Explore the vast range of titles available.

Type 1 Diabetes in the BB Rat: A Polygenic Disease Robert H. Wallis 1 , KeSheng Wang 2 , 3 , Leili Marandi 1 , Eugene Hsieh 1 , 4 , Terri Ning 1 , Gary Y.C. Chao 1 , Janice Sarmiento 1 , Andrew D. Paterson 2 , 5 and Philippe Poussier 1 1 Sunnybrook Health Sciences Centre Research Institute, Departments of Medicine and Immunology, University of Toronto, Toronto, Ontario, Canada; the 2 Program in Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada; the 3 Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City, Tennessee; the 4 Department of Laboratory Medicine and Pathology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; and the 5 Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada. Corresponding author: Philippe Poussier, philippe.poussier{at}sri.utoronto.ca . R.H.W., K.W., L.M., and E.H. contributed equally to this article. Abstract OBJECTIVE Two type 1 diabetes susceptibility genes have been identified in the spontaneously diabetic biobreeding diabetes-prone (BBDP) rat, the major histocompatibility complex (MHC) ( RT1 ) class II u haplotype (Iddm1) and Gimap5 (Iddm2). The strong effects of these have impeded previous efforts to map additional loci. We tested the hypothesis that type 1 diabetes is a polygenic disease in the BBDP rat. RESEARCH DESIGN AND METHODS We performed the most comprehensive genome-wide linkage analysis for type 1 diabetes, age of disease onset (AOO), and insulitis subphenotypes in 574 F2 animals from a cross-intercross between BBDP and type 1 diabetes–resistant, double congenic ACI.BBDP- RT1u,Gimap5 (ACI.BB 1u.lyp ) rats, where both Iddm1 and Iddm2 were fixed as BBDP. RESULTS A total of 19% of these F2 animals developed type 1 diabetes, and eight type 1 diabetes susceptibility loci were mapped, six showing significant linkage (chromosomes 1, 3, 6 [two loci], 12, and 14) and two (chromosomes 2 and 17) suggestive linkage. The chromosomes 6, 12, and 14 intervals were also linked to the severity of islet infiltration by immunocytes, while those on chromosomes 1, 6 (two loci), 14, 17, and a type 1 diabetes–unlinked chromosome 8 interval showed significant linkage to the degree of islet atrophy. Four loci exhibited suggestive linkage to AOO on chromosomes 2 (two loci), 7, and 18 but were unlinked to type 1 diabetes. INS , PTPN22 , IL2/IL21 , C1QTNF6 , and C12orf30 , associated with human type 1 diabetes, are contained within the chromosomes 1, 2, 7, and 12 loci. CONCLUSIONS This study demonstrates that the BBDP diabetic syndrome is a complex, polygenic disease that may share additional susceptibility genes besides MHC class II with human type 1 diabetes. Footnotes The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. See accompanying original article, p. 796 . Received September 2, 2008. Accepted December 18, 2008. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details. © 2009 by the American Diabetes Association.

With the advent of high through-put sequencing (HTS), the emerging science of metagenomics is transforming our understanding of the relationships of microbial communities with their environments. While metagenomics aims to catalogue the genes present in a sample through assessing which genes are actively expressed, metatranscriptomics can provide a mechanistic understanding of community inter-relationships. To achieve these goals, several challenges need to be addressed from sample preparation to sequence processing, statistical analysis and functional annotation. Here we use an inbred non-obese diabetic (NOD) mouse model in which germ-free animals were colonized with a defined mixture of eight commensal bacteria, to explore methods of RNA extraction and to develop a pipeline for the generation and analysis of metatranscriptomic data. Applying the Illumina HTS platform, we sequenced 12 NOD cecal samples prepared using multiple RNA-extraction protocols. The absence of a complete set of reference genomes necessitated a peptide-based search strategy. Up to 16% of sequence reads could be matched to a known bacterial gene. Phylogenetic analysis of the mapped ORFs revealed a distribution consistent with ribosomal RNA, the majority from Bacteroides or Clostridium species. To place these HTS data within a systems context, we mapped the relative abundance of corresponding Escherichia coli homologs onto metabolic and protein-protein interaction networks. These maps identified bacterial processes with components that were well-represented in the datasets. In summary this study highlights the potential of exploiting the economy of HTS platforms for metatranscriptomics.

A Novel Susceptibility Locus on Rat Chromosome 8 Affects Spontaneous but Not Experimentally Induced Type 1 Diabetes Robert H. Wallis 1 , KeSheng Wang 2 , Dominika Dabrowski 1 , Leili Marandi 1 , Terri Ning 1 , Eugene Hsieh 1 3 , Andrew D. Paterson 2 4 , John P. Mordes 5 , Elisabeth P. Blankenhorn 6 and Philippe Poussier 1 1 Departments of Medicine and Immunology, Sunnybrook and Women's College Health Sciences Centre Research Institute, University of Toronto, Toronto, Ontario, Canada 2 Program in Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada 3 Department of Laboratory Medicine and Pathology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada 4 Department of Public Health Sciences, University of Toronto, Toronto, Ontario, Canada 5 Diabetes Division, University of Massachusetts Medical School, Worcester, Massachusetts 6 Department of Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania Address correspondence and reprint requests to Philippe Poussier, Sunnybrook and Women's Health Sciences Centre, 2075 Bayview Ave., Room A3 38, Toronto, Ontario, Canada, M4N 3M5. E-mail: philippe.poussier{at}sri.utoronto.ca Abstract OBJECTIVE—The biobreeding diabetes-prone (BBDP) rat spontaneously develops type 1 diabetes. Two of the genetic factors contributing to this syndrome are the major histocompatibility complex (Iddm1) and a Gimap5 mutation (Iddm2) responsible for a T-lymphopenia. Susceptibility to experimentally induced type 1 diabetes is widespread among nonlymphopenic (wild-type Iddm2) rat strains provided they share the BBDP Iddm1 allele. The question follows as to whether spontaneous and experimentally induced type 1 diabetes share susceptibility loci besides Iddm1. Our objectives were to map a novel, serendipitously discovered Iddm locus, confirm its effects by developing congenic sublines, and assess its differential contribution to spontaneous and experimentally induced type 1 diabetes. RESEARCH DESIGN AND METHODS—An unexpected reduction in spontaneous type 1 diabetes incidence (86 to 31%, P < 0.0001) was observed in a BBDP line congenic for a Wistar Furth–derived allotypic marker, RT7 (chromosome 13). Genome-wide analysis revealed that, besides the RT7 locus, a Wistar Furth chromosome 8 fragment had also been introduced. The contribution of these intervals to diabetes resistance was assessed through linkage analysis using 134 F2 (BBDP × double congenic line) animals and a panel of congenic sublines. One of these sublines, resistant to spontaneous type 1 diabetes, was tested for susceptibility to experimentally induced type 1 diabetes. RESULTS—Both linkage analysis and congenic sublines mapped a novel locus (Iddm24) to the telomeric 10.34 Mb of chromosome 8, influencing cumulative incidence and age of onset of spontaneous type 1 diabetes but not insulitis nor experimentally induced type 1 diabetes. CONCLUSIONS—This study has identified a type 1 diabetes susceptibility locus that appears to act after the development of insulitis and that regulates spontaneous type 1 diabetes exclusively. BBDP, biobreeding diabetes prone BBDR, biobreeding diabetes resistant LOD, logarithm of odds mAb, monoclonal antibody RGSC, Rat Genome Sequencing Consortium Footnotes Published ahead of print at http://diabetes.diabetesjournals.org on 27 March 2007. DOI: 10.2337/db06-1790. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Accepted March 2, 2007. Received December 22, 2006. DIABETES

We are exposed to millions of microbial and dietary antigens via the gastrointestinal tract, which likely play a key role in type 1 diabetes (T1D). We differentiated the effects of these two major environmental factors on gut immunity and T1D. Diabetes-prone BioBreeding (BBdp) rats were housed in specific pathogen-free (SPF) or germ-free (GF) conditions and weaned onto diabetes-promoting cereal diets or a protective low-antigen hydrolyzed casein (HC) diet, and T1D incidence was monitored. Fecal microbiota 16S rRNA genes, immune cell distribution, and gene expression in the jejunum were analyzed. T1D was highest in cereal-SPF (65%) and cereal-GF rats (53%) but inhibited and delayed in HC-fed counterparts. Nearly all HC-GF rats remained diabetes-free, whereas HC-fed SPF rats were less protected (7 vs. 29%). Bacterial communities differed in SPF rats fed cereal compared with HC. Cereal-SPF rats displayed increased gut CD3+ and CD8α+ lymphocytes, ratio of Ifng to Il4 mRNA, and Lck expression, indicating T-cell activation. The ratio of CD3+ T cells expressing the Treg marker Foxp3+ was highest in HC-GF and lowest in cereal-SPF rats. Resident CD163+ M2 macrophages were increased in HC-protected rats. The cathelicidin antimicrobial peptide (Camp) gene was upregulated in the jejunum of HC diet–protected rats, and CAMP+ cells colocalized with CD163. A cereal diet was a stronger promoter of T1D than gut microbes in association with impaired gut immune homeostasis.

Thymectomy and Radiation-Induced Type 1 Diabetes in Nonlymphopenic BB Rats Sheela Ramanathan 1 2 3 , Marie-Therese Bihoreau 4 , Andrew D. Paterson 5 , Leili Marandi 1 2 3 , Dominique Gauguier 4 and Philippe Poussier 1 2 3 1 Sunnybrook and Women’s College Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada 2 Department of Medicine, University of Toronto, Toronto, Ontario, Canada 3 Department of Immunology, University of Toronto, Toronto, Ontario, Canada 4 the Welcome Trust Centre for Human Genetics, University of Oxford, Oxford, U.K. 5 Program in Genetics and Genomics Biology, Hospital for Sick Children, Toronto, Ontario, Canada Abstract Spontaneous type 1 diabetes in BB rats is dependent on the RT1 u MHC haplotype and homozygosity for an allele at the Lyp locus, which is responsible for a peripheral T-lymphopenia. Genetic studies have shown that there are other, as yet unidentified, genetic loci contributing to diabetes susceptibility in this strain. BB rats carrying wild-type Lyp alleles are not lymphopenic and are resistant to spontaneous diabetes (DR). Here we show that thymectomy and exposure to one sublethal dose of γ-irradiation (TX-R) at 4 weeks of age result in the rapid development of insulitis followed by diabetes in 100% of DR rats. Administration of CD4 + 45RC − T-cells from unmanipulated, syngeneic donors immediately after irradiation prevents the disease. Splenic T-cells from TX-R-induced diabetic animals adoptively transfer type 1 diabetes to T-deficient recipients. ACI, WF, WAG, BN, LEW, PVG, and PVG.RT1 u strains are resistant to TX-R-induced insulitis/diabetes. Genetic analyses revealed linkage between regions on chromosomes 1, 3, 4, 6, 9, and 16, and TX-R-induced type 1 diabetes in a cohort of nonlymphopenic F 2 (Wistar Furth × BBDP ) animals. This novel model of TX-R-induced diabetes in nonlymphopenic BB rats can be used to identify environmental and cellular factors that are responsible for the initiation of antipancreatic autoimmunity. Footnotes Address correspondence and reprint requests to Philippe Poussier, Sunnybrook and Women’s Health Sciences Centre, 2075 Bayview Ave., Room A3 38, Toronto, Ontario, Canada M4N 3M5. E-mail: ppoussie{at}sten.sunnybrook.utoronto.ca . Received for publication 1 April 2002 and accepted in revised form 26 June 2002. FACS, fluorescence-activated cell sorting; KRV, Kilham’s rat virus; mAb, monoclonal antibody; MNC, mononuclear cell; PE, phycoethrin; SPF, specific pathogen free; TX-R, γ-irradiation; VAF, virus antibody free. DIABETES

Ikaros transcription factors are essential regulators of lymphopoiesis and the development of the immune system. We now show that Ikaros is expressed in hormone-producing pituitary corticomelanotroph cells, where it binds the proopiomelanocortin promoter and regulates endogenous gene expression. Loss of Ikaros in vivo results in contraction of the pituitary corticomelanotroph population, reduced circulating adrenocorticotrophic hormone levels, and adrenal glucocorticoid insufficiency. While hemopoietic reconstitution failed to correct this hormonal deficit, the phenotype of reduced body weight and diminished survival was rescued by systemic glucocorticoid-hormone administration. Given the established immunomodulatory properties of glucocorticoid hormones, these findings reveal a novel role for Ikaros in orchestrating immune-endocrine development and function.