Mapping of the Hmg1 gene and of seven related sequences in the mouse

The High Mobility Group 1 protein (HMG1) is an abundant and highly conserved chromosomal protein. Mouse HMG1 is encoded by the Hmg1 gene, containing four introns, but the murine genome contains many related sequences that are mostly retrotransposed pseudogenes. By using an interspecific cross, we have mapped the functional Hmg1 gene on mouse Chromosome (Chr) 5 and seven Hmg1-related sequences on Chrs 6, 8, 17, 18, and X.     

Localization of two mouse genes encoding the protein tyrosine kinase receptor-related protein RYK

We have mapped the gene encoding the murine RYK growth factor receptor protein tyrosine kinase by genetic linkage analysis with recombinant inbred strains of mouse. Two distinct Ryk loci (Ryk-1 and Ryk-2) were identified. Ryk-1 mapped to Chromosome (Chr) 9, whereas Ryk-2 mapped to Chr 12. A similar arrangement of RYK-related loci was previously determined in the human. Synteny has already been established between murine Chr 9 in the region of Ryk-1, and human chromosome 3q11–12, the location of the human RYK-1 gene. However, the Ryk-2/RYK-2 loci on murine Chr 12 and human chr 17p13.3 define a new region of synteny.     

The α-subunit of the skeletal muscle sodium channel is encoded proximal to Tk-1 on mouse Chromosome 11

Recent evidence suggests that the human neuromuscular disorders, hyperkalemic periodic paralysis and paramyotonia congenita, are both caused by genetic defects in the -subunit of the adult skeletal muscle sodium channel, which maps near the growth hormone cluster (GH) on Chromosome (Chr) 17q. In view of the extensive homology between this human chromosome and mouse Chr 11, we typed an interspecies backcross to determine whether the murine homolog (Scn4a) of this sodium channel gene mapped within the conserved chromosomal segment. The cytosolic thymidine kinase gene, Tk-1, was also positioned on the genetic map of Chr 11. Both Scn4a and Tk-1 showed clear linkage to mouse Chr 11 loci previously typed in this backcross, yielding the map order: Tr ^J-(Re, Hox-2, Krt-1)-Scn4a-Tk-1. No mouse mutant that could be considered a model of either hyperkalemic periodic paralysis or paramyotonia congenita has been mapped to the appropriate region of mouse Chr 11. These data incorporate an additional locus into the already considerable degree of homology observed for these human and mouse chromosomes. These data are also consistent with the view that the conserved segment region may extend to the telomere on mouse Chr 11 and on human 17q.     

A multipoint genetic linkage map of mouse chromosome 18

We have mapped 13 loci on mouse Chromosome 18 by Southern blot analysis of restriction fragment length polymorphisms among progeny from an interspecific backcross: (C57BL/6J X Mus spretus) X M. spretus. Complete haplotype analysis of 136 of these progeny was used to establish gene order and estimate genetic distances between loci. The gene order (from centromere to telomere) and recombination distances (in centimorgans) were as follows: PGK-1rs5-4.3-Tpi-10-11.8-(Egr-1, Hmg17-rs9)-2.1-Fgfa-2.2-Grl-1-10.1-(Cdx-1, Csfmr, Pdgfrb, Pdea, Rps14)-2.1-Adrb-2-22.9-Mbp. Pgk-1rs5, Tpi-10, Hmg17-rs9, and Rps14 had not been previously mapped in the mouse; Egr-1 had only been syntenically assigned to mouse Chr 18. Nine of the loci, spanning 18 cM, have homologs on the distal long arm of human Chr5--a region rich in genes encoding growth factors and receptors. An additional previously unmapped gene, Drd-1, predicted to be on mouse Chr 18 based on its human chromosomal location, was mapped to the middle region of mouse Chr 13.     

Genetic and physical mapping of the natural resistance-associated macrophage protein 1 (NRAMP1) in chicken

The chicken natural resistance-associated macrophage protein 1 (NRAMP1) gene has been mapped by linkage analysis by use of a reference panel to develop the chicken molecular genetic linkage map and by fluorescence in situ hybridization. The chicken homolog of the murine Nramp1 gene was mapped to a linkage group located on Chromosome (Chr) 7q13, which includes three genes (CD28, NDUSF1, and EF1B) that have previously been mapped either to mouse Chr 1 or to human Chr 2q. Physical mapping by pulsed-field gel electrophoresis revealed that NRAMP1 is tightly linked to the villin gene and that the genomic organization (gene order and presence of CpG islands) of the chromosomal region carrying NRAMP1 is well conserved between the chicken and mammalian genomes. The regions on mouse Chr 1, human Chr 2q, and chicken Chr 7q that encompass NRAMP1 represent large conserved chromosomal segments between the mammalian and avian genomes. The chromosome mapping of the chicken NRAMP1 gene is a first step in determining its possible role in differential susceptibility to salmonellosis in this species.     

Mapping of ornithine aminotransferase gene sequences to mouse Chromosomes 7, X,and 3

Ornithine aminotransferase (OAT), a mitochondrial matrix enzyme, is deficient in patients with gyrate atrophy of the choroid and retina. In human, the OAT structural gene maps to Chromosome (Chr) 10q26 and several OAT-related sequences, some of which are known to be processed pseudogenes, which map to Xp11.3–11.21. Here, we report chromosomal localization in the mouse of the OAT gene and related sequences. Genomic DNA blot analysis of a well-characterized panel of Chinese hamster x mouse somatic cell hybrids using a human OAT probe revealed two murine loci, one on mouse Chr 7 and the other on Chr X. In addition, segregation of restriction fragment length polymorphisms (RFLPs) detected by the OAT probe in recombinant inbred (RI) strains detected a third locus on Chr 3 and positioned the X locus near Cf-8 and Rsvp. Progeny of an intersubspecific backcross were used to map the Chr 7 locus between Tyr and Int-2, near Cyp2e-1.     

YAC Contigs of theRab1andwobbler(wr) Spinal Muscular Atrophy Gene Region on Proximal Mouse Chromosome 11 and of the Homologous Region on Human Chromosome 2p

Despite rapid progress in the physical characterization of murine and human genomes, little molecular information is available on certain regions, e.g., proximal mouse chromosome 11 (Chr 11) and human chromosome 2p (Chr 2p). We have localized thewobblerspinal atrophy genewrto proximal mouse Chr 11, tightly linked toRab1,a gene coding for a small GTP-binding protein, andGlns-ps1,an intronless pseudogene of the glutamine synthetase gene. We have now used these markers to construct a 1.3-Mb yeast artificial chromosome (YAC) contig of theRab1region on mouse Chr 11. Four YAC clones isolated from two independent YAC libraries were characterized by rare-cutting analysis, fluorescencein situhybridization (FISH), and sequence-tagged site (STS) isolation and mapping.Rab1andGlns-ps1were found to be only 200 kb apart. A potential CpG island near a methylatedNarI site and a trapped exon,ETG1.1,were found between these loci, and a new STS,AHY1.1,was found over 250 kb fromRab1.Two overlapping YACs were identified that contained a 150-kb region of human Chr 2p, comprising theRAB1locus,AHY1.1,and the human homologue ofETG1.1,indicating a high degree of conservation of this region in the two species. We mappedAHY1.1and thus humanRAB1on Chr 2p13.4–p14 using somatic cell hybrids and a radiation hybrid panel, thus extending a known region of conserved synteny between mouse Chr 11 and human Chr 2p. Recently, the geneLMGMD2Bfor a human recessive neuromuscular disease, limb girdle muscular dystrophy type 2B, has been mapped to 2p13–p16. The conservation between the mouseRab1and humanRAB1regions will be helpful in identifying candidate genes for thewobblerspinal muscular atrophy and in clarifying a possible relationship betweenwrandLMGMD2B.     

Synteny conservation of the Huntington's disease gene and surrounding loci on mouse Chromosome 5

The mouse homologs of the Huntington's disease (HD) gene and 17 other human Chromosome (Chr) 4 loci (including six previously unmapped) were localized by use of an interspecific cross. All loci mapped in a continuous linkage group on mouse Chr 5, distal to En2 and Il6, whose human counterparts are located on Chr y. The relative order of the loci on human Chr 4 and mouse Chr 5 was maintained, except for a break between D5H4S115E and Idua/rd, with relocation of the latter to the opposite end of the map. The mouse HD homolog (Hdh) mapped within a cluster of seven genes that were completely linked in our data set. In human these loci span a1.8 Mb stretch of human 4p 16.3 that has been entirely cloned. To date, there is no phenotypic correspondence between human and mouse mutations mapping to this region of synteny conservation.     

The Lxl gene maps to mouse Chromosome 17 and codes for a protein that is homologous to glucose and polyspecific transmembrane transporters

A novel mouse gene, provisionally named Lx1, has been cloned and sequenced. Lx1 most likely represents the mouse homolog of the rat gene OCT1, which encodes a polyspecific transmembrane transporter that is possibly involved in drug elimination. The LX1 predicted protein is highly hydrophobic, possesses twelve putative transmembrane domains, and also shares significant homology with members of the sugar transporter family, particularly the novel liver-specific transporter NLT. Lx1 mRNA is expressed at high levels in mouse liver, kidney, and intestine, and at low levels in the adrenals and in lactating mammary glands. The Lx1 gene maps very close to the imprinted Igf2r/Mpr300 gene on mouse Chromosome (Chr) 17, in a region that is syntenic to human Chr 6q. Chr 6q has been previously associated with transient neonatal diabetes mellitus and breast cancer. Received: 11 March 1996 / Accepted: 5 June 1996     

Genomic structure and chromosomal localization of the mouse gene Punc

The mouse gene Punc encodes a member of the immunoglobulin superfamily of cell surface proteins. It is highly expressed in the developing embryo in nervous system and limb buds. At mid-gestation, however, expression levels of Punc decrease sharply. To allow investigation of such a regulatory mechanism, the genomic locus encompassing the Punc gene was cloned, characterized, and mapped. Fluorescent in situ hybridization was used to determine the chromosomal location of the Punc gene of mouse and human. Mouse Punc maps to Chromosome (Chr) 9 in the region D-E1, whereas the human PUNC gene is localized to Chr 15 at 15q22.3-23, a region known to be syntenic to mouse 9D-E1. The human PUNC gene therefore maps close to a genetic locus that is linked to Bardet-Biedl Syndrome, an autosomal recessive human disorder. Confirmation for the location of human PUNC was obtained through sequence relationships between mouse Punc cDNA, human PUNC cDNA, genomic sequence upstream of the murine Punc gene, and human STS markers that had been previously mapped on Chr 15. The STS sequence WI-14920 is in fact derived from the 3′-untranslated region of the human PUNC gene. WI-14920 had been placed at 228cR from the top of the Chr 15 linkage group, which provided positional information for the human PUNC gene at high resolution. Thus, this study identifies PUNC as the gene corresponding to a previously anonymous marker and serves as a basis to investigate its role in genetic disorders. Received: 8 July 1998 / Accepted: 14 October 1998     

Isolation of two murine H1 histone genes and chromosomal mapping of the H1 gene complement

The mammalian H1 histone gene complement consists of at least seven H1 protein isoforms. These include five S-phase-dependent H1 protein subtypes and two more distantly related proteins, which are expressed upon terminal differentiation (H1⁰) or during the pachytene stage of spermatogenesis (H1t). In the past, three replication-dependent murine H1 genes plus the H1 ⁰ and H1t genes have been isolated and characterized. In this report, we describe the sequences of two more H1 genes, and we show that all five murine replication-dependent H1 genes and the H1t gene map to the region A2-3 on Chromosome (Chr) 13. This is in agreement with our previous finding that the human H1 histone gene complement maps to 6p21.3, which corresponds to the A2-3 region on the murine Chr 13. Previous reports have shown that the replication-independent H1 ⁰ genes map to syntenic regions on Chrs 22 (human H1⁰) and 15 (murine H1 ⁰).     

The Mouse Spam1 maps to proximal Chromosome 6 and is a candidate for the sperm dysfunction in Rb(6.16)24Lub and Rb(6.15)lAld heterozygotes

We have determined the chromosomal localization of the murine gene encoding the 68-kDa sperm adhesion molecule 1, Spam1 or Ph-20. Using two independent approaches, fluorescence in situ hybridization (FISH) and interspecific backcross analysis, we show that Spam1 maps to proximal mouse Chromosome (Chr) 6. This map position is within the conserved linkage group corresponding to human Chr 7q, where the human homolog, SPAM 1, has been shown to map previously. Genetic mapping shows the gene to be very closely linked to Met, one of the most proximal loci on MMU 6. It thus places the gene near the centromere and the junction of the Rb(6.16)24Lub and Rb(6.15)1Ald translocations. The essential role of the Spam1 sperm antigen in mouse sperm-egg interactions and its gene location provide strong support for its candidacy as the gene involved in the dysfunction of mouse sperm bearing the Rb(6.16)24Lub or Rb(6.15)1Ald translocation. Received: 16 July 1996 / Accepted: 23 September 1996     

Genomic organization and mapping of the human and mouse neuronal β2-nicotinic acetylcholine receptor genes

As a first step in determining whether there are polymorphisms in the nicotinic acetylcholine receptor (nAChR) genes that are associated with nicotine addiction, we isolated genomic clones of the β2-nAChR genes from human and mouse BAC libraries. Although cDNA sequences were available for the human gene, only the promoter sequence had been reported for the mouse gene. We determined the genomic structures by sequencing 12 kb of the human gene and over 7 kb of the mouse gene. While the sizes of exons in the mouse and human genes are the same, the introns differ in size. Both promoters have a high GC content (60–80%) proximal to the AUG and share a neural-restrictive silencer element (NRSE), but overall sequence identity is only 72%. Using a 6-Mb YAC contig of Chr 1, we mapped the human β2-nAChR gene, CHRNB2, to 1q21.3 with the order of markers cen, FLG, IVL, LOR, CHRNB2, tel. The mouse gene, Acrb2, had previously been mapped to Chr 3 in a region orthologous to human Chr 1. We refined mapping of the mouse gene and other markers on a radiation hybrid panel of Chr 3 and found the order cen, Acrb2, Lor, Iv1, Flg, tel. Our results indicate that this cluster of markers on human Chr 1 is inverted with respect to its orientation on the chromosome compared with markers in the orthologous region of mouse Chr 3. Received: 26 January 1999 / Accepted: 10 May 1999     

Mapping of the structural gene for S-adenosyl homocysteine hydrolase to mouse Chromosome 2, and related sequences to Chromosomes 8 and X

Comparative mapping studies in human and mouse have shown that, to date, human Chromosome (Chr) 20 is completely syntenic with distal mouse Chr 2. The structural locus for S-adenosyl-l-homocysteine hydrolase (EC 3.3.1.1) in human, AHCY, maps to 20 qterq13.1, and we report here that the homologous locus in the mouse, Ahcy, maps to distal mouse Chr 2 with gene order Pcna-Ahcy-Ada. Analysis of 123 progeny of an interspecific backcross between a laboratory stock, AN, and Mus spretus using a rat cDNA probe revealed the presence of at least two other Ahcy-related sequences segregating independently in the mouse genome. One, Ahcy-rs1, was mapped to Chr 8 in the BXH recombinant inbred strains, and the other, Ahcy-rs2, shows a pattern of inheritance consistent with X-linkage.     

The fit-1 common integration locus in human and mouse is closely linked to MYB

The fit-1 locus was originally identified as a common insertion site for feline leukemia virus (FeLV) in thymic lymphosarcomas induced by FeLV-myc recombinant viruses, suggesting that it harbors a gene that cooperates with Myc in T-cell leukemogenesis. We have previously mapped the fit-1 locus to feline Chromosome (Chr) B2. We have now identified conserved sequences that allow the mapping of the murine homolog using the European Interspecific Backcross (EUCIB). This shows that fit-1 is located on mouse Chr 10, 1cM proximal to Ahi-1, a murine retroviral integration locus that is closely linked to Myb. Moreover, the physical linkage to MYB is maintained in the human genome, as shown by cloning of the human homolog of fit-1 from a Chr 6 cosmid library and a series of overlapping PAC clones. Generation of a contig map around the human homolog of fit-1 reveals that it is approximately 100-kb upstream of MYB. In addition to fit-1 and Ahi-1, two other common insertion sites, Mis-2 and Mml-1, have also been mapped adjacent to Myb on mouse Chr 10. Previous analysis of tumors carrying insertions at fit-1, Mml-1, Mis-2 and Ahi-1 showed no obvious abnormalities in Myb expression. However, the cluster of viral insertion loci in this region suggests either the presence of a closely linked activation target or that subtle effects on Myb have been overlooked. Received: 9 October 1998 / Accepted: 12 January 1999     

Mapping of recombinant retrovirus integration sites that cause expression of the viral genome in murine embryonal carcinoma cells

Murine embryonal carcinoma (EC) cells do not normally express Moloney murine leukemia virus genes. Earlier, rare EC cell lines were isolated that expressed proviral neomycin resistance (neo) gene. This expression was dependent on cellular enhancer or promoter sequences that flank the proviral integration site. Four such integration sites, designated as Mint (for Moloney murine leukemia virus integration and expression sites in EC cells), have been mapped on mouse chromosomes. Minta, Mintb, Mintc and Mintd are unlinked and mapped on different chromosomes (Chr), Chr 10, Chr 1, Chr 5 and the X Chr, respectively. None of these loci appear to be linded to any known Mo-MuLV proviral integration sites previously mapped. These enhancer and promoter loci may represent a new set of genes active in undifferentiated embryonic cells.The terminology for Mint genes has been discussed with and approved by the International Committee on Standard Genetic Nomenclature for Mice (M.T. Davisson, The Jackson Laboratory, Bar Harbor, Me.).