID: PMC1626599  PMID: 17088944
16.  Authors' Reply 
PLoS Medicine  2006;3(3):e166.
PMCID: PMC1420397
17.  A Critical Reassessment of the Role of Mitochondria in Tumorigenesis 
PLoS Medicine  2005;2(11):e296.
Mitochondrial DNA (mtDNA) is being analyzed by an increasing number of laboratories in order to investigate its potential role as an active marker of tumorigenesis in various types of cancer. Here we question the conclusions drawn in most of these investigations, especially those published in high-rank cancer research journals, under the evidence that a significant number of these medical mtDNA studies are based on obviously flawed sequencing results.
Methods and Findings
In our analyses, we take a phylogenetic approach and employ thorough database searches, which together have proven successful for detecting erroneous sequences in the fields of human population genetics and forensics. Apart from conceptual problems concerning the interpretation of mtDNA variation in tumorigenesis, in most cases, blocks of seemingly somatic mutations clearly point to contamination or sample mix-up and, therefore, have nothing to do with tumorigenesis.
The role of mitochondria in tumorigenesis remains unclarified. Our findings of laboratory errors in many contributions would represent only the tip of the iceberg since most published studies do not provide the raw sequence data for inspection, thus hindering a posteriori evaluation of the results. There is no precedent for such a concatenation of errors and misconceptions affecting a whole subfield of medical research.
The role of mitochondria in tumorigenesis remains unclear; in this paper Salas and colleagues raise concerns over many published studies
PMCID: PMC1240051  PMID: 16187796
18.  Variants of CEP68 Gene Are Associated with Acute Urticaria/Angioedema Induced by Multiple Non-Steroidal Anti-Inflammatory Drugs 
PLoS ONE  2014;9(3):e90966.
Non-steroidal anti-inflammatory drugs (NSAIDs) are the most consumed drugs worldwide because of their efficacy and utility in the treatment of pain and inflammatory diseases. However, they are also responsible for an important number of adverse effects including hypersensitivity reactions. The most important group of these reactions is triggered by non-immunological, pharmacological mechanisms catalogued under the denomination of cross-intolerance (CRI), with acute urticaria/angioedema induced by multiple NSAIDs (MNSAID-UA) the most frequently associated clinical entity. A recent genome-wide association study identified the gene encoding the centrosomal protein of 68 KDa (CEP68) as the major locus associated with aspirin intolerance susceptibility in asthmatics. In this study, we aimed to assess the role of this locus in susceptibility to CRI to NSAIDs by examining 53 common gene variants in a total of 635 patients that were classified as MNSAID-UA (n = 399), airway exacerbations (n = 110) or blended pattern (n = 126), and 425 controls. We found in the MNSAID-UA group a number of variants (17) associated (lowest p-value = 1.13×10−6), including the non-synonymous Gly74Ser variant (rs7572857) previously associated with aspirin intolerance susceptibility in asthmatics. Although not being significant in the context of multiple testing, eight of these variants were also associated with exacerbated respiratory disease or blended reactions. Our results suggest that CEP68 gene variants may play an important role in MNSAID-UA susceptibility and, despite the different regulatory mechanisms involved depending on the specific affected organ, in the development of hypersensitivity reactions to NSAIDs.
PMCID: PMC3949706  PMID: 24618698
19.  Genetic Variation in Genes Encoding Airway Epithelial Potassium Channels Is Associated with Chronic Rhinosinusitis in a Pediatric Population 
PLoS ONE  2014;9(3):e89329.
Apical potassium channels regulate ion transport in airway epithelial cells and influence air surface liquid (ASL) hydration and mucociliary clearance (MCC). We sought to identify whether genetic variation within genes encoding airway potassium channels is associated with chronic rhinosinusitis (CRS).
Single nucleotide polymorphism (SNP) genotypes for selected potassium channels were derived from data generated on the Illumnia HumanHap550 BeadChip or Illumina Human610-Quad BeadChip for 828 unrelated individuals diagnosed with CRS and 5,083 unrelated healthy controls from the Children's Hospital of Philadelphia (CHOP). Statistical analysis was performed with set-based tests using PLINK, and corrected for multiple testing.
Set-based case control analysis revealed the gene KCNMA1 was associated with CRS in our Caucasian subset of the cohort (598 CRS cases and 3,489 controls; p = 0.022, based on 10,000 permutations). In addition there was borderline evidence that the gene KCNQ5 (p = 0.0704) was associated with the trait in our African American subset of the cohort (230 CRS cases and 1,594 controls). In addition to the top significant SNPs rs2917454 and rs6907229, imputation analysis uncovered additional genetic variants in KCNMA1 and in KCNQ5 that were associated with CRS.
We have implicated two airway epithelial potassium channels as novel susceptibility loci in contributing to the pathogenesis of CRS.
PMCID: PMC3940609  PMID: 24595210
20.  Uncovering the Rare Variants of DLC1 Isoform 1 and Their Functional Effects in a Chinese Sporadic Congenital Heart Disease Cohort 
PLoS ONE  2014;9(2):e90215.
Congenital heart disease (CHD) is the most common birth defect affecting the structure and function of fetal hearts. Despite decades of extensive studies, the genetic mechanism of sporadic CHD remains obscure. Deleted in liver cancer 1 (DLC1) gene, encoding a GTPase-activating protein, is highly expressed in heart and essential for heart development according to the knowledge of Dlc1-deficient mice. To determine whether DLC1 is a susceptibility gene for sporadic CHD, we sequenced the coding region of DLC1 isoform 1 in 151 sporadic CHD patients and identified 13 non-synonymous rare variants (including 6 private variants) in the case cohort. Importantly, these rare variants (8/13) were enriched in the N-terminal region of the DLC1 isoform 1 protein. Seven of eight amino acids at the N-terminal variant positions were conserved among the primates. Among the 9 rare variants that were predicted as “damaging”, five were located at the N-terminal region. Ensuing in vitro functional assays showed that three private variants (Met360Lys, Glu418Lys and Asp554Val) impaired the ability of DLC1 to inhibit cell migration or altered the subcellular location of the protein compared to wild-type DLC1 isoform 1. These data suggest that DLC1 might act as a CHD-associated gene in addition to its role as a tumor suppressor in cancer.
PMCID: PMC3938602  PMID: 24587289
21.  Mitochondrial DNA Haplogroup Confers Genetic Susceptibility to Nasopharyngeal Carcinoma in Chaoshanese from Guangdong, China 
PLoS ONE  2014;9(1):e87795.
Recent studies have shown association of mtDNA background with cancer development. We analyzed mitochondrial DNA (mtDNA) control region variation of 201 patients with nasopharyngeal carcinoma (NPC) and of 201 normal controls from Chaoshan Han Chinese to discern mtDNA haplogroup effect on the disease onset. Binary logistic regression analysis with adjustment for gender and age revealed that the haplogroup R9 (P = 0.011, OR = 1.91, 95% CI = 1.16–3.16), particularly its sub-haplogroup F1 (P = 0.015, OR = 2.43, 95% CI = 1.18–5.00), were associated significantly with increased NPC risk. These haplogroups were further confirmed to confer high NPC risk in males and/or individuals ≥40 years of age, but not in females or in subjects <40 years old. Our results indicated that mtDNA background confers genetic susceptibility to NPC in Chaoshan Han Chinese, and R9, particularly its sub-haplogroup F1, is a risk factor for NPC.
PMCID: PMC3909237  PMID: 24498198
22.  TRAF5 and TRAF3IP2 Gene Polymorphisms Are Associated with Behçet's Disease and Vogt-Koyanagi-Harada Syndrome: A Case-Control Study 
PLoS ONE  2014;9(1):e84214.
TRAF5 and TRAF3IP2 have been reported to be associated with several autoimmune diseases. Behçet's disease (BD) and Vogt-Koyanagi-Harada (VKH) syndrome are two autoimmune uveitis entities whereby both genetic and environmental factors are thought to be involved.
The role of TRAF5 and TRAF3IP2 in BD and VKH has not yet been reported and was therefore the subject of this study.
The study included 789 BD patients, 940 VKH patients and 1601 healthy unrelated individuals. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or TaqMan® SNP Genotyping Assay. Real-Time PCR was used to detect mRNA expression from PBMCs obtained from healthy controls with (n = 22) or without (n = 79) stimulation. Levels of TNF-α, IL-6 and IL-8 in culture supernatants were measured by ELISA (n = 22).
Three SNPs (rs6540679, rs12569232, rs10863888) of TRAF5 and rs13210247 of TRAF3IP2 were significantly associated with Behçet's disease and VKH syndrome (corrected P values ranging from 9.45×10−12 to 0.027). TRAF3IP2 rs33980500 and rs13190932 were not polymorphic in Han Chinese. Following stimulation by lipopolysaccharide (LPS), carriers of the GG genotype of rs6540679/TRAF5 had a higher TRAF5 mRNA expression (p = 0.004) and an increased TNF-α (p = 0.0052) and IL-6 (p = 0.0014) level compared with AA and AG genotype carriers.
This study provides evidence that TRAF5 and TRAF3IP2 genes are involved in the development of BD and VKH syndrome. Functional research suggested that TRAF5 gene polymorphisms may regulate TRAF5 expression and downstream inflammatory cytokines such as TNF-α and IL-6.
PMCID: PMC3885545  PMID: 24416204
23.  Genetic Heterogeneity of Susceptibility Gene in Different Ethnic Populations: Refining Association Study of PTPN22 for Graves’ Disease in a Chinese Han Population 
PLoS ONE  2013;8(12):e84514.
In our previous studies, we presumed subtypes of Graves’ disease (GD) may be caused by different major susceptibility genes or different variants of a single susceptibility gene. However, more evidence is needed to support this hypothesis. Single-nucleotide polymorphism (SNP) rs2476601 in PTPN22 is the susceptibility loci of GD in the European population. However, this polymorphism has not been found in Asian populations. Here, we investigate whether PTPN22 is the susceptibility gene for GD in Chinese population and further determine the susceptibility variant of PTPN22 in GD. We conducted an imputation analysis based on the results of our genome-wide association study (GWAS) in 1,536 GD patients and 1,516 control subjects. Imputation revealed that 255 common SNPs on a linkage disequilibrium (LD) block containing PTPN22 were associated with GD (P<0.05). Nine tagSNPs that captured the 255 common variants were selected to be further genotyped in a large cohort including 4,368 GD patients and 4,350 matched controls. There was no significant difference between the nine tagSNPs (P>0.05) in either the genotype distribution or allelic frequencies between patients and controls in the replication study. Although the combined analysis exhibited a weak association signal (Pcombined = 0.003263 for rs3811021), the false positive report probability (FPRP) analysis indicated it was most likely a false positive finding. Our study did not support an association of common SNPs in PTPN22 LD block with GD in Chinese Han population. This suggests that GD in different ethnic population is probably caused by distinct susceptibility genes.
PMCID: PMC3875558  PMID: 24386393
24.  Population Genetic Studies Revealed Local Adaptation in a High Gene-Flow Marine Fish, the Small Yellow Croaker (Larimichthys polyactis) 
PLoS ONE  2013;8(12):e83493.
The genetic differentiation of many marine fish species is low. Yet local adaptation may be common in marine fish species as the vast and changing marine environment provides more chances for natural selection. Here, we used anonymous as well as known protein gene linked microsatellites and mitochondrial DNA to detect the population structure of the small yellow croaker (Larimichthys polyactis) in the Northwest Pacific marginal seas. Among these loci, we detected at least two microsatellites, anonymous H16 and HSP27 to be clearly under diversifying selection in outlier tests. Sequence cloning and analysis revealed that H16 was located in the intron of BAHCC1 gene. Landscape genetic analysis showed that H16 mutations were significantly associated with temperature, which further supported the diversifying selection at this locus. These marker types presented different patterns of population structure: (i) mitochondrial DNA phylogeny showed no evidence of genetic divergence and demonstrated only one glacial linage; (ii) population differentiation using putatively neutral microsatellites presented a pattern of high gene flow in the L. polyactis. In addition, several genetic barriers were identified; (iii) the population differentiation pattern revealed by loci under diversifying selection was rather different from that revealed by putatively neutral loci. The results above suggest local adaptation in the small yellow croaker. In summary, population genetic studies based on different marker types disentangle the effects of demographic history, migration, genetic drift and local adaptation on population structure and also provide valuable new insights for the design of management strategies in L. polyactis.
PMCID: PMC3861527  PMID: 24349521
25.  Chronic Clomipramine Treatment Reverses Core Symptom of Depression in Subordinate Tree Shrews 
PLoS ONE  2013;8(12):e80980.
Chronic stress is the major cause of clinical depression. The behavioral signs of depression, including anhedonia, learning and memory deficits, and sleep disruption, result from the damaging effects of stress hormones on specific neural pathways. The Chinese tree shrew (Tupaia belangeri chinensis) is an aggressive non-human primate with a hierarchical social structure that has become a well-established model of the behavioral, endocrine, and neurobiological changes associated with stress-induced depression. The tricyclic antidepressant clomipramine treats many of the core symptoms of depression in humans. To further test the validity of the tree shrew model of depression, we examined the effects of clomipramine on depression-like behaviors and physiological stress responses induced by social defeat in subordinate tree shrews. Social defeat led to weight loss, anhedonia (as measured by sucrose preference), unstable fluctuations in locomotor activity, sustained urinary cortisol elevation, irregular cortisol rhythms, and deficient hippocampal long-term potentiation (LTP). Clomipramine ameliorated anhedonia and irregular locomotor activity, and partially rescued the irregular cortisol rhythm. In contrast, weight loss increased, cortisol levels were even higher, and in vitro LTP was still impaired in the clomipramine treatment group. These results demonstrate the unique advantage of the tree shrew social defeat model of depression.
PMCID: PMC3846567  PMID: 24312510

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