Mapping of Arthritis Susceptibility Genes

描述(由申请人提供)：用人软骨蛋白多糖(PG)聚集素系统免疫BALB/c小鼠可诱导进行性多发性关节炎。这种小鼠模型(PG诱导的关节炎；PGIA)与类风湿性关节炎(RA)有相似之处，临床评估、实验室测试、X光和腹泻关节的组织病理学表明。与RA相似，PGIA是一种T细胞依赖、抗体/B细胞介导的自身免疫性疾病。年龄和性别与疾病的发展和严重程度的关联，以及由主要组织相容性复合体(MHC)和非MHC相关基因共同决定的疾病易感性的隐性遗传，是使该模型成为遗传学研究的理想工具的额外特征。虽然MHC在RA和PGIA中都是一个关键的预测因素，但MHC本身不足以诱导自身免疫性疾病。虽然大规模的全基因组关联(GVA)研究反复表明某些染色体区域与类风湿性关节炎之间存在关联，但在这个异质性的人类群体中，还没有一个基因被确定为致病基因。在过去的10年里，我们测试了6个不同基因杂交的3200多只F2杂交小鼠(包括1292只关节炎小鼠)。共检测到29个控制PGIA的基因座(Pgia1-Pgia29)。其中许多数量性状基因座(QTL)与大鼠和小鼠胶原诱导性关节炎(CIA)相关，与其他自身免疫模型的QTL共定位，与类风湿关节炎GWA研究中发现的人类基因组区域相对应。我们的假设是，如果一个基因组位点在不同的自身免疫或关节炎模型中共享，它可能涉及类似的免疫调节途径，这些途径也在类风湿性关节炎中起作用，或许在一般的自身免疫性疾病中也起作用。我们有意排除了两个携带相同H_2d MHC等位基因的小鼠的MHC效应，并在BALB/c(PGIA敏感株)背景中产生了5个在第3、7、8、15和19号染色体上含有DBA/2(PGIA抗性株)等位基因的同源株。主要的QTL被选为与人类基因组的同线区域相对应，在那里已经识别了几个与RA相关的QTL。在对这些同基因和亚基因小鼠品系进行初步测试后，我们选择了3号染色体上的Pgia26(Chr3)进行后续研究，以将染色体间隔缩小到可管理的大小，并识别(在Pgia26a基因座内)疾病抑制基因和(在Pgia26b基因座上)致病基因。我们选择了Pgia26，因为它似乎拥有在PGIA中调节关节炎易感性和严重程度的最复杂的位点之一(仅次于MHC)，而人ChR1上相应的(共线)区域(ChR195.2-151.7 MBP，包括PTPN22)显示出与RA最显著的连锁，仅次于MHC。在实验性关节炎的基因组研究历史上，我们已经确定了可能是与关节炎相关的最小大小的基因组区域，现在我们正在筛选区间特异性同源基因(IVSC)菌株来进一步缩小这些关键基因的大小。我们提出了两个特定的目标来选择抑制疾病的Pgia26a(chr3：90.4/92.7-96.4/99.9mbp)和促进关节炎的pgia26b(chr3：108.1/109.2-115.8/121.1 mbp)的IVSC菌株，以将染色体区域缩小到可管理的大小(目标1A和2A)，然后制作详细的物理图谱并介绍候选基因的定位克隆(目标1B和2B)。选定的基因将被测试它们在关节炎关节和关节引流淋巴结中的表达，并进行测序，它们的体内(影响关节炎)功能将在携带结构和/或功能改变基因(S)和改变疾病表型的基因敲除或体外干细胞小鼠中进行测试。

DESCRIPTION (provided by applicant): Systemic immunization of BALB/c mice with human cartilage proteoglycan (PG) aggrecan induces progressive polyarthritis. This murine model (PG-induced arthritis; PGIA) shares similarities with rheumatoid arthritis (RA) as indicated by clinical assessments, laboratory tests, x-ray and histopathology of diarthrodial joints. Similar to RA, PGIA is a T cell-dependent and antibody/B cell-mediated autoimmune disease. Association of age and gender with disease development and severity, and recessive inheritance of disease susceptibility, dictated by both the major histocompatibility complex (MHC)- and non-MHC-associated genes are additional characteristics that make this model an ideal tool for genetic studies. While the MHC is a critical predictive factor both in RA and PGIA, the MHC alone is insufficient for the induction of autoimmune disease. Although large-scale genome-wide association (GVA) studies repeatedly showed linkage between certain chromosome regions and RA, not a single gene has been identified in the heterogeneous human population as a disease-inducing gene. During the past 10 years, we tested over 3,200 F2 hybrid (including 1,292 arthritic) mice of six different genetic intercrosses. A total of 29 genomic loci (Pgia1-Pgia29 ) controlling PGIA were identified. Many of these quantitative trait loci (QTLs) correlated with those identified in collagen-induced arthritis (CIA) in mice (mCia) and rats, colocalized with QTLs of other autoimmune models, and corresponded with human genomic regions identified in GWA studies of RA. Our hypothesis is that if a genomic locus is shared among different autoimmune or arthritis models, it is likely involved in similar immune regulatory pathways, which also operate in RA and perhaps in autoimmune diseases in general. We intentionally excluded the MHC effect using two murine strains carrying an identical H2d MHC allele, and we have generated five congenic strains containing DBA/2 (PGIA-resistant strain) alleles in chromosomes 3, 7, 8, 15 and 19 in BALB/c (PGIA-susceptible strain) background. The major QTLs were selected to correspond with syntenic regions of the human genome, where several RA-associated QTLs have been identified. After initial testing of these congenic and then subcongenic mouse strains, we selected Pgia26 on chromosome 3 (chr3) for subsequent studies to narrow the chromosome interval to a manageable size, and identify disease-suppressive (within the Pgia26a locus) and disease-promoting (in Pgia26b locus) genes. We selected Pgia26, because it appears to possess one of the most complex loci (after the MHC) regulating arthritis susceptibility and severity in PGIA, and the corresponding (syntenic) region on human chr1 (Chr1:95.2-151.7 Mbp region, including PTPN22) shows the most prominent linkage with RA, after the MHC. In the genomic research history of experimental arthritis, we have identified probably the smallest size of arthritis-associated genomic regions, and now we are in the process of selecting interval-specific congenic (IVSC) strains to reduce further the size of these critical loci. We propose two specific aims to select IVSC strains in both disease-suppressing Pgia26a (chr3:90.4/92.7-96.4/99.9 Mbp) and arthritis-promoting Pgia26b (chr3:108.1/109.2-115.8/121.1 Mbp position) to reduce the chromosome region to a manageable size (Aims 1A and 2A), and then prepare detailed physical maps and introduce positional candidate gene cloning (Aims 1B and 2B). Selected genes will be tested for their expression in arthritic joints and joint-draining lymph nodes, sequenced, and their in vivo (arthritis-affecting) function will be tested in either knockout or IVSC mice, carrying structurally and/or functionally altered gene(s) and altered disease phenotype.