Interferon-λ3 Promotes Epithelial Defense and Barrier Function Against Cryptosporidium parvum Infection.

BACKGROUND & AIMS: The epithelial response is critical for intestinal defense against Cryptosporidium, but is poorly understood. To uncover the host strategy for defense against Cryptosporidium, we examined the transcriptional response of intestinal epithelial cells (IECs) to C parvum in experimentally infected piglets by microarray. Up-regulated genes were dominated by targets of interferon (IFN) and IFN-λ3 was up-regulated significantly in infected piglet mucosa. Although IFN-λ has been described as a mediator of epithelial defense against viral pathogens, there is limited knowledge of any role against nonviral pathogens. Accordingly, the aim of the study was to determine the significance of IFN-λ3 to epithelial defense and barrier function during C parvum infection. METHODS: The significance of C parvum-induced IFN-λ3 expression was determined using an immunoneutralization approach in neonatal C57BL/6 mice. The ability of the intestinal epithelium to up-regulate IFN-λ2/3 expression in response to C parvum infection and the influence of IFN-λ2/3 on epithelial defense against C parvum invasion, intracellular development, and loss of barrier function was examined using polarized monolayers of a nontransformed porcine-derived small intestinal epithelial cell line (IPEC-J2). Specifically, changes in barrier function were quantified by measurement of transepithelial electrical resistance and transepithelial flux studies. RESULTS: Immunoneutralization of IFN-λ2/3 in C parvum-infected neonatal mice resulted in a significantly increased parasite burden, fecal shedding, and villus blunting with crypt hyperplasia during peak infection. In vitro, C parvum was sufficient to induce autonomous IFN-λ3 and interferon-stimulated gene 15 expression by IECs. Priming of IECs with recombinant human IFN-λ3 promoted cellular defense against C parvum infection and abrogated C parvum-induced loss of barrier function by decreasing paracellular permeability to sodium. CONCLUSIONS: These studies identify IFN-λ3 as a key epithelial defense mechanism against C parvum infection.

Networks Underpinning Symbiosis Revealed Through Cross-Species eQTL Mapping.

Organisms engage in extensive cross-species molecular dialog, yet the underlying molecular actors are known for only a few interactions. Many techniques have been designed to uncover genes involved in signaling between organisms. Typically, these focus on only one of the partners. We developed an expression quantitative trait locus (eQTL) mapping-based approach to identify cause-and-effect relationships between genes from two partners engaged in an interspecific interaction. We demonstrated the approach by assaying expression of 98 isogenic plants (Medicago truncatula), each inoculated with a genetically distinct line of the diploid parasitic nematode Meloidogyne hapla With this design, systematic differences in gene expression across host plants could be mapped to genetic polymorphisms of their infecting parasites. The effects of parasite genotypes on plant gene expression were often substantial, with up to 90-fold (P = 3.2 × 10-52) changes in expression levels caused by individual parasite loci. Mapped loci included a number of pleiotropic sites, including one 87-kb parasite locus that modulated expression of >60 host genes. The 213 host genes identified were substantially enriched for transcription factors. We distilled higher-order connections between polymorphisms and genes from both species via network inference. To replicate our results and test whether effects were conserved across a broader host range, we performed a confirmatory experiment using M. hapla-infected tomato. This revealed that homologous genes were similarly affected. Finally, to validate the broader utility of cross-species eQTL mapping, we applied the strategy to data from a Salmonella infection study, successfully identifying polymorphisms in the human genome affecting bacterial expression.

Increased exposure to acute thermal stress is associated with a non-linear increase in recombination frequency and an independent linear decrease in fitness in Drosophila.

BACKGROUND: Meiotic recombination rate has long been known to be phenotypically plastic. How plastic recombination evolves and is maintained remains controversial; though a leading model for the evolution of plastic recombination rests on the tenet that organismal fitness and recombination frequency are negatively correlated. Motivated by the mounting evidence that meiotic recombination frequencies increase in response to stress, here we test for a negative correlation between fitness and recombination frequency. Specifically, the fitness-associated recombination model (FAR) predicts that if stress increases meiotic recombination frequency, then increasing exposure to stressful conditions will yield an increasing magnitude of the recombinational response, while concomitantly decreasing fitness. RESULTS: We use heat shock as a stressor to test this prediction in Drosophila melanogaster. We find that increased exposure to heat shock conditions is associated with a non-linear increase in meiotic recombination frequency. We also find an independent effect of heat shock on organismal fitness, with fitness decreasing with increased duration of thermal stress. CONCLUSIONS: Our results thus support the foundation of the FAR model for the evolution of plastic recombination. Our data also suggest that modulating recombination frequency is one mechanism by which organisms can rapidly respond to environmental cues and confer increased adaptive potential to their offspring.

Improved structural annotation of protein-coding genes in the Meloidogyne hapla genome using RNA-Seq.

As high-throughput cDNA sequencing (RNA-Seq) is increasingly applied to hypothesis-driven biological studies, the prediction of protein coding genes based on these data are usurping strictly in silico approaches. Compared with computationally derived gene predictions, structural annotation is more accurate when based on biological evidence, particularly RNA-Seq data. Here, we refine the current genome annotation for the Meloidogyne hapla genome utilizing RNA-Seq data. Published structural annotation defines 14 420 protein-coding genes in the M. hapla genome. Of these, 25% (3751) were found to exhibit some incongruence with RNA-Seq data. Manual annotation enabled these discrepancies to be resolved. Our analysis revealed 544 new gene models that were missing from the prior annotation. Additionally, 1457 transcribed regions were newly identified on the ends of as-yet-unjoined contigs. We also searched for trans-spliced leaders, and based on RNA-Seq data, identified genes that appear to be trans-spliced. Four 22-bp trans-spliced leaders were identified using our pipeline, including the known trans-spliced leader, which is the M. hapla ortholog of SL1. In silico predictions of trans-splicing were validated by comparison with earlier results derived from an independent cDNA library constructed to capture trans-spliced transcripts. The new annotation, which we term HapPep5, is publically available at www.hapla.org.

Aspergillus flavus infection induces transcriptional and physical changes in developing maize kernels.

Maize kernels are susceptible to infection by the opportunistic pathogen Aspergillus flavus. Infection results in reduction of grain quality and contamination of kernels with the highly carcinogenic mycotoxin, aflatoxin. To understanding host response to infection by the fungus, transcription of approximately 9000 maize genes were monitored during the host-pathogen interaction with a custom designed Affymetrix GeneChip® DNA array. More than 4000 maize genes were found differentially expressed at a FDR of 0.05. This included the up regulation of defense related genes and signaling pathways. Transcriptional changes also were observed in primary metabolism genes. Starch biosynthetic genes were down regulated during infection, while genes encoding maize hydrolytic enzymes, presumably involved in the degradation of host reserves, were up regulated. These data indicate that infection of the maize kernel by A. flavus induced metabolic changes in the kernel, including the production of a defense response, as well as a disruption in kernel development.

Canine hereditary ataxia in old english sheepdogs and gordon setters is associated with a defect in the autophagy gene encoding RAB24.

Old English Sheepdogs and Gordon Setters suffer from a juvenile onset, autosomal recessive form of canine hereditary ataxia primarily affecting the Purkinje neuron of the cerebellar cortex. The clinical and histological characteristics are analogous to hereditary ataxias in humans. Linkage and genome-wide association studies on a cohort of related Old English Sheepdogs identified a region on CFA4 strongly associated with the disease phenotype. Targeted sequence capture and next generation sequencing of the region identified an A to C single nucleotide polymorphism (SNP) located at position 113 in exon 1 of an autophagy gene, RAB24, that segregated with the phenotype. Genotyping of six additional breeds of dogs affected with hereditary ataxia identified the same polymorphism in affected Gordon Setters that segregated perfectly with phenotype. The other breeds tested did not have the polymorphism. Genome-wide SNP genotyping of Gordon Setters identified a 1.9 MB region with an identical haplotype to affected Old English Sheepdogs. Histopathology, immunohistochemistry and ultrastructural evaluation of the brains of affected dogs from both breeds identified dramatic Purkinje neuron loss with axonal spheroids, accumulation of autophagosomes, ubiquitin positive inclusions and a diffuse increase in cytoplasmic neuronal ubiquitin staining. These findings recapitulate the changes reported in mice with induced neuron-specific autophagy defects. Taken together, our results suggest that a defect in RAB24, a gene associated with autophagy, is highly associated with and may contribute to canine hereditary ataxia in Old English Sheepdogs and Gordon Setters. This finding suggests that detailed investigation of autophagy pathways should be undertaken in human hereditary ataxia.

Localization, morphology and transcriptional profile of Aspergillus flavus during seed colonization.

Aspergillus flavus is an opportunistic fungal pathogen that infects maize kernels pre-harvest, creating major human health concerns and causing substantial agricultural losses. Improved control strategies are needed, yet progress is hampered by the limited understanding of the mechanisms of infection. A series of studies were designed to investigate the localization, morphology and transcriptional profile of A. flavus during internal seed colonization. Results from these studies indicate that A. flavus is capable of infecting all tissues of the immature kernel by 96 h after infection. Mycelia were observed in and around the point of inoculation in the endosperm and were found growing down to the germ. At the endosperm-germ interface, hyphae appeared to differentiate and form a biofilm-like structure that surrounded the germ. The exact nature of this structure remains unclear, but is discussed. A custom-designed A. flavus Affymetrix GeneChip® microarray was used to monitor genome-wide transcription during pathogenicity. A total of 5061 genes were designated as being differentially expressed. Genes encoding secreted enzymes, transcription factors and secondary metabolite gene clusters were up-regulated and considered to be potential effector molecules responsible for disease in the kernel. Information gained from this study will aid in the development of strategies aimed at preventing or slowing down A. flavus colonization of the maize kernel.

Gene profiling of canine B-cell lymphoma reveals germinal center and postgerminal center subtypes with different survival times, modeling human DLBCL.

Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma subtype, and fewer than half of patients are cured with standard first-line therapy. To improve therapeutic options, better animal models that accurately mimic human DLBCL (hDLBCL) are needed. Canine DLBCL, one of the most common cancers in veterinary oncology, is morphologically similar to hDLBCL and is treated using similar chemotherapeutic protocols. With genomic technologies, it is now possible to molecularly evaluate dogs as a potential large-animal model for hDLBCL. We evaluated canine B-cell lymphomas (cBCL) using immunohistochemistry (IHC) and gene expression profiling. cBCL expression profiles were similar in many ways to hDLBCLs. For instance, a subset had increased expression of NF-κB pathway genes, mirroring human activated B-cell (ABC)-type DLBCL. Furthermore, immunoglobulin heavy chain ongoing mutation status, which is correlated with ABC/germinal center B-cell cell of origin in hDLBCL, separated cBCL into two groups with statistically different progression-free and overall survival times. In contrast with hDLBCL, cBCL rarely expressed BCL6 and MUM1/IRF4 by IHC. Collectively, these studies identify molecular similarities to hDLBCL that introduce pet dogs as a representative model of hDLBCL for future studies, including therapeutic clinical trials.

Genomic architecture of adaptive color pattern divergence and convergence in Heliconius butterflies.

Identifying the genetic changes driving adaptive variation in natural populations is key to understanding the origins of biodiversity. The mosaic of mimetic wing patterns in Heliconius butterflies makes an excellent system for exploring adaptive variation using next-generation sequencing. In this study, we use a combination of techniques to annotate the genomic interval modulating red color pattern variation, identify a narrow region responsible for adaptive divergence and convergence in Heliconius wing color patterns, and explore the evolutionary history of these adaptive alleles. We use whole genome resequencing from four hybrid zones between divergent color pattern races of Heliconius erato and two hybrid zones of the co-mimic Heliconius melpomene to examine genetic variation across 2.2 Mb of a partial reference sequence. In the intergenic region near optix, the gene previously shown to be responsible for the complex red pattern variation in Heliconius, population genetic analyses identify a shared 65-kb region of divergence that includes several sites perfectly associated with phenotype within each species. This region likely contains multiple cis-regulatory elements that control discrete expression domains of optix. The parallel signatures of genetic differentiation in H. erato and H. melpomene support a shared genetic architecture between the two distantly related co-mimics; however, phylogenetic analysis suggests mimetic patterns in each species evolved independently. Using a combination of next-generation sequencing analyses, we have refined our understanding of the genetic architecture of wing pattern variation in Heliconius and gained important insights into the evolution of novel adaptive phenotypes in natural populations.

Characterization of canine osteosarcoma by array comparative genomic hybridization and RT-qPCR: signatures of genomic imbalance in canine osteosarcoma parallel the human counterpart.

Osteosarcoma (OS) is the most commonly diagnosed malignant bone tumor in humans and dogs, characterized in both species by extremely complex karyotypes exhibiting high frequencies of genomic imbalance. Evaluation of genomic signatures in human OS using array comparative genomic hybridization (aCGH) has assisted in uncovering genetic mechanisms that result in disease phenotype. Previous low-resolution (10-20 Mb) aCGH analysis of canine OS identified a wide range of recurrent DNA copy number aberrations, indicating extensive genomic instability. In this study, we profiled 123 canine OS tumors by 1 Mb-resolution aCGH to generate a dataset for direct comparison with current data for human OS, concluding that several high frequency aberrations in canine and human OS are orthologous. To ensure complete coverage of gene annotation, we identified the human refseq genes that map to these orthologous aberrant dog regions and found several candidate genes warranting evaluation for OS involvement. Specifically, subsequenct FISH and qRT-PCR analysis of RUNX2, TUSC3, and PTEN indicated that expression levels correlated with genomic copy number status, showcasing RUNX2 as an OS associated gene and TUSC3 as a possible tumor suppressor candidate. Together these data demonstrate the ability of genomic comparative oncology to identify genetic abberations which may be important for OS progression. Large scale screening of genomic imbalance in canine OS further validates the use of the dog as a suitable model for human cancers, supporting the idea that dysregulation discovered in canine cancers will provide an avenue for complementary study in human counterparts.

Genome-wide linkage study of atopic dermatitis in West Highland White Terriers.

BACKGROUND: Canine atopic dermatitis (AD) is a common, heritable, chronic allergic skin condition prevalent in the West Highland White Terrier (WHWT). In canine AD, environmental allergens trigger an inflammatory response causing visible skin lesions and chronic pruritus that can lead to secondary bacterial and yeast infections. The disorder shares many of the clinical and histopathological characteristics of human AD and represents an animal model of this disorder that could be used to further elucidate genetic causes of human AD. Microsatellite markers genotyped in families of WHWTs affected with AD were used to perform a genome-wide linkage study in order to isolate chromosomal regions associated with the disorder. RESULTS: Blood samples and health questionnaires were collected from 108 WHWTs spanning three families. A linkage simulation using these 108 dogs showed high power to detect a highly penetrant mutation. Ninety WHWTs were genotyped using markers from the Minimal Screening Set 2 (MSS-2). Two hundred and fifty six markers were informative and were used for linkage analysis. Using a LOD score of 2.7 as a significance threshold, no chromosomal regions were identified with significant linkage to AD. LOD scores greater than 1.0 were located in a 56 cM region of chromosome 7. CONCLUSIONS: The study was unable to detect any chromosomal regions significantly linked to canine AD. This could be a result of factors such as environmental modification of phenotype, incorrect assignment of phenotype, a mutation of low penetrance, or incomplete genome coverage. A genome-wide SNP association study in a larger cohort of WHWTs may prove more successful by providing higher density coverage and higher statistical power.

Gene expression profile and response to maize kernels by Aspergillus flavus.

Aspergillus flavus causes an ear rot of maize, often resulting in the production of aflatoxin, a potent liver toxin and carcinogen that impacts the health of humans and animals. Many aspects of kernel infection and aflatoxin biosynthesis have been studied but the precise effects of the kernel environment on A. flavus are poorly understood. The goal of this research was to study the fungal response to the kernel environment during colonization. Gene transcription in A. flavus was analyzed by microarrays after growth on kernels of the four developmental stages: blister (R2), milk (R3), dough (R4), and dent (R5). Five days after inoculation, total RNA was isolated from kernels and hybridized to Affymetrix Gene Chip arrays containing probes representing 12,834 A. flavus genes. Statistical comparisons of the expression profile data revealed significant differences that included unique sets of upregulated genes in each kernel stage and six patterns of expression over the four stages. Among the genes expressed in colonized dent kernels were a phytase gene and six putative genes involved in zinc acquisition. Disruption of the phytase gene phy1 resulted in reduced growth on medium containing phytate as the sole source of phosphate. Furthermore, growth of the mutant (Δphy1) was 20% of the wild-type strain when wound inoculated into maize ears. In contrast, no difference was detected in the amount of aflatoxin produced relative to fungal growth, indicating that phy1 does not affect aflatoxin production. The study revealed the genome-wide effects of immature maize kernels on A. flavus and suggest that phytase has a role in pathogenesis.

Genomic hotspots for adaptation: the population genetics of Müllerian mimicry in Heliconius erato.

Wing pattern evolution in Heliconius butterflies provides some of the most striking examples of adaptation by natural selection. The genes controlling pattern variation are classic examples of Mendelian loci of large effect, where allelic variation causes large and discrete phenotypic changes and is responsible for both convergent and highly divergent wing pattern evolution across the genus. We characterize nucleotide variation, genotype-by-phenotype associations, linkage disequilibrium (LD), and candidate gene expression patterns across two unlinked genomic intervals that control yellow and red wing pattern variation among mimetic forms of Heliconius erato. Despite very strong natural selection on color pattern, we see neither a strong reduction in genetic diversity nor evidence for extended LD across either patterning interval. This observation highlights the extent that recombination can erase the signature of selection in natural populations and is consistent with the hypothesis that either the adaptive radiation or the alleles controlling it are quite old. However, across both patterning intervals we identified SNPs clustered in several coding regions that were strongly associated with color pattern phenotype. Interestingly, coding regions with associated SNPs were widely separated, suggesting that color pattern alleles may be composed of multiple functional sites, conforming to previous descriptions of these loci as "supergenes." Examination of gene expression levels of genes flanking these regions in both H. erato and its co-mimic, H. melpomene, implicate a gene with high sequence similarity to a kinesin as playing a key role in modulating pattern and provides convincing evidence for parallel changes in gene regulation across co-mimetic lineages. The complex genetic architecture at these color pattern loci stands in marked contrast to the single casual mutations often identified in genetic studies of adaptation, but may be more indicative of the type of genetic changes responsible for much of the adaptive variation found in natural populations.

The effect of temperature on Natural Antisense Transcript (NAT) expression in Aspergillus flavus.

Naturally occurring Antisense Transcripts (NATs) compose an emerging group of regulatory RNAs. These regulatory elements appear in all organisms examined, but little is known about global expression of NATs in fungi. Analysis of currently available EST sequences suggests that 352 cis NATs are present in Aspergillus flavus. An Affymetrix GeneChip microarray containing probes for these cis NATs, as well as all predicted genes in A. flavus, allowed a whole genome expression analysis of these elements in response to two ecologically important temperatures for the fungus. RNA expression analysis showed that 32 NATs and 2,709 genes were differentially expressed between 37 degrees C, the optimum temperature for growth, and 28 degrees C, the conducive temperature for the biosynthesis of aflatoxin (AF) and many other secondary metabolites. These NATs correspond to sense genes with diverse functions including transcription initiation, carbohydrate processing and binding, temperature sensitive morphogenesis, and secondary metabolism. This is the first report of a whole genome transcriptional analysis of NAT expression in a fungus.

Does strong linkage disequilibrium guarantee redundant association results?

A substantial amount of effort has been expended recently towards the identification and evaluation of tag single nucleotide polymorphisms; markers that, due to linkage disequilibrium (LD) patterns in the genome, are able to act as "proxies" for other polymorphic sites. As such, these tag markers are assumed to capture, on their own, a large proportion of the genetic variation contributed by a much greater number of polymorphic sites. One important consequence of this is the potential ability to reduce the cost of genotyping in an association study without a corresponding loss of power. This application carries an implicit assumption that strong LD between markers implies high correlation between the accompanying association test results, so that once a tag marker is evaluated for association, its outcome will be representative of all the other markers for which it serves as proxy. We examined this assumption directly. We find that in the null hypothesis situation, where there is no association between the markers and the phenotype, the relationship between LD and the correlation between association test outcomes is clear, though it is not always ideal. In the alternative case, when genetic association does exist in the region, the relationship becomes much more complex. Here, reasonably high LD between markers does not necessarily imply that the association test result of one marker is a direct substitute for that of the other. In these cases, eliminating one of these markers from the set to be genotyped in an association study will lead to a reduction in overall power.

Comprehensive transcriptome profiling in tomato reveals a role for glycosyltransferase in Mi-mediated nematode resistance.

Root-knot nematode (RKN; Meloidogyne spp.) is a major crop pathogen worldwide. Effective resistance exists for a few plant species, including that conditioned by Mi in tomato (Solanum lycopersicum). We interrogated the root transcriptome of the resistant (Mi+) and susceptible (Mi-) cultivars 'Motelle' and 'Moneymaker,' respectively, during a time-course infection by the Mi-susceptible RKN species Meloidogyne incognita and the Mi-resistant species Meloidogyne hapla. In the absence of RKN infection, only a single significantly regulated gene, encoding a glycosyltransferase, was detected. However, RKN infection influenced the expression of broad suites of genes; more than half of the probes on the array identified differential gene regulation between infected and uninfected root tissue at some stage of RKN infection. We discovered 217 genes regulated during the time of RKN infection corresponding to establishment of feeding sites, and 58 genes that exhibited differential regulation in resistant roots compared to uninfected roots, including the glycosyltransferase. Using virus-induced gene silencing to silence the expression of this gene restored susceptibility to M. incognita in 'Motelle,' indicating that this gene is necessary for resistance to RKN. Collectively, our data provide a picture of global gene expression changes in roots during compatible and incompatible associations with RKN, and point to candidates for further investigation.

A unified mixed-model method for association mapping that accounts for multiple levels of relatedness.

As population structure can result in spurious associations, it has constrained the use of association studies in human and plant genetics. Association mapping, however, holds great promise if true signals of functional association can be separated from the vast number of false signals generated by population structure. We have developed a unified mixed-model approach to account for multiple levels of relatedness simultaneously as detected by random genetic markers. We applied this new approach to two samples: a family-based sample of 14 human families, for quantitative gene expression dissection, and a sample of 277 diverse maize inbred lines with complex familial relationships and population structure, for quantitative trait dissection. Our method demonstrates improved control of both type I and type II error rates over other methods. As this new method crosses the boundary between family-based and structured association samples, it provides a powerful complement to currently available methods for association mapping.

Measures of human population structure show heterogeneity among genomic regions.

Estimates of genetic population structure (F(ST)) were constructed from all autosomes in two large SNP data sets. The Perlegen data set contains genotypes on approximately 1 million SNPs segregating in all three samples of Americans of African, Asian, and European descent; and the Phase I HapMap data set contains genotypes on approximately 0.6 million SNPs segregating in all four samples from specific Caucasian, Chinese, Japanese, and Yoruba populations. Substantial heterogeneity of F(ST) values was found between segments within chromosomes, although there was similarity between the two data sets. There was also substantial heterogeneity among population-specific F(ST) values, with the relative sizes of these values often changing along each chromosome. Population-structure estimates are often used as indicators of natural selection, but the analyses presented here show that individual-marker estimates are too variable to be useful. There is inherent variation in these statistics because of variation in genealogy even among neutral loci, and values at pairs of loci are correlated to an extent that reflects the linkage disequilibrium between them. Furthermore, it may be that the best indications of selection will come from population-specific F(ST) values rather than the usually reported population-average values.

Genetic polymorphisms and the risk of stroke after cardiac surgery.

BACKGROUND AND PURPOSE: Stroke represents a significant cause of morbidity and mortality after cardiac surgery. Although the risk of stroke varies according to both patient and procedural factors, the impact of genetic variants on stroke risk is not well understood. Therefore, we tested the hypothesis that specific genetic polymorphisms are associated with an increased risk of stroke after cardiac surgery. METHODS: Patients undergoing cardiac surgery utilizing cardiopulmonary bypass surgery were studied. DNA was isolated from preoperative blood and analyzed for 26 different single-nucleotide polymorphisms. Multivariable logistic regression modeling was used to determine the association of clinical and genetic characteristics with stroke. Permutation analysis was used to adjust for multiple comparisons inherent in genetic association studies. RESULTS: A total of 1635 patients experiencing 28 strokes (1.7%) were included in the final genetic model. The combination of the 2 minor alleles of C-reactive protein (CRP; 3'UTR 1846C/T) and interleukin-6 (IL-6; -174G/C) polymorphisms, occurring in 583 (35.7%) patients, was significantly associated with stroke (odds ratio, 3.3; 95% CI, 1.4 to 8.1; P=0.0023). In a multivariable logistic model adjusting for age, the CRP and IL-6 single-nucleotide polymorphism combination remained significantly associated with stroke (P=0.0020). CONCLUSIONS: We demonstrate that common genetic variants of CRP (3'UTR 1846C/T) and IL-6 (-174G/C) are significantly associated with the risk of stroke after cardiac surgery, suggesting a pivotal role of inflammation in post-cardiac surgery stroke.

Association of genetic polymorphisms with risk of renal injury after coronary bypass graft surgery.

BACKGROUND: Post-cardiac surgery renal dysfunction is a common, serious, multifactorial disorder, with interpatient variability predicted poorly by preoperative clinical, procedural, and biological markers. Therefore, we tested the hypothesis that selected gene variants are associated with acute renal injury, reflected by a serum creatinine level increase after cardiac surgery. METHODS: One thousand six hundred seventy-one patients undergoing aortocoronary surgery were studied. Clinical covariates were recorded. DNA was isolated from preoperative blood; mass spectrometry was used for genotype analysis. A model was developed relating clinical and genetic factors to postoperative acute renal injury. RESULTS: A race effect was found; therefore, Caucasians and African Americans were analyzed separately. Overall, clinical factors alone account poorly for postoperative renal injury, although more so in African Americans than Caucasians. When 12 candidate polymorphisms were assessed, 2 alleles (interleukin 6 -572C and angiotensinogen 842C) showed a strong association with renal injury in Caucasians (P < 0.0001; >50% decrease in renal filtration when they present together). Using less stringent criteria for significance (0.01 > P > 0.001), 4 additional polymorphisms are identified (apolipoproteinE 448C [4], angiotensin receptor1 1166C, and endothelial nitric oxide synthase [eNOS] 894T in Caucasians; eNOS 894T and angiotensin-converting enzyme deletion and insertion in African Americans). Adding genetic to clinical factors resulted in the best model, with overall ability to explain renal injury increasing approximately 4-fold in Caucasians and doubling in African Americans (P < 0.0005). CONCLUSION: In this study, we identify genetic polymorphisms that collectively provide 2- to 4-fold improvement over preoperative clinical factors alone in explaining post-cardiac surgery renal dysfunction. From a mechanistic perspective, most identified genetic variants are associated with increased renal inflammatory and/or vasoconstrictor responses.