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 Taming of the cat. Genetic and archaeological findings hint that wildcats became housecats earlier--and in a different place--than previously thought.

Abstract: Genetic and archaeological findings hint that wildcats became house cats earlier—and in a different place—than previously thought

Secreted frizzled-related protein-4 reduces sodium–phosphate co-transporter abundance and activity in proximal tubule cells

Abstract: The phosphatonin, secreted frizzled-related protein-4 (sFRP-4), induces phosphaturia and inhibits 25-hydroxyvitamin D 1α-hydroxylase activity normally induced in response to hypophosphatemia. To determine the mechanism by which sFRP-4 alters renal phosphate (Pi) transport, we examined the effect of sFRP-4 on renal brush border membrane (BBMV) Na+-dependent Pi uptake, and the abundance and localization of the major Na+–Pi-IIa co-transporter in proximal tubules and opossum kidney (OK) cells. Infusion of sFRP-4 increased renal fractional excretion of Pi and decreased renal β-catenin concentrations. The increase in renal Pi excretion with sFRP-4 infusion was associated with a 21.9±3.4% decrease in BBMV Na+-dependent Pi uptake (P<0.001) compared with a 39.5±2.1% inhibition of Na+-dependent Pi transport in renal BBMV induced by PTH (P<0.001). sFRP-4 infusion was associated with a 30.7±4.8% decrease in Na+–Pi-IIa co-transporter protein abundance (P<0.01) assessed by immunoblotting methods compared to a 45.4±8.8% decrease induced by PTH (P<0.001). In OK cells, sFRP-4 reduced surface expression of a heterologous Na+–Pi-IIa co-transporter. We conclude that sFRP-4 increases renal Pi excretion by reducing Na+–Pi-IIa transporter abundance in the brush border of the proximal tubule through enhanced internalization of the protein.

Emergence of the keratinocyte growth factor multigene family during the great ape radiation.

Abstract: The structural gene for human keratinocyte growth factor (KGF), a member of the fibroblast growth factor family, consists of three coding exons and two introns typical of other fibroblast growth factor loci. A portion of the KGF gene, located on chromosome 15, is amplified to approximately 16 copies in the human genome, and these highly related copies (which consist of exon 2, exon 3, the intron between them, and a 3' noncoding segment of the KGF transcript) are dispersed to multiple human chromosomes. The KGF-like sequences are transcriptionally active, differentially regulated in various tissues, and composed of three distinct classes of coding sequences that are 5% divergent from each other and from the authentic KGF sequence. Multiple copies of KGF-like genes were also discovered in the genomic DNAs of chimpanzee and gorilla but were not found in lesser apes (gibbon), Old World monkeys (African green monkey and macaques), mice, or chickens. The pattern of evolutionary occurrence suggests that a primordial KGF gene was amplified and chromosomally dispersed subsequent to the divergence of orangutan from African apes but before the trichotomous divergence of human, chimpanzee, and gorilla 5-8 million years ago. The appearance of a transcriptionally active and chromosomally dispersed multigene KGF family may have implications in the evolution of the great apes and humans.

Genetic variation within and among lion tamarins

Abstract: The golden lion tamarin Leontopithecus rosalia rosalia, one of the rarest and most endangered of New World primates, has been the focus of an intensive research and conservation effort for two decades. During that period, managed breeding from 44 founders has brought the captive population to over 400 individuals, a number that equals or exceeds the estimated number of free-ranging golden lion tamarins. The extent of genetic variation among golden lion tamarins was estimated with an electrophoretic survey of 47 allozyme loci from 67 captive and 73 free-ranging individuals. The amount of variation was low, compared to 15 other primate species, with 4% of the loci being polymorphic (P), and with an average heterozygosity H estimate of 0.01 in these callitrichids. Electrophoretic analyses of captive and free-ranging animals (N = 31) of two allopatric morphotypes, Leontopithecus rosalia chrysopygus and L. r. chrysomelas, were similar to the L. r. rosalia findings insofar as they also revealed limited genetic polymorphism. Computation of the Neigenetic distance measurements showed that the three morphotypes were genetically very similar, although discernible differentiation had occurred at two loci. These data are consistent with the occurrence of recent reproductive isolations of these subspecies.

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.