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Mapping of two genes encoding members of a distinct subfamily of MAX interacting proteins: MAD to human chromosome 2 and mouse chromosome 6, and MXI1 to human chromosome 10 and mouse chromosome 19.

Both the MAD and the MXI1 genes encode basic-helix-loop-helix-leucine zipper (bHLH-Zip) transcription factors which bind Max in vitro, forming a sequence-specific DNA-binding complex similar to the Myc-Max heterodimer. Mad and Myc compete for binding to Max. In addition, Mad has been shown to act as a transcriptional repressor while Myc appears to function as an activator. Mxi1 also appears to lack a transcriptional activation domain. Therefore, Mxi1 and Mad might antagonize Myc function and are candidate tumor suppressor genes. We report here the mapping of the MAD and MXI1 genes in human and mouse by fluorescence in situ hybridization (FISH) and by recombination mapping. The MAD gene was mapped to human chromosome 2 at band p13 by FISH and to mouse chromosome 6 by meiotic mapping. The MXI1 gene was mapped to human chromosome 10 at band q25 and on mouse chromosome 19 at region D by FISH. There was a second site of hybridization on mouse chromosome 2 at region C, which may represent a pseudogene or a related sequence. The mapping results confirm regions of conservation between human chromosome 2p13 and mouse chromosome 6 and between chromosome 10q25 and mouse chromosome 19D. Human chromosomes 2p13 and 10q25 have been involved in specific tumors where the role of Mad and Mxi1 can now be investigated.

Animals↗

The mouse CD7 gene: identification of a new element common to the human CD7 and mouse Thy-1 promoters.

Human CD7 (hCD7) is a 40 000 Mr member of the immunoglobulin gene superfamily that is expressed early in natural killer (NK) and T-lymphocyte development. CD7 is involved in lymphocyte activation, as ligation of CD7 activates NK and TCRgammadelta T lymphocytes, and ligation of CD7 on TCRalphabeta T lymphocytes induces a non-mitogenic calcium flux. We have previously cloned and characterized the gene for human CD7 (hCD7) and have described its expression in transgenic mice. Recently a mouse cDNA homologous to hCD7 was reported, which we mapped to the corresponding mouse chromosomal location as hCD7. We now report the identification and characterization of a mouse CD7 (mCD7) genomic clone. We demonstrated that the mCD7 gene was similar both in size and structural organization to hCD7. Comparison of the 5' flanking sequences of the mCD7 and hCD7 genes revealed two regions of sequence similarity. Electrophoretic mobility shift assay confirmed both of these regions to be sites of tissue-restricted protein binding in vitro. The more 3' similarity region also shared sequence with a region in the mouse Thy-1 gene 5' flanking region, suggesting that this sequence may be a cis-acting regulatory element common to all three genes. Thus, the promoter regions and exonic organization were similar in the human CD7, mouse CD7, and mouse Thy-1 genes.

Amino Acid Sequence↗

Amplification and novel locations of endogenous mouse mammary tumor virus genomes in mouse T-cell lymphomas.

Endogenous mouse mammary tumor virus genomes are amplified and located in novel cell DNA sequences in many mouse T-cell lymphomas. Transplanted tumors recovered from the same mouse strain and shown to be of independent origin by chromosomal analysis, by the presence of JH immunoglobulin gene rearrangements, or by the integration patterns of exogenous Moloney MuLV genomes frequently showed similar patterns of novel mouse mammary tumor virus-containing cell DNA fragments. This process of amplification and relocation can occur within a limited number of cell generations and in C57BL/6 mice does not lead to the synthesis of mature virus-encoded proteins. In some instances, amplified mouse mammary tumor virus genomes contained novel restriction cleavage sites in the gag-pol region. The restricted time course of occurrence, lack of synthesis of mature virion proteins, and apparent site specificity indicate that this process of retrovirus amplification differs significantly from virus replication after exogenous infection.

Animals↗

Organization and expression of mouse mammary tumor virus sequences in normal and neoplastic C3Hf/HeSed mouse tissues.

The organization and expression of germinally transmitted mouse mammary tumor virus (MMTV) proviruses in C3Hf/HeSed mouse tissues were examined. Digestion with the restriction enzymes EcoRI, BamHI, and HindIII and hybridization with cloned probes specific for the long terminal repeat and the 5' and 3' regions of the MMTV genome revealed three full-length (units Ib, II, and V) and two subgenomic (units I and IX) MMTV proviruses in C3Hf/HeSed mouse germ line DNA. The EcoRI fragments (15.0 and 5.7 kilobase pairs [kbp]) that contained unit Ib were previously described as separate, subgenomic MMTV proviruses. The methylated state of each full-length MMTV provirus was examined in DNA from C3Hf/HeSed mouse livers, spleens, mammary glands, and mammary tumors by digestion with EcoRI or BamHI in combination with the methyl-sensitive restriction enzymes HhaI or HpaII. Unit Ib contained HhaI- and HpaII-sensitive sites in spleen, mammary gland, and mammary tumor DNA but was completely methylated in liver DNA. Units II and V contained HhaI- and HpaII-sensitive sites in mammary gland and mammary tumor DNA, but the sites were extensively methylated in spleen and liver DNA. The HhaI-sensitive sites were mapped to the 5' end of the 5' and 3' long terminal repeats of each full-length MMTV provirus. C3Hf/HeSed mouse tissue RNA was examined for MMTV transcripts. Mammary glands contained MMTV RNA species of 9.0, 3.8, and 1.7 kb. Mammary tumors contained high levels of the 9.0- and 3.8-kb transcripts but lacked the 1.7-kb species. A very low level of the 3.8-kb MMTV transcript was present in spleens. Livers lacked detectable MMTV RNA. These results implicate mammary tissue as the site of unit V activation in the formation of MMTV virions.

Animals↗

Comparison of effect of tumor promoter treatments on DNA methylation status and gene expression in B6C3F1 and C57BL/6 mouse liver and in B6C3F1 mouse liver tumors.

The effects of different liver tumor-promoting treatments (i.e., a choline-devoid, methionine-deficient (CMD) diet, phenobarbital (PB), or both) on Ha-ras and raf methylation status and expression were determined in mouse strains with different susceptibilities to liver tumor formation: the relatively sensitive B6C3F1 and the relatively resistant C57BL/6. Additionally, B6C3F1 mouse liver tumors, spontaneous or PB induced, were assessed for alterations in global DNA methylation status and expression of Ha-ras and raf. The CMD diet led to hypomethylation of Ha-ras and raf after 12 wk of administration in B6C3F1 and C57BL/6 mice. At this early phase of tumor promotion, the frequency of increased expression of both Ha-ras and raf mRNAs was higher in the B6C3F1 but not the C57BL/6 mice. This is a mechanism that may, in part, underlie the heightened sensitivity of the B6C3F1 mouse to liver tumorigenesis. Subpopulations of B6C3F1 mouse liver tumors displayed altered global methylation status, with both hypomethylation and hypermethylation evident. Carcinomas were significantly more hypomethylated than adenomas. The level of raf mRNA was not changed in spontaneous or PB-induced B6C3F1 mouse liver tumors. Increased expression of Ha-ras was evident in some spontaneous B6C3F1 liver tumors and in most of the PB-induced liver tumors. These experiments support the concept that altered DNA methylation plays a key role in tumorigenesis and indicate that the high propensity of the B6C3F1 mice to liver tumorigenesis may be due, in part, to a decreased ability to maintain normal methylation status.

Animals↗

Mouse ret finger protein (rfp) proto-oncogene is expressed at specific stages of mouse spermatogenesis.

Many proteins involved in the regulation of cell growth and differentiation possess structural motifs that participate in specific molecular interactions. The human rfp (ret finger protein) has a tripartite motif, consisting of two novel zinc fingers (the RING linger and the B box) and a coiled-coil domain, and belongs to the B box zinc finger protein family. Rfp becomes oncogenic when its tripartite motif is recombined with the tyrosine kinase domain from the c-ret proto-oncogene. To further understand the function of rfp during normal development and cellular differentiation, we cloned the mouse rfp cDNA and analyzed its pattern of expression and subcellular distribution. We found that the mouse rfp cDNA shared a 98.4% homology with the human sequence. The gene mapped to human chromosome 6 and mouse chromosome 13 indicating that it was linked to a several other genes encoding proteins that possess common domains. rfp transcripts and protein were ubiquitous in day 10.5-13.5 mouse embryos, however, they were restricted in adult mice, with the highest level of expression in pachytene spermatocytes and round spermatids of differentiating sperm. The rfp protein was detected within cell nuclei as nuclear bodies similar to the PODs (PML oncogenic domains) observed with another B box family member, PML (promyelocytic leukemia protein). These results suggest that rfp may function in the regulation of cell growth and differentiation during mouse embryogenesis and sperm differentiation.

Amino Acid Sequence↗

Gene encoding a novel murine tissue inhibitor of metalloproteinases (TIMP), TIMP-3, is expressed in developing mouse epithelia, cartilage, and muscle, and is located on mouse chromosome 10.

Remodeling of the extracellular matrix (ECM) is an essential component of normal development and is also involved in the pathogenesis of arthritis and the spread of cancer. The matrix metalloproteinases and their natural inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), play an important role in this context. We have isolated mouse cDNA clones encoding a novel member of the TIMP family, designated TIMP-3. We have assigned the Timp-3 locus to the [C1-D1] region of mouse chromosome 10 using both genetic and cytogenetic methods. The conceptual translation product of the Timp-3 cDNA shows a high degree of similarity with ChIMP-3, a recently cloned chicken metalloproteinase inhibitor, as well as significant structural similarity with the amino acid sequences of the previously isolated members of this family, TIMP-1 and TIMP-2. The pattern of expression of Timp-3 in the developing mouse embryo is distinct from that previously reported for Timp-1. Timp-3 is expressed in cartilage and skeletal muscle, in myocardium, in the skin, oral and nasal epithelium, in the newborn mouse liver, in the epithelium of some tubular structures such as the developing bronchial tree, oesophagus, colon, urogenital sinus, bile duct, in the kidney, salivary glands, and in the choroid plexus of the brain. The patterns of Timp-3 expression in surface epithelia and in the epithelial lining of many tubular organs suggests that TIMP-3 may be involved in regulating ECM remodeling during the folding of epithelia and during the formation, branching, and expansion of epithelial tubes. In the mouse placenta, expression is seen in the trophoblast, raising the possibility that TIMP-3 may be involved in regulating trophoblastic invasion of the uterus. We propose a role for TIMP-3 in musculoskeletal and cardiac development, in the morphogenesis of certain epithelial structures, and placental implantation.

Amino Acid Sequence↗

Analysis of type II collagen-reactive T cells in the mouse. I. Different regulation of autoreactive vs. non-autoreactive anti-type II collagen T cells in the DBA/1 mouse.

The T cell reactivity against type II collagen (CII) was analyzed in the collagen-induced arthritis-susceptible mouse strain DBA/1. It was shown that the proliferative response in lymph node cells from rat CII-immunized mice was mainly directed against a foreign determinant present on all heterologous CII tested but not on autologous CII. A T cell line with this reactivity reacted with high sensitivity with CII and the determinant was mapped to the CB11 fragment of CII. A weak autoreactive response could be detected in the primary cultures using high concentrations of mouse CII and this reactivity remained after several stimulations with high concentrations of rat CII but not with low concentrations of rat CII. A similar response against mouse CII but with only limited cross-reactivity to rat CII was seen when culturing the cells with mouse CII as antigen. The optimal concentration for the autoreactive response was always more than 100-fold higher than for the response of the T cells specific for heterologous CII. An anti-CII T cell response could also be detected in spleen cells from unimmunized mice and the strongest response was obtained using autologous CII. These results suggest that T cells recognizing self CII are normally activated in the DBA/1 mouse and possibly as a consequence exhibit a clonal anergy pattern with a weak proliferative response only at high concentrations of CII.

Animals↗

Mouse bone marrow micronucleus test results do not predict the germ cell mutagenicity of N-hydroxymethylacrylamide in the mouse dominant lethal assay.

N-Hydroxymethylacrylamide (NHMA), a mouse carcinogen inactive in the Salmonella assay and mouse micronucleus (MN) assay, was tested for reproductive effects in a mouse continuous breeding study. In that study, increased embryonic deaths were observed after 13 weeks exposure of parental animals to NHMA via drinking water (highest dose, 360 ppm); the results indicated the possible induction of chromosome damage in germ cells of treated males. An additional mouse MN test was conducted using a 31-day treatment period to better match the dosing regimen used in the breeding study; the results were negative. Additional studies were conducted to explore the germ cell activity of NHMA. A male mouse dominant lethal study was conducted using a single intraperitoneal injection of 150 mg/kg NHMA; the results were negative. A follow-up study was conducted using fractionated dosing, 50 mg/kg/day for 5 days; again, no increase in dominant lethal mutations was observed. NHMA (180-720 ppm) was then administered to male mice in drinking water for 13 weeks, during which three sets of matings occurred. Two weeks after mating, females were killed and the uterine contents were analyzed. Large, dose-related increases in dominant lethal mutations were observed with increasing length of exposure. The magnitude of the increases stabilized after 8 weeks of treatment. However, the frequency of micronucleated peripheral blood erythrocytes was not elevated in mice treated for 13 weeks with NHMA in drinking water. Thus, NHMA appears to be unique in inducing genetic damage in germ cells but not somatic cells of male mice.

Acrylamides↗

Potent clastogenicity of the human carcinogen etoposide to the mouse bone marrow and mouse lymphoma L5178Y cells: comparison to Salmonella responses.

The suspect human carcinogen, etoposide, is known to be genotoxic, producing both gene and chromosomal mutations, probably by virtue of its ability to inhibit topoisomerase II activity. The present paper describes assays conducted using the Salmonella assay, the mouse lymphoma tk+/- assay (gene and chromosomal mutation analysis and molecular analysis of tk-/- mutants) and the mouse bone marrow micronucleus assay. Nonreproducible, weak, dose-related increases in mutation frequency in strain TA98 (but not TA1538 or TA1537) of Salmonella typhimurium were observed. Etoposide was highly mutagenic at the heterozygous thymidine kinase (tk+/-) locus of L5178Y mouse lymphoma cells at concentrations below 0.1 micrograms/ml. Mostly small colony mutants were induced, consistent with the potent clastogenicity also observed. Molecular analysis of mutants indicated that 83% and 92% of large and small colony mutants, respectively, had lost the entire target gene sequence. Chromosomally aberrant L5178Y cells were approximately 2 to 600-fold more prevalent than small tk-/- mutant colonies. This suggests that the viable target for etoposide-mediated clastogenesis in the selective assay is approximately one-fifth of chromosome 11b, itself being approximately one-fortieth of the mouse genome. An unusually potent response was observed for etoposide in the mouse bone marrow micronucleus assay (63.1 +/- 18 MPE/1,000 PE 24 hours after an oral dose of 1 mg/kg). The minimum detectable dose level in the assay was between 0.01 and 0.1 mg/kg. At dose levels between 1 and 15 mg/kg, an inverse dose response was observed. This reduction in assay response was not due to the small concommitant decrease in the incidence of polychromatic erythrocytes, a conclusion based on studies with N-methyl-N-nitrosourea. Animals sampled 48 hours after dosing with etoposide (10 mg/kg) had no polychromatic erythrocytes in the bone marrow. These observations for the micronucleus assay await explanation. The chemical structure of etoposide is displayed and discussed within the context of such strong mutagenic activity being associated with a nonelectrophilic agent.

Animals↗

A study of hetero-specific sperm-egg interactions in the rat, mouse, and deer mouse using in vitro fertilization and sperm injection.

Hetero-specific fertilization of zone-free eggs is used in these experiments as a tool to analyze the barriers to hybridization and to gain insight into the mechanisms of normal fertilization. When the zonae of rat eggs, which are a barrier to hetero-specific fertilization, are removed with pronase, the eggs can be fertilized by mouse sperm and the zygotes start to develop normally. A rat egg fertilized with mouse sperm completes meiosis and forms both male and female pronuclei. Chromosomes from both parents are found on he spindle at the metaphase stage of the first cleavage division. Under present culture conditions, embryos develop only to the two-cell stage, but this initial development of the hybrid is apparently normal. The question of whether sperm and egg membrane fusion is requisite for normal development is addressed by injecting sperm directly into the cytoplasm of unfertilized eggs. The injection of mouse sperm into rat eggs frequently leads to activation and formation of male and female pronuclei. The first cleavage division is indistinguishable from that following hetero-specific fertilization. Capacitated and uncapacitated sperm react alike when injected into eggs. Egg activation, however, is necessary for male pronucleus formation. Sperm from the deer mouse Peromyscus maniculatus bairdii, which are incapable of fertilizing even zonea-free eggs, respond like mouse sperm when injected into rat eggs. These data indicate that sperm interactions with the egg cytoplasm are less species-specific than interactions at the egg surface. Furthermore, the normal surface interactions of sperm and eggs are not essential for the start of development.

Animals↗

A missense mutation of mouse OCTN2, a sodium-dependent carnitine cotransporter, in the juvenile visceral steatosis mouse.

Carnitine is an essential cofactor for the mitochondrial beta-oxidation of long-chain fatty acids. The juvenile visceral steatosis (JVS) mouse, an animal model of systemic carnitine deficiency, is inherited in an autosomal recessive manner. Recently, a human OCTN2 gene encoding a sodium-dependent carnitine cotransporter was isolated and mapped to human chromosome 5q31. Since the mouse jvs locus was assigned to the region of chromosome 11 where it is syntenic to human chromosome 5q31, we isolated the mouse octn2 gene and screened for its mutation in the jvs mouse. DNA sequencing analysis disclosed a missense mutation from CTG (Leu) to CGG (Arg) at codon 352 located within the sixth transmembrane domain of octn2. This amino acid replacement possibly causes the conformational change of the protein that leads to dysfunction of the gene product. Hence, we conclude that octn2 is a candidate gene responsible for the JVS mouse.

Amino Acid Sequence↗

Characterization of the cDNA and gene for mouse tumour necrosis factor alpha converting enzyme (TACE/ADAM17) and its location to mouse chromosome 12 and human chromosome 2p25.

Numerous proteins are cleaved or "shed" from their membrane-bound form. One such protein, tumour necrosis factor alpha (TNF-alpha), is synthesized as a type 2 transmembrane protein. Recently, a human protease responsible for this shedding, the TNF-alpha converting enzyme (TACE/ADAM17), was isolated. TACE/ADAM17 is a member of the adamalysin class of zinc-binding metalloproteases or ADAM (a disintegrin and metalloprotease). We report the isolation and characterization of the mouse TACE/ADAM17 cDNA and gene. Mouse TACE/ADAM17 has a 92% amino-acid identity with the human protein and was ubiquitously expressed. A recombinant form of the protease is found to cleave a peptide representing the cleavage site of precursor mouse TNF-alpha. An alternatively spliced form of mouse TACE/ADAM17 was found that would produce a soluble protein. The gene for TACE/ADAM17 is approximately 50 kb and contains 19 exons. Chromosomal mapping places TACE/ADAM17 on mouse chromosome 12 and human chromosome 2p25.

ADAM Proteins↗

Chromosomal localization of mouse bullous pemphigoid antigens. BPAG1 and BPAG2: identification of a new region of homology between mouse and human chromosomes.

Two bullous pemphigoid antigens, BPAG1 and BPAG2, have been recently cloned and mapped to human chromosomes 6p12-p11 and 10q24.3, respectively. In this study, we localized the corresponding mouse genes by interspecific backcross analysis. Bpag-1 mapped to the proximal region of mouse chromosome 1, identifying a new region of homology between human chromosome 6 and mouse chromosome 1. Bpag-2 mapped to the distal end of mouse chromosome 19 in a region of homology to human chromosome 10q. These assignments confirm and extend the relationships between the human and the mouse chromosomes.

Amino Acid Sequence↗

Chromosome mapping of the human (RECA) and mouse (Reca) homologs of the yeast RAD51 and Escherichia coli recA genes to human (15q15.1) and mouse (2F1) chromosomes by direct R-banding fluorescence in situ hybridization.

We mapped the human (RECA) and mouse (Reca) homologs of the yeast RAD51 and Escherichia coli recA genes to human and mouse chromosomes by direct R-banding fluorescence in situ hybridization. This gene was assigned to human chromosome 15q15.1 and to mouse chromosome 2F1, respectively. This is the first report on the precise localization of this gene to human and mouse chromosomes. This gene was mapped to a region on human chromosome 15q15.1 and mouse 2F1 that is believed to be a conserved syntenic group.

Animals↗

Isolation of the mouse homologue of BRCA1 and genetic mapping to mouse chromosome 11.

The BRCA1 gene is in large part responsible for hereditary human breast and ovarian cancer. Here we report the isolation of the murine Brca1 homologue cDNA clones. In addition, we identified genomic P1 clones that contain most, if not all, of the mouse Brca1 locus. DNA sequence analysis revealed that the mouse and human coding regions are 75% identical at the nucleotide level while the predicted amino acid identity is only 58%. A DNA sequence variant in the Brca1 locus was identified and used to map this gene on a (Mus m. musculus Czech II x C57BL/KsJ)F1 x C57BL/KsJ intersubspecific backcross to distal mouse chromosome 11. The mapping of this gene to a region highly syntenic with human chromosome 17, coupled with Southern and Northern analyses, confirms that we isolated the murine Brca1 homologue rather than a related RING finger gene. The isolation of the mouse Brca1 homologue will facilitate the creation of mouse models for germline BRCA1 defects.

Amino Acid Sequence↗

Inactivation of the mouse HPRT locus by a 203-bp retroposon insertion and a 55-kb gene-targeted deletion: establishment of new HPRT-deficient mouse embryonic stem cell lines.

To obtain useful hypoxanthine phosphoribosyl-transferase (HPRT)-deficient mouse ES cell lines, two different methods were employed: (i) selection of spontaneous 6-TG-resistant mutants and (ii) gene targeting of the HPRT locus. The first approach resulted in the establishment of E14.1TG3B1, a spontaneous HPRT-deficient cell line with an insertional mutation of 203 bp in the third exon of the HPRT gene. The insert is highly homologous to the B2 mouse repetitive element and has all the expected retroposon characteristics, thus providing an example of gene inactivation by retroposon insertion. This clone exhibited stable 6-TG resistance and high germ-line transmission frequency. Thus E14.1TG3B1 is a useful ES cell line for modifying the mouse genome using the HPRT gene as a selection marker and for transmission at a high frequency into the mouse germ line. The second approach resulted in a 55-kb deletion of the mouse HPRT locus, demonstrating the feasibility of replacement-targeting vectors to generate large genomic DNA deletions.

Animals↗

The cataract Shionogi mouse, a sister strain of the non-obese diabetic mouse: similar class II but different class I gene products.

We have studied with a series of monoclonal antibodies and restriction fragment analysis the K, D, and class II region of the major histocompatibility complex of the non-obese diabetic mouse in comparison with its sister strains, the non-obese non-diabetic and cataract Shionogi mouse. (1) K region: Monoclonal antibody 31-3-4S (anti-Kd) reacted with splenocytes from non-obese diabetic mice while other anti-K (Kb, Kk, Kq) monoclonals did not react. Splenocytes from non-obese non-diabetic mice reacted with both anti-Kb and Kk monoclonals while splenocytes from cataract Shionogi mice reacted with anti-Kd and Kk monoclonals. Both sister strains, therefore, differ from the non-obese diabetic and other known mice strains by monoclonal analysis of H-2K. (2) D region: Splenocytes from both non-obese diabetic and non-obese non-diabetic mice reacted with monoclonal antibody 28-14-8S (anti-Db) while splenocytes from cataract Shionogi mice did not react with any anti-D monoclonal antibody tested. (3a) Class II region (non-obese diabetic and non-obese non-diabetic mice): Three of 11 monoclonal antibodies to class II molecules reacted with splenocytes of the non-obese diabetic mouse. The 3 reacting monoclonals have I-Ak primary specificities though additional anti-I-Ak monoclonal antibodies were negative. Among these monoclonals, 39B and 40A reacted with the non-obese diabetic mouse but not with the non-obese non-diabetic mouse, while 10-2-16 reacted with non-obese diabetic, non-obese non-diabetic and cataract Shionogi mice. Monoclonal MKD6 (anti-I-Ad) reacted with non-obese non-diabetic but not non-obese diabetic mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗