Stephen J. O'Brien

Bio: Stephen J. O'Brien is an academic researcher from Saint Petersburg State University of Information Technologies, Mechanics and Optics. The author has contributed to research in topics: Population & Gene. The author has an hindex of 153, co-authored 1062 publications receiving 93025 citations. Previous affiliations of Stephen J. O'Brien include University College Cork & QIMR Berghofer Medical Research Institute.

The microRNA‑200 family acts as an oncogene in colorectal cancer by inhibiting the tumor suppressor RASSF2

Abstract: This study aimed to determine whether manipulation of the microRNA-200 (miR-200) family could influence colon adenocarcinoma cell behavior. The miR-200 family has a significant role in tumor suppression and functions as an oncogene. In vitro studies on gain and loss of function with small interfering RNA demonstrated that the miR-200 family could regulate RASSF2 expression. Knockdown of the miR-200 family in the HT-29 colon cancer cell line increased KRAS expression but decreased signaling in the MAPK/ERK signaling pathway through reduced ERK phosphorylation. Increased expression of the miR-200 family in the CCD-841 colon epithelium cell line increased KRAS expression and led to increased signaling in the MAPK/ERK signaling pathway but increased ERK phosphorylation. Functionally, knockdown of the miR-200 family led to decreased cell proliferation in the HT-29 cells; therefore, increased miR-200 family expression could increase cell proliferation in the CCD-841 cell line. The present study included a large paired miR array dataset (n=632), in which the miR-200 family was significantly found to be increased in colon cancer when compared with normal adjacent colon epithelium. In a miR-seq dataset (n=199), the study found that miR-200 family expression was increased in localized colon cancer compared with metastatic disease. Decreased expression was associated with poorer overall survival. The miR-200 family directly targeted RASSF2 and was inversely correlated with RASSF2 expression (n=199, all P<0.001). Despite the well-defined role of the miR-200 family in tumor suppression, the present findings demonstrated a novel function of the miR-200 family in tumor proliferation.

The effect of RANTES chemokine genetic variants on early HIV-1 plasma RNA among African American injection drug users.

Abstract: HIV-1 plasma RNA is a prognostic indicator of HIV-1, and increased levels of HIV-1 plasma RNA are associated with rapid progression to AIDS. Because chemokines and chemokine receptors are involved in the binding and entry of HIV-1, possible effects of host genetics on viral RNA levels should be visible in early infection. HIV-1 plasma RNA was measured within 2 years of seroconversion in 198 seroincident injection drug users followed in the AIDS Link to Intravenous Experience cohort. Genetic variants were identified in the chemokine receptors (CCR2, CCR5, and CCR5 promoter) and the chemokine RANTES using TaqMan and restriction fragment length polymorphism assays. Linear regression of RANTES haplotypes on early HIV-1 plasma RNA identified individuals homozygous for the RANTES R1 haplotype as having a lower viral load by almost one-half log 10 unit compared with those bearing non-RANTES R1 haplotypes (-0.43, 95% confidence interval: -0.74, -0.12). Genetic variants in RANTES may downregulate RANTES gene expression and increase early HIV-I plasma RNA. Because RANTES is a critical chemokine and competitively inhibits HIV-1 by binding to its receptor CCR5, treatment to enhance RANTES expression may assist in delaying the progression of AIDS by decreasing the initial viral load.

Chromosomal mapping of beta-globin and albino loci in the domestic cat A conserved mammalian chromosome group

Abstract: Siamese cats are homozygous for the recessive cs allele of the color (albino) locus. The c locus is shown here by backcross analysis to be linked to the beta-hemoglobin (HBB) locus in the cat at a distance of approximately eight centiMorgans. The HBB locus and, by inference, the c locus were assigned to feline chromosome D1, by analysis of genomic DNAs from a panel of rodent X cat somatic cell hybrids with a molecular clone of the human beta-globin locus. Evolutionary conservation of the synthetic homology of feline chromosome D1 and human chromosome 11 is extensive. Comparison of high resolution G-trypsin-banded preparations of the two chromosomes permitted cytological alignment of the long arm of the conserved chromosomes providing that a minimum of one paracentric inversion is hypothesized. The placement of the albino locus on conserved syntenic groups of several markers (HBB, HRAS, LDHA) in both cat and mouse strongly indicates the conservative placement of the as yet unmapped human albino locus in the homologous syntenic group on human chromosome 11p.

Initial sequencing and analysis of the human genome.

Abstract: The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

Genome-wide association study of 14,000 cases of seven common diseases and 3,000 shared controls

Abstract: There is increasing evidence that genome-wide association ( GWA) studies represent a powerful approach to the identification of genes involved in common human diseases. We describe a joint GWA study ( using the Affymetrix GeneChip 500K Mapping Array Set) undertaken in the British population, which has examined similar to 2,000 individuals for each of 7 major diseases and a shared set of similar to 3,000 controls. Case-control comparisons identified 24 independent association signals at P < 5 X 10(-7): 1 in bipolar disorder, 1 in coronary artery disease, 9 in Crohn's disease, 3 in rheumatoid arthritis, 7 in type 1 diabetes and 3 in type 2 diabetes. On the basis of prior findings and replication studies thus-far completed, almost all of these signals reflect genuine susceptibility effects. We observed association at many previously identified loci, and found compelling evidence that some loci confer risk for more than one of the diseases studied. Across all diseases, we identified a large number of further signals ( including 58 loci with single-point P values between 10(-5) and 5 X 10(-7)) likely to yield additional susceptibility loci. The importance of appropriately large samples was confirmed by the modest effect sizes observed at most loci identified. This study thus represents a thorough validation of the GWA approach. It has also demonstrated that careful use of a shared control group represents a safe and effective approach to GWA analyses of multiple disease phenotypes; has generated a genome-wide genotype database for future studies of common diseases in the British population; and shown that, provided individuals with non-European ancestry are excluded, the extent of population stratification in the British population is generally modest. Our findings offer new avenues for exploring the pathophysiology of these important disorders. We anticipate that our data, results and software, which will be widely available to other investigators, will provide a powerful resource for human genetics research.