Pertussis toxin (PTX) is a potent ancillary adjuvant used to elicit several different autoimmune diseases, including experimental allergic encephalomyelitis (EAE). To delineate the genetics of PTX effect in EAE, we mapped EAE-modifying (eae-m) loci in cohorts of backcross mice immunized with and without PTX. In this study, we analyzed the genetic basis of EAE susceptibility and severity and the intermediate phenotypes of mononuclear cell infiltration, suppuration, and demyelination. In animals immunized with PTX, one major locus, eae9, controls disease susceptibility and severity. Eae9 also regulates the extent of mononuclear cell infiltration of the spinal cord in male mice. Without PTX, five eae-m loci were noted, including three new loci in intervals on chromosomes 8 (eae14), 10 (eae17), and 18 (eae18). Taken together, these results suggest that eae9 controls the effects of PTX in EAE susceptibility, and is capable of overriding the other genetic checkpoints in the pathogenesis of this disease.

In earlier studies of the Iddm14 diabetes susceptibility locus in the rat, we identified an allele of the T-cell receptor (TCR) β-chain, Tcrb-V13S1A1, as a candidate gene. To establish its importance, we treated susceptible rats with a depleting anti-rat Vβ13 monoclonal antibody and then exposed them to either polyinosinic:polycytidylic acid or a diabetogenic virus to induce diabetes. The overall frequency of diabetes in the controls was 74% (n = 50), compared with 17% (n = 30) in the anti-Vβ13–treated animals, with minimal islet pathology in nondiabetic treated animals. T cells isolated from islets on day 5 after starting induction showed a greater proportion of Vβ13+ T cells than did peripheral lymph node T cells. Vβ13 transcripts recovered from day 5 islets revealed focused Jβ usage and less CDR3 diversity than did transcripts from peripheral Vβ13+ T cells. CDR3 usage was not skewed in control Vβ16 CDR3 transcripts. Anti-rat Vβ13 antibody also prevented spontaneous diabetes in BBDP rats. The Iddm14 gene is likely to be Tcrb-V13, indicating that TCR β-chain usage is a determinant of susceptibility to autoimmune diabetes in rats. It may be possible to prevent autoimmune diabetes by targeting a limited element of the T-cell repertoire.

External ear hole closure in LG/J mice represents a model of regenerative response. It is accompanied by the formation of a blastema-like structure and the re-growth of multiple tissues, including cartilage. The ability to regenerate tissue is heritable. An F34 advanced intercross line of mice (Wustl:LG,SM-G34) was generated to identify genomic loci involved in ear hole closure over a 30-day healing period. We mapped 19 quantitative trait loci (QTL) for ear hole closure. Individual gene effects are relatively small (0.08 mm), and most loci have co-dominant effects with phenotypically intermediate heterozygotes. QTL support regions were limited to a median size of 2 Mb containing a median of 19 genes. Positional candidate genes were evaluated using differential transcript expression between LG/J and SM/J healing tissue, function analysis and bioinformatic analysis of single-nucleotide polymorphisms in and around positional candidate genes of interest. Analysis of the set of 34 positional candidate genes and those displaying expression differences revealed over-representation of genes involved in cell cycle regulation/DNA damage, cell migration and adhesion, developmentally related genes and metabolism. This indicates that the healing phenotype in LG/J mice involves multiple physiological mechanisms.

Iddm14 (formerly Iddm4) is a non-MHC-linked genetic locus associated with autoimmune diabetes. Its effects have been well-documented in BB-derived rats in which diabetes is either induced by immunologic perturbation or occurs spontaneously. The role of Iddm14 in non-BB rat strains is unknown. Our goal was to extend the analysis of Iddm14 in new diabetes-susceptible strains and to identify candidate genes in the rat Iddm14 diabetes susceptibility locus that are common to these multiple diabetic strains. To determine if Iddm14 is important in strains other than BB, we first genotyped a (LEW.1WR1 × WF)F2 cohort in which diabetes was induced by perturbation with polyinosinic:polycytidylic acid. We found that Iddm14 is a major determinant of diabetes susceptibility in LEW.1WR1 rats. We then used nucleotide sequencing to establish a strain distribution pattern of polymorphisms (insertions, deletions, and single nucleotide polymorphisms [SNPs]) that predicts susceptibility to diabetes in a panel of inbred and congenic rats. Using the positional information from the congenic strains and the new linkage data, we identified a susceptibility haplotype in the T-cell receptor Vβ chain (Tcrb-V) locus. This haplotype includes Tcrb-V13, which is identical in five susceptible strains but different in resistant WF and F344 rats. We conclude that Iddm14 is a powerful determinant of both spontaneous and induced autoimmune diabetes in multiple rat strains, and that Tcrb-V13 SNPs constitute a haplotype of gene elements that may be critical for autoimmune diabetes in rats.

OBJECTIVETo identify genes that confer susceptibility to autoimmune diabetes following viral infection in the LEW.1WR1 rat.RESEARCH DESIGN AND METHODSAbout 2% of LEW.1WR1 rats develop spontaneous autoimmune diabetes. Immunological perturbants including viral infection increase both the frequency and tempo of diabetes onset. To identify diabetes susceptibility genes (LEW.1WR1 × WF), F2 rats were infected with Kilham rat virus following brief pretreatment with polyinosinic:polycytidylic acid. This treatment induces diabetes in 100% of parental LEW.1WR1 rats and 0% of parental WF rats. Linkage to diabetes was analyzed by genome-wide scanning.RESULTSAmong 182 F2 rats, 57 (31%) developed autoimmune diabetes after a mean latency of 16 days. All diabetic animals and ∼20% of nondiabetic animals exhibited pancreatic insulitis. Genome-wide scanning revealed a requirement for the Iddm14 locus, long known to be required for diabetes in the BB rat. In addition, a new locus near the RT1 major histocompatibility complex (MHC) was found to be a major determinant of disease susceptibility. Interestingly, one gene linked to autoimmune diabetes in mouse and human, UBD, lies within this region.CONCLUSIONSThe Iddm14 diabetes locus in the rat is a powerful determinant of disease penetrance in the LEW.1WR1 rat following viral infection. In addition, a locus near the MHC (Iddm37) conditions diabetes susceptibility in these animals. Other, as-yet-unidentified genes are required to convert latent susceptibility to overt diabetes. These data provide insight into the polygenic nature of autoimmune diabetes in the rat and the interplay of genetic and environmental factors underlying disease expression.