Enrichment of cis-regulatory gene expression SNPs and methylation quantitative trait loci among bipolar disorder susceptibility variants

We conducted a systematic study of top susceptibility variants from a genome-wide association (GWA) study of bipolar disorder to gain insight into the functional consequences of genetic variation influencing disease risk. We report here the results of experiments to explore the effects of these susceptibility variants on DNA methylation and mRNA expression in human cerebellum samples. Among the top susceptibility variants, we identified an enrichment of cis regulatory loci on mRNA expression (eQTLs), and a significant excess of quantitative trait loci for DNA CpG methylation, hereafter referred to as methylation quantitative trait loci (mQTLs). Bipolar disorder susceptibility variants that cis regulate both cerebellar expression and methylation of the same gene are a very small proportion of bipolar disorder susceptibility variants. This finding suggests that mQTLs and eQTLs provide orthogonal ways of functionally annotating genetic variation within the context of studies of pathophysiology in brain. No lymphocyte mQTL enrichment was found, suggesting that mQTL enrichment was specific to the cerebellum, in contrast to eQTLs. Separately, we found that using mQTL information to restrict the number of single-nucleotide polymorphisms studied enhances our ability to detect a significant association. With this restriction a priori informed by the observed functional enrichment, we identified a significant association (rs12618769, P(bonferroni)<0.05) from two other GWA studies (TGen+GAIN; 2191 cases and 1434 controls) of bipolar disorder, which we replicated in an independent GWA study (WTCCC). Collectively, our findings highlight the importance of integrating functional annotation of genetic variants for gene expression and DNA methylation to advance the biological understanding of bipolar disorder.

S3-5: Next Generation Sequencing Reveals Co-Activating Events in the MAPK and P13K/AKT Pathways in Metastatic Triple Negative Breast Cancers

INTRODUCTION: The clinical application of next generation sequencing to comprehensively characterize groups of driving mutations in individual metastatic triple negative breast cancer (mTNBC) genomes has the potential to reveal therapeutically relevant pathway dependencies. Towards this end, we harvested tissue from 14 patients with mTNBC and are conducting deep whole genome and transcriptome sequencing for each case to identify mutations that can guide therapeutic targeting within available phase I/II clinical trials.

METHODS: Metastatic tumor tissue was harvested from 14 mTNBC patients, and 7 samples have undergone total genome and transcriptome sequencing with the others currently underway. We are utilizing the Life Technologies SOLiD® system to sequence germline and tumor DNA to sufficient depth to identify somatic genome alterations including point mutations, indels, and structural events including translocations. Furthermore, RNA-seq is being performed on these tumors, along with a series of age- and ethnicity-matched normal breast controls to perform deep differential expression analysis, isoform expression analysis, and fusion transcript detection. Our team of genome scientists and clinical oncologists are evaluating the sequencing findings and are prioritizing the investigational therapeutic options for each patient.

RESULTS: Our whole genome and transcriptome sequencing study has revealed numerous known and novel mutations in mTNBC. However, all patients’ cancers analyzed to date had alterations that would activate the MAPK pathway, but through various mechanisms in different patients. These include BRAF amplification and overexpression, NF1 homozygous deletion, and consistent IQGAP3 overexpression. Furthermore, all patients’ cancers also harbor mutations that would activate the PI3K/AKT pathway including PTEN homozygous deletion or down-regulation, consistent INPP4B down-regulation, FBXW7 homozygous deletion, and ERAS overexpression. Moreover, although we and others show ERBB4 down-regulation in breast tumors, we are the first to report unique somatic genomic events that significantly alter the ERBB4 locus leading to its loss in the majority (5/7) of our patients’ tumors. Importantly, we are beginning to use these insights to prioritize therapeutic targeting and have observed that one chemotherapy-refractory mTNBC patient, with a high-level BRAF amplification/overexpression along with down-regulation of PTEN and INPP4B, had a major response to combined mek plus akt inhibitors on a phase I study.

CONCLUSIONS: Comprehensive genomic and transcriptomic interrogation of mTNBCs has revealed events supporting co-activation of the MAPK and PI3K/AKT pathways in all the tumors albeit by different mutational mechanisms and supports potential effectiveness of combination therapy in the treatment of mTNBC. We plan to treat these patients with combined mek plus akt inhibitors on a new phase I study beginning in August 2011 to determine the effectiveness of co-inhibition of these pathways based on this frequent genomic context.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr S3-5.

Genome-wide association study of CSF biomarkers Abeta1-42, t-tau, and p-tau181p in the ADNI cohort

OBJECTIVES

CSF levels of Aβ1-42, t-tau, and p-tau181p are potential early diagnostic markers for probable Alzheimer disease (AD). The influence of genetic variation on these markers has been investigated for candidate genes but not on a genome-wide basis. We report a genome-wide association study (GWAS) of CSF biomarkers (Aβ1-42, t-tau, p-tau181p, p-tau181p/Aβ1-42, and t-tau/Aβ1-42).

METHODS

A total of 374 non-Hispanic Caucasian participants in the Alzheimer's Disease Neuroimaging Initiative cohort with quality-controlled CSF and genotype data were included in this analysis. The main effect of single nucleotide polymorphisms (SNPs) under an additive genetic model was assessed on each of 5 CSF biomarkers. The p values of all SNPs for each CSF biomarker were adjusted for multiple comparisons by the Bonferroni method. We focused on SNPs with corrected p<0.01 (uncorrected p<3.10×10(-8)) and secondarily examined SNPs with uncorrected p values less than 10(-5) to identify potential candidates.

RESULTS

Four SNPs in the regions of the APOE, LOC100129500, TOMM40, and EPC2 genes reached genome-wide significance for associations with one or more CSF biomarkers. SNPs in CCDC134, ABCG2, SREBF2, and NFATC4, although not reaching genome-wide significance, were identified as potential candidates.

CONCLUSIONS

In addition to known candidate genes, APOE, TOMM40, and one hypothetical gene LOC100129500 partially overlapping APOE; one novel gene, EPC2, and several other interesting genes were associated with CSF biomarkers that are related to AD. These findings, especially the new EPC2 results, require replication in independent cohorts.

Genome-wide SNP genotyping study using pooled DNA to identify candidate markers mediating susceptibility to end-stage renal disease attributed to Type 1 diabetes

AIMS

Genetic factors play a major role in the progression of kidney disease in diabetes. To identify candidate single nucleotide polymorphisms (SNPs) with potential effects on susceptibility to end-stage renal disease (ESRD), we performed a whole genome association scan using pooled DNA from Caucasian individuals with Type 1 diabetes.

METHODS

We utilized the Illumina Infinium II HumanHap 550 beadchip platform to genotype 555 352 SNPs in DNA pools comprised of 547 cases with ESRD and 549 control subjects with Type 1 diabetes duration > 20 years and no ESRD. Pooled probe intensity was used to predict mean allele frequency (MAF) for each locus. Individual genotyping was performed using the iPLEX assay in conjunction with the MassARRAY platform (Sequenom).

RESULTS

We identified 2870 markers showing substantial differences in MAF (5.0-10.7%) between pools. To initiate validation of these findings, we genotyped 22 high-ranking markers in 462 individuals with ESRD and 470 unaffected control subjects selected from the genome-wide SNP genotyping study sample. We observed the strongest evidence for association between ESRD and rs1749824, located in the ZMIZ1 gene [OR = 1.47 (1.21-1.78) per copy of T allele; P = 8.1 x 10(-5)] and rs9298190, located in the musculin gene [OR = 1.56 (1.28-1.91) per copy of C allele; P = 1.6 x 10(-5)]. Evidence for nominal association with markers in or near the IRS2, TMPO, BID, KLRA1, ELMO1 and CNDP1 genes was also observed (P < or = 0.0006).

CONCLUSIONS

These findings identify several novel loci which may contribute to ESRD susceptibility in individuals with Type 1 diabetes.

Genome-wide linkage analysis of ADHD using high-density SNP arrays: novel loci at 5q13.1 and 14q12

Previous genome-wide linkage studies applied the affected sib-pair design; one investigated extended pedigrees of a genetic isolate. Here, results of a genome-wide high-density linkage scan of attention-deficit/hyperactivity disorder (ADHD) using an array-based genotyping of approximately 50 K single nucleotide polymorphism (SNPs) markers are presented. We investigated eight extended pedigrees of German origin that were non-related, not part of a genetic isolate and ascertained on the basis of clinical referral. Two parametric analyses maximizing LOD scores (MOD) and a non-parametric analysis for both a broad and a narrow phenotype approach were conducted. Novel linkage loci across all families were detected at 2q35, 5q13.1, 6q22-23 and 14q12, within individual families at 18q11.2-12.3. Further linkage regions at 7q21.11, 9q22 and 16q24.1 in all families, and at 1q25.1, 1q25.3, 9q31.1-33.1, 9q33, 12p13.33, 15q11.2-13.3 and 16p12.3-12.2 in individual families replicate previous findings. High-resolution linkage mapping points to several novel candidate genes characterized by dense expression in the brain and potential impact on disorder-relevant synaptic transmission. Our study provides further evidence for common gene effects throughout different populations despite the complex multifactorial etiology of ADHD.

Structural insights into the mechanical regulation of molecular recognition sites

Intriguing experimental and computational data are emerging to suggest that mechanical forces regulate the functional states of some proteins by stretching them into nonequilibrium states. Using the extracellular matrix protein fibronectin as an example, we discuss molecular design principles that might control the exposure of a protein's recognition sites, and/or their relative distances, in a force-dependent manner. Fibronectin regulates many cellular functions by binding directly to integrins. Although integrins have a key role in the transduction of force across the cell membrane by coupling the extracellular matrix to the cytoskeleton, the studies reviewed here suggest that fibronectin might be one of the molecules responsible for the initial transformation of mechanical force into a biochemical signal.

Regulation of the 2-oxoglutarate dehydrogenase lipoate succinyltransferase complex from cauliflower by nucleotide. Pre-steady state kinetics and physical studies

Analysis of the binding of thiamin pyrophosphate to the 2-oxoglutarate dehydrogenaselipoate succinyltransferase multienzyme complex using pre-steady state kinetic methods revealed that the presence of 2-oxoglutarate is not necessary for binding, although it does stabilize the complex by slowing the rate of dissociation of the holoenzyme. The rate of binding of thiamin-PPi to the enzyme and the subsequent enzyme activation are not limited by a reaction at C-2 of the thiazolium ring of thiamin-PPi since no kinetic isotope effect is observed when 2-D-thiamin-PPi is substituted for the protonated cofactor. The presence of 5'-AMP, which activates the reaction producing both a V and a Km response, causes a significant increase in kon for thiamin-PPi. The AMP analog 1,N6-ethenoadenosine-5'-monophosphate (epsilon-AMP) also activates the reaction, but shows only a K effect, with no influence on V. This effector reduces Kd for the thiamin-PPi2-oxoglutarate dehydrogenase complex by increasing kon. The change in kon for thiamin-PPi in response to changes in hydrogen ion concentration shows pK values which are unaffected by the addition of AMP, in this respect resembling the steady state kinetic response of V/Km and differing from the pH profile of V. The dissociation constant of holoenzyme is relatively insensitive to pH over the range pH 6 to 9, but in the presence of AMP the Kd, which is decreased in the range from pH 7 to 8, increases sharply at higher or lower pH values.

Structural mapping of rabbit muscle phosphofructokinase. Distance between the adenosine cyclic 3',5'-phosphate binding site and a reactive sulfhydryl group

The cAMP binding site of rabbit muscle phosphofructokinase has been labeled with the fluorescent molecule 5'-(p-fluorosulfonylbenzoyl)-2-aza-1,N6-ethenoadenosine. The most reactive sulfhydry- group of this modified enzyme, which is catalytically active, has been labeled with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole and with N-]4-(dimethylamino)-3,5-dinitrophenyl]maleimide. The calculated distances between the cAMP binding site and the most reactive sulfhydryl group, as determined by resonance energy transfer measurements, are 31 and 26 A, respectively, for the two sulfhydryl group labels. Both steady-state and fluorescent -ifetime techniques were used to measure the energy transfer efficiencies in 50 mM potassium phosphate (pH 8.0) and 1 mM ethylenediaminetetraacetic acid, and a value of 2/3 was assumed for the donor-acceptor orientation factor. If the difference in calculated distances is attributed to a difference in the orientation factor for the two donor-acceptor ,airs, the actual distance between the cAMP ligand binding site and the most reactive sulfhydryl group on phosphofructokinase is shown to be 28 +/- 6 A.

Effects of magnification and observation time on target identification in simulated orbital reconnaissance

When deciding what telescopic power is required to find objects of interest on the ground while flying over the earth at relatively high speeds, the positive value of an increased magnification must be balanced against the negative effects of a decreased observation time and an increased movement rate. The relative trade-off between these two factors—magnification and time—was compared in a series of three studies in which photographic imagery was used to simulate a telescopic view of the earth from a spacecraft orbiting at 175 nautical miles. Target acquisition decreased as image scale factor decreased and as image movement rate increased. When a change in scale factor was inversely proportional to a change in observation time, the positive effects of an increased image scale factor tended to exceed the negative effects of a decreased observation time and increased image movement rate within the limits of this study. The theoretical and practical implications of these and other results are discussed.