Variations in a locus at chromosome 10q26 are strongly associated with the risk of age-related macular degeneration (AMD). The most significantly associated haplotype includes a nonsynonymous SNP rs10490924 in the exon 1 of ARMS2 and rs11200638 in the promoter region of HTRA1. It is under debate which gene(s), ARMS2, HTRA1 or some other genes are functionally responsible for the genetic association. To verify whether the associated variants correlate with a higher HTRA1 expression level as previously reported, HTRA1 mRNA and protein were measured in a larger human retina-RPE-choroid samples (n = 82). Results show there is no significant change of HTRA1 mRNA level among genotypes at rs11200638, rs10490924 or an indel variant of ARMS2. Furthermore, two AMD-associated synonymous SNPs rs1049331 and rs2293870 in HTRA1 exon 1 do not change its protein level either. These results suggest that the AMD-associated variants in the chromosome 10q26 locus do not significantly affect the expression of HTRA1.
Using A/J mice, which are susceptible to Staphylococcus aureus, we sought to identify genetic determinants of susceptibility to S. aureus, and evaluate their function with regard to S. aureus infection. One QTL region on chromosome 11 containing 422 genes was found to be significantly associated with susceptibility to S. aureus infection. Of these 422 genes, whole genome transcription profiling identified five genes (Dcaf7, Dusp3, Fam134c, Psme3, and Slc4a1) that were significantly differentially expressed in a) S. aureus –infected susceptible (A/J) vs. resistant (C57BL/6J) mice and b) humans with S. aureus blood stream infection vs. healthy subjects. Three of these genes (Dcaf7, Dusp3, and Psme3) were down-regulated in susceptible vs. resistant mice at both pre- and post-infection time points by qPCR. siRNA-mediated knockdown of Dusp3 and Psme3 induced significant increases of cytokine production in S. aureus-challenged RAW264.7 macrophages and bone marrow derived macrophages (BMDMs) through enhancing NF-κB signaling activity. Similar increases in cytokine production and NF-κB activity were also seen in BMDMs from CSS11 (C57BL/6J background with chromosome 11 from A/J), but not C57BL/6J. These findings suggest that Dusp3 and Psme3 contribute to S. aureus infection susceptibility in A/J mice and play a role in human S. aureus infection.
Staphylococcus aureus causes life-threatening infections in humans. Host genetic determinants influence the outcome of S. aureus infection, yet are poorly understood. Susceptible A/J and resistant C57BL/6J mice provide a unique platform to study the genetic difference responsible for variable host response to S. aureus infection. We showed that chromosome 11 in A/J was responsible for susceptibility to S. aureus. We further identified a QTL locus on Chromosome 11 significantly associated with S. aureus susceptibility. Five genes in the QTL (Dcaf7, Dusp3, Fam134c, Psme3, and Slc4a1) were significantly differently expressed in a) susceptible vs. resistant mice, and b) humans with S. aureus blood stream infection vs. healthy human subjects. Three genes (Dusp3, Psme3, and Dcaf7) were down-regulated in susceptible A/J mice. siRNA-mediated knockdown of Dusp3 and Psme3 in bone marrow derived macrophage (BMDMs) significantly enhanced cytokine responses through NF-κB activity upon S. aureus challenge in a pattern that was also present in S. aureus-challenged BMDMs from susceptible CSS11 (chr. 11 from A/J but otherwise C57BL/6J) mice, but not resistant C57BL/6J mice. These findings suggest that Dusp3 and Psme3 contribute to S. aureus infection susceptibility in A/J mice and play a role in human S. aureus infection.
Relatively little is known about the interaction between genes and environment in the complex etiology of age-related macular degeneration (AMD). This study aimed to identify novel factors associated with AMD by analyzing gene-smoking interactions in a genome-wide association study of 1207 AMD cases and 686 controls of Caucasian background with genotype data on 668,238 single nucleotide polymorphisms (SNPs) after quality control. Participants’ history of smoking at least 100 cigarettes lifetime was determined by a self-administered questionnaire. SNP associations modeled the effect of the minor allele additively on AMD using logistic regression, with adjustment for age, sex, and ever/never smoking. Joint effects of SNPs and smoking were examined comparing a null model containing only age, sex, and smoking against an extended model including genotypic and interaction terms. Genome-wide significant main effects were detected at three known AMD loci: CFH (P=7.51×10−30), ARMS2 (P=1.94×10−23), and RDBP/CFB/C2 (P=4.37×10−10), while joint effects analysis revealed three genomic regions with P<10−5. Analyses stratified by smoking found genetic associations largely restricted to non-smokers, with one notable exception: the chromosome 18q22.1 intergenic SNP rs17073641 (between SERPINB8 and CDH7), more strongly associated in non-smokers (OR=0.57, P=2.73×10−5), with an inverse association among smokers (OR=1.42, P=0.00228), suggesting that smoking modifies the effect of some genetic polymorphisms on AMD risk.
Age-related macular degeneration; age-related maculopathy; genome wide association studies (GWAS); gene-environment interaction; genome wide gene-environment interaction studies; smoking; smoking-gene interactions
The human tau gene, which promotes assembly of neuronal microtubules, has been associated with several rare neurologic diseases that clinically include parkinsonian features. We recently observed linkage in idiopathic Parkinson disease (PD) to a region on chromosome 17q21 that contains the tau gene. These factors make tau a good candidate for investigation as a susceptibility gene for idiopathic PD, the most common form of the disease.
To investigate whether the tau gene is involved in idiopathic PD.
Design, Setting, and Participants
Among a sample of 1056 individuals from 235 families selected from 13 clinical centers in the United States and Australia and from a family ascertainment core center, we tested 5 single-nucleotide polymorphisms (SNPs) within the tau gene for association with PD, using family-based tests of association. Both affected (n = 426) and unaffected (n = 579) family members were included; 51 individuals had unclear PD status. Analyses were conducted to test individual SNPs and SNP haplotypes within the tau gene.
Main Outcome Measure
Family-based tests of association, calculated using asymptotic distributions.
Analysis of association between the SNPs and PD yielded significant evidence of association for 3 of the 5 SNPs tested: SNP 3, P = .03; SNP 9i, P = .04; and SNP 11, P = .04. The 2 other SNPs did not show evidence of significant association (SNP 9ii, P = .11, and SNP 9iii, P = .87). Strong evidence of association was found with haplotype analysis, with a positive association with one haplotype (P = .009) and a negative association with another haplotype (P = .007). Substantial linkage disequilibrium (P<.001) was detected between 4 of the 5 SNPs (SNPs 3,9i, 9ii, and 11).
This integrated approach of genetic linkage and positional association analyses implicates tau as a susceptibility gene for idiopathic PD.
Humans vary in their susceptibility to acquiring Staphylococcus aureus infection, and research suggests that there is a genetic basis for this variability. Several recent genome-wide association studies (GWAS) have identified variants that may affect susceptibility to infectious diseases, demonstrating the potential value of GWAS in this arena.
We conducted a GWAS to identify common variants associated with acquisition of S. aureus bacteremia (SAB) resulting from healthcare contact. We performed a logistic regression analysis to compare patients with healthcare contact who developed SAB (361 cases) to patients with healthcare contact in the same hospital who did not develop SAB (699 controls), testing 542,410 SNPs and adjusting for age (by decade), sex, and 6 significant principal components from our EIGENSTRAT analysis. Additionally, we evaluated the joint effect of the host and pathogen genomes in association with severity of SAB infection via logistic regression, including an interaction of host SNP with bacterial genotype, and adjusting for age (by decade), sex, the 6 significant principal components, and dialysis status. Bonferroni corrections were applied in both analyses to control for multiple comparisons.
Ours is the first study that has attempted to evaluate the entire human genome for variants potentially involved in the acquisition or severity of SAB. Although this study identified no common variant of large effect size to have genome-wide significance for association with either the risk of acquiring SAB or severity of SAB, the variant (rs2043436) most significantly associated with severity of infection is located in a biologically plausible candidate gene (CDON, a member of the immunoglobulin family) and may warrant further study.
The genetic architecture underlying SAB is likely to be complex. Future investigations using larger samples, narrowed phenotypes, and advances in both genotyping and analytical methodologies will be important tools for identifying causative variants for this common and serious cause of healthcare-associated infection.
Genomics; Genome-wide association study; Case–control study; Staphylococcus aureus; Bacteremia; Gram-positive bacterial infections; Polymorphism, single-nucleotide; Infections; Nosocomial; Cross infection
Successful aging (SA) is a multi-dimensional phenotype involving preservation of cognitive ability, physical function, and social engagement throughout life. Multiple components of SA are heritable, supporting a genetic component. The Old Order Amish are genetically and socially isolated with homogeneous lifestyles, making them a suitable population for studying the genetics of SA. DNA and measures of SA were collected on 214 cognitively intact Amish individuals over age 80. Individuals were grouped into a 13-generation pedigree using the Anabaptist Genealogy Database. A linkage screen of 5,944 single nucleotide polymorphisms (SNPs) was performed using 12 informative sub-pedigrees with an affected-only 2-point and multipoint linkage analysis. Eleven SNPs produced 2-point LOD scores >2, suggestive of linkage. Multipoint linkage analyses, allowing for heterogeneity, detected significant lod scores on chromosomes 6 (HLOD = 4.50), 7 (LOD* = 3.11), and 14 (HLOD = 4.17), suggesting multiple new loci underlying SA.
Amish; longevity; genetic epidemiology; family-based study; population isolate
To identify novel late-onset Alzheimer disease (LOAD) risk genes, we have analyzed Amish populations of Ohio and Indiana. We performed genome-wide SNP linkage and association studies on 798 individuals (109 with LOAD). We tested association using the Modified Quasi-Likelihood Score (MQLS) test and also performed two-point and multipoint linkage analyses. We found that LOAD was significantly associated with APOE (P=9.0×10-6) in all our ascertainment regions except for the Adams County, Indiana, community (P=0.55). Genome-wide, the most strongly associated SNP was rs12361953 (P=7.92×10-7). A very strong, genome-wide significant multipoint peak (recessive HLOD=6.14, dominant HLOD=6.05) was detected on 2p12. Three additional loci with multipoint HLOD scores >3 were detected on 3q26, 9q31, and 18p11. Converging linkage and association results, the most significantly associated SNP under the 2p12 peak was at rs2974151 (P=1.29×10-4). This SNP is located in CTNNA2, which encodes catenin alpha 2, a neuronal-specific catenin known to have function in the developing brain. These results identify CTNNA2 as a novel candidate LOAD gene, and implicate three other regions of the genome as novel LOAD loci. These results underscore the utility of using family-based linkage and association analysis in isolated populations to identify novel loci for traits with complex genetic architecture.
GWAS; Linkage; founder population; Amish; Alzheimer
Candida albicans is the most common human fungal pathogen causing mucosal and systemic infections. However, human antifungal immunity remains poorly defined. Here, by integrating transcriptional analysis and functional genomics, we identified Candida-specific host defense mechanisms in humans. Candida induced significant expression of genes from the type I interferon (IFN) pathway in human peripheral blood mononuclear cells. This unexpectedly prominent role of type I IFN pathway in anti-Candida host defense was supported by additional evidence. Polymorphisms in type I IFN genes modulated Candida-induced cytokine production and were correlated with susceptibility to systemic candidiasis. In in-vitro experiments, type I IFNs skewed Candida-induced inflammation from a Th17-response toward a Th1-response. Patients with chronic mucocutaneaous candidiasis displayed defective expression of genes in the type I IFN pathway. These findings indicate that the type I IFN pathway is a main signature of Candida-induced inflammation and plays a crucial role in anti-Candida host defense in humans.
To examine overall diet quality in relation to advanced age-related macular degeneration (AMD).
This case-control study identified 437 advanced AMD patients and 259 unrelated controls using stereoscopic color fundus photographs. Participants were predominantly non-Hispanic white men and women from North Carolina and Tennessee. A 97-item Block food frequency questionnaire was used to gather diet information, and overall diet quality was measured using the Healthy Eating Index (HEI) and Alternate Healthy Eating Index (AHEI).
Participants in the highest quartile of diet quality had significantly reduced odds of AMD according to the AHEI score (0.54, 95% confidence interval 0.30 – 0.99) and non-significantly reduced odds of AMD according to the HEI (0.75, 0.41 – 1.38). Odds of AMD were also 51% lower in the highest quartile of fish intake compared to the lowest quartile (odds ratio = 0.49, 0.26 – 0.90).
We found that advanced AMD was significantly related to overall diet quality. The AHEI score may be a useful instrument for assessing AMD risk due to diet, and it could potentially be improved by incorporating more specific information regarding micronutrient intake.
(See the editorial commentary by Bagni and Whitby, on pages 873–4.)
Background. Candidemia is a severe invasive fungal infection with high mortality. Recognition of Candida species is mediated through pattern recognition receptors such as Toll-like receptors (TLRs). This study assessed whether genetic variation in TLR signaling influences susceptibility to candidemia.
Methods. Thirteen mostly nonsynonymous single nucleotide polymorphisms (SNPs) in genes encoding TLRs and signaling adaptors MyD88 and Mal/TIRAP were genotyped in 338 patients (237 white, 93 African American, 8 other race) with candidemia and 351 noninfected controls (263 white, 88 African American). The SNPs significant in univariate analysis were further analyzed with multivariable logistic regression to determine association with clinical outcomes. Functional consequences of these polymorphisms were assessed via in vitro stimulation assays.
Results. Analyses of TLR SNPs revealed that 3 TLR1 SNPs (R80T, S248N, I602S) were significantly associated with candidemia susceptibility in whites. This association was not found in African Americans, likely due to lower power in this smaller study population. Furthermore, these TLR1 polymorphisms displayed impaired cytokine release by primary monocytes. No associations with susceptibility to candidemia were observed for SNPs in TLR2, TLR4, TLR6, TLR9, MyD88, or TIRAP.
Conclusions. Nonsynonymous SNPs in TLR1 are associated with impaired TLR1 function, decreased cytokine responses, and predisposition to candidemia in whites.
Genome-wide association (GWAS) methods have identified genes contributing to Parkinson disease (PD); we sought to identify additional genes associated with PD susceptibility.
A two stage design was used. First, individual level genotypic data from five recent PD GWAS (Discovery Sample: 4,238 PD cases and 4,239 controls) were combined. Following imputation, a logistic regression model was employed in each dataset to test for association with PD susceptibility and results from each dataset were meta-analyzed. Second, 768 SNPs were genotyped in an independent Replication Sample (3,738 cases and 2,111 controls).
Genome-wide significance was reached for SNPs in SNCA (rs356165, G: odds ratio (OR)=1.37; p=9.3 × 10−21), MAPT (rs242559, C: OR=0.78; p=1.5 × 10−10), GAK/DGKQ (rs11248051, T:OR=1.35; p=8.2 × 10−9/ rs11248060, T: OR=1.35; p=2.0×10−9), and the HLA region (rs3129882, A: OR=0.83; p=1.2 × 10−8), which were previously reported. The Replication Sample confirmed the associations with SNCA, MAPT, and the HLA region and also with GBA (E326K OR=1.71; p=5 × 10−8 Combined Sample) (N370 OR=3.08; p=7 × 10−5 Replication sample). A novel PD susceptibility locus, RIT2, on chromosome 18 (rs12456492; p=5 × 10−5 Discovery Sample; p=1.52 × 10−7 Replication sample; p=2 × 10−10 Combined Sample) was replicated. Conditional analyses within each of the replicated regions identified distinct SNP associations within GBA and SNCA, suggesting that there may be multiple risk alleles within these genes.
We identified a novel PD susceptibility locus, RIT2, replicated several previously identified loci, and identified more than one risk allele within SNCA and GBA.
We assessed the role of genetic variation in cytokine and cytokine receptor genes in susceptibility and severity of bloodstream infections with Candida species, which revealed a major role for functional polymorphisms in interleukin-10 and interleukin-12p40 in predisposing to persistent fungemia.
Background. Candida bloodstream infections cause significant morbidity and mortality among hospitalized patients. Although clinical and microbiological factors affecting prognosis have been identified, the impact of genetic variation in the innate immune responses mediated by cytokines on outcomes of infection remains to be studied.
Methods. A cohort of 338 candidemia patients and 351 noninfected controls were genotyped for single-nucleotide polymorphisms (SNPs) in 6 cytokine genes (IFNG, IL10, IL12B, IL18, IL1β, IL8) and 1 cytokine receptor gene (IL12RB1). The association of SNPs with both candidemia susceptibility and outcome were assessed. Concentrations of pro- and antiinflammatory cytokines were measured in in vitro peripheral blood mononuclear cell stimulation assays and in serum from infected patients.
Results. None of the cytokine SNPs studied were associated with susceptibility to candidemia. Persistent fungemia occurred in 13% of cases. In the multivariable model, persistent candidemia was significantly associated with (odds ratio [95% confidence interval]): total parenteral nutrition (2.79 [1.26–6.17]), dialysis dependence (3.76 [1.46–8.64]), and the SNPs IL10 rs1800896 (3.45 [1.33–8.93]) and IL12B rs41292470 (5.36 [1.51–19.0]). In vitro production capacity of interleukin-10 and interferon-γ was influenced by these polymorphisms, and significantly lower proinflammatory cytokine concentrations were measured in serum from patients with persistent fungemia.
Conclusions. Polymorphisms in IL10 and IL12B that result in low production of proinflammatory cytokines are associated with persistent fungemia in candidemia patients. This provides insights for future targeted management strategies for patients with Candida bloodstream infections.
Age-related macular degeneration (AMD) is a complex degenerative retinal disease influenced by both genetic and environmental risk factors. We assessed whether single nucleotide polymorphisms (SNPs) in the NOS2A gene increase risk and modulate the effect of smoking in AMD. 998 Caucasian subjects (712 AMD cases and 286 controls) were genotyped for 17 SNPs in NOS2A. Multivariable logistic regression models containing SNP genotypes, age, sex, smoking status and genotype/smoking interaction were constructed. SNP rs8072199 was significantly associated with AMD (OR = 1.3; 95% CI : 1.02, 1.65; P = 0.035). A significant interaction with smoking was detected at rs2248814 (P = 0.037). Stratified data by genotypes demonstrated that the association between AMD and smoking was stronger in carriers of AA genotypes (OR = 35.98; 95% CI: 3.19, 405.98) than in carriers of the AG genotype (OR=3.05; 95% CI: 1.36, 6.74) or GG genotype (OR=2.1; 95% CI: 0.91, 4.84). The results suggest a possible synergistic interaction of AA genotype with smoking, although the result bears replication in larger samples. Our data suggests that SNPs in the NOS2A gene are associated with increased risk for AMD and might modulate the effect of smoking on AMD.
association; age-related macular degeneration; polymorphism; gene-environment interaction
Tuberculosis (TB) is a global public health problem and a source of preventable deaths each year, with 8.8 million new cases of TB and 1.6 million deaths worldwide in 2005. Approximately, 10% of infected individuals develop pulmonary or extrapulmonary TB, suggesting that host defense factors influence development of active disease. Toll-like receptor’ (TLR) polymorphisms have been associated with regulation of TLR expression and development of active TB. In the present study, 71 polymorphisms in TLR1, TLR2, TLR4, TLR6, and TLR9 were examined from 474 (295 cases and 179 controls) African-Americans, 381 (237 cases and 144 controls) Caucasians, and from 667 (321 cases and 346 controls) Africans from Guinea-Bissau for association with pulmonary TB using generalized estimating equations and logistic regression. Statistically significant associations were observed across populations at TLR9 and TLR2. The strongest evidence for association came at an insertion (I)/deletion (D) polymorphism (−196 to −174) in TLR2 that associated with TB in both Caucasians (II vs. ID&DD, OR=0.41 [95% CI 0.24–0.68], p=0.0007) and Africans (II vs. ID&DD, OR=0.70 [95% CI 0.51–0.95], p=0.023). Our findings in three independent population samples indicate that variations in TLR2 and TLR9 might play important roles in determining susceptibility to TB.
tuberculosis; toll-like receptors; polymorphism; innate immunity
Tuberculosis (TB) has substantial mortality worldwide with 5-10% of those exposed progressing to active TB disease. Studies in mice and humans indicate that the inducible nitric oxide synthase (iNOS) molecule plays an important role in immune response to TB. A mixed case-control association study of individuals with TB, relatives, or close contact controls was performed in 726 individuals (279 case and 166 control African-Americans; 198 case and 123 control Caucasians). Thirty-nine single nucleotide polymorphisms (SNPs) were selected from the NOS2A gene for single SNP, haplotype, and multilocus interaction analyses with other typed candidate genes using generalized estimating equations. In African-Americans, ten NOS2A SNPs were associated with TB. The strongest associations were observed at rs2274894 (odds ratio (OR) = 1.84, 95% confidence interval (CI) [1.23-2.77], p = 0.003) and rs7215373 (OR 1.67, 95% CI [1.17-2.37], p = 0.004), both of which passed a false discovery rate (FDR) correction for multiple comparisons (q*=0.20). The strongest gene-gene interactions were observed between NOS2A rs2248814 and IFNGR1 rs1327474 (p = 0.0004) and NOS2A rs944722 and IFNGR1 rs1327474 (p = 0.0006). Three other SNPs in NOS2A interacted with TLR4 rs5030729 and five other NOS2A SNPs interacted with IFNGR1 rs1327474. No significant associations were observed in Caucasians. These results suggest that NOS2A variants may contribute to TB susceptibility, particularly in individuals of African descent, and may act synergistically with SNPs in TLR4 and IFNGR1.
tuberculosis; epistasis; complex disease; infectious disease; genetic epidemiology
The findings of this study provide the first evidence suggesting that ARMS2 interacts with hormone replacement therapy (HRT) to modulate AMD risk and are consistent with previous reports demonstrating a protective relationship between exogenous estrogen use and neovascular AMD. These results highlight the genetic and environmental complexity of the etiologic architecture of AMD.
To investigate whether female reproductive history and hormone replacement therapy (HRT) or birth control pills (BCPs) influence risk for age-related macular degeneration (AMD) and whether genetic factors interact with HRT to modulate AMD risk.
Related and unrelated female participants (n = 799) were examined and data were analyzed with generalized estimating equations with adjustment for age and smoking. Individuals with AMD grades 1 to 2 were considered to be unaffected (n = 239) and those with grades 3 to 5 were considered affected (n = 560).
When comparing all cases with controls, significant inverse associations were observed for HRT (odds ratio [OR] = 0.65, 95% CI 0.48–0.90, P = 0.008) and BCPs (OR = 0.60, 95% CI 0.36–0.10, P = 0.048). When analyses were stratified by AMD severity (early versus geographic atrophy versus neovascular), the inverse association remained significant (HRT OR = 0.45, 95% CI 0.30–0.66, P < 0.0001; BCP OR = 0.55, 95% CI 0.32–0.96, P = 0.036) only when comparing neovascular AMD with the control. All pair-wise HRT-genotype and BCP-genotype interactions were examined, to determine whether HRT or BCP modifies the effect of established genetic risk factors. The strongest interactions were observed for HRT x ARMS2 coding SNP (R73H) rs10490923 (P = 0.007) and HRT x ARMS2 intronic SNP rs17623531 (P = 0.019).
These findings provide the first evidence suggesting that ARMS2 interacts with HRT to modulate AMD risk and are consistent with previous reports demonstrating a protective relationship between exogenous estrogen use and neovascular AMD. These results highlight the genetic and environmental complexity of the etiologic architecture of AMD; however, further replication is necessary to validate them.
Recently, vacuolar protein sorting 35 (VPS35) and eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) have been identified as 2 causal Parkinson disease (PD) genes. We used whole exome sequencing for rapid, parallel analysis of variations in these 2 genes.
We performed whole exome sequencing in 213 patients with PD and 272 control individuals. Those rare variants (RVs) with <5% frequency in the exome variant server database and our own control data were considered for analysis. We performed joint gene-based tests for association using RVASSOC and SKAT (Sequence Kernel Association Test) as well as single-variant test statistics.
We identified 3 novel VPS35 variations that changed the coded amino acid (nonsynonymous) in 3 cases. Two variations were in multiplex families and neither segregated with PD. In EIF4G1, we identified 11 (9 nonsynonymous and 2 small indels) RVs including the reported pathogenic mutation p.R1205H, which segregated in all affected members of a large family, but also in 1 unaffected 86-year-old family member. Two additional RVs were found in isolated patients only. Whereas initial association studies suggested an association (p = 0.04) with all RVs in EIF4G1, subsequent testing in a second dataset for the driving variant (p.F1461) suggested no association between RVs in the gene and PD.
We confirm that the specific EIF4G1 variation p.R1205H seems to be a strong PD risk factor, but is nonpenetrant in at least one 86-year-old. A few other select RVs in both genes could not be ruled out as causal. However, there was no evidence for an overall contribution of genetic variability in VPS35 or EIF4G1 to PD development in our dataset.
Background. Candidemia is an important cause of morbidity and mortality in critically ill patients or patients undergoing invasive treatments. Dectin-1 is the main β-glucan receptor, and patients with a complete deficiency of either dectin-1 or its adaptor molecule CARD9 display persistent mucosal infections with Candida albicans. The role of genetic variation of DECTIN-1 and CARD9 genes on the susceptibility to candidemia is unknown.
Methods. We assessed whether genetic variation in the genes encoding dectin-1 and CARD9 influence the susceptibility to candidemia and/or the clinical course of the infection in a large cohort of American and Dutch candidemia patients (n = 331) and noninfected matched controls (n = 351). Furthermore, functional studies have been performed to assess the effect of the DECTIN-1 and CARD9 genetic variants on cytokine production in vitro and in vivo in the infected patients.
Results. No significant association between the single-nucleotide polymorphisms DECTIN-1 Y238X and CARD9 S12N and the prevalence of candidemia was found, despite the association of the DECTIN-1 238X allele with impaired in vitro and in vivo cytokine production.
Conclusions. Whereas the dectin-1/CARD9 signaling pathway is nonredundant in mucosal immunity to C. albicans, a partial deficiency of β-glucan recognition has a minor impact on susceptibility to candidemia.
Nitric oxide synthase (NOS) genes (NOS1, NOS2A, and NOS3) may create excess nitric oxide that contributes to neurodegeneration in Parkinson’s disease (PD). NOS genes might also interact with one another or with environmental factors in PD. Coding and tagging single nucleotide polymorphisms (SNPs) (27 NOS1, 18 NOS2A, and 5 NOS3 SNPs) were genotyped in families with PD (1,065 cases and 1,180 relative and other controls) and were tested for allelic associations with PD using the association in the presence of linkage test and the pedigree disequilibrium test (PDT), allelic associations with age-at-onset (AAO) using the quantitative transmission disequilibrium test, and interactions using the multifactor dimensionality reduction-PDT. Gene-environment interactions involving cigarette smoking, caffeine, nonsteroidal anti-inflammatory drugs, and pesticides were examined using generalized estimating equations in participants with environmental data available. Significant associations with PD were detected for the NOS1 SNPs rs3782218, rs11068447, rs7295972, rs2293052, rs12829185, rs1047735, rs3741475, and rs2682826 (range of p=0.00083–0.046) and the NOS2A SNPs rs2072324, rs944725, rs12944039, rs2248814, rs2297516, rs1060826, and rs2255929 (range of p=0.0000040–0.047) in earlier-onset families with sporadic PD, and some SNPs were also associated with earlier AAO. There was no compelling statistical evidence for gene-gene interactions. However, of the significantly associated SNPs, interactions were found between pesticides and the NOS1 SNPs rs12829185, rs1047735, and rs2682826 (range of p=0.012–0.034) and between smoking and the NOS2A SNPs rs2248814 (p=0.021) and rs1060826 (p=0.013). These data implicate NOS1 and NOS2A as genetic risk factors for PD and demonstrate that their interactions with established environmental factors may modulate the environmental effects.
Parkinson disease; nitric oxide synthase; case-control studies; risk factors
The cognitive profile of early onset Parkinson’s disease (EOPD) has not been clearly defined. Mutations in the parkin gene are the most common genetic risk factor for EOPD and may offer information about the neuropsychological pattern of performance in both symptomatic and asymptomatic mutation carriers.
EOPD probands and their first-degree relatives who did not have Parkinson’s disease (PD) were genotyped for mutations in the parkin gene and administered a comprehensive neuropsychological battery. Performance was compared between EOPD probands with (N=43) and without (N=52) parkin mutations. The same neuropsychological battery was administered to 217 first-degree relatives to assess neuropsychological function in individuals who carry parkin mutations but do not have PD.
No significant differences in neuropsychological test performance were found between parkin carrier and non-carrier probands. Performance also did not differ between EOPD non-carriers and carrier subgroups (i.e. heterozygotes, compound heterozygotes/homozygotes). Similarly, no differences were found among unaffected family members across genotypes. Mean neuropsychological test performance was within normal range in all probands and relatives.
Carriers of parkin mutations, whether or not they have PD, do not perform differently on neuropsychological measures as compared to non-carriers. The cognitive functioning of parkin carriers over time warrants further study.
Parkinson’s disease; genetics; neuropsychological assessment; genotype; PARK2; parkin mutation
Exposure to Staphylococcus aureus has a variety of outcomes, from asymptomatic colonization to fatal infection. Strong evidence suggests that host genetics play an important role in susceptibility, but the specific host genetic factors involved are not known. The availability of genome-wide single nucleotide polymorphism (SNP) data for inbred Mus musculus strains means that haplotype association mapping can be used to identify candidate susceptibility genes. We applied haplotype association mapping to Perlegen SNP data and kidney bacterial counts from Staphylococcus aureus-infected mice from 13 inbred strains and detected an associated block on chromosome 7. Strong experimental evidence supports the result: a separate study demonstrated the presence of a susceptibility locus on chromosome 7 using consomic mice. The associated block contains no genes, but lies within the gene cluster of the 26-member extended kallikrein gene family, whose members have well-recognized roles in the generation of antimicrobial peptides and the regulation of inflammation. Efficient mixed-model association (EMMA) testing of all SNPs with two alleles and located within the gene cluster boundaries finds two significant associations: one of the three polymorphisms defining the associated block and one in the gene closest to the block, Klk1b11. In addition, we find that 7 of the 26 kallikrein genes are differentially expressed between susceptible and resistant mice, including the Klk1b11 gene. These genes represent a promising set of candidate genes influencing susceptibility to Staphylococcus aureus.
host genetic susceptibility; infectious disease; kallikrein gene family
The purpose of this study was to evaluate the effect of 2-deoxy-D-glucose (2-DG) on the spatial distribution of the genetic expression of key elements involved in angiogenesis, hypoxia, cellular metabolism, and apoptosis in LHBETATAG retinal tumors.
The right eye of each LHBETATAG transgenic mouse (n = 24) was treated with either two or six subconjunctival injections of 2-DG (500 mg/kg) or saline control at 16 weeks of age. A gene expression array analysis was performed on five different intratumoral regions (apex, center, base, anterior-lateral, and posterior-lateral) using Affymetrix GeneChip Mouse Gene 1.0 ST arrays. To test for treatment effects of each probe within each region, a two-way analysis of variance was used.
Significant differences between treatment groups (ie, 0, 2, and 6 injections) were found as well as differences among the five retinal tumor regions evaluated (P < 0.01). More than 100 genes were observed to be dysregulated by ≥2-fold difference in expression between the three treatment groups, and their dysregulation varied across the five regions assayed. Several genes involved in pathways important for tumor cell growth (ie, angiogenesis, hypoxia, cellular metabolism, and apoptosis) were identified.
2-DG was found to significantly alter the gene expression in LHBETATAG retinal tumor cells according to their location within the tumor as well as the treatment schedule. 2-DG’s effects on genetic expression found here correlate with previous reported results on varied processes involved in its in vitro and in vivo activity in inhibiting tumor cell growth.
retinoblastoma; hypoxia; genetic expression; glycolytic inhibitor; 2-DG
More than 800 published genetic association studies have implicated dozens of potential risk loci in Parkinson's disease (PD). To facilitate the interpretation of these findings, we have created a dedicated online resource, PDGene, that comprehensively collects and meta-analyzes all published studies in the field. A systematic literature screen of ∼27,000 articles yielded 828 eligible articles from which relevant data were extracted. In addition, individual-level data from three publicly available genome-wide association studies (GWAS) were obtained and subjected to genotype imputation and analysis. Overall, we performed meta-analyses on more than seven million polymorphisms originating either from GWAS datasets and/or from smaller scale PD association studies. Meta-analyses on 147 SNPs were supplemented by unpublished GWAS data from up to 16,452 PD cases and 48,810 controls. Eleven loci showed genome-wide significant (P<5×10−8) association with disease risk: BST1, CCDC62/HIP1R, DGKQ/GAK, GBA, LRRK2, MAPT, MCCC1/LAMP3, PARK16, SNCA, STK39, and SYT11/RAB25. In addition, we identified novel evidence for genome-wide significant association with a polymorphism in ITGA8 (rs7077361, OR 0.88, P = 1.3×10−8). All meta-analysis results are freely available on a dedicated online database (www.pdgene.org), which is cross-linked with a customized track on the UCSC Genome Browser. Our study provides an exhaustive and up-to-date summary of the status of PD genetics research that can be readily scaled to include the results of future large-scale genetics projects, including next-generation sequencing studies.
The genetic basis of Parkinson's disease is complex, i.e. it is determined by a number of different disease-causing and disease-predisposing genes. Especially the latter have proven difficult to find, evidenced by more than 800 published genetic association studies, typically showing discrepant results. To facilitate the interpretation of this large and continuously increasing body of data, we have created a freely available online database (“PDGene”: http://www.pdgene.org) which provides an exhaustive account of all published genetic association studies in PD. One particularly useful feature is the calculation and display of up-to-date summary statistics of published data for overlapping DNA sequence variants (polymorphisms). These meta-analyses revealed eleven gene loci that showed a statistically very significant (P<5×10−8; a.k.a. genome-wide significance) association with risk for PD: BST1, CCDC62/HIP1R, DGKQ/GAK, GBA, LRRK2, MAPT, MCCC1/LAMP3, PARK16, SNCA, STK39, SYT11/RAB25. In addition and purely by data-mining, we identified one novel PD susceptibility locus in a gene called ITGA8 (rs7077361, P = 1.3×10−8). We note that our continuously updated database represents the most comprehensive research synopsis of genetic association studies in PD to date. In addition to vastly facilitating the work of other PD geneticists, our approach may serve as a valuable example for other complex diseases.
Vitamin D and vitamin D receptor (VDR) have been postulated as environmental and genetic factors in neurodegeneration disorders including multiple sclerosis (MS), Alzheimer disease (AD), and recently Parkinson disease (PD). Given the sparse data on PD and VDR, we conducted a two-stage study to evaluate the genetic effects of VDR in PD. In the discovery stage, 30 tagSNPs in VDR were tested for association with PD risk as a discrete trait and age-at-onset of PD as a quantitative trait in 770 Caucasian PD families. In the validation stage, 18 VDR SNPs were tested in an independent Caucasian cohort (267 cases and 267 controls) constructed from a genome-wide association study (GWAS). In the discovery dataset, SNPs in the 5′ end of VDR were associated with both risk and age-at-onset with more significant evidence of association with age-at-onset (nominal p=0.0008 for the most significant SNPs). These SNPs were also associated with AD in a recent GWAS. In the validation dataset, SNPs in the 3′ end of VDR were associated with age-at-onset (nominal p=0.003 for the most significant SNPs but not risk. The most significant 3′end SNP has been be associated with both MS and AD. Our findings suggest VDR as a potential susceptibility gene and support an essential role of vitamin D in PD.
VDR; vitamin D; Parkinson Disease; genetics; age-at-onset