Selective linkage disruption in human-Chinese hamster cell hybrids: deletion mapping of the leuS, hexB, emtB, and chr genes on human chromosome 5

A scaffold for the Chinese hamster genome

Chinese hamster ovary (CHO) cells are a prevalent tool in biological research and are among the most widely used host cell lines for production of recombinant therapeutic proteins. While research in other organisms has been revolutionized through the development of DNA sequence-based tools, the lack of comparable genomic resources for the Chinese hamster has impeded similar work in CHO cell lines. A comparative genomics approach, based upon the completely sequenced mouse genome, can facilitate genomic work in this important organism. Using chromosome synteny to define regions of conserved linkage between Chinese hamster and mouse chromosomes, a working scaffold for the Chinese hamster genome has been developed. Mapping CHO and Chinese hamster sequences to the mouse genome creates direct access to relevant information in public databases. Additionally, mapping gene expression data onto a chromosome scaffold affords the ability to interpret information in a genomic context, potentially revealing important structural and regulatory features in the Chinese hamster genome. Further development of this genomic scaffold will provide opportunities to use biomolecular tools for research in CHO cell lines today and will be an asset to future efforts to sequence the Chinese hamster genome.

Determination of the 'critical region' for cat-like cry of Cri-du-chat syndrome and analysis of candidate genes by quantitative PCR

Cri-du-chat (CDC, OMIM 123450) is a chromosomal syndrome that results from partial deletions on the short arm of chromosome 5. The clinical features of CDC normally include high-pitched cat-like cry, mental retardation, microcephaly, hypertelorism and epicanthic folds. The cat-like cry is the most prominent clinical characteristic in newborn children and is usually considered as diagnostic for the CDC syndrome. Using a strategy of 'phenotype dissection', the critical region for cat-like cry was mapped to the chromosomal segment 5p15.3-5p15.2 in previous reports. In this study, the distal breakpoints of two interstitial deletions in two clinical distinctive CDC patients are analysed, one with and one without the cat-like cry. Using PCR, the critical region for the cat-like cry is mapped to a short 640 kbp region on chromosome 5p. Genome analysis of this critical region reveals a gene-rich sequence containing five known genes, five putative genes and three spliced EST sequences, altogether 71 predicted exons. Three genes, FLJ25076, a homolog to a ubiquitin-conjugating enzyme UBC-E2, FLJ20303, a nucleolar protein NOP2, which may play a role in the regulation of the cell cycle and MGC5309, a protein with similarity to Nut2, a Drosophila transcriptional coactivator, have been characterized and expression profiles determined by quantitative PCR. These results suggest that one candidate gene, FLJ25076, encodes a ubiquitin-conjugated enzyme E2 type, which is locally expressed in thoracic and scalp tissues. The other two genes are expressed uniformly in all tissues tested, which suggest that they are housekeeping genes.

A radiation hybrid map of human chromosome 5 with integration of cytogenetic, genetic, and transcript maps

One of the major goals of the human genome project is to establish a physical map of each human chromosome with a density of sequence-tagged site (STS) markers exceeding one every 100 kb. We report here the generation of a human chromosome 5-specific radiation hybrid (RH) map that includes 556 markers. Of these markers, 132 loci are ordered with a maximum likelihood ratio of >1000:1 compared with the next most likely order. An additional 113 loci were ordered relative to these backbone markers with a maximum likelihood ratio of >10:1 but <1000:1. Together, these 245 loci form an ordered framework map for the chromosome. Using this framework, >300 more markers were localized based on two-point analysis with the ordered set. On average, there are 50 markers in common with the RH map presented here and other chromosome 5 maps included in the current whole genome cytogenetic, genetic, and physical maps. The accuracy of all the maps is evident in that there are no more than two discrepancies between any one of them and these data. All of the maps encompassing chromosome 5 complement each other providing excellent STS coverage with >2200 loci combined. The chromosome 5-specific RH map contains 20% of these independent loci. In addition, our RH map contains STSs derived from clones suitable for fluorescent in situ hybridization, allowing alignment to the cytogenetic map. Together, these maps will assist in the assembly of sequence-ready contigs and will aid in the identification of disease loci on chromosome 5 by positional cloning and positional candidate approaches.

A high-resolution physical and transcript map of the Cri du chat region of human chromosome 5p

A high-resolution physical and transcription map has been generated of a 3.5-Mb region of 5p15.2 that is associated with the Cri du chat (CDC) syndrome. Utilizing a variety of resources including a natural deletion panel, a chromosome specific radiation hybrid panel, and YAC, PAC, and BAC genomic clones we have ordered > 60 STSs within this region. Approximately 45% of these STSs were obtained from publicly available whole genome maps, thus allowing for integration of this map with currently available resources. Thirteen of these markers were ESTs. In addition, > 70 exon trapped products have been mapped on the natural deletion panel and bacterial clone resource. The combination of these resources has allowed for the identification of 17 transcripts within this region, all of which represent candidate genes for CDC. Further characterization of the genomic contig also revealed that this region of 5p15 contains a large number of repetitive elements.

Tay-Sachs disease screening and diagnosis: evolving technologies

Tay-Sachs disease (TSD) is an autosomal recessive, progressive, and fatal neurodegenerative disorder. Within the last 25 years, the discovery of the enzymatic basis of the disease, the deficiency of the enzyme hexosaminidase A, has made possible both enzymatic diagnosis of TSD and heterozygote identification. TSD is the first genetic condition for which a community-based heterozygote screening program was attempted with the intention of reducing the incidence of a genetic disease. In this article we review the clinical, biochemical, and molecular features of TSD as well as the development of laboratory technology that has been deployed in community genetic screening programs. We describe the assay procedures used and some of the limitations in their accuracy. We consider the impact of DNA-based technology on the process of identification of individuals carrying mutant genes associated with TSD and we discuss the social context within which genetic screening occurs.

Molecular analysis of the 18q- syndrome--and correlation with phenotype

Seven individuals with deletions of the distal long arm of chromosome 18 were evaluated at the clinical, cytogenetic, and molecular levels. The patients had varying degrees of typical clinical findings associated with the 18q- syndrome. Cytogenetic analysis revealed deletions from 18q21.3 or 18q22.2 to qter. Somatic cell hybrids derived from the patients were molecularly characterized using ordered groups of probes isolated from a chromosome 18-specific library. In general, the size of the deletion could be correlated with the severity of the phenotype. Based on the clinical pictures of these seven patients, a preliminary phenotypic map for the clinical features associated with deletions of the distal portion of the long arm has been generated. Furthermore, genes previously localized to 18q21 were mapped relative to the chromosome breakpoints present in these patients.

Clinical phenotype and molecular analysis of a three-generation family with an interstitial deletion of the short arm of chromosome 5

We report on a 3-generation family with an interstitial deletion of the short arm of chromosome 5. Varied manifestations were found among the affected individuals including microcephaly, hypertonia, and micrognathia; mental retardation was common to all affected individuals. High resolution chromosome analysis was interpreted as del(5) (pter- > p14.3::p13.3- > qter). Molecular comparison of the deletion in this family with individuals with other 5p deletions suggests that the clinical findings are due specifically to the chromosomal material deleted from 5p13.

Systematic generation of sequence-tagged sites for physical mapping of human chromosomes: application to the mapping of human chromosome 7 using yeast artificial chromosomes

Basic to the development of long-range physical maps of DNA are the detection and localization of landmarks within recombinant clones. Sequence-tagged sites (STSs), which are short stretches of DNA that can be specifically detected by the polymerase chain reaction (PCR), can be used as such landmarks. Our interest is to construct physical maps of whole human chromosomes by localizing STSs within yeast artificial chromosome (YAC) clones. Here we describe a generalized strategy for the systematic generation of large numbers of STSs specific for human chromosome 7. These STSs can be detected by PCR assays developed following the sequencing of anonymous pieces of chromosome 7 DNA, which was derived from flow-sorted chromosomes or from lambda clones made from DNA of a human-hamster hybrid cell line. Our approach for STS generation is tailored for the development of PCR assays capable of screening a large YAC library. In this study, we report the generation of 100 new STSs specific to human chromosome 7.

The human chromosome content in human x rodent somatic cell hybrids analyzed by a screening technique using Alu PCR

The ubiquitous nature of the Alu sequence throughout the human genome forms the basis of an assay we present here for analyzing the human chromosome content of human x rodent somatic cell hybrids. A human-specific Alu primer was used both to amplify sequences and to 32P label the products in a polymerase chain reaction (PCR) technique. Unlabeled inter-Alu PCR products from two series of human x rodent hybrids were used to prepare dot blots which were probed with labeled inter-Alu products prepared from between 10(3) and 10(4) hybrid cells. In the first series we demonstrate that a labeled inter-Alu probe from the hybrid DL18ts, containing a single chromosome 18, on a dot blot hybridized only with those inter-Alu products containing chromosome 18. Similar specificity for human chromosome 5 was shown when a Southern blot of the PCR products was hybridized with a probe made from the hybrid HHW 213, which contains only chromosome 5p. Using a dot blot from a second series of control hybrids, 15 of which contained single human chromosomes, hybridization of a labeled probe from the hybrid 18X4-1 was shown to react specifically with the controls that expressed chromosome 18. Application of the technique reported here allows simple and rapid characterization of the human chromosome content in human x rodent hybrids.

Parental origin of chromosome 5 deletions in the cri-du-chat syndrome

The parental origin of de novo deletions leading to the cri-du-chat syndrome has been investigated. Since the cri-du-chat syndrome is correlated with deletions involving the short arm of chromosome 5 (5p), DNA fragments known to detect restriction fragment length polymorphisms (RFLPs) along 5p were used to establish whether the paternal or the maternal chromosome had suffered the deletion. In cases where only one parent was available, somatic cell hybrids were used in conjunction with RFLP analysis to determine the origin of the deleted chromosome. The deleted chromosome 5 was of paternal origin in 20/25 cases.

A molecular genetic linkage map of mouse chromosome 13 anchored by the beige (bg) and satin (sa) loci

A molecular genetic linkage map of mouse chromosome 13 was constructed using cloned DNA markers and interspecific backcross mice from two independent crosses. The map locations of Ctla-3, Dhfr, Fim-1, 4/12, Hexb, Hilda, Inhba, Lamb-1.13, Ral, Rrm2-ps3, and Tcrg were determined with respect to the beige (bg) and satin (sa) loci. The map locations of these genes confirm and extend regions of homology between mouse chromosome 13 and human chromosomes 5 and 7, and identify a region of homology between mouse chromosome 13 and human chromosome 6. The molecular genetic linkage map of chromosome 13 provides a framework for establishing linkage relationships between cloned DNA markers and known mouse mutations and for identifying homologous genes in mice and humans that may be involved in disease processes.

Familial 5q11.2----q13.3 segmental duplication cosegregating with multiple anomalies, including schizophrenia

We report on 2 relatives with a segmental duplication of 5q11.2----13.3. The phenotype is surprisingly limited for the degree of chromosome imbalance, the propositus presenting with schizophrenia. Using RFLP markers, we have shown that the gene for HEXB lies within the duplicated region. We suggest this region as a candidate region for the location of a single major gene which predisposes to schizophrenia and which may be assessed by linkage analysis.

Deletion mapping of DNA markers to a region of chromosome 5 that cosegregates with schizophrenia

Two independent lines of evidence support the localization of a schizophrenia susceptibility locus to the proximal long arm of chromosome 5. A partial trisomy of chromosome 5 (5q11.2-q13.3) cosegregates with the disorder in a Canadian family of Chinese descent, and DNA markers from proximal 5q cosegregate with schizophrenia (plus related disorders) in families of British and Icelandic descent. We constructed a human:hamster hybrid cell line (HHW 1064) whose only human complement is a chromosome 5 that is missing the trisomic region associated with schizophrenia. In combination with a "matched" cell hybrid (HHW 105) containing an intact chromosome 5, we physically mapped DNA markers relative to the trisomy. "Schizophrenia-linked" DNA markers p105-153Ra (D5S39) and p105-599Ha (D5S76) map within the trisomy and proximal to the 5q11.2 breakpoint, respectively. The hybrid cell lines HHW 105 and HHW 1064 together provide a means to identify and generate syntenic DNA markers to further investigate the location of a schizophrenia locus.

Prenatal diagnosis and carrier detection of a cryptic translocation by using DNA markers from the short arm of chromosome 5

DNA markers from the short arm of chromosome 5 were used to examine a large family in which a microscopically undetectable translocation was segregating. In addition to confirming that three retarded children were hemizygous for loci distal to 5p14, these analyses identified five individuals as being carriers of the balanced translocation. The use of molecular probes provided informed genetic counseling to the family for the first time. With the DNA markers from 5p, prenatal diagnosis was performed on two fetal chorionic villus samples, both of which were found to have unbalanced karyotypes. The identification of translocation carriers was complicated by recombination between the small translocated segment of 5p and the corresponding region on the normal homologue, which changed the haplotype of the translocated 5p segment.

Chromosomal localization of ARSB, the gene for human N-acetylgalactosamine-4-sulphatase

A deficiency of N-acetylgalactosamine-4-sulphatase (G4S, gene symbol ARSB), results in the accumulation of undegraded substrate and the lysosomal storage disorder, Maroteaux-Lamy syndrome (mucopolysaccharidosis type VI). In situ hybridization using an 3H-labelled human G4S genomic DNA fragment to human metaphase chromosomes localized ARSB to chromosome 5q13-5q14. This location is consistent with, an refines, previous chromosomal assignments based on the expression of human G4S in somatic cell hybrids.

Isolation of DNA markers in the direction of the Huntington disease gene from the G8 locus

To facilitate identification of additional DNA markers near and on opposite sides of the Huntington disease (HD) gene, we developed a panel of somatic-cell hybrids that allows accurate subregional mapping of DNA fragments in the distal portion of 4p. By means of the hybrid-cell mapping panel and a library of DNA fragments enriched for sequences from the terminal one-third of the short arm of chromosome 4, 105 DNA fragments were mapped to six different physical regions within 4p15-4pter. Four polymorphic DNA fragments of particular interest were identified, at least three of which are distal to the HD-linked D4S10 (G8) locus, a region of 4p previously devoid of DNA markers. Since the HD gene has also recently been shown to be distal to G8, these newly identified DNA markers are in the direction of the HD gene from G8, and one or more of them may be on the opposite side of HD from G8.

A fine structure physical map of the short arm of chromosome 5

A series of somatic cell hybrids that retain abnormal chromosomes 5 from 11 different persons with deletions or translocations involving 5p have been isolated. One hundred twenty DNA fragments isolated from a genomic library enriched for sequences from 5p were regionally localized by Southern blot analysis of the hybrid cell deletion mapping panel, including five DNA fragments that reveal restriction fragment length polymorphisms. The fine structure physical map of 5p together with the identification of additional polymorphic loci will facilitate the construction of a complete linkage map of this region. In addition, DNA fragments localized to a region near the 5p15.2-5p15.3 border, which appears to be the segment of 5p that is critical in producing the phenotype associated with the cri du chat syndrome when it is rendered hemizygous by deletion, will be useful in a molecular and DNA level analysis of this deletion syndrome.

Assignment of genes encoding dihydrofolate reductase and hexosaminidase B to Mus musculus chromosome 13

The murine gene encoding dihydrofolate reductase (DHFR) has been localized to a particular mouse chromosome by complementation mapping. Microcells prepared from diploid mouse fibroblasts were fused with mutant hamster cells lacking the dihydrofolate reductase gene (Dhfr), and DHFR+ microcell hybrids were selected in medium lacking purines and pyrimidines. The complemented hybrids expressed wild-type levels of DHFR enzyme activity, and selectively retained a single mouse chromosome--chromosome 13. Genomic Southern blots of DNAs prepared from these hybrids and from an independently derived collection of clones isolated without selection on the DHFR phenotype confirmed the assignment of murine Dhfr gene sequences to chromosome 13. This assignment provides further evidence for the existence of genetic homology between regions of mouse chromosome 13 and human chromosome 5. In support of this view, we show that the gene encoding hexosamindase B, a chromosome 5 marker in man, also maps to mouse chromosome 13.

A cell hybrid and recombinant DNA library that facilitate identification of polymorphic loci in the vicinity of the Huntington disease gene

Somatic cell hybrids were selected that retain a derivative chromosome 5 from an individual in which the p15.1-pter segment of chromosome 5 is replaced with the p15.1-pter segment of chromosome 4. Hybrids that retain this derivative chromosome exclusively were found to be positive for G8, a DNA marker closely linked to the Huntington disease gene on chromosome 4p. From one such hybrid, a segregant was isolated that had deleted the entire q arm of the derivative chromosome but retained the p arm intact as its only detectable human DNA. A complete recombinant DNA library was prepared from this cell line, and the inserts in approximately 1/3 of the recombinant phage with human DNA were shown to be derived from 4pter-4p15.1, which represents only approximately 1% of the total human genome. The cell hybrid and DNA library represent a rapid and efficient means to identify and isolate many polymorphic DNA markers close to and flanking the Huntington disease gene.

Threonyl-tRNA synthetase gene maps close to leucyl-tRNA synthetase gene on human chromosome 5

The structural gene for threonyl-tRNA synthetase was mapped to human chromosome 5 by an analysis of the isoelectric focusing patterns of this enzyme from human X Chinese hamster interspecific somatic cell hybrids. The threonyl-tRNA synthetase gene is the fourth of seven aminoacyl-tRNA synthetase genes mapped in humans to be assigned to this chromosome. Regional mapping studies showed that the threonyl-tRNA synthetase gene is on the short arm of chromosome 5, p13-cen, and is close to, but separable from, the gene for leucyl-tRNA synthetase which maps to 5cen-5q11.

Chromosomal localization of human gene for histidyl-tRNA synthetase: clustering of genes encoding aminoacyl-tRNA synthetases on human chromosome 5

The gene encoding histidyl-tRNA synthetase was localized to human chromosome 5 using human-Chinese hamster ovary cell hybrids. Seven of the functionally related genes encoding the 20 different aminoacyl-tRNA synthetases have not been mapped in humans and four are located on a single chromosome, number 5, which represents less than 7% of the total genome. Thus, there appears to be significant clustering of this group of genes which may reflect their evolutionary relatedness or common factors involved in regulating their expression.

Higher eukaryotic aminoacyl-tRNA synthetases in physiologic and pathologic states

The aminoacyl-tRNA synthetases play a dual role in cell metabolism by synthesizing aminoacyl-tRNAs and an odd dinucleotide diadenosine-5', 5''-P1, P4-tetraphosphate which appears to be involved in DNA replication and the control of cell proliferation. This review is a synthesis of recent results on the structure, genetics, cell biology, physiology, role in neoplasia, and role in autoimmune myositis of the higher eukaryotic aminoacyl-tRNA synthetases.

Molecular analysis of an unbalanced deletion of the short arm of chromosome 5 that produces no phenotype

A family has been identified in which an interstitial, apparently unbalanced deletion of the short arm of chromosome 5 could be traced through six individuals in 3 generations. Remarkably, all of the individuals with the deletion are completely asymptomatic and show no physical or mental abnormalities. The deletion was confirmed at the molecular level by identifying DNA probes that mapped within the deleted portion of chromosome 5. Through the use of somatic cell hybrids and quantitative Southern blots, we demonstrated that these individuals do indeed have an unbalanced deletion and are haploid for several million base pairs of DNA in 5p14 without showing any discernable phenotype.

Ribosomal protein gene sequences map to human chromosomes 5, 8, and 17

DNA sequences complementary to six mammalian ribosomal protein (r-protein) cDNAs are assigned to human chromosomal linkage groups in human-Chinese hamster hybrid cell clones. Ten r-protein DNA fragments map to chromosomes 5, 8 and 17, indicating that these important, housekeeping genes are distributed to multiple sites in the human genome. Each of the chromosome assignments, determined initially by surveying Chinese hamster-human hybrid cell clones with complex karyotypes using Chinese hamster and human cDNA probes, were confirmed in critical minipanels of highly reduced or monochromosomal hybrid cells. As all 10 fragments mapped to only three human chromosomes, r-protein sequences appear to be distributed nonrandomly within human DNA. The r-protein S14 sequence assigned to human chromosome 5 (5q23-5q33) rescues Chinese hamster emetine-resistance mutations (emt b) in interspecific hybrids. Therefore, this sequence corresponds to the transcriptionally active human RPS14 gene. In contrast, other r-protein DNA sequences examined likely are a mixture of functional genes and inactive pseudogenes.

Genetic counterselective procedure to isolate interspecific cell hybrids containing single human chromosomes: construction of cell hybrids and recombinant DNA libraries specific for human chromosomes 3 and 4

Counterselection against genes on human chromosome 5 was applied to interspecific human-Chinese hamster cell hybrids which retained this and one additional human chromosome in order to generate cell hybrids retaining single, nonselected human chromosomes. Using this procedure, stable cell hybrids which retain human chromosome 3 exclusively or human chromosome 4 exclusively were isolated. Complete recombinant genomic DNA libraries were prepared from each hybrid using the lambda cloning vector EMBL-4. These libraries represent sources of human DNA fragments derived specifically from chromosomes 3 and 4, respectively. Low-copy or unique human DNA fragments isolated from both libraries were analyzed to confirm their chromosomal origin and to determine the complexity of their hybridization patterns to total human DNA. These single human chromosome libraries represent a means to efficiently saturate chromosomes 3 and 4 with informative, polymorphic genetic markers. DNA fragments from the chromosome 4 library will be particularly useful in identifying additional genetic markers close to the Huntington's disease gene. The same genetic counterselective procedure can be utilized to derive several additional cell hybrids with single human chromosomes.

Assignment of human 3-hydroxy-3-methylglutaryl coenzyme A reductase gene to q13----q23 region of chromosome 5

We have used hamster cDNA probes for 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase (HMGCR) to determine the chromosomal location of the human gene for HMG CoA reductase. Southern blot analysis of genomic DNA from 16 independent mouse-human somatic cell hybrids showed that the human gene for HMG CoA reductase resides on chromosome 5. Analysis of Chinese hamster-human somatic cell hybrids selectively retaining human 5 or a portion of it showed that the gene locus for HMG CoA reductase can be assigned to the q13----q23 region of chromosome 5.

Synthesis and incorporation of human ribosomal protein S14 into functional ribosomes in human-Chinese hamster cell hybrids containing human chromosome 5: human RPS14 gene is the structural gene for ribosomal protein S14

In Chinese hamster ovary cells, mutations in the RPS14 gene (which was previously designated emtB) render cells resistant to normally cytotoxic concentrations of the protein synthesis inhibitor, emetine. Several lines of evidence indicate the RPS14 gene in Chinese hamster is the structural gene for ribosomal protein S14, including the finding that mutants with alterations in this gene produce an electrophoretically altered form of this protein. A human gene which complements the defect in CHO RPS14 mutants and renders them sensitive to emetine has previously been assigned to the long arm of chromosome 5. The analysis of ribosomal proteins extracted from CHO Emtr X human cell hybrids, which contain human chromosome 5 and are emetine sensitive, demonstrated the presence of both the normal human and altered hamster forms of ribosomal protein S14. Human chromosome 5, the emetine-sensitive phenotype, and the human form of ribosomal protein S14 segregate concordantly from hybrids, confirming that the human gene in question is the structural gene for this protein. In addition, the results indicate that in interspecific cell hybrids, the human form of S14 is either incorporated into functional ribosomes more efficiently than the altered hamster protein or the human gene is overexpressed relative to the corresponding hamster gene.

Deletion mapping of human chromosome 5 using chromosome-specific DNA probes

A complete genomic DNA library was prepared from a Chinese hamster-human cell hybrid that contains human chromosome 5 as its only human DNA. Unique or low-copy DNA fragments, isolated form recombinant bacteriophage that contained human DNA inserts, were regionally mapped on chromosome 5 using Southern blot analysis of genomic DNA from a series of hybrid cell lines that were selected as having deletions of various portions of 5q. The chromosome 5-specific DNA library, together with a genetic selective procedure allowing the isolation of hybrid cell lines with deletions of virtually any portion of 5q, will provide a means to construct very accurate physical and recombinational maps of this human chromosome. This system represents an excellent opportunity to examine very precisely the relationship between physical and genetic distances for many loci along the length of this autosome.

Molecular approach to analyzing the human 5p deletion syndrome, cri du chat

DNA unique or low-copy fragments were isolated from a genomic DNA library specific for the short (p) arm of human chromosome 5. These chromosome 5p-specific DNA fragments were used to analyze, by Southern blot experiments, somatic cell hybrids that retained either a normal chromosome 5 homolog or a homolog with a partial deletion of 5p, which was derived from either of two persons with the common human deletion syndrome, cri du chat or 5p- syndrome. In these studies, two classes of DNA fragments were identified, those located outside the region deleted in the persons with cri du chat and those located within the deleted region. This latter class of DNA probes will help to define, at the molecular level, a region of 5p that is critical in producing the phenotype associated with the cri du chat syndrome.

Integration of a dominant selectable marker into human chromosomes and transfer of marked chromosomes to mouse cells by microcell fusion

A method for the production of stable mouse-human cell hybrids containing a single human chromosome is described. As a first step in this method, a cloned selectable marker, the E. coli xanthine-guanine phosphoribosyltransferase (Ecogpt) gene, was transferred to human cells to generate cell lines each carrying Ecogpt integrated into a different site. Human chromosomes marked with Ecogpt were transferred further into mouse cells by microcell fusion. Monochromosomal hybrids, in which the human chromosome is maintained by selection, have been produced for chromosomes 2, 5, 16, and a rearranged chromosome involving a translocation between chromosomes 1 and 2. In addition to these monochromosomal hybrids, we have also obtained monochromosomal hybrids for human chromosomes 6, 12, and 17 by selection for the loss of marked chromosome from the microcell hybrids each containing two human chromosomes. Although the human chromosome present in these hybrids cannot be maintained by selection, 80-90% of cells retained the transferred chromosome on continuous growth for 15 days. Monochromosomal hybrids would provide biological materials to construct genetic maps of human chromosomes. In addition, chromosomes marked with dominant selectable markers can be transferred further to any cell line of interest in inter- or intra-species combination.

Molecular genetic analysis of human alcohol dehydrogenase

Human alcohol dehydrogenase (ADH) consists of a complex group of isozymes encoded by at least five non-identical genes, two of which have previously been shown through enzymatic analysis to possess polymorphic variants. Using a cDNA probe the ADH2 gene encoding the beta subunit of human ADH was mapped to human chromosome 4. The cDNA probe for ADH2 was also used to detect a restriction fragment length polymorphism present in human populations. This polymorphism may help establish whether certain ADH allelic variants are linked with certain types of altered alcohol tolerance observed in various individuals. The restriction fragment length polymorphism may also be of use in genetic linkage studies of other genes located near ADH on human chromosome 4.

Mapping of the gene coding for the human GM2 activator protein to chromosome 5

The gene coding for the GM2 activator protein has been mapped to human chromosome 5, using an enzyme-linked immunoadsorbent assay (ELISA) to identify the human protein in human-mouse somatic cell hybrids.

Assignment of human dihydrofolate reductase gene to band q23 of chromosome 5 and of related pseudogene psi HD1 to chromosome 3

The chromosomal location of the human dihydrofolate reductase (DHFR; EC 1.5.1.3) gene that is amplified in a methotrexate-resistant human cell line has been investigated by screening a number of human-Chinese hamster ovary cell hybrids containing terminal and interstitial deletions in human chromosome 5. A correlation of genomic blotting data with the chromosome 5 constitution of the individual hybrids has allowed the assignment of the human DHFR gene to 5q23. The present work also establishes the location of the related intronless pseudogene psi HD1 in chromosome 3.

Transfer of Chinese hamster chromosome 1 to mouse cells and regional assignment of 7 genes: a combination of gene transfer and microcell fusion

We have used a combination of chromosome-mediated gene transfer and microcell fusion techniques to transfer Chinese hamster chromosome 1 to mouse cells. Microcell hybrids containing a single hamster chromosome were analyzed to map genes on this chromosome. We have confirmed the assignment of seven markers (GSR, NP, EST-D, ADK, PEP-S, PGM2, and PEP-B) to hamster chromosome 1. Segregation among the linked markers was induced by X irradiation followed by selection for the retention or loss of human hprt. Cosegregation of markers in independent subclones made it possible to determine the gene order for the seven loci. The gene order proposed for these loci is as follows: pter-GSR-NP-EST-D-ADK-(PEP-S, PGM2)-PEP-B-qter. In addition GSR, NP, EST-D, and ADK have been assigned to pter-1q12; PEP-S and PGM2 to 1q12-1q21, and PEP-B to 1q32-1qter. These regional assignments and gene order on chromosome 1 have provided the information relevant to the linkages conserved between Chinese hamster, mouse, and man.

Assignment of the human MARS gene, encoding methioninyl-tRNA synthetase, to chromosome 12 using human X Chinese hamster cell hybrids

We have isolated interspecific somatic cell hybrids between a temperature-sensitive Chinese hamster ovary (CHO) cell methioninyl -tRNA synthetase mutant and human peripheral leukocytes. The hybrids were selected at 39 degrees C which requires the retention and expression of the human gene, MARS , which complements the defective CHO gene. In vitro heat-inactivation experiments on the methioninyl -tRNA synthetase activity in cell-free extracts from heat-resistant hybrids indicate that the human form of this enzyme and, therefore, the human MARS gene is present in hybrid cells. Cytogenetic analysis of three independent temperature-resistant hybrids revealed the presence of a single human chromosome, number 12. Two other independent hybrids examined contained human chromosome 12 as well as a second human chromosome. Electrophoretic analysis of extracts from hybrid cell lines for a human chromosome 12 marker isozyme, LDH-B, showed a pattern of heterotetrameric bands consistent with the presence of the human form of this enzyme in these cells. The correlation between the presence of the human form of methioninyl -tRNA synthetase and human chromosome 12 in temperature-resistant hybrids indicates that the human MARS locus is located on this chromosome.

Gene mapping and linkage analysis in Chinese hamster: assignment of the genes for APRT, LDHA, IDH2, and GAA to chromosome 3

Interspecific somatic cell hybrids were generated by fusion of Chinese hamster spleen cells or primary fibroblasts with cells from an adenine phosphoribosyltransferase (APRT)-deficient mouse subline derived from LMTK- Cl.1D. Subclones which had been selected for either retention or loss of APRT were subjected to combined isozyme and chromosome segregation analysis. Concordant expression or segregation of Chinese hamster APRT, lactate dehydrogenase A (LDHA), isocitrate dehydrogenase 2 (IDH2), and alpha-glucosidase (GAA) with Chinese hamster chromosome 3 allowed provisional assignment of all four loci to that chromosome. Exceptional subclones, in which coordinate segregation of these syntenic markers was disrupted by chromosome breakage or deletions, allowed further localization of these genes to specific regions of the 3 chromosome.

Isolation and characterization of interspecific heat-resistant hybrids between a temperature-sensitive chinese hamster cell asparaginyl-tRNA synthetase mutant and normal human leukocytes: assignment of human asnS gene to chromosome 18

We isolated interspecific somatic cell hybrids between human peripheral leukocytes and a temperature-sensitive CHO cell line with a thermolabile asparaginyl-tRNA synthetase. The hybrids were selected at 39 degrees C so as to require the expression of the human gene complementing the deficient CHO enzyme. In vitro heat-inactivation profiles of cell-free extracts from temperature-resistant hybrid cells indicate the presence of two forms of asparaginyl-tRNA synthetase. One form is very resistant to thermal inactivation, like the normal human enzyme, while the other form is very thermolabile, like the altered enzyme from the CHO parent. Hybrids and temperature-sensitive segregants derived from them were analyzed for the expression of known human chromosomal marker enzymes. The strong correlation between the expression of the human form of asparaginyl-tRNA synthetase and the presence of human chromosome 18 in hybrids suggests that the human gene, asnS, which corrects the heat-sensitive phenotype of the CHO asparaginyl-tRNA synthetase mutant, is located on chromosome 18.