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Biomedical subjects

D J Gilbert

Publications and source records attributed to D J Gilbert.

At least 217 records · Page 12Linked to original sources

Localization of new genes and markers to the distal part of the human major histocompatibility complex (MHC) region and comparison with the mouse: new insights into the evolution of mammalian genomes.

We have refined and extended the map of the distal half of the human major histocompatibility complex. The map is continuous from HLA-E to 1000 kb telomeric of HLA-F and includes six new markers and genes. In addition, the corresponding sequences that were not previously mapped in the mouse genome have been located. The human and the mouse organizations have therefore been compared. This comparison allows us to demonstrate that the structure of the distal part of the MHC is similar in the two species. In addition, this comparison shows the presence of a breakpoint of synteny telomeric of the distal part of the H-2 region. Indeed, the region telomeric of HLA in human is found on a chromosome different from that carrying H-2 in mouse. The mapping analysis of paralogous genes (structurally related genes) around the breakpoint shows that the human organization probably represents the putative human/mouse ancestral one. This evolutionary breakpoint was precisely mapped in human, and the surrounding region was cloned into yeast artificial chromosomes. Finally, we show that the region found around the breakpoint was involved several times in chromosome recombinations in the mouse lineage, as it seems to correspond also to the t-complex distal inversion point.

Animals↗

Chromosomal assignment and genomic structure of Il15.

Interleukin-15 (IL-15) is a novel cytokine whose effects on T-cell activation and proliferation are similar to those of interleukin-2 (IL-2), presumably because IL-15 utilizes the beta and gamma chains of the IL-2 receptor. Murine IL-15 cDNA and genomic clones were isolated and characterized. The murine Il15 gene was found to consist of eight exons spanning at least 34 kb and was localized to the central region of mouse chromosome 8 by interspecific backcross analysis. Intron positions in a partial human IL15 genomic clone were identical with positions of corresponding introns in the murine gene. The human IL15 gene was mapped to human chromosome 4q31 by fluorescence in situ hybridization.

Amino Acid Sequence↗

The beta crystallin genes on human chromosome 22 define a new region of homology with mouse chromosome 5.

The human beta crystallin genes CRYBB2, CRYBB2P1, CRYBB3, and CRYBA4 are located in 22q11.2. Using interspecific backcross analysis, we mapped the mouse homologues of CRYBB2, CRYBB3, and CRYBA4 (i.e., Crybb2, Crybb3, and Cryba4) to the central region of mouse chromosome 5. The homologue of human CRYBB2P1 is absent in mouse. These assignments define a new region of homology in human and mouse.

Animals↗

Genomic organization and chromosomal location of the mouse type I BMP-2/4 receptor.

We have characterized the structure of a mouse bone morphogenetic protein (BMP) type I receptor gene that can bind both BMP-2 and BMP-4. The mouse BMP-2/4 receptor gene is encoded by 11 exons and spans approximately 38-kb. Most of the intron/exon boundaries are not conserved compared to the kinase domain of the related, activin type II receptor. In addition, whereas the activin type II receptor gene contains large introns (> 40 kb), the largest intron of the BMP-2/4 receptor gene is only 6.4-kb. The BMP-2/4 receptor gene (Bmpr) was mapped to mouse chromosome 14. Bmpr is closely linked to Rbp3 in the region containing pugnose, a mutation that alters bone development. Knowledge of the genomic structure of Bmpr provides important information to create Bmpr-deficient mice.

Amino Acid Sequence↗

Gene structure and chromosomal localization of the mouse homologue of rat OX40 protein.

The OX40 protein is expressed only on activated rat CD4+ T blasts and is a member of a superfamily of cell surface molecules which includes CD40, CD30, CD95 (Fas), CD27, 4-1BB antigens and the receptors for tumor necrosis factor (TNF) and nerve growth factor (NGF). The proteins of this group are related to each other by having three to six repeats of a cysteine-rich sequence in their extracellular domains. Members of this family of receptors have also been shown to bind to ligands which are structurally related to TNF. The mouse homologue of the rat OX40 protein was cloned at the cDNA and genomic levels. The gene structure shows that there are several intron/exon borders shared between OX40 and CD27, CD40, TNF receptor type I, CD95 and 4-1BB genes. This group of genes is less closely related structurally to the gene structure of the NGF receptor. The gene encoding murine OX40 has been placed on mouse chromosome 4, in an area which contains the genes for TNF receptor type II and 4-1BB, and is syntenic with a region of human chromosome 1 which contains human TNF receptor type II, OX40, and CD30 genes.

Animals↗

Cloning and analysis of gene regulation of a novel LPS-inducible cDNA.

The expression of many genes is altered upon the activation of macrophages by bacterial LPS. These genes play a crucial role in the orchestration of various responses to protect the host against infection. A novel 2.3 kilobase (kb) cDNA, designated IRG1, was obtained from a cDNA library prepared with RNA isolated from RAW 264.7 following lipopolysaccharide stimulation. Sequence analysis of the clone revealed no identity to any known genes but showed the presence of many potential phosphorylation sites suggesting that IRG1 protein product may be regulated at this level. Furthermore, IRG1 contains the motif for glycosaminoglycan attachment site, implying that IRG1 may be a proteoglycan. By interspecific back-cross analysis, Irg1 was mapped to mouse chromosome 14 linked to Tyrp2 and Rap2a. The IRG1 message appears 1.5 h following LPS exposure and its induction was not dependent on new protein synthesis. In fact, cycloheximide induced the expression of IRG1, suggesting that a protein repressor prevents the expression of IRG1 when uninduced. The role of the protein kinase A pathway in regulating the induction of IRG1 by LPS is questionable, because although forskolin inhibited its induction, neither dibutyrl-cAMP nor 8-(4-chlorophenylthio)-cAMP had much effect on its expression. In contrast, activation of protein kinase C potentiated the LPS response. Chelation of extracellular calcium inhibited IRG1 4 h after LPS induction, while increasing intracellular calcium had little effect on the levels of the IRG1 transcript. Inhibiting tyrosine phosphorylation abrogated the induction of IRG1 by LPS. Hence, the induction of IRG1 by LPS is mediated by tyrosine kinase and protein kinase C pathway.

Amino Acid Sequence↗

Characterization and mapping of three new mammalian ATP-binding transporter genes from an EST database.

Analysis of the human expressed sequence tag (EST) database identified four clones that contain sequences of previously uncharacterized genes, members of the ATP-binding cassette (ABC) superfamily. Two new ABC genes (EST20237, 31252) are located at Chromosome (Chr) 1q42 and 1q25 respectively in humans, as determined by FISH; at locations distinct from previously mapped genes of this superfamily. Two additional clones, EST 600 and EST 1596, were found to represent different ATP-binding domains of the same gene, ABC2. This gene was localized to 9q34 in humans by FISH and to the proximal region of Chr 2 in mice by linkage analysis. All genes display extensive diversity in sequence and expression pattern. We present several approaches to characterizing EST clones and demonstrate that the analysis of EST clones from different tissues is a powerful approach to identify new members of important gene families. Some drawbacks of using EST databases, including chimerism of cDNA clones, are discussed.

ATP-Binding Cassette Transporters↗

Isolation of LERK-5: a ligand of the eph-related receptor tyrosine kinases.

Hek and elk are members of the eph-related family of receptor tyrosine kinases. Recently we isolated four cDNAs encoding membrane-bound ligands to hek and elk [Beckman et al. (1994) EMBO J. 13, 3757-3762; Kozlosky et al. (1995) Oncogene 10, 299-306]. Because of the promiscuous nature of their binding, we have termed these proteins ligands of the eph-related kinases or LERKs. A search of GenBank revealed an expressed sequence tag (EST) with homology to the LERKs. Using this EST as a probe, we have isolated human and murine cDNAs that encode a protein which we call LERK-5. The human and murine cDNAs encode proteins of 333 and 336 amino acids, respectively, with a 97% amino acid identity; LERK-5 has an amino acid identity of 27-59% with the other reported LERKs. LERK-5 is a ligand for both elk and hek and induces receptor phosphorylation. It is expressed in adult lung and kidney and the fetal tissues heart, lung, kidney, and brain. In addition, Southern blot analysis of DNA from interspecific backcross mice indicated that LERK-5 (Eplg5) maps to the proximal region of mouse chromosome 8.

Amino Acid Sequence↗

Arc, a growth factor and activity-regulated gene, encodes a novel cytoskeleton-associated protein that is enriched in neuronal dendrites.

Neuronal activity is an essential stimulus for induction of plasticity and normal development of the CNS. We have used differential cloning techniques to identify a novel immediate-early gene (IEG) cDNA that is rapidly induced in neurons by activity in models of adult and developmental plasticity. Both the mRNA and the encoded protein are enriched in neuronal dendrites. Analysis of the deduced amino acid sequence indicates a region of homology with alpha-spectrin, and the full-length protein, prepared by in vitro transcription/translation, coprecipitates with F-actin. Confocal microscopy of the native protein in hippocampal neurons demonstrates that the IEG-encoded protein is enriched in the subplasmalemmal cortex of the cell body and dendrites and thus colocalizes with the actin cytoskeletal matrix. Accordingly, we have termed the gene and encoded protein Arc (activity-regulated cytoskeleton-associated protein). Our observations suggest that Arc may play a role in activity-dependent plasticity of dendrites.

Actins↗

Embryo brain kinase: a novel gene of the eph/elk receptor tyrosine kinase family.

A new gene belonging to the Eph/Eck/Elk receptor tyrosine kinase family has been cloned from mouse brain. The gene maps to mouse chromosome 4. In the adult brain it is expressed exclusively and abundantly in the hippocampus. We propose to name it Ebk (embryo brain kinase), as in situ hybridisation shows expression in many parts of the developing mouse brain. The most abundant expression is in the subcommissural organ, and the earliest expression is in the forebrain neural folds, in rhombomeres 2-6, and in somites and heart. Other regions positive at various stages include the cochlear duct, trigeminal ganglion, lung, first branchial arch, and tooth primordia. Also positive are areas of mesenchyme underlying various epithelia during morphogenesis, especially in the mouth and nose, as well as in the eyelids and toes. We compare these patterns with the available data on the 12 other known members of this gene family. Most of them, like Ebk, are expressed in brain (especially adult hippocampus and embryonic rhombomeres) and in organs rich in epithelia (especially lung), although the spatial and temporal patterns differ. We suggest that combinatorial patterns of these receptors act as labels for the regional identity of neurons and epithelia, and could mediate fine control of neurite pathfinding and epithelial morphogenesis.

Aging↗

Genomic imprinting of Mash2, a mouse gene required for trophoblast development.

The mouse gene Mash2 encodes a transcription factor required for development of trophoblast progenitors. Mash2-homozygous mutant embryos die at 10 days postcoitum from placental failure. Here we show that Mash2 is genomically imprinted. First, Mash2+/- embryos inheriting a wild-type allele from their father die at the same stage as -/- embryos, with a similar placental phenotype. Second, the Mash2 paternal allele is initially expressed by groups of trophoblast cells at 6.5 and 7.5 days post-coitum, but appears almost completely repressed by 8.5 days post-coitum. Finally, we have genetically and physically mapped Mash2 to the distal region of chromosome 7, within a cluster of imprinted genes, including insulin-2, insulin-like growth factor-2 and H19.

Alleles↗

Chromosomal assignment of the heparin-binding cytokine genes MDK and PTN in mouse and man.

MDK and PTN are two members of a family of heparin-binding cytokines thought to be involved in a number of developmental processes. The locations for these genes were determined in man and mouse using somatic cell hybrid analysis and interspecific backcross analysis. Human MDK was mapped to 11p13-->p11. MDK in the mouse (Mdk) was mapped to a syntenic region of mouse Chromosome 2. A pseudogene of Mdk was mapped to mouse Chromosome 11. The closely related human gene PTN was mapped to a separate location on human chromosome region 7q22-->qter.

Animals↗

Chromosomal localization of a gene, GF1, encoding a novel zinc finger protein reveals a new syntenic region between man and rodents.

The Gfi1 gene encodes a zinc finger protein which binds DNA and is involved in transcriptional regulation. Gfi1 was assigned to the central portion of mouse Chr 5 by interspecific backcross mapping and to human chromosome band 1p22 and rat chromosome band 14p22 by fluorescence in situ hybridization (FISH). Comparative mapping data presented here describes a new syntenic region between man and rodents.

Animals↗

Localization of the murine homolog of the anaplastic lymphoma kinase (AlK) gene on mouse chromosome 17.

The murine homolog of the human anaplastic lymphoma kinase gene, which encodes a membrane-spanning receptor tyrosine kinase in the insulin receptor kinase subfamily, was assigned to mouse Chromosome 17 by interspecific backcross analysis. This assignment further confirms the homology between a portion of the distal Chromosome 17 and the short arm of human chromosome 2 and extends this region in the mouse by an additional 3 cM.

Anaplastic Lymphoma Kinase↗

Scleraxis: a basic helix-loop-helix protein that prefigures skeletal formation during mouse embryogenesis.

Members of the basic helix-loop-helix (bHLH) family of transcription factors have been shown to regulate growth and differentiation of numerous cell types. Cell-type-specific bHLH proteins typically form heterodimers with ubiquitous bHLH proteins, such as E12, and bind a DNA consensus sequence known as an E-box. We used the yeast two-hybrid system to screen mouse embryo cDNA libraries for cDNAs encoding novel cell-type-specific bHLH proteins that dimerize with E12. One of the cDNAs isolated encoded a novel bHLH protein, called scleraxis. During mouse embryogenesis, scleraxis transcripts were first detected between day 9.5 and 10.5 post coitum (p.c.) in the sclerotome of the somites and in mesenchymal cells in the body wall and limb buds. Subsequently, scleraxis was expressed at high levels within mesenchymal precursors of the axial and appendicular skeleton and in cranial mesenchyme in advance of chondrogenesis; its expression pattern in these cell types foreshadowed the developing skeleton. Prior to formation of the embryonic cartilaginous skeleton, scleraxis expression declined to low levels. As development proceeded, high levels of scleraxis expression became restricted to regions where cartilage and connective tissue formation take place. Scleraxis bound the E-box consensus sequence as a heterodimer with E12 and activated transcription of a reporter gene linked to its DNA-binding site. The expression pattern, DNA-binding properties and transcriptional activity of scleraxis suggest that it is a regulator of gene expression within mesenchymal cell lineages that give rise to cartilage and connective tissue.

Amino Acid Sequence↗