Experiment
To generate a four-way autoimmunity advanced intercross line genetically diverse MRL/MpJ mice, which are susceptible to autoimmune pancreatitis, and resistant mice, CAST/EiJ, BXD2/TyJ, and NZM2410/J and their offspring were intercrossed at an equal strain and sex distribution for several generations. Parental origin of generation 1 (G1) offspring mice
were considered when setting up mating for the generation of G2 mice in order to maintain an equal distribution of the original strains. The same procedure was folllowed for intercrossing G2 mice. At least 50 breeding pairs were used as parentals for the next generation of mice.
Phenotyping of the G4 mice was performed at 6 months of age by scoring the severity of autoimmune pancreatitis (AIP) typical pancreatic lesions. The data from all chromosomes was analyzed together with an additive model and their log p value and tested positively against 1000 permutations for pointwise signifcance (p<0.0001).
Of the 351 mice analysed (163 males and 188 females), 45 animals displayed signs of parenchymal destruction and were classified as AIP stage 2 or 3 (stage 4 was not observed). Those animals represented 17.6% of the females and only 7.4% of the males and 12.8% of all mice. Interestingly, similar percentages of G4 mice developed spontaneous arthritis and lupus nephritis.
Five QTL were significantly linked to the severity of autoimmune pancreatitis with a LOD score >3.
QTL Aips1, autoimmune pancreatitis severity 1, mapped to Chromosome 2 with a peak LOD score of 4.4 and peaks at 64.9 and 74.7 Mbp. The confidence interval spanned 56.3 to 81.9 Mbp. Aips1 overlapped autominnumity QTL Eae21. [Table 2]. Hnrnpa3, Nfe2l2, Ssb, and Ubr3 are potential candidate genes for Aips1. [Table 3.]
QTL Aips2, autoimmune pancreatitis severity 2, mapped to Chromosome 4, peaking at 18.0 Mbp with a LOD score of 3.2 between flanking markers rs6222797 and rs13476580. The confidence interval spanned from 7.1 (rs3718711) to 32.3 Mbp (rs3667007). Aips2 overlapped known autoimmunity QTL Aaom1 and Lxw1. [Table 2. Fig 3.]
QTL Aips3, autoimmune pancreatitis severity 3, also mapped to Chromosome 4, peaking at 82.4 and 103.6 Mbp with a LOD score of 3.2. The 95% confidence interval spanned from 81.3 to 120.7 Mbp. Aip3 overlapped with known autoimmunity QTL Sle2, Adaz1, Agnm2, Pgia27 and Psds1. [Table 2.]
QTL Aips4, autoimmune pancreatitis severity 4, mapped to Chromosome 5, peaking at 83.5 Mbp with a LOD score of 3.5. The 95% confidence interval spanned from 74.8 to 96.6 Mbp. Aips4 overlapped with QTL Cdcs10. [Table 2.]
QTL Aips5, autoimmune pancreatitis severity 5, mapped to Chromosome 6, peaking at 121.2 Mbp (rs3695724) with a LOD score of 5.4 and 95% confidence interval that spanned from 111.2 (rs13478971) to 133.9 Mbp (rs63389420). Aips5 overlapped with autoimmunity QTL Cia3. [Table 2. Fig 3.] Potential candidate genes for Aips5 are Clec4a2 and Pparg. [Table 3].
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