Bbaa1^C57BL/6NCr
QTL Variant Detail

Summary

• QTL variant: Bbaa1^C57BL/6NCr
• Name: B.burgdorferi-associated arthritis 1; C57BL/6NCr
• MGI ID: MGI:2155832
• QTL: Bbaa1 Location: Chr4:55250930-55251078 bp Genetic Position: Chr4, cM position of peak correlated region/allele: 43.3 cM
• QTL Note: genome coordinates based on the marker associated with the peak LOD score

Variant origin

• Strain of Specimen: C57BL/6NCr

Variant description

• Allele Type: QTL
• Mutation: Undefined
• This allele confers resistance to severe B.burgdorferi-associated arthritis compared to C3H/HeNCr.
• Inheritance: Recessive

Notes

Candidate Genes

J:243935

Previous studies revealed a major, differential contribution of Type I IFN to the development of Lyme arthritis in C3H mice, which could be overcome by blocking the Type I IFN receptor signaling with neutralizing mAb or by gene ablation (19, 20). It was noted that Bbaa1, a QTL controlling the severity of Lyme arthritis on Chr4 encompassed a cluster of 15 Type I IFN genes, prompting a more mechanistic analysis of the role of Bbaa1 as a regulator of Lyme arthritis severity (30, 32).

In the current study the analysis of QTL Bbaa1 on Chromosome 4 was extended and the type I IFN gene cluster was identified as positional candidates for Bbaa1. Two mouse strains, C57BL/6 and C3H/He, display extremes of arthritis severity and have been used extensively as experimental models for study of disease. Reciprocal interval specific congenic lines (ISCL) were developed between C3H/HeNCrl (C3H) and C57BL/6Ncr (B6) mice to assess the contribution of Bbaa1 to Lyme arthritis and RA, and the dependence on production of type I IFN.

Reciprocal ISCL for Bbaa1 on Chr 4 were generated and indicated as B6.C3-Bbaa1(9.32-94.96) Mbp and C3.B6-Bbaa1(3.58-150.8) Mbp. B6, C3H, B6.C3-Bbaa1 and C3.B6-Bbaa1 mice were infected with 2 x 10⁴ B. burgdorferi (strain N40) and arthritis was assessed at 4 weeks post infection. Ankle measurements were obtained using a metric caliper before and at 4 weeks of infection. IFNAR1 blocking mAb MAR1-5A3 or isotope control (Bio-XCell) was administered by a single injection the day before infection with B. burgdorferi or the administration of K/BxN serum. (K/BxN serum was collected from KRN/NOD offspring at the peak of spontaneous arthritis (9 weeks)). K/BxN serum was administered by injection on days 0 and 2. Gene expression of joint tissue was examined in the tibiotarsal joints. Bone marrow-derived macrophages (BMDMs) were isolated from the femurs and tibias. Statistical analysis was performed using Prism 5.0c software. Statistical significance (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).

Experimental results demonstrated that Bbaa1 regulates arthritis severity on the B6 background, [Fig 1]. More severe ankle swelling and arthritic lesions were seen in the infected B6.C3-Bbaa1 mice than in the parental B6 mice. Although the B6.C3-Bbaa1 congenic interval was large (9.32-94.97 Mbp) and encoded numerous genes, it nevertheless encompassed the IFN/cluster (88.5-88.7 Mbp) that encode Type I IFNs implicated in Lyme arthritis. All IFN and IFN proteins signal through the IFNAR receptor, comprised of IFNAR1 and IFNAR2 chains.

To determine if the greater arthritis in B6.C3-Bbaa1 mice relative to B6 mice was dependent on Type I IFN, B6.C3-Bbaa1 mice were treated with a blocking mAb to IFNAR1 component of the Type I IFN receptor (MAR1-5A3) one day prior to infection. B6.C3-Bbaa1 mice treated with isotype control mAb developed more severe Lyme arthritis than B6 mice as assessed by ankle measurement and lesion scoring [Fig. 2], similar to the results of Fig. 1. Administration of the receptor blocking mAb reduced arthritis severity to levels indistinguishable from wild type B6. Thus, the increased arthritis severity of B6.C3- Bbaa1 mice was a function of Type I IFN responses dependent on feed forward amplification through the IFNAR1 receptor, and identified the IFN cluster as a positional candidate for Bbaa1.

Type I IFNs have also been identified in patients with various manifestations of Lyme disease, including skin lesions and cognitive deficits, and have been implicated in in B lymphocyte accumulation in the lymph nodes of infected mice.

Mapping and Phenotype information for this QTL, its variants and associated markers

J:52017

A genome scan was performed on 150 animals from an (C3H/HeNCr x C57BL/6NCr)F2 intercross (195 loci, average spacing = 20 cM) to identify QTLs associated with Lyme disease related arthritis phenotypes such as ankle swelling, thickening of tendon sheath, and tissue histopathology. C3H/HeNCr develop severe arthritis after infection with B.burgdorferi where as C57BL/6NCr develops mild arthritis.

Linkage was detected for ankle swelling on mouse chromosome 4 between flanking markers D4Mit87 and D4Mit145 with a peak LOD score of 4.70 at D4Mit145. The QTL was labeled Bbaa1, B. burgdorferi-asociated arthritis phenotype 1. The C3H/HeNCr allele conferred dominant influence to susceptibility to severe arthritis at this locus. Mapping between 33-45 cM it is syntenic with regions 9q32-q33, and 9p21-p23 of the human genome. The Lps gene, Tlr4, is a possible candidate gene for Bbaa1.

Another QTL linked to ankle swelling mapped to mouse chromosome 5 between flanking markers D5Mit24 and D5Mit98 with a peak LOD score of 4.07 at D5Mit431. This QTL was labeled Bbaa2. Recessively inherited C3H/HeNCr alleles influenced susceptibility to severe arthritis at this locus. Mapping between 60-80cM Bbaa2 is syntentic with regions 22q11, 12q22-24.3, 7q11.23, and 7q21.3-q22.1 of the human genome. Interaction appears to occur between Bbaa1 and Bbaa2.

Linkage to histopathology and tendon sheath thickness was detected on mouse chromosome 5 between flanking markers D5Mit308 and D5Mit91 with a peak LOD score of 3.68 at D5Mit91. The thickness of tendon sheath was associated with a LOD score of 4.07 at D5Mit312 in this same interval. This QTL was labeld Bbaa3. Dominantly inherited alleles from C3H/HeNCr conferred arthritic severity. Mapping between 44-53cM Bbaa3 is syntenic with region 4q11-q21.1 of the human genome. Possible candidate genes for Bbaa3 are Bmp3, Ibsp, Spp1, Pdgfra, and Gro1.

Linkage to histopathology scoring was also detected on mouse chromosome 11 between flanking markers D11Mit350 and D11Mit120 with a peak LOD score of 3.91 at D11Mit120. This QTL was labeled Bbaa4. Recessively inherited alleles from C3H/HeNCr mice contribute to severe arthritis at this locus. Mapping between 34-47cM Bbaa4 is syntenic with regions 17p11-p13 and 17q11-q12 of the human genome. Possible candidate genes for Bbaa4 are Tnfaip1, Pafah1b1, and Nos2.

Linkage to a QTL regulating the elevation to total IgM production and B.burgdorferi-specific IgM production was detected on mouse chromosome 6 mapping between flanking markers D6Mit105 abd D6Mit15. The QTL was labeled Bbaa5 with linkage to total IgM mapping between 45-74cM, with a peak LOD score of 6.52 at D6Mit338, and specific IgM mapping to 67-74cM, with a peak LOD score of 4.96 at D6Mit15 within the same interval. Recessively inherited allelesfrom C57BL/6NCr mice contribute to lower levels of IgM production at this locus. Mapping between 45-74cM Bbaa5 is syntenic with regions 3p24-p26, 3q21-q25, 10q11.2 and 12p11-13 of the human genome.

Linkage to total IgG and total IgM production was detected on mouse chromosome 12 between flanking markers D12Mit121 and D12Mit133. This QTL was labeled Bbaa6 with linkage to total IgM mapping between 46-56cM, with a peak LOD score of 4.71 at D12Mit133, and total IgG with a peak LOD of 3.61 also at D12Mit133. Recessively inherited alleles from C3H/HeNCr mice contributed to elevated levels of both IgG and IgM production. Mapping between 46-56cM this QTL is syntenic with regions 14q24.3-q32.3 and 14q32.1-q32.3 of the human genome. Interaction appears to occurbetween Bbaa6 and Bbaa9 with respect to total IgG production.

Linkage to B.burgdorferi-specific IgM production was detected on mouse chromosome 11 between flanking markers D11Mit82 and D11Mit235 with a peak LOD score of 3.79 at D11Mit51. This QTL was labeled Bbaa7. Dominantly inherited alleles from C57BL/6NCr mice influence lower Ig levels at this locus. Mapping between 14-20cM Bbaa7 is syntenic with regions 16p13.3 and 5q31.1-q35 of the human genome.

Linkage to B.burgdorferi-specific IgM production wasalso detected on mouse chromosome 17 between flanking markers D17Mit175 and D17Mit215 with a peak LOD score of 3.78 at D17Mit232. This QTL is Bbaa8. Mice with heterozygous alleles at Bbaa8 had the lowest levels if specific IgM. Mapping between 17-23cM Bbaa8 is syntenic with regions 19q13.3-13.4, 16p12-13.4 and 6p13.2-p21.2 of the human genome.

Linkage to total IgG production was detected on mouse chromosome 9 between flanking markers D9Mit48 and D9Mit73 with a peak LOD score of 3.62 at D9Mit73. This QTLislabeled Bbaa9. Dominantly inherited alleles from C57BL/6NCr mice reduced the levels of total IgG at this locus. Mapping between 34-41cM Bbaa9 is syntenic with region 15q21-q25 of the human genome.

J:73060

Composite interval mapping (CIM) was used for localization of QTL involved in modulating response to infection with Borrelia burgdorferi. Parental strains C3H/HeN and C3H/HeJ are susceptible to B.burgdorferi-induced arthritis whereas parental strains C57BL/6N and BALB/cAnN are resistant. Four different backcrosses and the reanalysis of a previous intercross were performed.

In the (C57BL/6N X C3H/HeN)F1 X C57BL/6N backcross a novel QTL, Bbaa13 was identified on

on Chr 4. Bbaa13 was linked to ankle swelling at 6.5 cM with marker D4Mit264, LRT=18.6 accounting for 10.7% of variance. [Table 2.]

In the reanalysis of the (C57BL/6N X C3H/HeN)F2 intercross another novel, Chr 4 QTL, Bbaa23, was identified. Bbaa23 is linked to the number of B.burgdorferi in heart tissue post-infection. It mapped to 49.6 cM with marker D4Mit219, LRT=21.6 accounting for 11.2% of variation. [Table 2.]

The reanalysis of the (C57BL/6N X C3H/HeN)F2 intercross also confirmed the previoulsy identified Bbaa1 QTL on Chr 4. Using CIM Bbaa1, linked to ankle swelling, mapped to 28.6 cM with marker D4Mit139, LRT=19.6. [Table 3.]

C3H/HeN-derived alleles are associated with increased arthritis susceptibility and severity at all QTL mapped in this experiment.

References

• Original: J:52017 Weis JJ, et al., Identification of quantitative trait loci governing arthritis severity and humoral responses in the murine model of Lyme disease. J Immunol. 1999 Jan 15;162(2):948-56
• All: 5 reference(s)