A glutaminase (gis) gene maps to mouse chromosome 1, rat chromosome 9, and human chromosome 2

A rat cDNA clone encoding a portion of phosphate-activated glutaminase was used to identify DNA restriction fragment length polymorphisms (RFLPs) in sets of somatic cell hybrids and between wild-derived and inbred strains of mice. Segregation of rat and mouse chromosomes among somatic cell hybrids indicated assignment to rat chromosome 9 and mouse chromosome 1. Analysis of chromosome 1 alleles for several genes in an interspecific cross between Mus spretus and C3H/HeJ-gld/gld mice indicates that glutaminase can be positioned within 5.5 +/- 2.0 cM proximal to Ctla-4. Similarly, human-hamster somatic cell hybrids were examined for RFLPs, and four human EcoRI restriction fragments were found to hybridize with the rat glutaminase probe. Two of these restriction fragments cosegregated and mapped to human chromosome 2 in a region that is syntenic with mouse chromosome 1 and rat chromosome 9.     

A molecular genetic linkage map of mouse chromosome 7

The homology between mouse chromosome 7 and human chromosomes 11, 15, and 19 was examined using interspecific backcross animals derived from mating C3H/HeJ-gld/gld and Mus spretus mice. In an earlier study, we reported on the linkage relationships of 16 loci on mouse chromosome 7 and the homologous relationship between this chromosome and the myotonic dystrophy gene region on human chromosome 19. Segregation analyses were used to extend the gene linkage relationships on mouse chromosome 7 by an additional 21 loci. Seven of these genes (Cyp2a, D19F11S1h, Myod-1, Otf-2, Rnu1p70, Rnu2pa, and Xrcc-1) were previously unmapped in the mouse. Several potential mouse chromosome 7 genes (Mel, Hkr-1, Icam-1, Pvs) did not segregate with chromosome 7 markers, and provisional chromosomal assignments were made. This study establishes a detailed molecular genetic linkage map of mouse chromosome 7 that will be useful as a framework for determining linkage relationships of additional molecular markers and for identifying homologous disease genes in mice and humans.     

Establishment of a molecular genetic map of distal mouse chromosome 1: further definition of a conserved linkage group syntenic with human chromosome 1q

A linkage map of distal mouse chromosome 1 was constructed by restriction fragment length polymorphism analysis of DNAs from seven sets of recombinant inbred (RI) strains. The data obtained with seven probes on Southern hybridization combined with data from previous studies suggest the gene order Cfh, Pep-3/Ren-1,2, Ly-5, Lamb-2, At-3, Apoa-2/Ly-17,Spna-1. These results confirm and extend analyses of a large linkage group which includes genes present on a 20-30 cM span of mouse chromosome 1 and those localized to human chromosome 1q21-32. Moreover, the data indicate similar relative positions of human and mouse complement receptor-related genes REN, CD45, LAMB2, AT3, APOA2, and SPTA. These results suggest that mouse gene analyses may help in detailed mapping of human genes within such a syntenic group.     

The syntenic relationship of proximal mouse chromosome 7 and the myotonic dystrophy gene region on human chromosome 19q

The syntenic relationship of the myotonic dystrophy (DM) gene region on human chromosome 19q and proximal mouse chromosome 7 was examined using an interspecific backcross between C3H/HeJ-gld/gld mice and Mus spretus. Segregation analyses were used to order homologs of nine human loci linked with the DM gene. Their order from the centromere was Prkcg, [Apoe, Atpa-2, Ckmm, D19S19h, Ercc-2], Cyp2b, Mag, Lhb. Two other murine loci, D7Rp2 and Ngfg, were also positioned within this interval. Homologs for five human chromosome 11 and 15 loci (Calc, Fes, Hras-1, Igflr, Tyr) were localized within an 18-cM span telomeric to Lhb. Comparison of the gene orders indicates an inversion extending from Prkcg through the interval between Mag and Lhb. This study establishes a detailed map of proximal mouse chromosome 7 that will be useful in identifying and determining whether new human chromosome 19 probes are linked to the DM region.     

Mapping of Col3a1 and Col6a3 to proximal murine chromosome 1 identifies conserved linkage of structural protein genes between murine chromosome 1 and human chromosome 2q

We have investigated the degree of synteny between the long arm (q) of human chromosome 2 and the proximal portion of mouse chromosome 1. To define the limits of synteny, we have determined whether mouse homologs of seven human genes mapping to chromosome 2q cosegregated with anchor loci on mouse chromosome 1. The loci investigated were NEB/Neb, ELN/Eln, COL3A1/Col3a1, CRYG/Len-2, FN1/Fn-1, VIL/Vil, and COL6A3/Col6a3. Ren-1,2 and Acrg were included as two proximal mouse chromosome 1 anchor loci. The segregation of restriction fragment length polymorphisms at these loci was analyzed in the progeny of Mus spretus x C57BL/6J hybrids backcrossed to the C57BL/6J inbred strain. We found that five of the structural protein loci and the two anchor loci form a linkage group on proximal murine chromosome 1. The proposed gene order of this group of linked markers is centromere - Col3a1 - Len-2-Fn-1-Vil-Acrg-Col6a3-Ren1,2. Neb and Eln are linked neither to each other nor to any other marker on proximal mouse chromosome 1. Therefore, the mouse loci Col3a1 and Col6a3 are identified as flanking markers of the linkage group of structural protein loci. The estimated genetic map distances are Col3a1-13.3 cM-Len-2-3.4 cM-Fn-1-3.8 cM-Vil-9.6 cM-Acrg-2.1 cM-Col6a3-18.3 cM-Ren1,2. The available map information for human chromosome 2q markers and mouse chromosome 1 markers presented here tentatively identifies Col3a1 and Col6a3 as the border markers that define the limits of the syntenic chromosome segment. The order of mouse genes on chromosome 1 and their human homologs on chromosome 2q also appears to be conserved, suggesting that mapping of murine genes on the conserved segment may be useful to predict gene order in man.     

Characterization of lymphoproliferation induced by interactions between lprcg and gld genes.

The lprcg gene is the novel mutation at the lpr locus characterized by its complementary to the gld gene in induction of lymphoproliferation in the mouse. Because of the potential usefulness of mice with this mutation in studies on the interrelationship between lpr and gld, we were urged to characterize the lymphoproliferative disease developing in (CBA/K1Jms-lprcg/lprcg x C3H/HeJ-gld/gld) F1 hybrid (lprcg-gld) mice. Despite the milder lymphadenopathy in the lprcg-gld mice, the expanding lymph node cells showed the same surface marker pattern as that in C3H/HeJ-lpr/lpr, C3H/HeJ-gld/gld, and CBA/K1Jms-lprcg/lprcg mice, characterized by the positivity for Thy-1, B220, Ly-6, and Ly-24, and the negativity for L3T4, Lyt-2 (hence designated double-negative cells), and sIg. Furthermore, these cells proved to be of a T-cell lineage based on the rearrangement of the TCR beta-chain gene, the same as the already known double-negative cells. Noticeably, in lprcg-gld mice, serum IgG and autoantibodies of the IgG class were not elevated at an early age but were slightly elevated at an advanced age despite early elevation of the serum IgM and IgM autoantibodies. These results suggest that the lymphoproliferative mice carrying lprcg and gld genes in a heterozygous state will serve as a new tool for inquiring into the interrelationship among lpr, gld, and lprcg.     

Assignment of the structural gene for argininosuccinate synthetase to proximal mouse chromosome 2

In order to develop linkage markers for the murine argininosuccinate synthetase locus (Ass-1), we have searched for restriction fragment length polymorphisms in the mouse genome using cloned sequences from the mouse arginosuccinate synthetase structural gene. Five restriction fragment length polymorphisms were found among the recombinant inbred progenitor strains AKR/J, BALB/cByJ, C3H/HeJ, C57BL/6J, C57L/J, DBA/2J, and SWR/J. Of these, four polymorphisms were found to distinguish the SWR/J strain from the other six strains, which all had the same fragment. The fifth polymorphism revealed differences among the progenitor strains for recombinant inbred strain sets AKXL, BXD, and SWXL. The strain distribution pattern for this polymorphism indicated close linkage of Ass-1 to Hc (the fifth component of complement) on proximal mouse chromosome 2 with a recombination fraction of 0.016 and a 95% confidence interval of 0.003 to 0.054. These data place Ass-1 in a syntenic group with the genes Hc, Abl, Fpgs, and Ak-1 whose linkage has been conserved between human chromosome 9q and mouse chromosome 2.     

A linkage map of mouse Chromosome 1 using an interspecific cross segregating for the gld autoimmunity mutation

An interspecific backross was used to define a high resolution linkage map of mouse Chromosome (Chr) 1 and to analyze the segregation of the generalized lymphoproliferative disease (gld) mutation. Mice homozygous for gld have multiple features of autoimmune disease. Analysis of up to 428 progeny from the backcross [(C3H/HeJ-gld x Mus spretus)F₁ x C3H/HeJ-gld] established a map that spans 77.6 cM and includes 56 markers distributed over 34 ordered genetic loci. The gld mutation was mapped to a less than 1 cM segment on distal mouse Chr 1 using 357 gld phenotype-positive backcross mice. A second backcross, between the laboratory strains C57BL/6J and SWR/J, was examined to compare recombination frequency between selected markers on mouse Chr 1. Significant differences in crossover frequency were demonstrated between the interspecific backcross and the inbred laboratory cross for the entire interval studied. Sex difference in meiotic crossover frequency was also significant in the laboratory mouse cross. Two linkage groups known to be conserved between segments of mouse Chr 1 and the long arm of human Chrs 1 and 2 where further defined and a new conserved linkage group was identified that includes markers of distal mouse Chr 1 and human Chr 1, bands q32 to q42.     

Serum IgG from an autoimmune prone mouse C3H/HeJ-gld/gld supports the interleukin-3-dependent cell line through an autocrine mechanism

C3H/HeJ-gld/gld(C3H/gld) mice have been shown to develop massive lymphadenopathy with autoimmunity. In this study, we tested whether C3H/gld-IgG supports the growth of the IL-3-dependent cell line, FDC-P2/185-4. Serum IgG from C3H/gld mice stimulated FDC-P2/185-4 cells to proliferate. On the other hand, IgG from C3H/HeJ-+/+ did not show such activity. This activity increased with age in both sexes of C3H/gld mice. It was suggested that a monomeric IgG component was responsible for the proliferative activity of C3H/gld mouse sera. The cell-induced growth required Fc gamma receptors on FDC-P2/185-4 cells. FDC-P2/185-4 cells stimulated with C3H/gld-IgG, secreted IL-3, and grew by themselves, indicating an autocrine mechanism. Thus, cytokines produced by serum IgG may play an important role in the development of disease in mice bearing the autosomal recessive mutation gld.     

The pronatriodilatin gene is located on the distal short arm of human chromosome 1 and on mouse chromosome 4.

Atrial natriuretic factors (ANF) are polypeptides having natriuretic, diuretic, and smooth muscle-relaxing activities that are synthesized from a single larger precursor: pronatriodilatin. Chromosomal assignment of the gene coding for human pronatriodilatin was accomplished by in situ hybridization of a [3H]-labeled pronatriodilatin probe to human chromosome preparations and by Southern blot analysis of somatic cell hybrid DNAs with normal and rearranged chromosomes 1. The human pronatriodilatin gene was mapped to the distal short arm of chromosome 1, in band 1p36. Southern blot analysis of mouse X Chinese hamster somatic cell hybrids was used to assign the mouse pronatriodilatin gene to chromosome 4. This assignment adds another locus to the conserved syntenic group of homologous genes located on the distal half of the short arm of human chromosome 1 and on mouse chromosome 4.     

Definition of mouse chromosome 1 and 3 gene linkage groups that are conserved on human chromosome 1: Evidence that a conserved linkage group spans the centromere of human chromosome 1

Comparative mapping between the human and the mouse genomes allows characterization of linkage groups that have been conserved over evolution. In this study, genes previously localized to adjacent regions of human chromosome 1 were mapped to discrete regions on distal mouse chromosomes 1 and 3 using an interspecific cross. Linkage analysis in mouse defined two groups in which the gene order appears to be the same as that in humans: 15 genes localized between human chromosome 1q21 and 1q32 were found to span 29.5 cM on distal mouse chromosome 1; 6 genes localized between human chromosome 1q21 and 1p22 spanned 15.6 cM on distal mouse chromosome 3. These data suggest that gene order within large chromosome segments may remain stable over long periods of evolution and that the position of the centromere may reflect a late event in the evolution of higher eukaryotic organisms. These studies provide a model for examination of specific evolutionary events.     

Serum IgG from CBA/K1Jms-lprcg/lprcg mice induces interleukin 3 in an interleukin-3-dependent cell line--possible correlation with lymphadenopathy

Serum IgG of CBA-K1Jms-lprcg/lprcg (lprcg/lprcg) mice with spontaneous systemic lymphadenopathy supported the proliferation of an IL-3-dependent cell line, FDC-P2/185-4. The lprcg/lprcg IgG induced IL-3 synthesis in FDC-P2/185-4 cells, and cells grew by an autocrine mechanism. There was virtually no time lag between the appearance of lymphadenopathy and an increase of IL-3-inducing activity in the sera. We have previously shown that serum IgG from other autoimmune mice with lymphadenopathy, MRL/Mp-lpr/lpr(MRL/lpr) and C3H/HeJ-gld/gld(C3H/gld), also induces IL-3 synthesis and cell growth in FDC-P2/185-4 cells. Furthermore, neither F1 (lprcg/+) mice between lprcg/lprcg and CBA(-)+/+ nor those (lpr-gld) between C3H-lpr/lpr and C3H/gld showed such IL-3-inducing activity, while those (lprcg-gld) between lprcg/lprcg and C3H/gld showed activity much lower than that of their parental strains but significantly higher than that of normal CBA(-)+/+ mice. This result is consistent with the incidence and degree of lymphadenopathy in these F1 mice. Our results suggest that expression of IgG(s) with cytokine-inducing activity might be controlled by these mutant genes, lpr, gld, and lprcg, and might be related to lymphadenopathy in these mice.     

Localization of the murine macrophage colony-stimulating factor gene to chromosome 3 using interspecific backcross analysis

The chromosomal location of the murine macrophage colony-stimulating factor (Csfm) gene was determined by interspecific backcross analysis. We mapped Csfm to mouse chromosome 3, 2.5 cM distal to Ngfb and Nras and 1.3 cM proximal to Amy-2. CSFM maps to human chromosome 5q, while AMY2, NGFB, and NRAS map to human chromosome 1p. The chromosomal location of Csfm thus disrupts a previously identified conserved linkage group between mouse chromosome 3 and human chromosome 1. The location of Csfm also identifies yet another mouse chromosome that shares synteny with human chromosome 5q, a region involved in several different types of myeloid disease.     

Chromosomal localization of zinc finger protein genes in man and mouse

We have determined the mouse and human chromosomal location of a gene (Zfp-3) that codes for a protein that contains potential DNA zinc-binding fingers. An analysis of the segregation of restriction fragment length polymorphisms in recombinant inbred strains and in an interspecific backcross demonstrated that Zfp-3 is located on mouse chromosome 11. Zfp-3 is very closely linked to the Trp53-1 locus but unlinked to another finger protein gene Zfp-4 located on mouse chromosome 8. In humans ZFP3 has been localized to chromosome 17p12-17pter and thus is part of the conserved linkage group between this chromosome and the distal half of mouse chromosome 11.     

A brain L-type calcium channel alpha 1 subunit gene (CCHL1A2) maps to mouse chromosome 14 and human chromosome 3.

A rat brain cDNA probe was used to localize a gene encoding the alpha 1 subunit of neuronal dihydropyridine-sensitive L-type calcium channels in the mouse and human genomes. Hybridization of the probe to Southern blots made with DNAs from a Chinese hamster x mouse somatic cell hybrid panel indicated that this gene maps to mouse chromosome 14 (Chr 14). Southern blot analysis of an intersubspecies cross demonstrated that the calcium channel alpha 1 subunit gene, termed Cchl1a2, can be positioned 7.5 cM proximal to Np-1. Similarly, segregation among human X rodent somatic cell hybrids indicated that CCHL1A2 maps to human chromosome 3. These assignments are consistent with a region of linkage homology between human chromosome 3p and a proximal region of mouse Chr 14.     

Rapid and efficient construction of yeast artificial chromosome contigs in the mouse genome with interspersed repetitive sequence PCR (IRS-PCR): Generation of a 5-cM, >5 megabase contig on mouse Chromosome 1

We have developed a new technique for the generation of YAC contigs in the mouse genome that is based on the ability to detect overlapping clones by hybridization of shared IRS-PCR products. As a demonstration of the technique, a 5-cM, >5 megabase contig was developed on the distal half of mouse Chromosome (Chr) 1, spanning the region from Lamb2 to At3. The contig covers roughly 5% of the genetic distance of the chromosome and is comprised of more than 80 clones; 71 probes were assigned physical order on the chromosome, of which 59 were new markers generated in this study. Eight of the new probes were shown to be polymorphic between C3H/HeJ-gld and M. spretus. Three probes were mapped on a [(C3H/HeJ-gld x M. spretus) x C3H/HeJ-gld] interspecific backcross to integrate the physical map with a high-resolution genetic map of the region.     

Identification of Soat1 as a quantitative trait locus gene on mouse chromosome 1 contributing to hyperlipidemia

We previously identified two closely linked quantitative trait loci (QTL) on distal chromosome 1 contributing to major variations in plasma cholesterol and triglyceride levels in an intercross derived from C57BL/6 (B6) and C3H/HeJ (C3H) apolipoprotein E-deficient (apoE(-/-)) mice. Soat1, encoding sterol o-acyltransferase 1, is a functional candidate gene located underneath the proximal linkage peak. We sequenced the coding region of Soat1 and identified four single nucleotide polymorphisms (SNPs) between B6 and C3H mice. Two of the SNPs resulted in amino-acid substitutions (Ile147Val and His205Tyr). Functional assay revealed an increased enzyme activity of Soat1 in peritoneal macrophages of C3H mice relative to those of B6 mice despite comparable protein expression levels. Allelic variants of Soat1 were associated with variations in plasma cholesterol and triglyceride levels in an intercross between B6.apoE(-/-) and C3H.apoE(-/-) mice. Inheritance of the C3H allele resulted in significantly higher plasma lipid levels than inheritance of the B6 allele. Soat1 variants were also significantly linked to major variations in plasma esterified cholesterol levels but not with free cholesterol levels. Trangenic expression of C3H Soat1 in B6.apoE(-/-) mice resulted in elevations of plasma cholesterol and triglyceride levels. These results indicate that Soat1 is a QTL gene contributing to hyperlipidemia.     

Mapping of PRM1 to human chromosome 16 and tight linkage of Prm-1 and Prm-2 on mouse chromosome 16

The protamines are small, arginine-rich nuclear proteins that replace histones and transition proteins late in the haploid phase of spermatogenesis in mammals. The two mouse genes encoding protamines--Prm-1 and Prm-2--have been molecularly cloned and mapped to mouse chromosome 16 (MMU 16). A cDNA clone of mouse Prm-1 that hybridized to the corresponding human gene was used to analyze a panel of somatic cell hybrids made between human lymphoblasts and the E36 hamster cell line. The human gene, which we have designated PRM 1, was syntenic with human chromosome 16 (HSA 16) and discordant with all other human chromosomes. Linkage analysis in the mouse was accomplished using the backcross (Czech II x BALB/c Pt) x Czech II to map Prm-1 and Prm-2 to a position near the 5' terminus of MMU 16. No recombination between Prm-1 and Prm-2 was observed among 89 progeny of the Czech II x BALB/c cross or among 94 progeny of the backcross (CBA/J x BALB/cJ) x BALB/cJ, demonstrating that the two loci are separated by less than 1.6 cM on MMU 16. This tight linkage may be of functional significance, as Prm-1 and Prm-2 are among a limited number of genes known to be expressed postmeiotically in male haploid germ cells.     

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.