Experiment
To investigate the contribution of non-MHC genes to epidermolysis bulls acquisita (EBA)
an outbred four-way autoimmune-prone intercross line was generated. The line originated from MRL/MpJ, BXD2/TyJ, NZM2410/J and CAST mice. A classical quantitative trait mapping approach identified six loci controlling susceptibility to murine Eba.
MRL/MpJ mice are susceptible to EBA following immunization with mCOL7C in contrast with the NZM2410/J, BXD2/TyJ and CAST mice which were resistant to EBA induction. MRL/MpJ mice were intercrossed with each of the resistant strains and the offspring of each generation were intercrossed for several generations.
250 G4 mice from the four-way intercross line were immunized with GST-mCOL7C and clinically monitored for a period of 12 weeks for the presence of skin lesions. Disease extent was expressed as body surface area covered by skin lesions and ranged from 0.1 to 51.5%. Full blown disease was detected in 33% of the mice.
Data regarding the onset of disease as well as maximum disease score was analyzed. All QTL were found significant (P<0.001) by a point-wise permutation.
EBA onset was associated with four chromosomes:
Ebao1, epidermolysis bullosa acquisita onset 1, mapped to Chromosome 9 with a peak at rs4135590 (logP 3.8, bp 42796186). The locus was flanked by markers rs13480150 (bp 39531947) and rs13480173 (bp 46336655). The region covered 7 Mbp and contained 147 genes.
Ebao2, epidermolysis bullosa acquisita onset 2, mapped to Chromosome 12 with a peak at rs3716095 (logP 3.2, bp 87934638). This locus was flanked by markers rs13481561 (bp 83267516) and rs6390948 (bp 109917259). This region covered 300 genes.
Ebao3, epidermolysis bullosa acquisita onset 3, mapped to Chromosome 14 with a peak at rs13482216 (logP 2.2, bp 62510281). This locus was flanked by markers rs4230248 (bp 31996605) and rs13582265 (bp 79420389), spanning a 38 Mbp region.
Ebao4, epidermolysis bullosa acquisita onset 4, mapped to Chromosome 19 with a peak at mCV23069572 (logP 3.3, bp 52876222), flanked my markers mCV23390953 (bp 46090165) and the end of Chr 19.
[Table 2.]
Maximum disease activity was associated with three chromosomes:
Ebas1, epidermolysis bullosa acquisita severity 1, also mapped to Chromosome 19 with a peak at mCV23069572 (logP 2.5). The region was slightly larger than that of Eba4 mapping between flanking marker rs3687275 and the end of Chr 19.
Ebas2, epidermolysis bullosa acquisita severity 2, mapped to Chromosome 1 with a peak at rs3707642 (logP 2.92, bp 3187481) between flanking markers rs3683945 and rs3677683.
Ebas3, epidermolysis bullosa acquisita severity 3, mapped to Chromosome 15 with a peak at rs8259436 (logP 2.15, bp 74680379) between flanking markers rs3683495 and rs13482687.
[Table 3].
In addition QTL controlling the generation of anti-COL7-specific IgG isotypes in immunization induced EBA were identified:
[Table 4].
Accig1, anti COL7 IgG1 antibody 1, mapped to Chromosome 2 between markers rs13476472 and gnf02.076.311 with at peak at marker rs3674936.
Accig2, anti COL7 IgG1 antibody 2, mapped to Chromosome 6 between markers rs13479071 and rs3658783 with a peak at marker rs13479014.
Acigg3, anti COL7 IgG1 antibody 3, mapped to Chromosome 10 between rs3699409 and the end to Chr 10 with a peak at rs3669563.
Acigg4, anti COL7 IgG2a/c antibody 4, mapped to Chromosome 1 between markers gnf01.036.770 and rs13475851 with a peak at rs4137502.
Acigg5, anti COL7 IgG2a/c antibody 5, mapped to Chromosome 11 between markers rs3684076 and rs13481061 with a peak at rs13481009.
Acigg6, anti COL7 IgG2a/c antibody 6, mapped to Chromosome 13 between markers rs3655061 and rs13481992 with a peak at gnf13.079.671.
Acigg7, anti COL7 IgG2b antibody 7, mapped to Chromosome 6 between markers rs3671709 and rs6330932 with a peak at rs3718776.
Acigg8, anti COL7 IgG2b antibody 8, mapped to Chromosome 8 between markers rs13479807 and rs4227253 with a peak at rs3672639.
Acigg9, anti COL7 IgG2b antibody 9 mappped to Chromosome 8 between markers rs13479956 and rs4227398.
Acigg10, anti COL7 IgG2b antibody 10, mapped to Chromosome 14 between markers rs13482135 and rs13482231 with a peak at marker rs4230248.
Acigg11, anti COL7 IgG3 antibody 11, mapped to Chromosome 9 between rs13480421 and the end of Chr 9 with a peak at rs6385971.
Acigg12, anti COL7 IgG3 antibody 12, mapped to Chromosome 19 between markers rs6309315 and gnf19.035.019 with a peak at rs3686467.
Interestingly, analysis of a possible common genetic control of specific IgG production and clinical manifestation did not show an overlap of the identified QTL.
Analysis Tools