Cloning and functional characterization of a family of receptors for the melanotropic peptides.
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Adrenocorticotropic Hormone↗
Biomedical subjects
K R Johnson
Publications and source records attributed to K R Johnson.
A closely linked complex of mouse mast cell-specific chymase genes on chromosome 14.
Mouse mast cells differentially express at least four chymases (mouse mast cell protease (mMCP) 1, mMCP-2, mMCP-4, and mMCP-5), a tryptase (mMCP-6), and an exopeptidase (mouse mast cell carboxypeptidase A (mMC-CPA)). The previously uncharacterized 2.5-kilobase mMCP-2 gene was isolated and found to consist of 5 exons. The 5'-flanking region of this gene is 89, 93, and 42% similar to that of the mMCP-1, mMCP-4, and mMCP-5 genes, respectively. Inheritance patterns of restriction-enzyme fragment length polymorphisms of these six mast cell protease genes in recombinant inbred mouse strains and interspecific backcrosses were used to determine their chromosomal locations. The mMCP-6 and mMC-CPA genes are located on chromosomes 17 and 3, respectively, whereas the four mast cell chymase genes all reside on chromosome 14 linked to a gene complex that encodes four cytotoxic T lymphocyte granzymes. Pulsed-field gel electrophoresis of genomic DNA digests demonstrated that the mMCP-1, mMCP-2, and mMCP-5 genes are within 850 kilobases of each other. Although clustering of the serine protease genes on chromosome 14 may be important at a higher level of genomic organization, the ability to independently induce or suppress the steady-state levels of the four chymase transcripts by treatment of mast cells with cytokines suggests that gene clustering is not the most critical factor for coordinate expression of these proteases. Because of the unique features of their tertiary structures, the substrate specificities of the serine proteases encoded by genes at the chromosome 14 complex are predicted to be more limited than those of pancreatic chymotrypsin and pancreatic trypsin, whose genes reside on chromosomes 8 and 6, respectively. Based on present day genomic distribution and sequence similarities, we propose that a primordial gene that encoded a serine protease with restricted substrate specificity underwent extensive duplication and divergence to form a family of cytokine-regulated transcripts from genes on chromosome 14.
Amino Acid Sequence↗
Pigmentation phenotypes of variant extension locus alleles result from point mutations that alter MSH receptor function.
Coat colors in the chestnut horse, the yellow Labrador retriever, the red fox, and one type of yellow mouse are due to recessive alleles at the extension locus. Similarly, dominant alleles at this locus are often responsible for dark coat colors in mammals, such as the melanic form of the leopard, Panthera pardus. We show here that the murine extension locus encodes the melanocyte-stimulating hormone (MSH) receptor. In mice, the recessive yellow allele (e) results from a frameshift that produces a prematurely terminated, nonfunctioning receptor. The sombre (Eso and Eso-3J) and tobacco darkening (Etob) alleles, which both have dominant melanizing effects, results from point mutations that produce hyperactive MSH receptors. The Eso-3J receptor is constitutively activated, while the Etob receptor remains hormone responsive and produces a greater activation of its effector, adenylyl cyclase, than does the wild-type allele.
Alleles↗
Characterization of cDNA clones encoding the human homologue of Saccharomyces cerevisiae ribosomal protein L30.
We have isolated cDNA clones encoding the human homologue (hL30) of yeast ribosomal protein (r-protein) L30. The hL30 nucleotide (nt) sequence shows high homology to the yeast sequences and also to a partial Xenopus laevis sequence previously identified as an immunoglobulin heavy chain. The 5' end of hL30 is pyrimidine-rich, as is the case for most other mammalian r-protein mRNAs. The open reading frame consists of 157 codons with a C-terminal region that is different from corresponding regions of the yeast proteins. In several human tissue culture cells, the mRNA encoding hL30 is approx. 700 nt in length.
Amino Acid Sequence↗
P- and E-cadherin are in separate complexes in cells expressing both cadherins.
E- and P-cadherin are members of a family of calcium-dependent, cell surface glycoproteins involved in cell-cell adhesion. Extracellularly, the transmembrane cadherins self-associate, while intracellularly, they interact with the actin-based cytoskeleton. Several intracellular proteins, collectively termed catenins, are tightly associated with E- and P-cadherin. These proteins appear to link the cadherin to the cytoskeleton and have been proposed to be involved in concentrating cadherins at cell-cell adherens junctions. In this paper we report the production of monoclonal antibodies against both alpha- and beta-catenin and use these antibodies to show that in cells simultaneously expressing two different cadherins, E-cadherin and P-cadherin, each cadherin appears to be present in a separate cadherin/catenin complex.
Antibodies, Monoclonal↗
Rhabdomyosarcoma-derived cell lines exhibit aberrant expression of the cell-cell adhesion molecules N-CAM, N-cadherin, and cadherin-associated proteins.
Many cancer cells show aberrant adhesion properties that likely contribute to tumorigenesis, invasion, and metastasis. Here, we examine three MyoD-expressing, rhabdomyosarcoma-derived human cell lines (RD, A-204, and HS 729) for their expression of the neural cell adhesion molecule (N-CAM), N-cadherin, and the cadherin-associated proteins, alpha-catenin, beta-catenin, and plakoglobin, using specific antibodies and immunoblotting and immunocytochemical methods. Normally, during the formation of skeletal muscle, both N-CAM and N-cadherin are expressed and participate in mediating myoblast adhesion accompanying cell fusion. RD cells express N-CAM, N-cadherin, and the cadherin-associated proteins; however, N-CAM is expressed as a highly sialylated isoform that functions poorly in promoting Ca(2+)-independent cell aggregation. HS 729 cells express N-cadherin and its associated intracellular proteins but have no detectable N-CAM. A-204 cells express no detectable N-CAM or N-cadherin but do express cadherin-associated proteins. Thus, all three rhabdomyosarcoma cell lines exhibit some abnormality in the expression of adhesion molecules known to participate in skeletal myogenesis; however, no common defect was observed that might be considered as a characteristic marker for rhabdomyosarcomas.
Cadherins↗
Identification and genetic mapping of the murine gene and 20 related sequences encoding chromosomal protein HMG-17.
HMG-17 is an abundant, nonhistone chromosomal protein that binds preferentially to nucleosomal core particles of mammalian chromatin. The human gene for HMG-17 has been localized to Chromosome (Chr) 1p, but the murine gene has not been previously mapped. Here we identify the murine functional gene, Hmg17, from among more than 25 related sequences (probably processed pseudogenes) and show that it is located on mouse Chr 4, in a region known to have conserved linkage relationships with human Chr 1p. We also report the map locations of 20 additional Hmg17-related sequences on mouse Chrs 1, 2, 3, 5, 7, 8, 9, 13, 15, 16, 17, 18, and X. The multiple, dispersed members of the Hmg17 multigene family can be detected efficiently with a single cDNA probe and provide useful markers for genetic mapping studies in mice.
Animals↗
3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL): cloning and characterization of a mouse liver HL cDNA and subchromosomal mapping of the human and mouse HL genes.
3-Hydroxy-3-methylglutaryl coenzyme A lyase (HL) is a homodimeric mitochondrial matrix enzyme that catalyzes the last step of ketogenesis. Using a human HL cDNA as a probe, we isolated a 1.4-kb mouse HL cDNA (HLM) from a mouse liver library and extended the sequence in the 5' direction, using RACE PCR to include the complete coding sequence. The nucleotide sequence of the mouse HL coding region is 85.7% identical to human HL, and 52.6% to Ps. mevalonii HL. Peptide identities of 87.4% and 54.3% respectively were observed. Southern analysis of 29 strains of laboratory mice and of Mus spretus revealed a total of about 25 kb of hybridizing fragments and three polymorphic fragments in both EcoRI and Hin-dIII digestions. The mouse HL locus (Hmgcl) was localized on Chromosome (Chr) 4: Pmv-19-12.6 +/- 3.6 cM-Hmgcl-7.3 +/- 2.3 cM-Xmv-8-1.5 +/- 1.0 cM-Gpd-1. The human HL locus (HMGCL) was mapped to distal Chr 1p by analysis of a human-hamster hybrid cell panel and by in situ hybridization.
Amino Acid Sequence↗
Encyclopedia of the mouse genome III. October 1993. Mouse chromosome 18.
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Animals↗
Genetic mapping of variable length rDNA segments to centromeric regions of mouse chromosomes 11, 12, 15, 16, and 18.
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Animals↗
Modelling relative masseter force from surface electromyograms during mastication in non-human primates.
The purpose was to analyse the relation between masseter electromyograms (EMGs) and relative masseter force during the power stroke of mastication. The electromyographic activity of the masseter was characterized by recording from bipolar surface electrodes placed over the superficial portion of the muscle; relative masseter force was estimated by characterizing surface bone strain along the lateral aspect of the zygomatic arch. The subjects were six adult macaques and one adult baboon. Masseter EMGs were quantified by r.m.s. analysis of the raw digitized EMG. The length of the time interval (the time constant) during which the r.m.s. values were calculated was repeatedly altered so as to determine which time constant was optimal for producing an EMG-derived waveform that best mimicked relative masseter force during the near-isometric phase of muscle contraction. The data indicate that between subjects this time constant varied from 35 to 72 ms, with an overall median of 42 ms and a grand mean of 49 ms. The use of a 42-ms time constant for all of the subjects resulted in an average latency between the masseter EMG waveform and relative masseter force of about 30 ms during the latter portion of the power stroke of mastication. This analysis provides, as a first approximation, an empirical basis for modelling relative jaw-muscle force using surface EMGs recorded during that portion of the power stroke of mastication when the jaw-closing muscles are contracting under near isometric conditions.
Animals↗
Muscle force recruitment and biomechanical modeling: an analysis of masseter muscle function during mastication in Macaca fascicularis.
The main purpose of this study is to test the hypothesis that as subjects chew with increasing levels of force, the ratio of the working- to balancing-side jaw-muscle force (W/B) decreases and begins to approach 1.0. We did this by analyzing relative masseter force in Macaca fascicularis using both strain gage and surface electromyographic (EMG) techniques. In addition, we also analyzed: 1) the relationship between jaw position using cineradiographic techniques and relative masseter force, 2) the timing differences between relative masseter force from the working and balancing sides, and 3) the loading and unloading characteristics of the masseter muscle. Our findings indicate that when macaques increase the amount of overall masticatory force during chewing, the W/B ratio for masseter force frequently (but not always) decreases and begins to approach 1.0. Therefore, our working hypothesis is not completely supported because the W/B ratio does not decrease with increasing levels of force in all subjects. The data also demonstrate timing differences in masseter force. During apple-skin mastication, the average peak masseter force on the working side occurs immediately at or slightly after the initial occurrence of maximum intercuspation, whereas the average peak masseter force on the balancing side occurs well before maximum intercuspation. On average, we found that peak force from the balancing-side masseter precedes the working-side masseter by about 26 msec. The greater the asynchrony between working- and balancing-side masseter force, the greater the difference in the relative magnitude of these forces. For example, in the subject with the greatest asynchrony, the balancing-side masseter had already fallen to about one-half of peak force when the working-side masseter reached peak force. Our data also indicate that the loading and unloading characteristics of the masseter differ between the working and balancing sides. Loading (from 50 to 100% of peak force) and unloading (from 100 to 50% of peak force) for the balancing-side masseter tends to be rather symmetrical. In contrast, the working-side masseter takes much longer to load from 50 to 100% of peak force than it does to unload from 100 to 50% of peak force. Finally, it takes on average about 35 msec for the working-side zygoma and 42 msec for the balancing-side zygoma to unload from 100 to 50% of peak force during apple-skin mastication, indicating that the unloading characteristics of the macaque masseter during mastication closely approximates its relaxation characteristics (as determined by muscle stimulation).
Animals↗
Influence of teeth, alveoli, and periodontal ligaments on torsional rigidity in human mandibles.
We investigated the influence of teeth, periodontal ligaments, and alveoli on the structural integrity of human mandibles loaded in torsion. Surface bone strain was recorded from the mandibular corpus below the first molar on each of four specimens. These specimens were loaded by an external force that caused primarily torsion about the long axis of the corpus, and bone strain was recorded under the following conditions: 1) all supporting structures intact, 2) all supporting structures intact and the M1 loaded by a simulated bite force, 3) M1 removed and 4) alveolar bone of the M1 removed. For comparative purposes, experiments were also designed to investigate the effects of intermittent holes on the torsional rigidity of a baboon femur. This permitted comparison of the mechanical behavior of the mandibles with that of a more homogeneous bony member. These experiments suggest that the presence of teeth within alveoli has a measurable role in the maintenance of torsional rigidity. The condition of the periodontal ligament also appears to influence these stress-bearing capabilities. Moreover, the alveolar bone supporting the teeth also provides structural support for countering torsional loads. For the specific case of corpus twisting, the mandible does not behave as a member with open or closed sections as predicted by theoretical models. The observed magnitudes of bone strain, however, conform more closely to the predictions generated by a closed-section model.
Adult↗
Genetic mapping of the murine gene and 14 related sequences encoding chromosomal protein HMG-14.
The high-mobility-group chromosomal protein HMG-14 preferentially binds to nucleosomal core particles of mammalian chromatin and may modulate the chromatin configuration of transcriptionally active genes. The human gene for HMG-14 has been localized to the Down syndrome region of Chromosome (Chr) 21 and may be involved in the etiology of this syndrome. Here we show, by means of genetic linkage analysis of interspecific and intersubspecific backcross mice, that the murine functional gene, Hmg14, is located on the distal end of mouse Chr 16, a region known to have conserved synteny with human Chr 21. In addition to the functional gene for HMG-14, both human and mouse genomes contain many related sequences that are probably processed pseudogenes. Here we map the locations of 14 Hmg14-related sequences in two mouse genomes. The 14 mapped loci are widely dispersed on ten chromosomes (Chrs 3, 5, 7, 9, 11, 12, 16, 17, 19, and X) and can be detected efficiently with a single cDNA probe. Thus, the Hmg14 multigene family is well suited to serve as genetic markers for other linkage studies in mice.
Animals↗
Characterization of cDNA clones for the alpha subunit of pyruvate dehydrogenase from Ascaris suum.
The pyruvate dehydrogenase complex of the adult parasitic nematode Ascaris suum functions in the reducing environment present in their anaerobic mitochondria. These organelles use fumarate and enoyl CoAs as terminal electron acceptors instead of oxygen. A lambda gt11 cDNA library was constructed from RNA isolated from adult ascarid muscle. Partial clones for the pyruvate dehydrogenase alpha subunit were isolated by screening the lambda gt11 library with a specific antiserum. Full-length clones (type I) were identified in a cDNA library prepared from RNA isolated from early embryos. During the hybridization screening, a second type of cDNA clone (type II) was identified. The nucleotide sequences of both clones are presented. The predicted amino acid sequences of the mature proteins are 91% identical to one another and about 55% identical to the predicted sequences of the alpha subunit of human pyruvate dehydrogenase. Northern blots were used to examine the expression of both mRNAs in various larval stages and in tissues of the adult. Type I sequences are found mainly in adult muscle. Type II sequences are abundant in third-stage larvae as well as in adult muscle.
Amino Acid Sequence↗
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.
Animals↗
Chromosomal localization of the murine gene and two related sequences encoding high-mobility-group I and Y proteins.
HMG-I and its isoform HMG-Y are members of the abundant high-mobility-group of nonhistone chromatin proteins; they bind to A + T-rich regions of chromosomal DNA and are expressed at high levels in rapidly dividing, undifferentiated mammalian cells. HMG-I and HMG-Y are alternatively spliced products of a single functional gene, designated Hmgi in the mouse. Here, we report the occurrence of at least three distinct Hmgi-related loci in the mouse. Only one of these loci was present in all of the 10 mouse strains examined; therefore, this locus most likely represents the transcriptionally active, functional gene, Hmgi. Genetic linkage analysis of interspecific and intersubspecific backcrosses showed that Hmgi is located in the t-complex region of mouse Chromosome 17. Two additional Hmgi-related sequences, Hmgi-rs1 and Hmgi-rs2, were found only in certain mouse strains and probably represent pseudogenes. Hmgi-rs1 is located on Chromosome 11; it was present in all of the standard laboratory inbred mouse strains examined but was absent in wild-derived inbred strains of Mus spretus, M. musculus castaneus, and M. m. molossinus. Hmgi-rs2 was found only in M. m. castaneus and is located on Chromosome 6. Hmgi genes have not been previously mapped in any species, but the location of the probable functional gene on murine Chromosome 17 suggests that the homologous gene in humans is located on Chromosome 6.
Animals↗