Hamster Somatic Cell Hybrids Research Articles

Chromosomal assignments of mammalian genes with an acute inflammation-regulated expression in liver.

A set of acute inflammation-regulated genes expressed in liver has been assigned to rat, mouse, and human chromosomes by detecting species-specific PCR amplicons in rat(x)mouse or mouse(x)hamster somatic cell hybrids or radiation hybrids or by in silico matches of corresponding rat cDNAs to various libraries of previously assigned rat, mouse, or human genes or expressed-sequence tags. This allowed us to assign 24, 22, and 21 inflammation-regulated genes to rat, mouse, and human chromosomes, respectively. From these assignments as well as those previously determined for a larger set of genes with an acute inflammation-regulated transcription in liver, we further investigated whether such genes are clustered onto given chromosomes. A cluster was found on rat Chromosome (Chr) 6q with a conserved synteny on mouse Chr 12 and human Chr 14q13-q32, and another cluster previously reported on human Chr 1q has been extended with five further genes. Our data suggest that during an acute inflammation, a higher-order regulation may control some liver-expressed genes that share a given chromosome area.

Assignment of the mouse and cow CXC chemokine genes

Gene specific PCR primers were constructed for five mouse and three bovine CXC chemokine genes. The mouse genes were assigned using SSCP analyses of the Jackson BSS backcross panel to two groups on chromosome 5. One group containing Gro1 and Mip2 cosegregated with reference markers Alb1 and Btc, and was positioned 2.2 cM proximal to a group comprising Ifi10, Mig, and Scyb5. The bovine genes IL8, GRO1, and GRO3, mapped using bovine × hamster somatic cell hybrids, were all found to be located on chromosome 6. The locations of these genes in these two animal species are consistent with the positions in humans (4q13→q21), and previous syntenic relationships among these three mammals.

Localization and genomic organization of sheep antimicrobial peptide genes

Antimicrobial peptides are an abundant and diverse component of animal innate immunity. Within mammalian species, defensins and cathelicidins are the two principal antimicrobial peptide families. We identified and sequenced ten new sheep genes which encode potential antimicrobial peptides including two β-defensins and eight cathelicidins. We mapped the two-exon β-defensin genes to sheep chromosome 26 and the four-exon cathelicidin genes to sheep chromosome 19 using sheep–hamster somatic cell hybrids in conjunction with flow-sorted sheep chromosomes. These assignments confirm homology between sheep, cattle, mouse, and human antimicrobial peptide gene families. Contig construction for the sheep cathelicidin gene family demonstrates that three genes, OaDodeA, OaDodeB, and OaMAP-34, are present head-to-tail in a 14.5 kb region, and that four proline/arginine-rich genes, OaBac5, OaBac7.5, OaBac11, and OaBac6, are arranged head-to-tail in a region covering 30.5 kb. This richly diverse family of sheep cathelicidin peptides is encoded in a gene array which may reflect the mechanism of its evolution.

Identification of a Novel HumanRAD51Homolog,RAD51B

The highly conservedSaccharomyces cerevisiaeRAD51 protein functions in both mitotic and meiotic homologous recombination and in double-strand break repair. Screening of the public cDNA sequence database forRAD51-like genes led to the identification of a partial sequence from a breast tissue library present in the I.M.A.G.E. (Integrated Molecular Analysis of Genes and their Expression) collection. An extended 1764-bp cDNA clone encoding an open reading frame of 350 amino acids was isolated. This clone showed significant amino acid identity with other human RAD51 homologs. The new homolog, namedRAD51B,was mapped to human chromosome 14q23–q24.2 using a panel of human–hamster somatic cell hybrids and fluorescencein situhybridization. Northern blot analysis demonstrated thatRAD51BmRNA is widely expressed and most abundant in tissues active in recombination. Functions associated with known RAD51 homologs suggest a role for RAD51B in meiotic recombination and/or recombinational repair.

Map integration at human chromosome 10: molecular and cytogenetic analysis of a chromosome-specific somatic cell hybrid panel and genomic clones, based on a well-supported genetic map.

Well-characterized, chromosome-specific somatic cell hybrid panels are powerful tools for the analysis of the human genome. We have characterized a panel of human x hamster somatic cell hybrids retaining fragments of human chromosome 10 by fluorescence in situ hybridization and associated them to genetic markers. Most of the hybrids were generated by the radiation-reduction method, starting from a chromosome 10-specific monochromosomal hybrid, whereas some were collected from hybrids retaining chromosome 10-specific fragments as a result of spontaneous in vitro rearrangements. PCR was used to score the retention of 57 microsatellite markers evenly distributed along a well-supported framework genetic map containing 149 loci uniquely placed at 69 anchor points (odds exceeding 1,000:1), with an average spacing of 2.8 cM. As an additional resource for genomic studies involving human chromosome 10, we report the cytogenetic localization of a series of YAC and PAC clones recognized by at least one genetic marker. Somatic cell hybrids provide a powerful source of partial chromosome paints useful for detailed clinical cytogenetic and primate chromosome evolution investigations. Furthermore, correlation of the above physical, genetic, and cytogenetic data contribute to an emerging consensus map of human chromosome 10.

Molecular Cloning and Functional Expression of Mouse Connexin-30,a Gap Junction Gene Highly Expressed in Adult Brain and Skin

A new gap junction gene isolated from the mouse genome codes for a connexin protein of 261 amino acids. Because of its theoretical molecular mass of 30.366 kDa, it is named connexin-30. Within the connexin gene family, this protein is most closely related to connexin-26 (77% amino acid sequence identity). The coding region of mouse connexin-30 is uninterrupted by introns and is detected in the mouse genome as a single copy gene that is assigned to mouse chromosome 14 by analysis of mouse x hamster somatic cell hybrids. Abundant amounts of connexin-30 mRNA (two transcripts of 2.0 and 2.3 kilobase pairs) were found after 4 weeks of postnatal development in mouse brain and skin. Microinjection of connexin-30 cRNA into Xenopus oocytes induced formation of functional gap junction channels that gated somewhat asymmetrically in response to transjunctional voltage and at significantly lower voltage (Vo = +38 and -46 mV) than the closely homologous connexin-26 channels (Vo = 89 mV). Heterotypic pairings of connexin-30 with connexin-26 and connexin-32 produced channels with highly asymmetric and rectifying voltage gating, respectively. This suggests that the polarity of voltage gating and the cationic selectivity of connexin-30 are similar to those of its closest homologue, connexin-26.

A novel zinc finger gene preferentially expressed in the retina and the organ of Corti localizes to human chromosome 12q24.3

A cDNA encoding a novel member of the zinc finger gene family, designated zφfOC1, has been cloned from the organ of Corti. This is the first transcriptional regulator cloned from this sensory epithelium. This transcript encodes a peculiar protein composed of 9 zinc finger domains and a few additional amino acids. The deduced polypeptide shares 66% amino acid similarity with MOK-2, another protein of only zinc finger motifs and preferentially expressed in transformed cell lines. Northern blot hybridization analysis reveals that zφOC1 transcripts are predominantly expressed in the retina and the organ of Corti and at lower levels in the stria vascularis, auditory nerve, tongue, cerebellum, small intestine and kidney. The human gene was mapped, using a human × hamster somatic cell hybrid panel and fluorescent in situ hybridization, to chromosome 12q24.3. Because of its relative abundance in sensorineural structures (retina and organ of Corti), this regulatory gene should be considered a candidate for hereditary disorders involving hearing and visual impairments that link to 12q24.3.

The Human L35a Ribosomal Protein (RPL35A) Gene Is Located at Chromosome Band 3q29–qter

Using a polymerase chain reaction (PCR)-based strategy that distinguishes functional intron-containing genes from pseudogenes, the chromosomal location of the human intron-containing L35a ribosomal protein gene (rpL35a, HGMW-approved symbol RPL35A) was previously deduced to be on chromosome 18 using DNAs from a panel of human–rodent somatic cell hybrids. The inability to detect rpL35a in a human–hamster somatic cell hybrid containing only human chromosome 18 led to a reinvestigation of the chromosomal location of the human rpL35a gene. A clone containing intron 2 of rpL35a was isolated, sequenced, and used to isolate a P1 clone containing the human intron-containing rpL35a gene. By fluorescencein situhybridization (FISH) analysis with the P1 clone as a probe, the rpL35a gene was located on chromosome band 3q29–qter. This location was confirmed by positive PCR analysis of a human–hamster somatic cell hybrid containing only human chromosome 3. The problem of using only human–rodent somatic cell hybrids for chromosome location is discussed.

Structure and Chromosomal Localization of the Human Salivary Mucin Gene, MUC7

We have isolated and characterized several MUC7 genomic clones encoding the human low-molecular-weight salivary mucin, MG2. The MUC7 gene spans ∼10.0 kb and comprises of three exons and two introns. Intron 1 is ∼1.7 kb long and is located in the 5′-untranslated region of the corresponding MUC7 cDNA. Intron 2 spans ∼6.0 kb and is located close to the boundary of the putative leader peptide and secreted protein. The entire region encoding the secreted peptide is located on exon 3, spanning ∼2.2 kb. The nucleotide sequence of sections of the MUC7 gene, including 1500 bp of the 5′-flanking region, was determined and analyzed for motifs identical or homologous to other known response elements. A modified RACE procedure was used to determine the 5′-end of the MUC7 mRNA. PCR, the human–hamster somatic cell hybrid panel PCRable DNAs kit, and anin situhybridization analysis on the complete metaphase chromosome spreads were used for the chromosomal localization of the MUC7 gene. It was mapped to chromosome 4q13–q21.

Sheep CENPB and CENPC genes show a high level of sequence similarity and conserved synteny with their human homologs.

Sheep CENPB and CENPC clones were isolated from a lung cDNA library. The DNA and predicted amino acid sequences of these clones were compared with their human and mouse homologs and shown to contain a high degree of sequence similarity. Sheep chromosomal assignments were made using a sheep x hamster somatic cell hybrid mini-panel. CENPB was assigned to sheep chromosome 13 and CENPC to chromosome 6. The previously reported assignments of CENPB and CENPC to human chromosomes 20 and 4, respectively, suggest conserved synteny between sheep chromosome 13 and human chromosome 20 and support conserved synteny between sheep chromosome 6 and human chromosome 4.

Mapping of the human BAX gene to chromosome 19q13.3–q13.4 and isolation of a novel alternatively spliced transcript, BAXδ

The BAX gene is a member of the Bcl-2 gene family; it encodes a 21-kDa protein whose association with Bcl-2 is believed to play a critical role in regulating apoptosis. Through analysis of human—hamster somatic cell hybrid DNA and by in situ hybridization to metaphase chromosomes, we have determined that the human BAX gene is located in the q13.3–q13.4 region of human chromosome 19. We have also isolated a BAX cDNA clone in which that part of the mRNA encoded by exon 3 is absent. The skipping of exon 3 and the resultant splicing of exons 2 and 4 maintains the original reading frame and predicts the existence of an interstitially truncated form of the major Bax protein (Baxα), termed Baxδ. Unlike two previously described variant forms of Baxα (Baxß and Baxτ), Baxδ retains the functionally critical C-terminal membrane anchor region as well as the Bcl-2 homology 1 and 2 (BH1 and BH2) domains.

The human gonadotropin-releasing hormone receptor gene (GNRHR) maps to chromosome band 4q13

A cDNA representing the high-affinity gonadotropin-releasing hormone (GnRH) receptor has been molecularly cloned from the human pituitary gland, a breast tumor cell line (MCF 7), and an ovarian tumor. The nucleotide sequence of this cDNA was determined, and its expression in various human tumors and tumor cell lines was demonstrated. In this study, we localized the gene encoding the GnRH receptor to human chromosome 4, using polymerase chain reaction (PCR) analysis of genomic DNA from human x hamster somatic cell hybrids. The gene was sublocalized to chromosome band 4q13 using fluorescence in situ hybridization with the GnRH receptor gene (GNRHR).

Characterization of the mouse loricrin gene: linkage with profilaggrin and the flaky tail and soft coat mutant loci on chromosome 3.

Loricrin is the major component of a specialized structure, termed the cornified cell envelope, that is formed beneath the plasma membrane of stratified squamous epithelial cells and is coexpressed with profilaggrin in terminally differentiating epidermal keratinocytes. Full-length cDNAs for both mouse and human loricrin have been cloned and characterized, as has the human gene. Here we report the isolation and characterization of the mouse loricrin gene. The gene has a simple structure consisting of a single intron of 1091 bp within the 5' noncoding sequence and an uninterrupted open reading frame. Using PCR analyses of DNAs isolated from mouse x Chinese hamster somatic cell hybrids, we have mapped both the loricrin and the profilaggrin genes to chromosome 3. Genetic linkage analysis has shown that mouse loricin and profilaggrin lie within 1.5 +/- 1.1 centimorgans of each other. We have further shown that both genes map in the vicinity of the flaky tail (ft) and soft coat (soc) loci. These mouse mutants exhibit a number of changes in their integument, suggesting that abnormalities in these genes may contribute to the mutant phenotype.

The Booroola Fecundity (FecB) Gene Maps to Sheep Chromosome 6

The Booroola (FecB) mutation in sheep is linked to markers from a region of syntenic homology to human chromosome HSA4q, but the chromosomal location in sheep has not been determined. Analysis of linkage in Booroola half-sib pedigrees and 17 full-sib families identified genetic linkage between platelet-derived growth factor receptor-α (PDGFRA) and αs1-casein (CSN1S1) at 12 cM (Zmax = 9.14) and between PDGFRA and the microsatellite markers BM143 and OarHH55 (Zmax = 6.28 and 3.83, respectively). The microsatellite markers OarAE101 and BM143 and genes from the linkage group (PDGFRA, SPP1, and EGF) were mapped in a partial sheep × hamster somatic cell hybrid panel. All markers identified bands specific to somatic cell hybrids containing the sheep chromosome t1 (rob6;24) or t1q (chromosome 6). In sheep the casein genes αs1 (CSN1S1), αs2 (CSN1S2), β (CSN2), and κ (CSN3) are tightly linked, and CSN2 has been mapped to sheep chromosome 6q23-q31. We conclude that the Booroola mutation is located within a conserved syntenic group that maps to sheep chromosome 6.

Assignment of the Human Diacylglycerol Kinase Gene (DAGK) to 12q13.3 Using Fluorescence in Situ Hybridization Analysis

A 1-kb cDNA probe specific for the human DAGK gene was prepared by polymerase chain reaction and used to assign it to human chromosome 12 using a human x hamster somatic cell hybrid mapping panel. To determine the chromosomal sublocalization of DAGK, used the 1-kg DAGK cDNA probe to isolate a DAGK-specific phage clone from a human chromosome 12 library by Southern blot techniques. This clone (phEDCDAGK) contained a 17-kb human genomic insert in the phage Charon 40 that hybridized to the 1-kb DAGK cDNA previously characterized.

Chromosomal assignments of mouse genes for connexin 50 and connexin 33 by somatic cell hybridization

The 12 known connexin genes coding for the subunit proteins of the gap junction channels and related in nucleotide sequence are widely dispersed in the mouse genome. By using a series of mouse X Chinese hamster somatic cell hybrids and molecular probes of murine connexin genes, we have assigned the connexin 50 gene to mouse chromosome 3. The connexin 33 gene has been mapped to the X chromosome, thus confirming the previous chromosomal assignment of this gene based on interspecific back-cross mapping.

Human rsk isoforms: cloning and characterization of tissue-specific expression.

Serine-threonine protein kinases in the ribosomal S6 kinase (rsk or p90rsk) family have been implicated as signaling intermediates in the cellular response to several growth factors. To investigate the molecular diversity of human p90rsk isoforms, mixed degenerate oligonucleotide polymerase chain reaction was used to isolate partial rsk cDNAs (1.1 kb). Three closely related human rsk cDNAs were obtained (HU-1, HU-2, HU-3). These cDNAs are encoded by separate genes based on DNA sequence diversity and distinct patterns seen with genomic Southern blots. Northern analysis revealed different sized mRNA transcripts for each isoform. A full-length HU-1 cDNA (3.1 kb) was subsequently isolated from a HeLa cell library. 5'-cDNA clones for HU-2 and HU-3 were isolated using the "rapid amplification of cDNA ends" strategy. Experiments using human x hamster somatic cell hybrids localized the HU-1 gene to human chromosome 3; HU-2 is on chromosome 6; and HU-3 is on the X chromosome. The tissue distribution of human rsk mRNAs was determined using ribonuclease protection assays. HU-3 mRNA was present in multiple RNA samples. HU-2 was expressed in fibroblast > muscle > lymphocyte = placenta > liver. HU-1 was expressed in Epstein-Barr virus lymphocyte > > muscle = liver > fat = placenta. These results indicate that the multiplicity of p90rsk isoforms is increased to at least three for humans and that marked tissue-/cell-specific differences in p90rsk isoform expression are present.

The human glutathione peroxidase genes GPX2, GPX3, and GPX4 map to chromosomes 14, 5, and 19, respectively

cDNA probes of human glutathione peroxidase (GSHPx) genes, including the classic GPX1 (GSHPx-1), the newly characterized GPX2 (GSHPx-GI), the plasma enzyme GPX3 (GSHPx-P), and the phospholipid hydroperoxide glutathione peroxidase GPX4 (PHGPX), were hybridized to Southern blots containing genomic DNA from human x hamster somatic cell hybrids. GPX2 was mapped to chromosome 14, GPX3 to chromosome 5 and GPX4 to chromosome 19. Additionally, human chromosomes 3 and 21 and the X chromosome were shown to contain sequences homologous to GPX1, as reported previously.

Localization of acyl coenzyme A:cholesterol acyltransferase gene to human chromosome 1q25

Acyl coenzyme A:cholesterol acyltransferase (ACAT) is an intracellular enzyme that catalyzes the formation of cholesterol esters from cholesterol and long-chain fatty acyl-coenzyme A. It is believed that ACAT plays a key role in lipoprotein metabolism and atherogenesis. Recently our laboratory succeeded in molecular cloning and functional expression of human macrophage ACAT cDNA. We have now mapped the ACAT gene to chromosome 1, band q25 by using fluorescence in situ hybridization to metaphase chromosomes, and by Southern blotting analysis of human--hamster somatic cell hybrid panels.

A radiation hybrid map of human chromosome 18

A human x Chinese hamster (CH) somatic cell hybrid subclone deficient in HPRT and containing only human chromosome 18 was irradiated with 7000 rad and fused to a thymidine kinase deficient CH cell line. Radiation-rescued hybrid cell lines, selected in HAT medium, were analyzed for human DNA with human interspersed-repeat sequence primers. Size and number of human chromosome fragments retained in a subset of hybrids were determined by FISH. A panel of 98 radiation hybrids (RH) was selected and analyzed for 90 chromosome 18-specific STSs by PCR, and for the D18Z1 centromeric marker by Southern blotting. STSs were developed from previously mapped RFLP loci and from published sequences. In addition, 32 novel STSs were generated from an 18-specific lambda library and from 18-specific YACs previously localized to chromosome bands by FISH. Marker retention frequency varied from 8-65% with an average of 24%. In selected RH the STS typing data were correlated with the chromosome 18 regions retained using 'reverse FISH' of IRS-PCR products from the RH to normal metaphase chromosomes. The order and intermarker distances of loci were determined using two-point and multipoint maximum likelihood methods. The resulting RH map covers most of chromosome 18 with four groups of tightly linked markers and three regions of loosely linked markers, one around the centromere and two on the long arm. More than a third of the markers are polymorphic and allow integration with the linkage map. This RH map provides a framework for establishing a clone contig of the entire chromosome 18.