Assignment of the gene for galactokinase to human chromosome 17 and its regional localisation to band q21-22

Molecular organization of recombinant human-Arabidopsis chromosomes in hybrid cell lines

Although plants and animals are evolutionarily distant, the structure and function of their chromosomes are largely conserved. This allowed the establishment of a human-Arabidopsis hybrid cell line in which a neo-chromosome was formed by insertion of segments of Arabidopsis chromosomes into human chromosome 15. We used this unique system to investigate how the introgressed part of a plant genome was maintained in human genetic background. The analysis of the neo-chromosome in 60- and 300-day-old cell cultures by next-generation sequencing and molecular cytogenetics suggested its origin by fusion of DNA fragments of different sizes from Arabidopsis chromosomes 2, 3, 4, and 5, which were randomly intermingled rather than joined end-to-end. The neo-chromosome harbored Arabidopsis centromeric repeats and terminal human telomeres. Arabidopsis centromere wasn’t found to be functional. Most of the introgressed Arabidopsis DNA was eliminated during the culture, and the Arabidopsis genome in 300-day-old culture showed significant variation in copy number as compared with the copy number variation in the 60-day-old culture. Amplified Arabidopsis centromere DNA and satellite repeats were localized at particular loci and some fragments were inserted into various positions of human chromosome. Neo-chromosome reorganization and behavior in somatic cell hybrids between the plant and animal kingdoms are discussed.

Thymidine kinase 1 through the ages: a comprehensive review

Proliferation markers, such as proliferating cell nuclear antigen (PCNA), Ki-67, and thymidine kinase 1 (TK1), have potential as diagnostic tools and as prognostic factors in assessing cancer treatment and disease progression. TK1 is involved in cellular proliferation through the recovery of the nucleotide thymidine in the DNA salvage pathway. TK1 upregulation has been found to be an early event in cancer development. In addition, serum levels of TK1 have been shown to be tied to cancer stage, so that higher levels of TK1 indicate a more serious prognosis. As a result of these findings and others, TK1 is not only a potentially viable biomarker for cancer recurrence, treatment monitoring, and survival, but is potentially more advantageous than current biomarkers. Compared to other proliferation markers, TK1 levels during S phase more accurately determine the rate of DNA synthesis in actively dividing tumors. Several reviews of TK1 elaborate on various assays that have been developed to measure levels in the serum of cancer patients in clinical settings. In this review, we include a brief history of important TK1 discoveries and findings, a comprehensive overview of TK1 regulation at DNA to protein levels, and recent findings that indicate TK1’s potential role in cancer pathogenesis and its growing potential as a tumor biomarker and therapeutic target.

XPA-210: a new proliferation marker to characterize tumor biology and progression of renal cell carcinoma

PURPOSE

Recent lung cancer data have shown an association of XPA-210, a key peptide of thymidine kinase, with advanced disease. We thus assessed its proliferation status in primary (M0) and metastatic (M1) renal cell carcinoma (RCC).

METHODS

Paraffin slides from 30 patients (mean age: 61.2 years; range: 42-84) with clear-cell RCC (M0 in 10; non-osseous M1 in 10; osseous M1 in 10) were T-matched for pT1/pT3. Corresponding malignant and benign renal parenchyma were immunohistochemically stained against XPA-210. Staining density was determined by a semi-quantitative score of positive cell shares. Staining intensity included the precise cellular location.

RESULTS

XPA-210 occurred predominantly in the nucleus, with a minor cytoplasmatic component. RCC tissue showed higher density and stronger intensity than did benign renal tissue in both nucleus (P = 0.005) and cytoplasm (P = 0.01). Density and intensity were positively associated with tumor diameters ≤7 cm, whereas they tended to correlate inversely in tumors >7 cm (P 0.07). Density of stained cells was significantly higher in metastatic than in localized RCC in both nucleus and cytoplasm (P < 0.04). Non-osseous M1 tissue showed significantly higher nuclear and cytoplasmatic expression than did M0 tissue (P < 0.05), whereas osseous M1 tissue did not.

CONCLUSIONS

In all RCC tissues, XPA-210 staining was significantly higher in the nucleus than in cytoplasm, potentially owing to large cytoplasmatic spaces as a characteristic histologic feature of clear-cell component. XPA-210 expression gradually increased from localized to metastatic disease, peaking in patients without bone involvement. Therefore, XPA-210 might aid the selection of appropriate adjuvant treatment in high-risk patients.

The molecular architecture of human N-acetylgalactosamine kinase

Galactokinase plays a key role in normal galactose metabolism by catalyzing the conversion of alpha-d-galactose to galactose 1-phosphate. Within recent years, the three-dimensional structures of human galactokinase and two bacterial forms of the enzyme have been determined. Originally, the gene encoding galactokinase in humans was mapped to chromosome 17. An additional gene, encoding a protein with sequence similarity to galactokinase, was subsequently mapped to chromosome 15. Recent reports have shown that this second gene (GALK2) encodes an enzyme with greater activity against GalNAc than galactose. This enzyme, GalNAc kinase, has been implicated in a salvage pathway for the reutilization of free GalNAc derived from the degradation of complex carbohydrates. Here we report the first structural analysis of a GalNAc kinase. The structure of the human enzyme was solved in the presence of MnAMPPNP and GalNAc or MgATP and GalNAc (which resulted in bound products in the active site). The enzyme displays a distinctly bilobal appearance with its active site wedged between the two domains. The N-terminal region is dominated by a seven-stranded mixed beta-sheet, whereas the C-terminal motif contains two layers of anti-parallel beta-sheet. The overall topology displayed by GalNAc kinase places it into the GHMP superfamily of enzymes, which generally function as small molecule kinases. From this investigation, the geometry of the GalNAc kinase active site before and after catalysis has been revealed, and the determinants of substrate specificity have been defined on a molecular level.

Cloning of the galactokinase cDNA and identification of mutations in two families with cataracts

Galactokinase is an essential enzyme for the metabolism of galactose and its deficiency causes congenital cataracts during infancy and presenile cataracts in the adult population. We have cloned the human galactokinase cDNA, which maps to chromosome 17q24, and show that the isolated cDNA expresses galactokinase activity in bacteria and mammalian cells. We also describe two different mutations in this gene in unrelated families with galactokinase deficiency and cataracts. The availability of the cloned galactokinase gene provides an important reference to identify mutations in patients with galactokinase deficiency and cataracts.

Regulation of galactose-1-phosphate uridyltransferase gene expression

Analysis of both the human and rat galactose-1-phosphate uridyltransferase (GALT) genes reveal 5' regulatory consensus sequences suggestive of a housekeeping gene. This is in accord with the finding of GALT activity in all tissues. However, the complications seen in galactosemia, in particular ovarian dysfunction and verbal dyspraxia, suggest organ-specific sensitivity to lack of GALT activity. Analysis of steady-state GALT mRNA and specific activity levels in adult rat organs reveals a marked difference between organs that correlates with the degree of organ dysfunction in humans with galactosemia. The organ variation in GALT mRNA and activity thus appears to be due to genetic regulation. Discernment of the pathophysiologic basis for the organ-specific complications requires an understanding of the basis for the differences in organ regulation. The present state of knowledge of the regulation of the Leloir enzymes in general, GALT in particular, from prokaryotes to mammals is discussed.

Mammalian deoxyribonucleoside kinases

The mammalian deoxyribonucleoside kinases are deoxycytidine kinase, thymidine kinase 1 and 2 and deoxyguanosine kinase. These enzymes phosphorylate deoxyribonucleosides and thereby provide an alternative to de novo synthesis of DNA precursors. Their activities are essential for the activation of several chemotherapeutically important nucleoside analogues. In recent years, these enzymes have been thoroughly characterised with regard to structure, substrate specificity and patterns of expression. In this review, these results are reviewed and furthermore, the physiologic metabolic role of the anabolic enzymes is discussed in relation to catabolic pathways. The significance of this information for the development of therapeutic protocols and choice of animal model systems is discussed. Finally, alternative pathways for nucleoside analogue phosphorylation are surveyed, such as the phosphotransfer capacity of 5'-nucleotidase.

A progressive early onset cataract gene maps to human chromosome 17q24

Cerulean cataract is an autosomal dominant, early onset, progressive cataract characterized by blue or white opacifications in the nucleus and cortex of the lens. A large four-generation pedigree in which cerulean cataract segregates was studied for linkage analysis. A genome wide search was undertaken after the plausible candidate genes were excluded and the cerulean cataract phenotype was mapped to chromosome 17q24. The three markers closest to the disease gene are D17S802 (Z)(theta) = 9.46 at (theta) = 0.085), D17S836 (Z(theta) = 5.26 at (theta) = 0.031) and AFMa238yb5 (Z(theta) = 7.11 at (theta) = 0.032). Multipoint linkage analyses yielded a maximum lod score of Z(theta) = 13.71, placing the cerulean cataract gene between D17S802 and D17S836 at (theta) = 0.048 and (theta) = 0.013, respectively.

Cloning of a human galactokinase gene (GK2) on chromosome 15 by complementation in yeast

A human cDNA encoding a galactokinase (EC 2.7.1.6) was isolated by complementation of a galactokinase-deficient (gal1-) strain of Saccharomyces cerevisiae. This cDNA encodes a predicted protein of 458 amino acids with 29% identity to galactokinase of Saccharomyces carlsbergensis. Previous studies have mapped a human galactokinase gene (GK1) to chromosome 17q23-25, closely linked to thymidine kinase. The galactokinase gene that we have isolated (GK2) is located on chromosome 15. The relationship between the disease locus for galactokinase deficiency galactosemia, which is responsible for cataracts in newborns and possibly presenile cataracts in adults, and the two galactokinase loci is unknown.

Gene mapping of ocular diseases

Increasing awareness of the role of genetic factors in the causation of many human eye diseases has made ocular genetics one of the fastest growing areas of ophthalmology. The objective of this paper is to present the basic principles of gene mapping and their application to ophthalmology. The techniques used to map the genome are reviewed with emphasis placed on molecular genetics. The advances in this area have already provided the major impetus to the areas of diagnosis and prevention of some genetic eye disorders. Tables are presented that list the autosomal, X-linked and mitochondrial assignment of eye genes and disorders with ocular involvement.

Normal expression of thymidine kinase and O6-methylguanine-DNA methyltransferase in cultured fibroblasts from individuals with hereditary galactokinase deficiency

Expression of the enzymes galactokinase, thymidine kinase, and O6-methylguanine-DNA methyltransferase is occasionally coordinately regulated in human cell lines. We have measured the activities of these three enzymes in extracts of fibroblasts from individuals with hereditary galactokinase deficiency. These cells do not express measurable galactokinase activity. The levels of O6-methylguanine-DNA methyltransferase were in the normal range in cells from three galactokinase-deficient individuals. The activity of thymidine kinase in the affected cells was in the normal range for two of the three individuals. The reduced thymidine kinase activity in the third individual reflected the extremely poor growth of the cells in culture. Immortalization of one galactokinase-deficient cell line resulted in loss of O6-methylguanine-DNA methyltransferase activity, but the galactokinase and thymidine kinase levels remained unchanged. The data indicate that the loss of galactokinase activity in these individuals is the consequence of an alteration of gene expression which does not involve coordinate silencing with the thymidine kinase and methyltransferase loci.

Molecular forms in human serum of enzymes synthesizing DNA precursors and DNA

Both thymidine kinase (TK) and DNA polymerase (DNAp) are present in measurable amounts in human serum. Even though the use of TK as a clinical marker is rapidly increasing there has been no attempt to characterize the serum TK in a wider extent, i.e.; with respect to Mw or other biochemical parameters. Therefore sera with high TK or DNAp activities derived from patients with cytomegalovirus (CMV) infection, B12-deficiency and leukaemia were fractionated by gel exclusion chromatography. The TK activity eluted as two peaks, one major TK activity with an apparent molecular weight (Mw) or 730 kD and one minor TK activity corresponding to a Mw of 58 kD. The amount of TK activity at 58 kD varied between 7 and 23% of total activity, depending on the serum fractionated. The DNAp activity in sera from patients with malignant disease and B12 deficiency eluted as a single peak corresponding to a Mw of 240 kD. A DNAp with a different Mw (greater than 1000 kD) was recovered from 1 of 3 investigated immunosuppressed patients with CMV infection. A similar pattern of enzyme forms was observed when sera were separated by glycerol gradient centrifugation. The effect of high salt and various reaction solution components on the enzymes were studied. The only condition found that affected the molecular forms of TK was the state of reduction. Incubation of sera with high concentrations of dithioerythritol (DTE) (400 mM) prior to separation transferred all serum TK to the 58 kD form, it also converted most of the serum DNAp from the 240 kD form to a smaller form (56 kD) without affecting the total recovery of enzymatic activity. The reaction product from both TK forms was exclusively monophosphate and none of the TK forms could efficiently utilize cytidine triphosphate as phosphate donor. The substrate kinetics of the small serum TK fraction was identical with those of an enzyme with similar size purified from proliferating HeLa cells, indicating that both serum TK activities are forms of TK 1, the proliferation associated cellular isozyme.

Thymidine kinase in human leukemia--expression of three isoenzyme variants in six patients with chronic myelocytic leukemia

In six patients with untreated, chronic myelocytic leukemia (CML), the dominating thymidine kinase (TK) activity was compared with the fetal form, TK 1, from mitogen stimulated and the adult form TK 2 from unstimulated normal human lymphocytes, and with TK-1-onc, TK-3-onc and TK-4-onc. This was done in human acute, myelocytic and monocytic leukemias, using the combined thymidine/dTTP enzyme kinetics for isoenzyme characterization. TK-1-onc was found in one, TK-2-onc in two and TK-3-onc in three CML patients. The suffix -onc indicates the difference in ATP kinetics and molecular weights between the normal and the leukemic thymidine kinases. A possible relation between the isoenzyme forms and the types of leukemias is discussed.

Transcriptional and posttranscriptional mechanisms regulate murine thymidine kinase gene expression in serum-stimulated cells

We previously isolated and characterized the structure of murine thymidine kinase (tk) genomic and cDNA sequences to begin a study designed to identify regions of the tk gene important for regulated expression during the transition of cells from G0 to a proliferating state. In this report, we describe the stable transfection of the cloned gene into L-M(TK-) cells and show that both thymidine kinase (TK) enzyme activity and DNA synthesis increase in parallel when transfectants in G0 arrest are stimulated by serum. To define promoter and regulatory regions more precisely, we have constructed a series of tk minigenes and have examined their expression in stable transfectants after serum stimulation. We have identified a 291-base-pair DNA fragment at the 5' end of the tk gene that has promoter function, and we have determined its sequence. In addition, we have found that DNA sequences which mediate serum-induced expression of TK are transcribed, since expression of the murine tk cDNA, fused to a promoter from either the murine tk gene, the simian virus 40 early region, or the herpes simplex virus tk gene, is stimulated by serum. Our constructs also reveal that the murine tk polyadenylation signal is not required for regulation, nor is most of the 3' untranslated region. RNA dot blot analysis indicates that murine cytoplasmic tk mRNA levels always parallel TK enzyme activity. Nuclear runon transcription assays show less than a 2-fold increase in transcription from the cloned tk gene in serum-stimulated transfectants, but an 11-fold increase in mouse L929 cells, which are inherently TK+. These results taken together suggest that the murine tk gene is controlled in serum-stimulated cells by a transcriptional mechanism influenced by DNA sequences that flank tk and also by a posttranscriptional system linked to gene sequences that are transcribed.

Transcriptional and posttranscriptional mechanisms regulate murine thymidine kinase gene expression in serum-stimulated cells

We previously isolated and characterized the structure of murine thymidine kinase (tk) genomic and cDNA sequences to begin a study designed to identify regions of the tk gene important for regulated expression during the transition of cells from G0 to a proliferating state. In this report, we describe the stable transfection of the cloned gene into L-M(TK-) cells and show that both thymidine kinase (TK) enzyme activity and DNA synthesis increase in parallel when transfectants in G0 arrest are stimulated by serum. To define promoter and regulatory regions more precisely, we have constructed a series of tk minigenes and have examined their expression in stable transfectants after serum stimulation. We have identified a 291-base-pair DNA fragment at the 5' end of the tk gene that has promoter function, and we have determined its sequence. In addition, we have found that DNA sequences which mediate serum-induced expression of TK are transcribed, since expression of the murine tk cDNA, fused to a promoter from either the murine tk gene, the simian virus 40 early region, or the herpes simplex virus tk gene, is stimulated by serum. Our constructs also reveal that the murine tk polyadenylation signal is not required for regulation, nor is most of the 3' untranslated region. RNA dot blot analysis indicates that murine cytoplasmic tk mRNA levels always parallel TK enzyme activity. Nuclear runon transcription assays show less than a 2-fold increase in transcription from the cloned tk gene in serum-stimulated transfectants, but an 11-fold increase in mouse L929 cells, which are inherently TK+. These results taken together suggest that the murine tk gene is controlled in serum-stimulated cells by a transcriptional mechanism influenced by DNA sequences that flank tk and also by a posttranscriptional system linked to gene sequences that are transcribed.

Physical linkage of the genes for platelet membrane glycoproteins IIb and IIIa

The fibrinogen receptor on human platelets is a prototypic member of the integrin family and is composed of subunit glycoproteins IIb (gpIIb) and IIIa (gpIIIa) in a 1:1 stoichiometric ratio. We have isolated cDNA clones for gpIIb and gpIIIa and localized both genes to chromosome 17. In the current study, several approaches were used to localize and map the genes for gpIIb and gpIIIa. A preliminary evaluation of subchromosomal localization was performed by using a panel of mouse-human somatic cell hybrids that contain different amounts of the long arm of human chromosome 17. Southern hybridization to the DNA of these hybrids shows that both genes map near the thymidine kinase gene. In situ hybridization to intact human chromosomes localized both genes to the 17q21-22 region. To better define the physical distance between the two genes, we examined the genomic hybridization pattern of each cDNA probe to high molecular weight restriction fragments separated by pulsed-field gel electrophoresis. Serial hybridizations of the same filter have allowed construction of long-range Mlu I and Sfi I restriction maps spanning more than 500 kilobases. Finally, nonoverlapping portions of the cDNAs for both gpIIb and gpIIIa were used to probe Sfi I digests of genomic DNA separated by field-inversion gels. This confirmed that the genes are physically linked within the same 260-kilobase Sfi I fragment and suggests that the gene for gpIIb is located on the 3' side of the gene for gpIIIa. These results suggest that coordinate expression of gpIIb and gpIIIa may depend on physical proximity.

Galactose and cataract

Galactosemia is a disorder caused by a deficiency of any one of three possible enzymes involved in the metabolism of galactose: galactokinase, transferase or epimerase. Any single deficient enzyme can result in cataract through the accumulation of galactitol in the lens. The ophthalmologist may play an important role in this disease, since early recognition of cataract development followed by the initiation of a galactose-free diet may lead to clearing of lenticular opacities. The clinical and laboratory findings that distinguish the three enzyme deficiency disorders of galactosemia are discussed. The biochemical genetics of each enzyme also are reviewed, along with the recent evidence linking heterozygous galactokinase deficiency and presenile cataract.

Regional mapping panel for human chromosome 17: application to neurofibromatosis type 1

A somatic cell hybrid mapping panel was constructed to localize cloned DNA sequences to any of 15 potentially different regions of human chromosome 17. Relatively high-resolution mapping is possible for 50% of the chromosome length in which 12 breakpoints are distributed over approximately 45 megabases, with an average spacing estimated at 1 breakpoint every 2-7 megabases. This high-resolution capability includes the pericentromeric region of 17 to which von Recklinghausen neurofibromatosis (NF1) has recently been mapped. Using 20 cloned genes and anonymous probes, we have tested the expected order and location of panel breakpoints and confirmed, refined, or corrected the regional assignment of several cloned genes and anonymous probes. Four markers with varying degrees of linkage to NF1 have been physically localized and ordered by the panel: the loosely linked markers myosin heavy chain 2 (25 cM) to p12----13.105 and nerve growth factor receptor (14 cM) to q21.1----q23; the more closely linked pABL10-41 (D17S71, 5 cM) to p11.2; and the tightly linked pHHH202 (D17S33) to q11.2-q12. Thus, physical mapping of linked markers confirms a pericentromeric location of NF1 and, along with other data, suggests the most likely localization is proximal 17q.

The physical map of Mus musculus chromosome 11 reveals evolutionary relationships with different syntenic groups of genes in Homo sapiens

The physical localization of sequences homologous to three cloned genes was determined by in situ hybridization to metaphase chromosomes. Previous work had assigned the skeletal myosin heavy chain gene cluster (Myh), the functional locus for the cellular tumor antigen p53 (Trp53-1), and the cellular homologue of the viral erb-B oncogene (Erbb) to Mus musculus chromosome 11 (MMU11). Our results provide regional assignments of Myh and Trp53-1 to chromosome bands B2----C, and of Erbb to bands A1----A4. Taken together with in situ mapping of three other loci on MMU 11 (Hox-2 homeobox-containing gene cluster, the Sparc protein, and the Colla-1 collagen gene), which have been reported elsewhere, these data allowed us to construct a physical map of MMU11 and to compare it with the linkage map of this chromosome. The map positions of the homologous genes on human chromosomes suggest evolutionary relationships of distinct regions of MMU11 with six different human chromosome arms: 1p, 5q, 7p, 16p, 17p, and 17q. The delineation of conserved chromosome regions has important implications for the understanding of karyotype evolution in mammalian species and for the development of animal models of human genetic diseases.

Chromosomal assignment of gene encoding the largest subunit of RNA polymerase II in the mouse

The gene encoding the largest subunit of RNA polymerase II was mapped to mouse chromosome 11 by Southern blotting analysis of mouse-Chinese hamster somatic cell hybrids and by in situ hybridization. This assignment extends the previously defined homology between mouse chromosome 11 and human chromosome 17.

Biochemical and genetic properties of oligomeric structures: a general approach

The oligomers constituted by association of different subunits can exist under multiple forms. In the case of the genetically variable proteins, such a multiplicity leads to numerous questions (i) on the enumerations: what is the number of active forms when a given subunit can make the oligomer inactive, or when the subunits are encoded by s alleles; (ii) on the subunit effects on biochemical properties: how to estimate these effects, are they equal, are there interactions between subunits, etc. Theoretical methods for the study of such oligomeric structures are developed, which mainly rely on linear model techniques. Peculiar properties examined are Vmax and Km, but also the quantities of the various oligomers, which depend on their association law. This approach is extended to the oligomers composed of different sets of subunits, as are for example some enzymes. These aspects are discussed from numerous bibliographic examples, with special reference to molecular interactions (protein complementation or molecular heterosis). Otherwise the genetic application of this theoretical approach is presented: it is possible to consider a genotype as an oligomer of alleles, and thus to study their effects and their interactions, in the one-locus case as well as in the several-loci case. The relevance of this generalization is discussed in connection with two other concepts, the "sequence space" used in molecular evolution and the regression of the genotypic values on the number of alleles used in quantitative genetics.

Purification of human galactokinase and evidence for its existence as a monomer form

A procedure for preparing a highly purified galactokinase (ATP:D-galactose 1-phosphotransferase, EC 2.7.1.6) from human erythrocytes and placenta is described, involving DEAE-Sephacel, ammonium sulfate fractionation, gel-filtration and a subsequent chromatography step on Blue Sepharose CL-6B. The final chromatography step yields a homogeneous preparation of high specific activity. The subunit molecular weight was determined to be 38 000 for both placental and erythrocyte galactokinases. Both active preparations of the native enzyme eluted from a gel filtration column gave a molecular weight of 37 000-38 000, thus suggesting the enzyme to be present in monomeric form. The isoelectric points for both crude and their respective purified enzymes was determined to be at pH 5.7. This method for purifying human galactokinase from placenta and erythrocytes represents a significant improvement over that previously reported and contradicts past evidence for the enzyme existing as a dimer.

A coordinate relationship between the GALK and the TK1 genes of the Chinese hamster

Chinese hamster cells in culture were treated with various concentrations of thymidine, 5-bromodeoxyuridine, trifluorothymidine, and 2-deoxy-D-galactose. Selection was made for deficiencies in the activities of galactokinase and thymidine kinase. Selection in the presence of thymidine, 5-bromodeoxyuridine, and trifluorothymidine was expected to produce clones deficient in thymidine kinase only, whereas those deficient in galactokinase were expected to be selected in the presence of 2-deoxy-D-galactose. However, it was found that clones growing in the presence of these inhibitors were frequently deficient in both enzymes. Or if a clone was deficient in only one, the deficiency frequently was not expected according to the selection procedure. This indicates some sort of coordinate relationship between the two gene loci, GALK and TK1, which specify galactokinase and thymidine kinase, respectively. GALK and TK1 are linked in all primates and rodents in which linkage determinations have been made. It is therefore probable that this linkage has been conserved for a long period of time. It is suggested that the apparent relationship between the two genes shown by the data presented here, as well as by others, supports the conclusion that linkage has been conserved by natural selection and is therefore not fortuitous.

The gene cluster for human U2 RNA is located on chromosome 17q21

The gene cluster for human U2 RNA has been mapped to chromosome 17q21 by in situ hybridization and hybridization analysis of DNA from mouse/human somatic cell hybrids.

Two homoeo box loci mapped in evolutionarily related mouse and human chromosomes

The homoeo box is a 180-base pair (bp) DNA sequence conserved in Drosophila homoeotic genes, which regulate early development. These DNA sequences are present in open reading frames and have been identified in specific gene transcripts in Drosophila and Xenopus embryos; they possess structural features in common with genes encoding some DNA-binding proteins. Homologous homoeo box sequences have been detected in species ranging from insects and annelids to vertebrates. The high degree of sequence conservation (70-90%) among different species suggests a strong evolutionary relationship and implies a common role in embryonic development. To test this hypothesis, one approach we have used is to examine the patterns of genetic organization of homoeo box sequences in mouse and human for any similarities; the second approach is to localize the chromosomal map positions of homoeo box sequences in the two species. A similar genomic organization and chromosomal distribution of homoeo box sequences would argue for a conserved function and might shed light on their mechanism of action. Here, we describe experiments which show that two homoeo box loci map, respectively, to evolutionarily related regions on mouse chromosome 11 and human chromosome 17.

Further regional localization of the genes for human acid alpha glucosidase (GAA), peptidase D (PEPD), and alpha mannosidase B (MANB) by somatic cell hybridization

We have further regionally localized the gene for human acid alpha glucosidase (GAA) to 17q21----q23 by examination of hybrid clones derived from a fusion between human fibroblasts carrying a 17/19 balanced translocation (17pter----17q23::19p13.3----19pter; 19qter----p13.3::17q23----17qter) and a mouse line deficient in thymidine kinase. These hybrids were constantly maintained in HAT selective media in order to select for the presence of the human thymidine kinase gene on the intact chromosome 17 (17q21-q22) or the 17/19 (17pter----17q23::19p13.3----19pter) translocation chromosome. We detected human GAA by rocket immunoelectrophoresis, using a human specific heterologous antibody raised against human acid alpha glucosidase (GAA) (Honig et al. 1984). Three secondary clones, which contained the 17/19 translocation and no intact chromosome 17 or 19, were still positive for GAA. Two of these secondary clones contained the distal portion of the 17/19 translocation chromosome, with a break in the band 17q21 (probably at 17q21.2), attached to a mouse chromosome. Combined with earlier results (Weil et al. 1979; Nickel et al. 1982; Honig et al. 1984), the gene for GAA can be assigned to 17q21.2----17q23. Additionally, these clones were negative for human peptidase D (PEPD), alpha mannosidase B (MANB), and phosphohexose isomerase (PHI). Combined with previous results (Ingram et al. 1977; Bruns et al. 1979), these results exclude the genes for PEPD and MANB from 19pter----19p13.3 and confirm the exclusion of the gene for PHI from this segment of chromosome 19 (Wilson et al. 1984; Ingram et al. 1977).

Cotransfer of syntenic human genes into mouse cells using isolated metaphase chromosomes or cellular DNA

Chromosome-mediated gene transfer (CMGT) of the human genes for hypoxanthine phosphoribosyl transferase (HPRT) and cytosol thymidine kinase (TK1) into HPRT deficient mouse A9 cells or TK deficient Swiss mouse 3T3TK- cells was found to occur at frequencies at least one order of magnitude higher than DNA-mediated gene transfer (DMGT). The frequency of CMGT into 3T3TK- cells was reduced by more than an order of magnitude by a posttreatment of the recipient cells with dimethyl sulphoxide (DMSO). After CMGT, expression of the non-selected genes coding for galactokinase (GALK) and acid alpha-glucosidase (GAA), both syntenic with TK1, was observed in a number of transformants. From the pattern of cotransfer, a tentative gene ordering of CENTROMERE-GALK-TK1-GAA on human chromosome 17 was deduced. Chromosome-mediated cotransfer of X-linked human phosphoglycerate kinase (PGK) with HPRT was observed in two out of 33 A9 transformants analysed. DNA-mediated cotransfer of a syntenic gene was only observed for GALK, cotransferred with TK1 in two out of 18 TK+ transformants of mouse LTK- cells. Therefore, with murine cells as recipients of human donor genetic material, CMGT results in a higher frequency of transfer and a higher incidence of cotransfer of syntenic genes than DMGT using cellular DNA in the same cell system.

Regional mapping of the human gene for lysosomal alpha-glucosidase by in situ hybridization

The current approach to the chromosomal localization of genes coding for lysosomal enzymes has been the correlation of enzymatic and karyotypic analyses of human-rodent somatic cell hybrids. The feasibility of regional mapping depends on the availability of human cells with informative chromosomal rearrangements. In this communication we report the first localization of a gene coding for a lysosomal enzyme by in situ hybridization. The application of an acid alpha-glucosidase cDNA probe to normal human chromosomes allowed direct regional mapping of the alpha-glucosidase locus (GAA) to the region q23----q25 of chromosome 17.

Isoelectric-focusing of galactokinase in lens and other tissues

Thin-layer isoelectric focusing was used to investigate galactokinase in lenses from humans, cows, rats, rabbits and also in other tissues (red cells, liver, kidney, brain, placenta) from these species. In each case the enzyme activity was present as a single isozyme. The isoelectric point was the same in lens, red cell and other tissues of the same species, but differed from species to species. Post-translational modification due to deamidation was not detected in the lens or red cell from these species. Galactokinase activities in whole tissue extract were determined in different tissues of the various species. There were wide variations in activity. In the adult human lens, both normal and cataractous, it was low. The findings indicate that isoelectric focusing of RBC galactokinase combined with specific enzyme staining allows one to monitor lens galactokinase in patients with cataracts.

Genetic analysis of the 15;17 chromosome translocation associated with acute promyelocytic leukemia

Somatic cell hybrids have been constructed between a thymidine kinase-deficient mouse cell line and blood leukocytes from a patient with acute promyelocytic leukemia showing the 15q+;17q- chromosome translocation frequently associated with this disease. One hybrid contains the 15q+ translocation chromosome and very little other human material. We have shown that the c-fes oncogene, which has been mapped to chromosome 15, is not present in this hybrid and, therefore, probably is translocated to the 17q- chromosome. Analysis of the genetic markers present in this hybrid has enabled a more precise localization of the translocation breakpoints on chromosomes 15 and 17. Our experiments also have enabled an ordering and more precise mapping of several genetic markers on chromosomes 15 and 17.

The eye and the chromosome

The first linkage of disease traits on the human X-chromosome was reported in 1937, and the first assignment of a human disease to an autosome was made 26 years later in 1963. Now, after only 19 years, there are at least 338 assignments to loci on the human chromosome map. This amazing expansion of information extends to eye diseases. In this review, basic mechanisms of mutation are discussed, and the basic methodologies used for gene assignments are explained. All of the eye-related, definite, autosomal assignments are presented. The diseases that have regional assignments on the X-chromosome are discussed, and the remaining X-linked eye diseases are listed in table form.

Genetic control of drug resistance: assignment of ama-1 to Chinese hamster chromosome 7, confirmation of assignment of genes coding for TK, GALK, and ACP to chromosome 7, and tentative assignment of TPI to chromosome 8

The gene which specifies a subunit of RNA polymerase II, ama-1, is assigned to chromosome 7 in the Chinese hamster. The assignment of genes coding for TK, GALK, and ACP to chromosome 7 is confirmed, with a provisional regional assignment of TK and GALK to 7q. On the basis of one clone with six subclones, a provisional assignment of TPI to Chinese hamster chromosome 8 is made. With the assignment of tk and ama-1 to chromosome 7 in the CHO cell line Ama1, this chromosome is shown to have two selectable markers.

Partial purification and characterization of the mRNA for human thymidine kinase and hypoxanthine/guanine phosphoribosyltransferase

We used direct microinjection of poly(A)+RNA into individual hypoxanthine/guanine phosphoribosyltransferase-deficient or thymidine kinase-deficient cells and detected the specific in vivo translation products as an assay for human hypoxanthine/guanine phosphoribosyltransferase or thymidine kinase mRNAs. The incorporation of [3H]hypoxanthine or [3H]thymidine into cells in response to injected mRNA was assayed in situ by autoradiography. Methylmercuric hydroxide/agarose gel analysis showed that human hypoxanthine/guanine phosphoribosyltransferase mRNA contains approximately 1,530 nucleotides, which is twice the number required for its protein coding capacity. The mRNA for human cytoplasmic thymidine kinase is estimated to be approximately the same length; thus, the size of the cytosol thymidine kinase subunit can be predicted to be approximately 47,000 daltons, if the full coding capacity of its mRNA is utilized.

Elucidation of an unbalanced chromosome translocation by gene dosage studies

A chromosome abnormality, 46,XY,1p+, was detected in cultured amniotic fluid cells. The chromosomes of both parents were normal and it was impossible to recognise the extra chromosomal material using current banding techniques. The activity of acid alpha-glucosidase was found to be consistently higher than controls whereas activity of several other lysosomal enzymes, galactokinase and thymidine kinase was not. The results suggest that the extra material is that part of the long arm of chromosome 17 bearing the gene for acid alpha-glucosidase but not the genes for galactokinase and thymidine kinase. This would narrow the assignment of the acid alpha-glucosidase locus to 17q22 leads to 17 qter.

Confirmational, provisional, and/or regional assignment of 15 enzyme loci onto Chinese hamster autosomes 1, 2, and 7

PEG-mediated fusion between mouse Cl1d cells and primary Chinese hamster spleen cells produced interspecific hybrids which slowly and nonrandomly segregated Chinese hamster chromosomes. Cytogenetic and isozyme analysis (31 loci) of HAT and BrdU selected hybrid clones and subclones and of members of a hybrid clone panel retaining different combinations of Chinese hamster chromosomes enabled provisional assignment of the following enzyme loci on Chinese hamster chromosomes: thymidine kinase, galactokinase, and acid phosphatase-1 to chromosome 7; galactose-1-phosphate uridyltransferase to chromosome 2; and adenosine kinase, esterase D, glutathione reductase, glyoxalase, nucleoside phosphorylase, peptidases B and S, and phosphoglucomutase (PGM) 2 to chromosome 1. Assignments of PGM1, 6-phosphogluconate dehydrogenase, and enolase 1 to chromosome 2 were confirmed, and a chromosome 2 deletion (q23-q33) enabled the provisional assignment of PGM1 to that region. The assignments provide markers for the study of the genetic consequences of chromosomal rearrangements in Chinese hamster cell lines and support the concept of conservation of mammalian autosomal linkage groups.

The genes for growth hormone and chorionic somatomammotropin are on the long arm of human chromosome 17 in region q21 to qter

We used a cloned cDNA probe for human growth hormone and Southern blotting techniques to analyze DNA from a series of rodent x human somatic cell hybrids for the presence of growth hormone-related sequences. Our results provide evidence for the assignment of the genes for growth hormone and chorionic somatomammotropin as well as a growth hormone-like gene to human chromosome 17. Analysis of mouse x human hybrid cells containing only part of the long arm of chromosome 17 enabled us to localize these genes to region 17q21 to 17qter.

Association of the herpes simplex-1 viral gene for thymidine kinase with the human gene for adenylate kinase-1 in biochemically transformed cells

The herpes simplex type 1 biochemically transformed human cell line, HB-1, was fused with thymidine kinase deficient rodent cells, and 18 hybrids were isolated using the HAT-ouabain selection system. The selected enzyme, viral thymidine kinase, was present in all 18 hybrids. In 16 of 18 hybrids the viral gene for thymidine kinase cosegregated with the human gene for adenylate kinase-1 (AK-1). Thirty-six bromodeoxyuridine (BrdUrd) resistant sublines were isolated from the 16 human AK-1 positive hybrids. Each BrdUrd-resistant subline was examined for the presence of the viral TK gene by back-selection in HAT medium, and for human AK-1. In all 36 BrdUrd-resistant sublines the viral TK gene cosegregated with the human AK-1 gene. These results indicate that the transforming viral DNA fragment was associated with a specific human chromosomal region in HB-1 cells.

DNA-mediated cotransfer of unlinked mammalian cell markers into mouse L cells

Purified DNA from three different types of mammalian cells was precipitated with calcium phosphate and added to mouse L cells deficient in thymidine kinase (TK). Donor DNA was prepared from three cell lines: (a) mouse cells transfected with UV-inactivated herpes simplex virus (HSV) type 1, or a purified fragment of HSV carrying the TK gene (b) human HeLa cells, and (c( CHO, a cell line derived from Chinese hamster ovaries. Several hypoxanthine-aminopterin-thymidine resistant colonies were isolated from each experiment. The origin of the TK that is expressed in these cells was studied by polyacrylamide gel electrohporesis, isoelectric focusing, or heat stability. The TK in all instances was of the donor origin. To determine the extent of gene transfer we have assayed the CHO and HeLa DNA transfectants for galactokinase (GALK), a marker closely linked to TK, and 25 other isozymes representing a large number of different chromosomes. No cotransfer of GALK was observed, indicating that the size of the transferred DNA segment is limited. We observed that, in one instance, esterase-D, an unlinked marker of Chinese hamster origin, was transferred along with TK. These experiments indicate that nonselected markers can be transferred by this method, although at a low efficiency.

Chromosome-mediated gene transfer results in two classes of unstable transformants

The human thymidine kinase gene has been transferred from HeLa S3 cells to mouse LM(TK-) cells via isolated metaphase chromosomes. Efficient transfer of the thymidine kinase gene (1.8 X 10(-5) colonies per recipient cell) was obtained when the donor chromosomes were precipitated with calcium phosphate and the recipient cells were treated with 10% (vol/vol) dimethyl sulfoxide. Thirty-five independent cell lines were analyzed in detail. Cytologically detectable donor chromosome fragments were observed in 14% of the cell lines. Many of the transformed cell lines were also found to express the human genes for galactokinase (23% of the transformed cell lines) and procollagen type I (69% of the transformed cell lines), which are syntenic to thymidine kinase on human chromosome 17. On the basis of stability analyses, three classes of transformed cell lines were defined and characterized. One class of transformants was stable, showing no loss of the transferred phenotype in the absence of selection. A second group of transformants was unstable, losing the thymidine kinase phenotype at a rate of 1.5-2.5% per day. This group of transformants was found to possess large donor chromosome fragments (macrotransgenomes) and relatively low levels of donor gene activity. The third group of transformants lost the thymidine kinase phenotype rapidly, at a rate of 6-10% per day. These cell lines contained small, cytologically undetectable transgenomes (microtransgenomes) and overexpressed the transferred thymidine kinase gene.

Cotransfer of linked eukaryotic genes and efficient transfer of hypoxanthine phosphoribosyltransferase by DNA-mediated gene transfer

The efficiency of DNA-mediated transfer of the gene (hprt) for hypoxanthine phosphoribosyltransferase (HPRT; IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) is dependent upon the recipient cell used. hprt has been transferred into mouse TG8 or Chinese hamster CHTG49 cells at a high frequency, similar to the frequency of the gene (tk) for thymidine kinase (TK; ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) transfer into mouse LMTK- cells (i.e., 10(-6)). In contrast, the frequency of transfer of hprt into mouse A9 cells was about two orders of magnitude less. The identification of efficient recipient cells for hprt transfer permits the use of DNA-mediated transfer as a bioassay for the gene. Cotransfer of the linked tk gene and the gene (galk) for galactokinase (ATP: D-galactose 1-phosphotransferase, EC 2.7.1.6) to LMTK- cells has been detected once among 87 tk transferrents. This suggests that the distance between the tk and galk genes in the Chinese hamster genome may be smaller than was previously thought. Significant differences between chromosome-mediated and DNA-mediated gene transfer were observed with respect to both the size of the transferred functional genetic fragment and the recipient cell specificity.

Gene transfer and gene mapping in mammalian cells in culture

The ability to transfer mammalian genes parasexually has opened new possibilities for gene mapping and fine structure mapping and offers great potential for contributing to several aspects of mammalian biology, including gene expression and genetic engineering. The DNA transferred has ranged from whole genomes to single genes and smaller segments of DNA. The transfer of whole genomes by cell fusion forms cell hybrids, which has promoted the extensive mapping of human and mouse genes. Transfer, by cell fusion, of rearranged chromosomes has contributed significantly to determining close linkage and the assignment of genes to specific chromosomal regions. Transfer of single chromosomes has been achieved utilizing microcells fused to recipient cells. Metaphase chromosomes have been isolated and used to transfer single-to-multigenic DNA segments. DNA-mediated gene transfer, simulating bacterial transformation, has achieved transfer of single-copy genes. By utilizing DNA cleaved with restriction endonucleases, gene transfer is being empolyed as a bioassay for the purification of genes. Gene mapping and the fate of transferred genes can be examined now at the molecular level using sequence-specific probles. Recently, single genes have been cloned into eucaryotic and procaryotic vectors for transfer into mammalian cells. Moreover, recombinant libraries in which entire mammalian genomes are represented collectively are a rich new source of transferable genes. Methodology for transferring mammalian genetic information and applications for mapping mammalian genes is presented and prospects for the future discussed.