Mapping of Arthritis Susceptibility Genes

描述（由申请人提供）：人软骨蛋白多糖（PG）聚集蛋白全身免疫BALB/c小鼠可诱导进行性多关节炎。该小鼠模型（pg诱导的关节炎；PGIA）与类风湿关节炎（RA）有相似之处，通过临床评估、实验室检查、x线和腹泻关节组织病理学显示。与RA类似，PGIA是一种T细胞依赖性和抗体/B细胞介导的自身免疫性疾病。年龄和性别与疾病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相关基因决定的疾病易感性的隐性遗传，是使该模型成为遗传研究的理想工具的附加特征。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。尽管大规模全基因组关联（GVA）研究反复显示某些染色体区域与类风湿关节炎之间存在联系，但在异种人群中没有一个基因被确定为致病基因。在过去的10年里，我们测试了超过3200只F2杂交小鼠（包括1292只关节炎小鼠），它们有6种不同的基因杂交。共鉴定出29个控制PGIA的基因座（Pgia1-Pgia29）。这些数量性状位点（qtl）中的许多位点与小鼠（mCia）和大鼠的胶原诱导关节炎（CIA）中鉴定的位点相关，与其他自身免疫模型的qtl共定位，并与类风湿关节炎的GWA研究中鉴定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性或关节炎模型中是共享的，那么它可能参与了类似的免疫调节途径，这些途径也在类风湿关节炎和一般自身免疫性疾病中起作用。我们有意排除MHC效应，使用两个携带相同H2d MHC等位基因的小鼠菌株，我们在BALB/c （pgia易感菌株）背景下产生了5个同源菌株，在第3、7、8、15和19染色体上含有DBA/2 （pgia抗性菌株）等位基因。选择的主要qtl与人类基因组的syntenic区域相对应，其中已鉴定出几个ra相关的qtl。在对这些同源和亚同源小鼠品系进行初步检测后，我们选择了3号染色体（chr3）上的Pgia26进行后续研究，以将染色体间隔缩小到可管理的大小，并确定了Pgia26a位点内的疾病抑制基因和Pgia26b位点内的疾病促进基因。我们选择Pgia26，是因为它似乎拥有调节PGIA关节炎易感性和严重程度的最复杂的位点之一（仅次于MHC），并且在人类chr1上的相应（syntenic）区域（chr1:95.2-151.7 Mbp区域，包括PTPN22）显示出与RA最突出的联系，仅次于MHC。在实验性关节炎的基因组研究历史中，我们已经确定了可能最小大小的关节炎相关基因组区域，现在我们正在选择间隔特异性同源（IVSC）菌株以进一步减小这些关键位点的大小。我们提出了两个特定的目标，即选择具有疾病抑制作用的Pgia26a （chr3:90.4/92.7-96.4/99.9 Mbp）和具有关节炎促进作用的Pgia26b （chr3:108.1/109.2-115.8/121.1 Mbp位置）的IVSC菌株，将染色体区域缩小到可管理的大小（aims 1A和2A），然后绘制详细的物理图谱并引入候选基因克隆（aims 1B和2B）。选定的基因将被测试其在关节炎关节和关节引流淋巴结中的表达，测序，并在基因敲除或IVSC小鼠中测试其体内（关节炎影响）功能，携带结构和/或功能改变的基因和改变的疾病表型。

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. PUBLIC HEALTH RELEVANCE: Rheumatoid arthritis (RA) is a complex joint disease affecting approximately 1 % of the human population. Large scale human familial genome-wide association studies have localized chromosome regions associated with RA, but no individual "causative" genes had been identified in the heterogeneous human population within these chromosome regions. We have developed a mouse model of RA, which shows many similarities to the human disease. We narrowed the genomic (chromosome) regions of a number of disease-associated regions, and selected a segment of mouse chromosome 3, which is highly associated with disease phenotype in our arthritis model. This chromosome region (Pgia26) contains both arthritis-promoting and -suppressing genes, and corresponds to a region of human chromosome 1, that shows the highest association with RA after the major histocompatibility complex (MHC). We propose to reduce the size of these regions in the mouse genome, which cannot be done in human population, and select candidate genes that may be involved in arthritis susceptibility and disease severity.