A genetic map of mouse chromosome 1 near the Lsh-Ity-Bcg disease resistance locus

Isozyme and restriction fragment length polymorphism (RFLP) analyses of backcross progeny, recombinant inbred strains, and congenic strains of mice positioned eight genetic markers with respect to the Lsh-Ity-Bcg disease resistance locus. Allelic isoforms of Idh-1 and Pep-3 and RFLPs detected by Southern hybridization for Myl-1, Cryg, Vil, Achrg, bcl-2, and Ren-1,2, between BALB/cAnPt and DBA/2NPt mice, were utilized to examine the cosegregation of these markers with the Lsh-Ity-Bcg resistance phenotype in 103 backcross progeny. An additional 47 backcross progeny from a cross between C57BL/10ScSn and B10.L-Lshr/s mice were examined for the cosegregation of Myl-1 and Vil RFLPs with Lsh phenotypic differences. Similarly, BXD recombinant inbred strains were typed for RFLPs upon hybridization with Vil and Achrg. Recombination frequencies generated in the different test systems were statistically similar, and villin (Vil) was identified as the molecular marker closest (1.7 +/- 0.8 cM) to the Lsh-Ity-Bcg locus. Two other DNA sequences, nebulin (Neb) and an anonymous DNA fragment (D2S3), which map to a region of human chromosome 2q that is homologous to proximal mouse chromosome 1, were not closely linked to the Lsh-Ity-Bcg locus. This multipoint linkage analysis of chromosome 1 surrounding the Lsh-Ity-Bcg locus provides a basis for the eventual isolation of the disease gene.     

The host resistance locus Bcg is tightly linked to a group of cytoskeleton-associated protein genes that include villin and desmin.

In the mouse, innate resistance or susceptibility to infection with a group of unrelated intracellular parasites which includes, Mycobacteria, Salmonella, and Leishmania is determined by the expression of a single dominant autosomal gene designated Bcg located on the proximal portion of chromosome 1. The gene is expressed at the level of the mature tissue macrophage and influences its capacity to restrict intracellular proliferation of the parasites. We have used restriction fragment length polymorphism analysis in segregating populations of inter- and intraspecific backcross mice and in recombinant inbred strains to position four new marker genes, transition protein 1 (Tp-1), desmin (Des), the alpha subunit of inhibin (Inha), and retinal S-antigen (Sag), in the vicinity of the host resistance locus, Bcg. The gene order for Tp-1, Des, Inha, and Sag was established in an eight-point testcross with respect to anchor loci previously assigned to that portion of mouse chromosome 1 and was found to be centromere-Fn-1-Tp-1-(Vil,Bcg)-Des-Inha-Akp-3-Acrg+ ++-Sag. Two of these new marker genes were found very tightly linked to Bcg: Des was located 0.3 +/- 0.3 cM distal from (Vil,Bcg) and 0.3 +/- 0.3 cM proximal to Inha. Tp-1 mapped 0.8 +/- 0.8 cM proximal and Sag 12.8 +/- 1.7 cM distal to (Vil,Bcg). Tp-1, Des, Inha, and Sag all fall within a large mouse chromosome 1 segment homologous with the telomeric region of the long arm of human chromosome 2 (2q). Our findings indicate that the two closest markers to the host resistance locus, Bcg, encode cytoskeleton-associated proteins which are capable of interaction with actin filaments.     

Synteny on mouse chromosome 5 of homologs for human DNA loci linked to the Huntington disease gene

Comparative mapping in man and mouse has revealed frequent conservation of chromosomal segments, offering a potential approach to human disease genes via their murine homologs. Using DNA markers near the Huntington disease gene on the short arm of chromosome 4, we defined a conserved linkage group on mouse chromosome 5. Linkage analyses using recombinant inbred strains, a standard outcross, and an interspecific backcross were used to assign homologs for five human loci, D4S43, D4S62, QDPR, D4S76, and D4S80, to chromosome 5 and to determine their relationships with previously mapped markers for this autosome. The relative order of the conserved loci was preserved in a linkage group that spanned 13% recombination in the interspecific backcross analysis. The most proximal of the conserved markers on the mouse map, D4S43h, showed no recombination with Emv-1, an endogenous ecotropic virus, in 84 outcross progeny and 19 recombinant inbred strains. Hx, a dominant mutation that causes deformities in limb development, maps approximately 2 cM proximal to Emv-1. Since the human D4S43 locus is less than 1 cM proximal to HD near the telomere of chromosome 4, the murine counterpart of the HD gene might lie between Hx and Emv-1 or D4S43h. Cloning of the region between these markers could generate new probes for conserved human sequences in the vicinity of the HD gene or possibly candidates for the murine counterpart of this human disease locus.     

Mapping of the gene coding for the muscle protein nebulin (Neb) to the proximal region of mouse chromosome 2.

Using five different series of recombinant inbred (RI) strains, we have mapped the gene encoding nebulin, a muscle-specific protein. The strain distribution pattern of Neb-specific RFLPs segregating in the RI strains showed significant concordance with those of Pmv-7 and Hc, two loci previously located to proximal mouse Chromosome 2. The gene order, intergene distances, and confidence intervals were determined according to standard maximum likelihood estimates as: centromere-Hc-5.4 cM (1.4 cM-15.4 cM; 95% confidence interval)-Neb-3.6 cM (1.5-6.7 cM)-Pmv-7.     

Mapping of the L-methylmalonyl-CoA mutase gene to mouse chromosome 17

In humans, methylmalonyl acidemia is caused by a deficiency of L-methylmalonyl-CoA mutase (MUT) controlled by a gene that has been mapped to chromosome 6. The mouse homolog of this gene has now been mapped to mouse chromosome 17. Recombinant inbred and congenic strains place the mouse Mut locus 1.06 cM distal to H-2, between Pgk-2 and Ce-2. The relative order of syntenic probes flanking H-2 on mouse chromosome 17 and HLA on human chromosome 6 is shown to be different.     

Linkage of loci affecting a murine liver protein and arylsulfatase B to chromosome 13

As-1 is the putative structural locus for murine arylsulfatase B, and Lth-1 determines the presence or absence of a 35 000 dalton acidic liver protein. As-1 and Lth-1 were found to be closely linked using recombinant inbred (RI) strains. Both loci were found to have been cotransferred with the pearl (pe) coat color mutation (chromosome 13) in the B6.C3H pe/pe congenic strain. The linkage relationships between pe, Lth-1, and As-1 were further defined in a backcross. On the basis of the RI data, the congenic strain result, and the backcross data, the following genetic distances were estimated: pe--As-1, 7.1 +/- 4.0 cM; As-1--Lth-1, 2.5 +/- 1.0 cM; and pe--Lth-1, less than 6.9 cM. As-1 and Lth-1 are the first biochemically defined loci to be added to the chromosome 13 linkage map.     

Mapping Creb-1 to chromosome 1 in the mouse.

The gene CREB1 encoding the cyclic AMP response element DNA binding protein was previously assigned to human 2q32.3-q34. In this study, a panel of 207 backcross mice made between C57BL/10ScSn (=B10) females and (B10 x B10.L-Lsh)F1 males were used to map Creb-1 with respect to Cryg and Lsh/Vil on mouse chromosome 1. A reverse-transcribed, polymerase chain reaction-amplified cDNA probe covering bp 39 to 554 of the human sequence identified restriction fragment length polymorphisms with 7/18 restriction endonucleases used to digest whole genomic mouse DNA from the parental strains. BglII and DraI RFLPs for Creb-1 were scored on a subpanel of 16/207 known recombinants between Cryg and Lsh/Vil, yielding 2/16 recombinants between Cryg and Creb-1 and 14/16 recombinants between Creb-1 and Lsh/Vil. The 16/207 recombinants observed between Lsh/Vil and Cryg provide an estimated recombination frequency of 0.077 +/- 0.019, equivalent to a map distance of 7.7 +/- 1.9 cM. This is in good agreement with previously published map distances. The number of recombinants observed between Creb-1 and the other markers place Creb-1 approximately 1 cM distal to Cryg and 7 cM proximal to Lsh/Vil.     

High-Resolution Linkage Map in the Vicinity of the Host Resistance Locus Bcg

The mouse chromosome 1 locus Bcg determines natural resistance/susceptibility of inbred mouse strains to infection with antigenically unrelated intracellular parasites, including several Mycobacterium species, Salmonella typhimurium, and Leishmania donovani. In our effort to clone Bcg, we have constructed a high-resolution genetic linkage map in the vicinity of the gene. We have developed eight new highly polymorphic markers (simple sequence repeats) corresponding to cloned genes (Vil, Inha, Des), microdissected chromosome 1 anonymous probes (λMm1C136, λMm1C163, λMm1C165), or novel DNA markers from the region obtained by chromosome walking (D1Mcg101 and D1Mcg105). We have followed the cosegregation of these markers with respect to Bcg in a novel panel of 1000 (C57L/J × C57BL/6J) × C57BL/6J segregating backcross mice. Additional segregation analyses were carried out in preexisting panels of intra- and interspecific backcross mice and recombinant inbred strains. Three of these markers were found to be very tightly linked to Bcg: λMm1C165 did not show recombination with Bcg in 1424 meioses analyzed, while D1Mcg105 and λMm1C136 were located 0.1 cM proximal and 0.2 cM distal to Bcg, respectively. This analysis enabled us to define further the proximal and distal boundaries of the Bcg interval: the proximal limit was defined by a single crossover occurring between D1Mcg105 and Bcg/λMm1C165/Vil, and the distal limit by 1 crossover between Bcg/λMm1C165/Vil and λMm1C136 in 1683 and 575 informative meioses, respectively, for a maximal interval of 0.3 cM. Combined pedigree analyses for the 30-cM segment overlaping Bcg on mouse chromosome 1 indicated the locus order and the interlocus distances (in cM): centromere-Col3a1-(8.8)-Cryg-(2.6)- λMm1C163 -(1.6)-Fn-1-(2.0)-Tp-1- (1.O)-D1Mcg105-(O.1)-λMm1C165/Vil/Bcg-(O.2)-λMm1C136-(0.3)-Des/D1Mit7-(0.1)-Inha-(2.8)-λMm1C153-(2.4)-λMm1C156-(1.2)-Pax-3-(5.6)-Akp-3-(O.8)-Acrg-(2.0)-Sag-(O.5)-Col6a3.     

Chromosomal localization of murine interleukin-1 alpha and beta genes

DNA analyses of mouse X Chinese hamster somatic cell hybrids and of recombinant inbred mouse strains have previously shown that the interleukin-1 alpha and beta genes are tightly linked on murine chromosome 2, approximately 4.7 cM distal to beta-2-microglobulin. In this study, using in situ chromosome hybridization, we show that the two interleukin-1 genes are located in the F region of murine chromosome 2 and discuss this physical map position in relation to conserved genetic linkage groups.     

DNA segments mapped by reciprocal use of microsatellite primers between mouse and rat

Rat microsatellite primers were used for detection of homologous DNA segments in the mouse species (Mus laboratorius, Mus musculus musculus, and Mus spretus). Twenty five (16.3%) of 153 rat primer pairs amplified specific DNA segments, when genomic DNA of mice was used as a template in the polymerase chain reaction (PCR). Size variation among inbred strains of mice was found for 13 DNA segments (8.5%). Eight out of the 13 polymorphic DNA segments were mapped to a particular chromosome with two sets of recombinant inbred strains, AKXL or BXD. Similarly, mouse microsatellite primers were used for detection of homologous DNA segments in rats (Rattus norvegicus). Twenty (12.0%) of 166 primer pairs amplified specific DNA segments from rat genome. Size variation among inbred strains of rats was found for seven DNA segments (4.2%). Eleven of these 20 DNA segments were mapped with a rat x mouse somatic cell hybrid clone panel and/or linkage analysis by use of backcross progeny. Our results suggest that the mapped DNA segments are really homologs between mouse and rat. These polymorphic DNA segments are useful genetic markers.     

Genetic mapping of the integrin alpha 1 gene (Vla1) to mouse chromosome 13.

The integrin alpha 1 chain (Vla1) associates with the beta 1 chain to form a heterodimer that functions as a dual laminin/collagen receptor in neural cells and hematopoietic cells. We have used an interspecies backcross gene-mapping technique to map the Vla1 gene to the distal end of chromosome 13 in the mouse genome. The Vla1 locus is located 3.5 cM distal to Ctla-3 and 7.8 cM distal to Htrla. We have further characterized this locus in recombinant inbred (RI) mice by examining the strain distribution patterns of nine genomic DNA restriction fragment length variants detected with alpha 1 cDNA probes. The RI gene mapping did not show linkage to previously mapped genes or mutants in the AXB, BXA, or AKXD RI sets and therefore defines a new genetic marker for the distal end of chromosome 13 in these RI sets.     

Linkage map of mouse chromosome 17: localization of 27 new DNA markers

Chromosome 17 of the laboratory variant of the house mouse (Mus musculus L.), MMU17, has been studied extensively, largely because of its involvement in the control of immune response and embryonic as well as male germ cell differentiation. A detailed linkage map of this chromosome is therefore a highly desired goal. As the first step toward achieving this goal, we have isolated, using a LINE 1 repetitive sequence as a probe, 52 anonymous DNA clones from MMU17. Twenty-seven repetitive sequence-free probes isolated from these clones displayed restriction fragment length variation among common inbred strains and could be mapped with the help of recombinant inbred strains, congenic strains, F2 segregants, or intra-t recombinants. Together with markers identified previously, the new markers can be used to construct a map of MMU17 that contains 125 DNA loci. The markers are distributed over a length of approximately 71 cM, which probably represents the entire length of MMU17. Most of the markers reside in the proximal portion of the chromosome, which contains the t and H-2 complexes; this chromosomal region is now fairly well mapped. The distal region of MMU17, on the other hand, is populated by only a few, rather imprecisely mapped markers. Molecular maps are available for most of the H-2 complex and for parts of the t complex.     

The Mos proto-oncogene maps near the centromere on mouse chromosome 4

The Mos proto-oncogene, the cellular homolog of the transforming gene of Moloney murine sarcoma virus, was originally assigned to mouse chromosome 4 using independent panels of mouse/hamster somatic cell hybrids. By in situ hybridization to metaphase chromosomes and standard genetic backcrosses, we have confirmed this assignment and determined that Mos maps near the centromere in a region devoid of other markers. We have also identified a restriction fragment length polymorphism (RFLP) that defines two alleles of the Mos locus in selected inbred strains of laboratory mice. Using the RFLP, we determined the strain distribution pattern for the Mos gene in three sets of recombinant inbred strains and in five strains congenic for histocompatibility antigen genes localized on chromosome 4. These results establish Mos as a useful marker in a poorly characterized region of the mouse genome. In addition, these results will facilitate the genetic analysis of the Mos locus.     

Immunodominance in the T cell response to multiple non-H-2 histocompatibility antigens. IV. Partial tissue distribution and mapping of immunodominant antigens

The immunization of C57BL/6 responder mice with spleen cells from H-2-matched BALB.B donors, which differ by multiple non-H-2 histocompatibility (H) antigens, results in the generation of cytotoxic T lymphocytes (CTL) that are specific for only a limited number of immunodominant antigens. Previous analysis of the genes encoding these dominant antigens has not mapped these genes to any of the non-H-2 H loci defined by congenic strains. It would have been expected that the histogenetic techniques employed for congenic strain selection would have preferentially identified the "strongest" H antigens. Therefore, we have investigated the possibility that immunodominant antigens do not belong to the class of non-H-2 H antigens encoded by genes mapping to H loci defined and mapped by congenic strains. The first experiments were aimed at identifying antigens that were expressed by independently derived inbred strains and were cross-reactive with the immunodominant cytotoxic T cell target (CTT-1) antigen of BALB.B. Strong cross-reaction with the C3H.SW (H-2b) strain was observed; the C3H gene encoding this antigen was mapped with BXH recombinant inbred strains. Contrary to the mapping of the CTT-1 gene to chromosome 1 in BALB.B, the C3H gene was shown to map to either chromosome 4 or chromosome 7. This result indicates that identical, or at least extensively cross-reactive, non-H-2 antigens may be encoded by genes mapping to independently segregating loci in different inbred strains. The tissue distribution of immunodominant antigens was approached by determining the reactivity of CTL specific for these antigens with either lymphoid-derived or fibroblast-derived targets. These CTL effectively lysed lymphoblast and lymphoid tumor targets but did not lyse an SV40-transformed fibroblast line that was shown to be efficiently lysed by CTL specific for non-H-2 H antigens defined by congenic strains. Therefore, it was concluded that immunodominant antigens detected by B6 anti-BALB.B CTL have a restricted tissue distribution in comparison to non-H-2 H antigens defined by congenic strains. The implications of these results for our understanding of the origin and heterogeneity of non-H-2 cell-surface antigen recognized by effector T cells are discussed.     

Genetic regulation of early survival and cyst number after peroral Toxoplasma gondii infection of A x B/B x A recombinant inbred and B10 congenic mice

Genetics of two traits, survival and brain cyst number after peroral Toxoplasma gondii infection, were studied by using recombinant inbred strains of mice derived from resistant A/J (A) and susceptible C57BL/6J (B) progenitors, F1 progeny of crosses between A/J and C57BL/6J mice, and congenic mice (B10 background). Analysis of strain distribution pattern of survival of A x B/B x A recombinant mice indicated that survival is regulated by a minimum of five genes. One of these genes appears to be linked to the H-2 complex and another is related to an as yet unmapped gene controlling resistance to Ectromelia virus. Associations of defined traits with resistance or susceptibility to Toxoplasma cyst formation were also analyzed. Cyst number is regulated by a locus on chromosome 17 within 0 to 4 centimorgans of the H-2 complex (p = 0.001). Mice with the H-2a haplotype are resistant and those with the H-2b haplotype are susceptible. This analysis also indicated that the Bcg locus on chromosome 1 may effect cyst number (map distance = 12 centimorgans, p = 0.05). Resistance to cyst formation is a dominant trait. To analyze relative roles of H-2 and Bcg loci on cyst numbers, C57BL10 (B10)-derived congenic strains of mice with known H-2 and Bcg type were studied. These studies indicated that the H-2 complex locus has the primary effect on cyst number.     

The Locus Encoding αa-Crystallin Is Closely Linked to H-2K on Mouse Chromosome 17

We have used a complementary DNA (cDNA) for mouse alpha A-crystallin to probe genomic DNA for restriction fragment length polymorphisms which could be used to map the alpha A-crystallin gene locus (Acry-1) in the mouse genome. Ten of 12 restriction endonucleases produced fragment polymorphism among various inbred strains of mice. A comprehensive strain survey conducted with six endonucleases resulted in the discovery of six allelic forms of Acry-1. Linkage analysis was conducted on DNA from three sets of recombinant inbred strains of mice and demonstrated close linkage of Acry-1 with the major histocompatibility complex (H-2) on chromosome 17. Analysis of congenic and recombinant congenic strains of mice confirmed the linkage of Acry-1 and H-2 and located the alpha A gene to the region between glyoxylase (Glo-1) and H-2K.     

Mapping of the mouse X chromosome using random genomic probes and an interspecific mouse cross.

Two libraries enriched in murine X chromosome material have been constructed in the lambda vector NM 1149 from flow-sorted chromosomes. Inserts of unique genomic sequence DNA were purified and their X chromosome specificity characterised by hybridisation to a panel of somatic cell hybrid lines. Of the first five such X chromosome-specific probes characterised, all detect restriction fragment length polymorphisms (RFLPs) between inbred mouse laboratory strains such as C57BL/6 and BALB/c and the SPE/Pas mouse strain established from a wild Mus spretus mouse, when their DNAs are digested with the restriction enzyme TaqI. Taking advantage of these RFLPs, all five probes have been localised on the X chromosome using an interspecific backcross between the B6CBARI and SPE/Pas mouse strains segregating the X chromosome markers hypoxanthine phosphoribosyl transferase (Hprt) and Tabby (Ta). Three of the probes map to the region between the centromere and Hprt, and two distal to Ta. Since such X-specific sequence probes detect RFLPs between M. spretus and M. musculus domesticus DNAs with high frequency, a large panel of well localised probes should soon be available for studies of biological problems associated with the X chromosome which can best be approached using the murine species.