O papel modulador do gene AIRE - capes

IMMUNOLOGYORIGINAL ARTICLEOnset of promiscuous gene expression in murine fetal thymusorgan cultureRenato Sousa Cardoso, 1 * DanielleA. R. Magalhães, 1 * Ana Maria T.Baião, 1 * Cristina Moraes Junta, 1Claudia Macedo, 1 Márcia M. C.Marques, 1 Elza Tiemi Sakamoto-Hojo, 2,3 Eduardo A. Donadi 4 andGeraldo A. S. Passos 1,51 Molecular Immunogenetics Group, Departmentof Genetics, Faculty of Medicine,2 Laboratory of Cytogenetics and MutagenesisDepartment of Genetics, Faculty of Medicine,3 Department of Biology (FFCLRP), 4 Departmentof Medicine, Faculty of Medicine, and5 Discipline of Genetics (DMEF), Faculty ofDentistry, University of São Paulo, RibeirãoPreto, SP, Brazildoi:10.1111/j.1365-2567.2006.02441.xReceived 4 January 2006; revised 27 June2006; accepted 28 June 2006.*These authors contributed equally to thiswork.Correspondence: Dr Geraldo A. S. Passos,Molecular Immunogenetics Group,Department of Genetics, Faculty of Medicine,14040–900, Ribeirão Preto, SP, Brazil.Email: passos@rge.fmrp.usp.brSenior author: Dr Geraldo A. S. PassosSummaryT-cell differentiation and induction of tolerance to self-antigens occursmainly in the thymus. Thymic stromal cells, specifically medullary thymicepithelial cells, express a diverse set of genes encoding parenchymalorgan-specific proteins. This phenomenon has been termed promiscuousgene expression (PGE) and has been implicated in preventing organspecificautoimmunity by inducing T-cell tolerance to self antigens. Earlythymopoiesis and the critical factors involved in T-cell differentiation canbe reproduced in vitro by murine fetal thymus organ culture (FTOC),which mimics the natural thymic microenvironment. To evaluate theoccurrence of PGE in FTOC, gene expression profiling during in vitro thymicdevelopment in BALB/c mice was performed using a set of nyloncDNA microarrays containing 9216 sequences. The statistical analysis ofthe microarray data (SAM program) revealed the temporal repression andinduction of 57 parenchymal and seven lymphoid organ-specific genes. Mostof the genes analysed are repressed during early thymic development (15–17 days post-coitum). The expression of the autoimmune regulator (AIRE)gene at 16 days post-coitum marks the onset of PGE. This precedes the inductionof parenchymal organ genes during the late developmental phase at20 days post-coitum. The mechanism of T-cell tolerance induction begins duringfetal development and continues into adulthood. Our findings are significantbecause they show a fine demarcation of PGE onset, which plays acentral role in induction of T-cell tolerance.Keywords: cDNA microarray; fetal thymus organ culture; promiscuousgene expression; thymus; T-cell toleranceIntroductionThe thymus is the key primary lymphoid organ that ismainly involved in the progressive differentiation ofthymocytes to mature T cells in which all developmentalstages are distinguishable by their expression of a combinationof clusters of differentiation (CD) cell-surfacemarkers. Studies with freshly obtained fetal thymusallowed for the demarcation of T-cell receptor b V(D)Jrecombination during in vivo thymus ontogeny amongdifferent inbred mouse strains; this contributed to therevealing of the effect of the genetic background on T-celldevelopment. 1–3 The control of gene expression duringthe development of this organ has gained priority amongseveral research groups, including our own, leading to theidentification of candidate genes involved in thymopoiesis.Using the cDNA microarray method, a dozenexpressed sequence tags have been found that are modulatedduring the in vivo development of the thymus. 4Using the same kind of analysis, the in vivo modulationof several cell-signalling genes was identified, includingthose of the calcium cascade pathway, which is importantfor individual stages of T-cell maturation and the controlof anergy during murine thymus ontogeny. 5Meanwhile, a better understanding of the central tolerancemechanism, that is, all the mechanisms by which Tcells contribute to self-tolerance by intrathymic recognitionof self-antigens, emerged from evidence thatÓ 2006 Blackwell Publishing Ltd, Immunology, 119, 369–375 369