Experiment
Experimental autoimmune encephalomyelitis (EAE) is an animal model for MS. The B10.RIII-H2r/SgKljLund (BR) mouse strain developes chronic EAE after immunization with the myelin basic pepetide (MBP). In contrast, the RIIIS/J strain is resistant to EAE development.
The authors previously reported a QTL on mouse Chr 16, Eae41, that was linked to the time of disease onset in male mice (J:96204). The peak marker (D16Mit84) for the linkage to the Eae41 QTL was located within the Cd200 gene.
The confidence interval for the previously identified QTL, Eae41, on Chr 16 spanned D16Mit194 (40.58 Mbp) to D16Mit49 (78.22.Mbp), peaking at 45.40 Mbp with marker D16Mit84. Congenic strains with RIIIS/J alleles in the linked region on Chr 16 on the BR (B10.RIII-H2r/SgKljLund) or B10.Q (B10.D1-H2q/SgKljLund) genetic backgrounds were generated to investigate the susceptibility to EAE.
A 66 Mpb RIIIS/J fragment was bred into the BR genome to establish a congenic strain B10.Cg-(D16Mit103-D16Mit173)RIIIS/J H2r/C1Lund, (C1). The C1 fragment was then backcrossed to generate the sub-interval congenic line B10.Cg-(D16Cd200r42-D16Mit173)RIIIS/J H2r/C2Lund, (C2). Disease severity was very low for both C1 and C2 mice in both males and females, but heterozygous C2 male mice had earlier onset, higher severity and incidence of disease compared to controls. [Table 1.]
C2 congenic mice were backcrossed to BR to produce mice with smaller congenic fragments creating B10.Cg-(D16Cd200r4-D16Mit15)RIIIS/J H2r/C3Lund,(C3), and B10.Cg-(D16Cd200r42-D16Mit44),RIII/J> H2r/C4LundC4, (C4), congenic mice. The C3 and C4 fragments contributed to the same EAE disease course, significantly different compared to controls. The data were pooled in the analysis. Heterozygous C3 and C4 male mice had an incidence of 100% compared with 40% in controls mice, p<0.01; and higher severity, p<0.01 and AUC (area under the curve is the mean of the total sum of scores for mice in the respective group), p<0.01. [Table 2].
Curator Note: We have created QTL symbols Eae41a, Eae41b and Eae41c respectively, for each of these QTL.
The congenic mice were also studied for two arthritis models; collagen induced arthritis (CIA) and collagen antibody induced arthritis (CAIA). In this experiment, there was no difference in disease development between the congenic and control mice.
Blockage of the interaction between Cd200 and its receptors results in early onset of EAE. Nearby is the Btla gene coding for the B and T lymphocyte attenuator protein which deliver inhibitory signals leading to suppression of lymphocyte activation.
Cd200 expression on T cells in the spleen was investigated using C1 and C2 congenic mice. The expression of CD200 and CD4+T cells was significantly lower in both homozygous and heterozygous congenic strains compare to littermate controls. To investigate the expression of BTLA on lymphocytes from BR and the congenic C4 mice, B cells, CD4+/-and CD8+T cells from the spleen were analyzed. Congenic mice with homozygous RIII/J or heterozygous alleles had a significantly higher expression of BTLA on B cells compared to littermate controls.
The B10.Cg-(D16Cd200r42-D16Mit138)RIIIS/J H2r/C5Lund (C5) congenic line was bred onto the B10.D1-H2q/SgKljLund strain that expressed the H2q MHC haplotype to investigate MOG peptide induced EAE. Results showed that in contrast to the C3/C4 congenic mice, induction of EAE in the C5 sub congenic lines resulted in milder disease compared to littermate controls. QTL were reported for disease onset (p<0.05) and total score for days 11-26 (p<0.05) for heterozygous mice with the BR genetic background; and for total score for days 22-28 (p<0.05) for mice homozygous for RIIIS/J alleles with a BQ background. [Table 3]. Curator Note: We have named these QTL Eae41d, Eae41e, and Eae41f respectively.
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