Peadar Ó Gaora

Comparative Genome Analysis and Gene Finding in Candida Species Using CGOB

The Candida Gene Order Browser (CGOB) was developed as a tool to visualize and analyze synteny relationships in multiple Candida species, and to provide an accurate, manually curated set of orthologous Candida genes for evolutionary analyses. Here, we describe major improvements to CGOB. The underlying structure of the database has been changed significantly. Genomic features are now based directly on genome annotations rather than on protein sequences, which allows non-protein features such as centromere locations in Candida albicans and tRNA genes in all species to be included. The data set has been expanded to 13 species, including genomes of pathogens (C. albicans, C. parapsilosis, C. tropicalis, and C. orthopsilosis), and those of xylose-degrading species with important biotechnological applications (C. tenuis, Scheffersomyces stipitis, and Spathaspora passalidarum). Updated annotations of C. parapsilosis, C. dubliniensis, and Debaryomyces hansenii have been incorporated. We discovered more than 1,500 previously unannotated genes among the 13 genomes, ranging in size from 29 to 3,850 amino acids. Poorly conserved and rapidly evolving genes were also identified. Re-analysis of the mating type loci of the xylose degraders suggests that C. tenuis is heterothallic, whereas both Spa. passalidarum and S. stipitis are homothallic. As well as hosting the browser, the CGOB website (http://cgob.ucd.ie) gives direct access to all the underlying genome annotations, sequences, and curated orthology data.

Next-Generation Sequencing Identifies TGF-β1-Associated Gene Expression Profiles in Renal Epithelial Cells Reiterated in Human Diabetic Nephropathy

Transforming growth factor-beta (TGF-β1) is implicated in the onset and progression of renal fibrosis and diabetic nephropathy (DN), leading to a loss of epithelial characteristics of tubular cells. The transcriptional profile of renal tubular epithelial cells stimulated with TGF-β1 was assessed using RNA-Seq, with 2027 differentially expressed genes identified. Promoter analysis of transcription factor binding sites in the TGF-β1 responsive gene set predicted activation of multiple transcriptional networks, including NFκB. Comparison of RNA-Seq with microarray data from identical experimental conditions identified low abundance transcripts exclusive to RNA-Seq data. We compared these findings to human disease by analyzing transcriptomic data from renal biopsies of patients with DN versus control groups, identifying a shared subset of 179 regulated genes. ARK5, encoding an AMP-related kinase, and TGFBI - encoding transforming growth factor, beta-induced protein were induced by TGF-β1 and also upregulated in human DN. Suppression of ARK5 attenuated fibrotic responses of renal epithelia to TGF-β1 exposure; and silencing of TGFBI induced expression of the epithelial cell marker - E-cadherin. We identified low abundance transcripts in sequence data and validated expression levels of several transcripts (ANKRD56, ENTPD8) in tubular enriched kidney biopsies of DN patients versus living donors. In conclusion, we have defined a TGF-β1-driven pro-fibrotic signal in renal epithelial cells that is also evident in the DN renal transcriptome.

Interaction of Developmental Transcription Factor HOX11 with Steroid Receptor Coactivator SRC-1 Mediates Resistance to Endocrine Therapy in Breast Cancer

Mechanisms of acquired resistance to endocrine therapy in breast cancer, a major clinical challenge, are poorly understood. We have used a mass spectrometry-based screen to identify proteins that are associated with the endocrine-resistant phenotype. In this study, we report the identification of a novel pathway of resistance to endocrine therapy involving interactions of the developmental transcription HOXC11 with the steroid receptor coactivator protein SRC-1, which is a strong predictor of reduced disease-free survival in breast cancer patients. HOXC11 and SRC-1 cooperate to regulate expression of the calcium-binding protein S100beta in resistant breast cancer cells. Nuclear HOXC11 and S100beta were found to strongly predict poor disease-free survival in breast cancer patients (n = 560; hazard ratios: 5.79 and 5.82, respectively; P < 0.0001). Elevated serum levels of S100beta detected in patients also predicted reduced disease-free survival (n = 80; hazard ratio: 5.3; P = 0.004). Our findings define a biomolecular interaction network that drives an adaptive response to endocrine therapy with negative consequences for survival in breast cancer.

Oviduct-Embryo Interactions in Cattle: Two-Way Traffic or a One-Way Street?

ABSTRACT This study examined the effect of the presence of single or multiple embryos on the transcriptome of the bovine oviduct. In experiment 1, cyclic (nonbred, n = 6) and pregnant (artificially inseminated, n = 11) heifers were slaughtered on Day 3 after estrus, and the ampulla and isthmic regions of the oviduct ipsilateral to the corpus luteum were separately flushed. Oviductal epithelial cells from the isthmus region, in which all oocytes/embryos were located, were snap-frozen for microarray analysis. In experiment 2, heifers were divided into cyclic (nonbred, n = 6) or pregnant (multiple embryo transfer, n = 10) groups. In vitro-produced presumptive zygotes were transferred endoscopically to the ipsilateral oviduct on Day 1.5 postestrus (n = 50 zygotes/heifer). Heifers were slaughtered on Day 3, and oviductal isthmus epithelial cells were recovered for RNA sequencing. Microarray analysis in experiment 1 failed to detect any difference in the transcriptome of the oviductal isthmus induced by the presence of a single embryo. In experiment 2, following multiple embryo transfer, RNA sequencing revealed 278 differentially expressed genes, of which 123 were up-regulated and 155 were down-regulated in pregnant heifers. Most of the down-regulated genes were related to immune function. In conclusion, the presence of multiple embryos in the oviduct resulted in the detection of differentially expressed genes in the oviductal isthmus; failure to detect changes in the oviduct transcriptome in the presence of a single embryo may be due to the effect being local and undetectable under the conditions of this study.

Global characterization of the SRC-1 transcriptome identifies ADAM22 as an ER-independent mediator of endocrine resistant breast cancer

The development of breast cancer resistance to endocrine therapy results from an increase in cellular plasticity that permits the emergence of a hormone-independent tumor. The steroid coactivator protein SRC-1, through interactions with developmental proteins and other nonsteroidal transcription factors, drives this tumor adaptability. In this discovery study, we identified ADAM22, a non-protease member of the ADAM family of disintegrins, as a direct estrogen receptor (ER)-independent target of SRC-1. We confirmed SRC-1 as a regulator of ADAM22 by molecular, cellular, and in vivo studies. ADAM22 functioned in cellular migration and differentiation, and its levels were increased in endocrine resistant-tumors compared with endocrine-sensitive tumors in mouse xenograft models of human breast cancer. Clinically, ADAM22 was found to serve as an independent predictor of poor disease-free survival. Taken together, our findings suggest that SRC-1 switches steroid-responsive tumors to a steroid-resistant state in which the SRC-1 target gene ADAM22 has a critical role, suggesting this molecule as a prognostic and therapeutic drug target that could help improve the treatment of endocrine-resistant breast cancer.

High-Throughput Proteomics Detection of Novel Splice Isoforms in Human Platelets

Alternative splicing (AS) is an intrinsic regulatory mechanism of all metazoans. Recent findings suggest that 100% of multiexonic human genes give rise to splice isoforms. AS can be specific to tissue type, environment or developmentally regulated. Splice variants have also been implicated in various diseases including cancer. Detection of these variants will enhance our understanding of the complexity of the human genome and provide disease-specific and prognostic biomarkers. We adopted a proteomics approach to identify exon skip events - the most common form of AS. We constructed a database harboring the peptide sequences derived from all hypothetical exon skip junctions in the human genome. Searching tandem mass spectrometry (MS/MS) data against the database allows the detection of exon skip events, directly at the protein level. Here we describe the application of this approach to human platelets, including the mRNA-based verification of novel splice isoforms of ITGA2, NPEPPS and FH. This methodology is applicable to all new or existing MS/MS datasets.

AIB1:ERα Transcriptional Activity Is Selectively Enhanced in Aromatase Inhibitor–Resistant Breast Cancer Cells

Purpose: The use of aromatase inhibitors (AI) in the treatment of estrogen receptor (ER)-positive, postmenopausal breast cancer has proven efficacy. However, inappropriate activation of ER target genes has been implicated in the development of resistant tumors. The ER coactivator protein AIB1 has previously been associated with initiation of breast cancer and resistance to endocrine therapy. Experimental Design: Here, we investigated the role of AIB1 in the deregulation of ER target genes occurring as a consequence of AI resistance using tissue microarrays of patients with breast cancer and cell line models of resistance to the AI letrozole. Results: Expression of AIB1 associated with disease recurrence (P = 0.025) and reduced disease-free survival time (P = 0.0471) in patients treated with an AI as first-line therapy. In a cell line model of resistance to letrozole (LetR), we found ERα/AIB1 promoter recruitment and subsequent expression of the classic ER target genes pS2 and Myc to be constitutively upregulated in the presence of both androstenedione and letrozole. In contrast, the recruitment of the ERα/AIB1 transcriptional complex to the nonclassic ER target cyclin D1 and its subsequent expression remained sensitive to steroid treatment and could be inhibited by treatment with letrozole. Molecular studies revealed that this may be due in part to direct steroid regulation of c-jun-NH2-kinase (JNK), signaling to Jun and Fos at the cyclin D1 promoter. Conclusion: This study establishes a role for AIB1 in AI-resistant breast cancer and describes a new mechanism of ERα/AIB1 gene regulation which could contribute to the development of an aggressive tumor phenotype. Clin Cancer Res; 18(12); 3305–15. ©2012 AACR.

Bi-directional gene set enrichment and canonical correlation analysis identify key diet-sensitive pathways and biomarkers of metabolic syndrome

BackgroundCurrently, a number of bioinformatics methods are available to generate appropriate lists of genes from a microarray experiment. While these lists represent an accurate primary analysis of the data, fewer options exist to contextualise those lists. The development and validation of such methods is crucial to the wider application of microarray technology in the clinical setting. Two key challenges in clinical bioinformatics involve appropriate statistical modelling of dynamic transcriptomic changes, and extraction of clinically relevant meaning from very large datasets.ResultsHere, we apply an approach to gene set enrichment analysis that allows for detection of bi-directional enrichment within a gene set. Furthermore, we apply canonical correlation analysis and Fishers exact test, using plasma marker data with known clinical relevance to aid identification of the most important gene and pathway changes in our transcriptomic dataset. After a 28-day dietary intervention with high-CLA beef, a range of plasma markers indicated a marked improvement in the metabolic health of genetically obese mice. Tissue transcriptomic profiles indicated that the effects were most dramatic in liver (1270 genes significantly changed; p < 0.05), followed by muscle (601 genes) and adipose (16 genes). Results from modified GSEA showed that the high-CLA beef diet affected diverse biological processes across the three tissues, and that the majority of pathway changes reached significance only with the bi-directional test. Combining the liver tissue microarray results with plasma marker data revealed 110 CLA-sensitive genes showing strong canonical correlation with one or more plasma markers of metabolic health, and 9 significantly overrepresented pathways among this set; each of these pathways was also significantly changed by the high-CLA diet. Closer inspection of two of these pathways - selenoamino acid metabolism and steroid biosynthesis - illustrated clear diet-sensitive changes in constituent genes, as well as strong correlations between gene expression and plasma markers of metabolic syndrome independent of the dietary effect.ConclusionBi-directional gene set enrichment analysis more accurately reflects dynamic regulatory behaviour in biochemical pathways, and as such highlighted biologically relevant changes that were not detected using a traditional approach. In such cases where transcriptomic response to treatment is exceptionally large, canonical correlation analysis in conjunction with Fishers exact test highlights the subset of pathways showing strongest correlation with the clinical markers of interest. In this case, we have identified selenoamino acid metabolism and steroid biosynthesis as key pathways mediating the observed relationship between metabolic health and high-CLA beef. These results indicate that this type of analysis has the potential to generate novel transcriptome-based biomarkers of disease.

Spatial differences in gene expression in the bovine oviduct

The aim of this study was to compare the transcriptome of the oviductal isthmus of pregnant heifers with that of cyclic heifers as well as to investigate spatial differences between the transcriptome of the isthmus and ampulla of the oviduct in pregnant heifers. After synchronizing crossbred beef heifers, those in standing oestrus (=Day 0) were randomly assigned to cyclic (non-bred, n=6) or pregnant (artificially inseminated, n=11) groups. They were slaughtered on Day 3 and both oviducts from each animal were isolated and cut in half to separate ampulla and isthmus. Each portion was flushed to confirm the presence of an oocyte/embryo and was then opened longitudinally and scraped to obtain epithelial cells which were snap-frozen. Oocytes and embryos were located in the isthmus of the oviduct ipsilateral to the corpus luteum Microarray analysis of oviductal cells revealed that proximity to the corpus luteum did not affect the transcriptome of the isthmus, irrespective of pregnancy status. However, 2287 genes were differentially expressed (P<0.01) between the ampulla and isthmus of the oviduct ipsilateral to the corpus luteum in pregnant animals. Gene ontology revealed that the main biological processes overrepresented in the isthmus were synthesis of nitrogen, lipids, nucleotides, steroids and cholesterol as well as vesicle-mediated transport, cell cycle, apoptosis, endocytosis and exocytosis, whereas cell motion, motility and migration, DNA repair, calcium ion homeostasis, carbohydrate biosynthesis, and regulation of cilium movement and beat frequency were overrepresented in the ampulla. In conclusion, large differences in gene expression were observed between the isthmus and ampulla of pregnant animals at Day 3 after oestrus.

Adaptation to AI therapy in breast cancer can induce dynamic alterations in ER activity resulting in estrogen independent metastatic tumours

Purpose: Acquired resistance to aromatase inhibitor (AI) therapy is a major clinical problem in the treatment of breast cancer. The detailed mechanisms of how tumor cells develop this resistance remain unclear. Here, the adapted function of estrogen receptor (ER) to an estrogen-depleted environment following AI treatment is reported. Experimental Design: Global ER chromatin immuno-precipitation (ChIP)-seq analysis of AI-resistant cells identified steroid-independent ER target genes. Matched patient tumor samples, collected before and after AI treatment, were used to assess ER activity. Results: Maintained ER activity was observed in patient tumors following neoadjuvant AI therapy. Genome-wide ER–DNA-binding analysis in AI-resistant cell lines identified a subset of classic ligand-dependent ER target genes that develop steroid independence. The Kaplan–Meier analysis revealed a significant association between tumors, which fail to decrease this steroid-independent ER target gene set in response to neoadjuvant AI therapy, and poor disease-free survival and overall survival (n = 72 matched patient tumor samples, P = 0.00339 and 0.00155, respectively). The adaptive ER response to AI treatment was highlighted by the ER/AIB1 target gene, early growth response 3 (EGR3). Elevated levels of EGR3 were detected in endocrine-resistant local disease recurrent patient tumors in comparison with matched primary tissue. However, evidence from distant metastatic tumors demonstrates that the ER signaling network may undergo further adaptations with disease progression as estrogen-independent ER target gene expression is routinely lost in established metastatic tumors. Conclusions: Overall, these data provide evidence of a dynamic ER response to endocrine treatment that may provide vital clues for overcoming the clinical issue of therapy resistance. Clin Cancer Res; 22(11); 2765–77. ©2016 AACR.