Localization of the osteocalcin gene cluster on mouse chromosome 3.
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Animals↗
Biomedical subjects
M F Seldin
Publications and source records attributed to M F Seldin.
The gene for the homeodomain-containing protein Cart-1 is expressed in cells that have a chondrogenic potential during embryonic development.
We have examined the expression of the gene for Cart-1, a new homeodomain-containing protein, during rat embryonic development. In early embryos, Cart-1 RNA was detected at high levels in head mesenchyme, lateral mesoderm, sclerotomes and limb bud mesenchyme. These tissues contain prechondrocytic mesenchymal cells responsible for the formation of the cartilaginous skeleton. In addition, Cart-1 RNA was also found in lung buds, tendons and mesonephros. Cells in these tissues have the potential of undergoing chondrogenesis either in explants for mesonephros and tendons, or in vivo for tendons and the precursors of bronchi cartilages. No hybridization was observed in brain, spinal cord, heart, spleen, gastrointestinal tract, liver and muscle. Our results support the hypothesis that Cart-1 may play a role in the pathway of chondrogenesis. The gene for Cart-1 was mapped to a segment of mouse chromosome 10 between the genes for phenylalanine hydroxylase and interferon gamma.
Animals↗
Glycine receptor beta-subunit gene mutation in spastic mouse associated with LINE-1 element insertion.
Congenital myoclonus is a widespread neurologic disorder characterized by hyperexcitability, muscular spasticity and myoclonus associated with marked reduction in neural glycine binding sites. The recessive mouse mutation spastic (spa) is a prototype of inherited myoclonus. Here we show that defects in the gene encoding the beta-subunit of the glycine receptor (Glrb) underlie spa: Glrb maps to the same region of mouse chromosome 3 as spa, and Glrb mRNA is markedly reduced throughout brains of spa mice, most likely as a result of an insertional mutation of a 7.1 kilobase LINE-1 element within intron 6 of Glrb. These results provide evidence that Glrb is necessary for postsynaptic expression of glycine receptor complexes, and suggest Glrb as a candidate gene for inherited myoclonus in other species.
Amino Acid Sequence↗
Characterization of an atypical member of the Na+/Cl(-)-dependent transporter family: chromosomal localization and distribution in GABAergic and glutamatergic neurons in the rat brain.
A 3.7-kb cDNA fragment, designated rat-XT1, was isolated from a rat whole-brain cDNA library. The nucleotide sequence of XT1 codes for a 727 amino acid protein with a calculated molecular mass of 81,139 Da and 12 putative transmembrane domains. This protein shares significant homology (28-32%) with the monoamine- (dopamine, norepinephrine, serotonin), amino acid- (taurine, proline, GABA, glycine), choline-, and betaine-, Na+/Cl(-)-dependent transporters. The homology is especially high within the first, second, sixth, and eighth transmembrane domains (45-75%). Thus, XT1 clearly belongs to the Na+/Cl(-)-dependent neurotransmitter transporter superfamily. However, XT1 may define a new subfamily of transporter because it differs structurally from other members of this family in that the extracellular loop linking transmembrane domains 7 and 8 and the C-terminal tail are significantly larger in size. Transient or stable expression of rat-XT1 failed to confer to the transfected cells the ability to transport actively any of the > 60 established or putative neurotransmitter substances assessed. Northern blot analyses of peripheral and neural tissues demonstrated that expression of the 8-kb XT1 mRNA is essentially restricted to the nervous system. In situ hybridization demonstrated a broad but discrete localization of XT1 message in the CNS, particularly in the cerebellum (Purkinje and granular cell layers), the hippocampus (pyramidal and granular cell layers), and the thalamus and throughout the cerebral cortex. This distribution parallels that of the neurotransmitters glutamate and aspartate; however, neither of these excitatory amino acids is a substrate for transport. One noticeable exception to the codistribution of the mRNA for rat-XT1 and these excitatory neurotransmitters is the cerebellar Purkinje cell layer, in which GABAergic neurons are localized. The gene encoding for XT1 is localized to the mouse chromosome 3 in the vicinity of the locus for the mouse neurological disorder spastic (spa).
Amino Acid Sequence↗
Myocyte nuclear factor, a novel winged-helix transcription factor under both developmental and neural regulation in striated myocytes.
A sequence motif (CCAC box) within an upstream enhancer region of the human myoglobin gene is essential for transcriptional activity in both cardiac and skeletal muscle. A cDNA clone, myocyte nuclear factor (MNF), was isolated from a murine expression library on the basis of sequence-specific binding to the myoglobin CCAC box motif and was found to encode a novel member of the winged-helix or HNF-3/fork head family of transcription factors. Probes based on this sequence identify two mRNA species that are upregulated during myocyte differentiation, and antibodies raised against recombinant MNF identify proteins of approximately 90, 68, and 65 kDa whose expression is regulated following differentiation of myogenic cells in culture. In addition, the 90-kDa form of MNF is phosphorylated and is upregulated in intact muscles subjected to chronic motor nerve stimulation, a potent stimulus to myoglobin gene regulation. Amino acid residues 280 to 389 of MNF demonstrate 35 to 89% sequence identity to the winged-helix domain from other known members of this family, but MNF is otherwise divergent. A proline-rich amino-terminal region (residues 1 to 206) of MNF functions as a transcriptional activation domain. These studies provide the first evidence that members of the winged-helix family of transcription factors have a role in myogenic differentiation and in remodeling processes of adult muscles that occur in response to physiological stimuli.
Amino Acid Sequence↗
Glycogen synthase: a putative locus for diet-induced hyperglycemia.
Inbred mouse strains fed a diabetogenic diet have different propensities to develop features analogous to type 2 diabetes mellitus. To define chromosomal locations that control these characteristics, recombinant inbred strains from diabetes-prone C57BL/6J (B/6J) and diabetes-resistant A/J strains were studied. Insulin levels and hyperglycemia correlated with two different regions of mouse chromosome 7 (two point LOD scores > 3.0). For insulin levels, 15 of 16 recombinant inbred strains were concordant with a region that contains the tubby mutation that results in hyperinsulinemia. For hyperglycemia, 19 of 23 strains were concordant with the D7Mit25 marker and 20 of 23 strains with the Gpi-1 locus on proximal mouse chromosome 7. Using more stringent criteria for hyperglycemia, 10 of 11 strains characterized as A/J or B/6J like were concordant with D7Mit25. This putative susceptibility locus is consistent with that of the glycogen synthase gene (Gys) recently suggested as a candidate locus by analyses of type 2 diabetes patients. Fractional glycogen synthase activity in isolated muscle was significantly lower in normal B/6J diabetic-prone mice compared with normal diabetic-resistant A/J mice, a finding similar to that reported in relatives of human patients with type 2 diabetes. These data, taken together, raise the possibility that defects in the Gys gene may in part be responsible for the propensity to develop type 2 diabetes.
Animals↗
Products, genetic linkage and limb patterning activity of a murine hedgehog gene.
The hedgehog (hh) segmentation gene of Drosophila melanogaster encodes a secreted signaling protein that functions in the patterning of larval and adult structures. Using low stringency hybridization and degenerate PCR primers, we have isolated complete or partial hh-like sequences from a range of invertebrate species including other insects, leech and sea urchin. We have also isolated three mouse and two human DNA fragments encoding distinct hh-like sequences. Our studies have focused upon Hhg-1, a mouse gene encoding a protein with 46% amino acid identity to hh. The Hhg-1 gene, which corresponds to the previously described vhh-1 or sonic class, is expressed in the notochord, ventral neural tube, lung bud, hindgut and posterior margin of the limb bud in developing mouse embryos. By segregation analysis the Hhg-1 gene has been localized to a region in proximal chromosome 5, where two mutations affecting mouse limb development previously have been mapped. In Drosophila embryos, ubiquitous expression of the Hhg-1 gene yields effects upon gene expression and cuticle pattern similar to those observed for the Drosophila hh gene. We also find that cultured quail cells transfected with a Hhg-1 expression construct can induce digit duplications when grafted to anterior or mid-distal but not posterior borders within the developing chick limb; more proximal limb element duplications are induced exclusively by mid-distal grafts. Both in transgenic Drosophila embryos and in transfected quail cells, the Hhg-1 protein product is cleaved to yield two stable fragments from a single larger precursor. The significance of Hhg-1 genetic linkage, patterning activity and proteolytic processing in Drosophila and chick embryos is discussed.
Animals↗
Identification of OX40 ligand and preliminary characterization of its activities on OX40 receptor.
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Amino Acid Sequence↗
Cloning, pharmacological characterization, and genomic localization of the human creatine transporter.
The complete coding sequence from a human creatine transporter cDNA was isolated from a kidney library. This transporter is a member of a superfamily of proteins which includes the family of Na(+)- and Cl(-)-dependent transporters responsible for the uptake of certain neurotransmitters (e.g. dopamine, GABA, serotonin, and norepinephrine), and amino acids (e.g. glycine). Within this family, the human creatine transporter is strongly related to a subfamily of sequences which includes the transporters for taurine, GABA, and betaine, and this cDNA is approximately 98% amino acid identical to sequences that have been reported from rat and rabbit as choline and creatine transporters respectively. Pharmacological characterization demonstrated that the protein product of this cDNA mediated high affinity (Km = 77 +/- 6 microM) creatine uptake, which was blocked by creatine analogs with high affinity. There was no specific transport of choline. Northern analysis demonstrated highest levels of mRNA expression in human skeletal muscle, kidney, and heart, with lower levels in brain and other tissues. Expression within the kidney was evenly distributed between cortex and medulla. Genetic mapping in the mouse localizes the creatine transporter to a region on the X chromosome in linkage conservation with the human region Xq28, the location of the genes for several neuromuscular diseases.
Amino Acid Sequence↗
Report and abstracts of the First International Workshop on Human Chromosome 1 Mapping 1994. Bethesda, Maryland, March 25-27, 1994.
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Chromosome Mapping↗
Cloning of the human glycine transporter type 1: molecular and pharmacological characterization of novel isoform variants and chromosomal localization of the gene in the human and mouse genomes.
We report the molecular cloning of a cDNA encoding a high affinity human glycine transporter. An open reading frame of 1914 nucleotides encodes a 638-amino acid protein that transports glycine in a Na+/Cl(-)-dependent manner. In common with other Na+/Cl(-)-dependent transporters, it possesses 12 putative transmembrane domains, according to its hydropathicity profile. This protein is the human homologue of a glycine transporter previously isolated from rat [glycine transporter type 1b (GlyT-1b)]. In addition to the human GlyT-1b, we also characterized a novel functional isoform produced by alternative splicing. This isoform, GlyT-1c, which is distinct from GlyT-2 recently characterized in rat, contains an additional exon encoding 54 amino acids in the amino-terminal part of GlyT-1b and is mainly expressed in brain. These two isoforms are products of the same gene and are localized on human chromosome 1p31.3, as well as on mouse chromosome 4, close to the locus for the spontaneous mouse neuromuscular mutation clasper. When expressed in COS-7 cells, both the human GlyT-1b and GlyT-1c display a time- and dose-dependent uptake of glycine, which is abolished when either Na+ or Cl- is substituted with other ions. For both GlyT-1b and GlyT-1c the affinities for glycine are similar, with Km values of 70-90 microM, and this uptake is inhibited by sarcosine with similar potencies. In addition to the three transporter isoforms present in the human genome, i.e., GlyT-1a, GlyT-1b, and GlyT-1c, point-mutated variants, which appear to be totally devoid of glycine uptake activity when expressed in COS-7 cells, were obtained by polymerase chain reaction amplification of mRNA from human substantia nigra. These variants point to regions of the glycine transporter that might be important in the processing or transport function of this protein.
Amino Acid Sequence↗
A glial-specific voltage-sensitive Na channel gene maps close to clustered genes for neuronal isoforms on mouse chromosome 2.
A variety of glial cell types express saxitoxin (STX)-binding voltage-sensitive Na channels (1,2), although the possible role of impulse conduction in these cells is not understood. Gautron et al. (1992) recently identified a 7.5 kb species of mRNA in type 1 astrocytes cultured from rat brain cerebrum that hybridized with a "common" Na channel probe but not with brain isoform-specific cDNA probes. Sequence data from cloned cDNAs demonstrate that it encodes a structurally atypical Na channel isoform. We have prepared a cDNA probe specific for a portion of subunit domain IV of the glial channel and mapped the location of the corresponding gene (Scn7a) to mouse chromosome 2. The Scn7a gene mapped 0.9 (+/- 0.9) cM distal to the Gcg locus; the location of the corresponding human gene (SCN7A) is predicted to be in the q36-q37 region of chromosome 2. This site lies just outside a cluster of genes for the brain-specific Na channel isoforms RI, RII and RIII which map proximal to Gcg (17). The presence of at least four genes from two distinct Na channel subfamilies suggests that multiple genetic defects for central and peripheral nervous system disorders ultimately may be linked to this area.
Animals↗
The heat stable antigen (mouse CD24) gene is differentially regulated but has a housekeeping promoter.
Expression of the mouse heat stable antigen (HSA or mouse CD24) shows tissue-specific as well as developmental regulation. During the maturation of several hematopoietic lineages, HSA expression is generally high in immature precursor cells and low or absent in terminally differentiated cells. We present evidence suggesting that this regulation of the HSA gene (Cd24a) occurs at the transcriptional level. In addition, sequence and methylation analysis of the Cd24a promoter revealed characteristics of both "housekeeping" and tissue-specific promoters, including a methylation-free, HpaII tiny fragment (HTF) island, multiple putative SP1 and AP-2 consensus binding sites, and a TATA box. Functional analysis of a 0.6-kilobase DNA fragment containing these elements fused to the CAT reporter gene in transient transfection experiments showed activity in both HSA expressing and non-expressing cell lines with a strength similar to that of the herpes-simplex virus-thymidine kinase promoter. Large fragments from the flanking region of the Cd24a promoter did not influence the ubiquitous nature of this promoter. Finally, we mapped the Cd24a, Cd24b, and Cd24c genes to mouse chromosomes 10, 8, and 14 respectively.
Animals↗
A single B1 subunit mapped to mouse chromosome 7 may be a common component of Na channel isoforms from brain, skeletal muscle and heart.
A beta 1 subunit associated with one or more isoforms of brain voltage-sensitive Na channels has previously been cloned, sequenced and expressed. Northern and Western blot analyses have suggested that homologues to this protein are expressed in skeletal muscle and heart. Here, reverse transcriptase-polymerase chain reaction (RT-PCR)/cloning reveals that transcripts encoding identical beta 1 subunit ORFs are expressed in adult rat brain, skeletal muscle and heart. Heterologous co-expression of beta 1 with brain (RIIA) and skeletal muscle (mu 1) alpha subunits caused a stabilization of normal, rapidly inactivating (mode 1) gating relative to anomalous, non-inactivating (mode 2) states and a negative shift in steady state inactivation. Chromosome mapping of the beta 1 subunit showed a single locus (Scn1b) in mouse chromosome 7 1.8 cM (+/- 1.2 cM) distal to D19F11S1h and 0.9 cM (+/- 0.9 cM) proximal to Pkca. This locus is in the region of the mouse mutant "quivering," characterized by a variety of neurological disorders and muscle paralysis. A mutation in a single beta 1 subunit forming functional complexes with multiple Na channel isoforms could underlie these deficits.
Animals↗
Nucleotide sequence, expression, and chromosomal mapping of Mrp and mapping of five related sequences.
We isolated and characterized a genomic clone for the mouse MARCKS-related protein, or MRP, also known as F52 and MacMARCKS. A 3699-bp plasmid contained 407 bp of 5'-flanking region, 186 bp of 5'-untranslated region, 600 bp of protein coding region, 784 bp of a single intron, 746 bp of 3'-untranslated region, and 976 bp of 3'-flanking region. The position of the single intron was identical to the intron position in all known MARCKS mRNAs. When the plasmid containing the genomic sequences was transfected into fibroblasts lacking endogenous Mrp expression, the 407 bp of promoter conferred high-level expression of the full-length, spliced mRNA. The putative promoter was therefore functional; however, despite tissue-specific regulation and transcriptional induction in some cells in a manner similar to that seen with MARCKS expression, the promoters were highly dissimilar at the level of primary sequence (37% identity over 407 bp). Mrp mapped to a position on mouse chromosome 4 that was closely linked to the Lck locus. Numerous additional species that hybridized to the MRP cDNA were noted on Southern blotting of mouse genomic DNA. Five related loci were labeled Mrp-rs1 through Mrp-rs5 (for Mrp-related sequences) and were mapped to mouse chromosomes 10, 17, 15, 13, and X, respectively. Three of these related sequences have been cloned, and all appear to represent pseudogenes.
3T3 Cells↗
Physical and linkage mapping of the human and murine genes for the alpha 1 chain of type IX collagen (COL9A1).
Type IX collagen, a member of the FACIT family of extracellular matrix proteins, is a heterotrimer composed of three genetically distinct alpha chains. The cDNAs for the human and mouse alpha 1 (IX) chains have been cloned. In this paper we confirm the mapping of the human COL9A1 gene to chromosome 6q12-q13 by fluorescence in situ hybridization utilizing two genomic clones which also contain short tandem repeat polymorphisms. We also report the characterization of these repeats and their incorporation into the chromosome 6 linkage map. The COL9A1 locus shows no recombination with the marker D6Z1 (Z = 27.61 at theta = O) and identifies the most likely locus order of KRAS1P-[D6Z1-COL9A1]-D6S30. In addition, using an interspecific backcross panel, we have mapped murine Col9a1 to mouse chromosome 1. Together with other comparative mapping results, these data suggest that the pericentric region of human chromosome 6 is homologous to the most proximal segment of mouse chromosome 1. These data may facilitate linkage studies with COL9A1 (or Col9a1) as a candidate gene for hereditary chondrodysplasias and osteoarthritis.
Alleles↗