Experimental allergic orchitis in mice. VI. Recombinations within the H-2S/H-2D interval define the map position of the H-2-associated locus controlling disease susceptibility

Identification of Orch3, a locus controlling dominant resistance to autoimmune orchitis, as kinesin family member 1C

Experimental autoimmune orchitis (EAO), the principal model of non-infectious testicular inflammatory disease, can be induced in susceptible mouse strains by immunization with autologous testicular homogenate and appropriate adjuvants. As previously established, the genome of DBA/2J mice encodes genes that are capable of conferring dominant resistance to EAO, while the genome of BALB/cByJ mice does not and they are therefore susceptible to EAO. In a genome scan, we previously identified Orch3 as the major quantitative trait locus controlling dominant resistance to EAO and mapped it to chromosome 11. Here, by utilizing a forward genetic approach, we identified kinesin family member 1C (Kif1c) as a positional candidate for Orch3 and, using a transgenic approach, demonstrated that Kif1c is Orch3. Mechanistically, we showed that the resistant Kif1c^D2 allele leads to a reduced antigen-specific T cell proliferative response as a consequence of decreased MHC class II expression by antigen presenting cells, and that the L⁵⁷⁸→P⁵⁷⁸ and S¹⁰²⁷→P¹⁰²⁷ polymorphisms distinguishing the BALB/cByJ and DBA/2J alleles, respectively, can play a role in transcriptional regulation. These findings may provide mechanistic insight into how polymorphism in other kinesins such as KIF21B and KIF5A influence susceptibility and resistance to human autoimmune diseases.

Although the etiology of autoimmunity is not well known, a variety of studies have demonstrated that genetic predisposition is a major contributor to disease susceptibility and resistance. The major histocompatibility complex (MHC) is the primary genetic determinant of autoimmune disease susceptibility with multiple additional interacting loci required. However, the identification and characterization of non–MHC genes has been problematic, since most autoimmune diseases are polygenic with the individual genes exhibiting only partial or minimal penetrance. We previously identified Orch3 (mouse chromosome 11) as the most important immune-suppressive locus controlling dominant resistance to autoimmune orchitis, the principal animal model of non-infectious testicular inflammatory/autoimmune disease. Here, using congenic mapping, we identified kinesin family member 1C (Kif1c) as a positional candidate for Orch3. Furthermore, over-expression of the Kif1c resistant allele in susceptible mice rendered animals autoimmune orchitis resistant, demonstrating that Kif1c is Orch3. We propose that Kif1c plays an immunoregulatory role by controlling the levels of MHC class II in antigen presenting cells and consequently impacting autoreactive orchitogenic T cell responses. These finding are particularly relevant since polymorphism in other kinesins such as KIF21B and KIF5A have been associated with susceptibility and resistance to human autoimmune disease.

Genetic mapping and physical cloning of UVB susceptibility region in mice

One of the most important goals of cancer research is to identify environmental and host factors that contribute to the malignant state. Human skin cancers are among the few tumor types for which the predominant environmental carcinogen is known. Ultraviolet light, a component of sunlight, is an important cause of skin cancer in humans. In humans and mice, ultraviolet B radiation induces systematic and local immunosuppression. A consequence of that is inappropriate immune surveillance of somatic tissues for evidence of malignantly transformed cells. The impairment of contact hypersensitivity, as it develops early and correlates well with tumor frequency in various mouse strains, has been used for over 15 y as a model of immunologic events occurring in photocarcinogenesis. In mice, as well as in humans, ultraviolet B radiation induced impairment of contact hypersensitivity is not uniform in all individuals; some individuals are susceptible to the deleterious effects of ultraviolet B, whereas others are resistant to ultraviolet B. We have defined the genetic locus responsible for ultraviolet B susceptibility and resistance in mice within the Bat5 and H-2D segment of the mouse chromosome 17.

Genes Encoding Three New Members of the Leukocyte Antigen 6 Superfamily and a Novel Member of Ig Superfamily, Together with Genes Encoding the Regulatory Nuclear Chloride Ion Channel Protein (hRNCC) and a Nω-Nω-Dimethylarginine Dimethylaminohydrolase Homologue, Are Found in a 30-kb Segment of the MHC Class III Region

Many of the genes in the class III region of the human MHC encode proteins involved in the immune and inflammatory responses. We have sequenced a 30-kb segment of the MHC class III region lying between the heat shock protein 70 and TNF genes as part of a program aimed at identifying genes that could be involved in autoimmune disease susceptibility. The sequence analysis has revealed the localization of seven genes, whose precise position and order is cen-G7-G6-G6A-G6B-G6C-G6D-G6E-tel, five of which are fully encoded in the sequence, allowing their genomic structures to be defined. Three of them (G6C, G6D, and G6E) encode putative proteins that belong to the Ly-6 superfamily, known to be GPI-anchored proteins attached to the cell surface. Members of the family are specifically expressed and are important in leukocyte maturation. A fourth gene, G6B, encodes a novel member of the Ig superfamily containing a single Ig V-like domain and a cytoplasmic tail with several signal transduction features. The G6 gene encodes a regulatory nuclear chloride ion channel protein, while the G6A gene encodes a putative homologue of the enzyme Nω,Nω-dimethylarginine dimethylaminohydrolase, which is thought to be involved in regulating nitric oxide synthesis. In addition, three microsatellite markers, 9N-1, 82-2, and D6S273 are contained within the sequence, the last two of which have been reported to be strongly associated with the autoimmune disease ankylosing spondylitis.

Molecular Analysis of the Major MHC Recombinational Hot Spot Located Within the G7c Gene of the Murine Class III Region That Is Involved in Disease Susceptibility

Recombination within the MHC does not occur at random, but crossovers are clustered in hot spots. We previously described a recombinational hotspot within the 50-kb Hsp70.3–G7 interval in the class III region of the mouse MHC. The parental haplotypes of recombinants with crossovers in this region represent the majority of the laboratory haplotypes (a, b, d, dx, k, m, p, px, q, s, and u). Using microsatellite markers and sequence-based nucleotide polymorphisms, the breakpoint intervals of 30 recombinants were mapped to a 5-kb-long interval within the G7c gene adjacent to G7a. Recombination within the G7c hot spot does not appear to be restricted to certain haplotypes. Sequence motifs that had been suggested to be associated with site-restricted meiotic recombination were absent in the vicinity of the G7c hot spot, and hence, these sequence motifs are no prerequisite for meiotic recombination. The G7c hot spot resides in a region to which a number of disease susceptibility loci have been mapped, including susceptibility to cleft palate, experimental autoimmune allergic orchitis, and chemically induced alveolar lung tumors. The exact localization of crossovers in recombinants that have been used in functional studies is important for mapping susceptibility genes and limits the number of candidate genes.

Multiple loci govern the bone marrow-derived immunoregulatory mechanism controlling dominant resistance to autoimmune orchitis

The existence of immunoregulatory genes conferring dominant resistance to autoimmunity is well documented. In an effort to better understand the nature and mechanisms of action of these genes, we utilized the murine model of autoimmune orchitis as a prototype. When the orchitis-resistant strain DBA/2J is crossed with the orchitis-susceptible strain BALB/cByJ, the F1 hybrid is completely resistant to the disease. By using reciprocal radiation bone marrow chimeras, the functional component mediating this resistance was mapped to the bone marrow-derived compartment. Resistance is not a function of either low-dose irradiation- or cyclophosphamide (20 mg/kg)-sensitive immunoregulatory cells, but can be adoptively transferred by primed splenocytes. Genome exclusion mapping identified three loci controlling the resistant phenotype. Orch3 maps to chromosome 11, whereas Orch4 and Orch5 map to the telomeric and centromeric regions of chromosome 1, respectively. All three genes are linked to a number of immunologically relevant candidate loci. Most significant, however, is the linkage of Orch3 to Idd4 and Orch5 to Idd5, two susceptibility genes which play a role in autoimmune insulin-dependent type 1 diabetes mellitus in the nonobese diabetic mouse.

A susceptibility gene for alveolar lung tumors in the mouse maps between Hsp70.3 and G7 within the H2 complex

Lung tumor susceptibility (LTS) in the mouse is influenced by multiple loci within the H2 complex. We compared the LTS of two H2 congenic strains with intra H2 recombinations, B10.A(1R) and B10.A(2R), whose genetic difference has been reduced to a region of approximately 50 kilobases within the C4-H2D interval, between Hsp70.3 and G7. After transplacental induction with N-ethyl-N-nitrosourea the load of alveolar lung tumors in strain B10.A(2R) is significantly higher than in strain B10.A(1R) (P < 0.001). For papillary tumors no significant differences were observed. We conclude that the alveolar lung tumor load is influenced by an LTS gene located within the Hsp70.3-G7 interval.

Meiotic recombination within the H-2K-H-2D interval: characterization of a panel of congenic mice, including 12 new strains, using DNA markers

Intra-H-2 recombinant congenic strains are widely used to localize traits to specific subregions of the major histocompatibility complex and have provided evidence for the existence of meiotic recombinational hotspots in mammals. Forty-seven intra-H-2 recombinant strains, including 12 not previously reported, have been identified by serological typing in our laboratory. We have extended the analysis of the crossover sites in these mice using DNA markers for Ab, Aa, Eb, Ea, Cyp21-ps, D17Tu3, Bat7, and Bat5. The recombinant chromosomes of these congenic strains include loci derived from the a, b, f, k, p, q, r, s, u, and v haplotypes of H-2, providing a diverse panel of strains. Although some alleles of Bat7 could not be distinguished from one another, results from the majority of strains indicated a probable gene order of C4Slp/D17Tu3-Bat7-Bat5-H-2D. No recombinants between Cyp21-ps, C4Slp, and D17Tu3 were observed. The crossover sites in 31 of the 47 intra-H-2 recombinants were within the C4Slp/D17Tu3-H-2D interval; of these 31 crossovers, three were bracketed by D17Tu3 and Bat7, ten by Bat7 and Bat5, seven by Bat5 and H-2D, and 11 by D17Tu3 and Bat5. The results from all 47 strains suggest recombinational hotspots within the C4Slp/D17Tu3-H-2D interval and emphasize the influence that specific haplotypes can have on preferred crossover sites.

Testis-/embryo-expressed genes are clustered in the mouse H-2K region

The major histocompatibility complex (MHC) of the mouse is located on chromosome 17 in the distal inversion of the t complex. In addition to genes playing major roles in the immune response, it contains a diversity of genes. In humans, numerous diseases are known to be associated with the MHC loci. Moreover, at least three recessive embryonic t-lethal mutations have been mapped to the MHC. Here a molecular genetic approach was used to study the detailed genomic structure of 240 kilobases (kb) surrounding the H-2K gene and 150 kb of a partly homologous region located in the distal inversion of the t complex. Combined with previous findings, the H-2K region was found to contain an impressively high density of genes--12 transcription units in 240 kb. Surprisingly, virtually all of these genes are expressed in testis and/or embryos. The genomic organization of this region is contrasted with the 150 kb of the homologous area where only three genes and an endogenous retrovirus reside.