Genetic and biochemical analysis of the a1 cell-surface antigen associated with human chromosome 11

Large-mutation spectra induced at hemizygous loci by low-LET radiation: evidence for intrachromosomal proximity effects

A mathematical model is used to analyze mutant spectra for large mutations induced by low-LET radiation. The model equations are based mainly on two-break misrejoining that leads to deletions or translocations. It is assumed, as a working hypothesis, that the initial damage induced by low-LET radiation is located randomly in the genome. Specifically, we analyzed data for two hemizygous loci: CD59- mutants, mainly very large-scale deletions (>3 Mbp), in human-hamster hybrid cells, and data from the literature on those HPRT- mutants which involve at least deletion of the whole gene, and often of additional flanking markers (approximately 50-kbp to approximately 4.4-Mbp deletions). For five data sets, we estimated f, the probability that two given breaks on the same chromosome will misrejoin to make a deletion, as a function of the separation between the breaks. We found that f is larger for nearby breaks than for breaks that are more widely separated; i.e., there is a "proximity effect". For acute irradiation, the values of f determined from the data are consistent with the corresponding break misrejoining parameters found previously in quantitative modeling of chromosome aberrations. The value of f was somewhat smaller for protracted irradiation than for acute irradiation at a given total dose; i.e., the mutation data show a decrease that was smaller than expected for dose protraction by fractionation or low dose rate.

Gamma-ray mutagenesis studies in a new human-hamster hybrid, A(L)CD59(+/-), which has two human chromosomes 11 but is hemizygous for the CD59 gene

Kraemer, S. M., Vannais, D. B., Kronenberg, A., Ueno, A. and Waldren, C. A. Gamma-Ray Mutagenesis Studies in a New Human-Hamster Hybrid, A(L)CD59(+/-), which has Two Human Chromosomes 11 but is Hemizygous for the CD59 Gene. Radiat. Res. 156, 10-19 (2001). We have developed a human-CHO hybrid cell line, named A(L)CD59(+/-), which has two copies of human chromosome 11 but is hemizygous for the CD59 gene and the CD59 cell surface antigen that it encodes. Our previous studies used the A(L) and A(L)C hybrids that respectively contain one or two sets of CHO chromosomes plus a single copy of human chromosome 11. The CD59 gene at 11p13.5 and the CD59 antigen encoded by it are the principal markers used in our mutagenesis studies. The hybrid A(L)CD59(+/-) contains two copies of human chromosome 11, only one of which carries the CD59 gene. The incidence of CD59 (-) mutants (formerly called S1(-)) induced by (137)Cs gamma rays is about fivefold greater in A(L)CD59(+/-) cells than in A(L) cells. Evidence is presented that this increase in mutant yield is due to the increased induction of certain classes of large chromosomal mutations that are lethal to A(L) cells but are tolerated in the A(L)CD59(+/-) hybrid. In addition, significantly more of the CD59 (-) mutants induced by (137)Cs gamma rays in A(L)CD59(+/-) cells display chromosomal instability than in A(L) cells. On the other hand, the yield of gamma-ray-induced CD59 (-) mutants in A(L)CD59(+/-) cells is half that of the A(L)C hybrid, which also tolerates very large mutations but has only one copy of human chromosome 11. We interpret the difference in mutability as evidence that repair processes involving the homologous chromosomes 11 play a role in determining mutant yields. The A(L)CD59(+/-) hybrid provides a useful new tool for quantifying mutagenesis and shedding light on mechanisms of genetic instability and mutagenesis.

Mutagenic effects of a single and an exact number of alpha particles in mammalian cells

One of the main uncertainties in risk estimation for environmental radon exposure using lung cancer data from underground miners is the extrapolation from high- to low-dose exposure where multiple traversal is extremely rare. The biological effects of a single alpha particle are currently unknown. Using the recently available microbeam source at the Radiological Research Accelerator Facility at Columbia University, we examined the frequencies and molecular spectrum of S1- mutants induced in human-hamster hybrid (A(L)) cells by either a single or an exact number of alpha particles. Exponentially growing cells were stained briefly with a nontoxic concentration of Hoechst dye for image analysis, and the location of individual cells was computer-monitored. The nucleus of each cell was irradiated with either 1,2,4, or 8 alpha particles at a linear energy transfer of 90 keV/microm consistent with the energy spectrum of domestic radon exposure. Although single-particle traversal was only slightly cytotoxic to A(L) cells (survival fraction approximately 0.82), it was highly mutagenic, and the induced mutant fraction averaged 110 mutants per 10(5) survivors. In addition, both toxicity and mutant induction were dose-dependent. Multiplex PCR analysis of mutant DNA showed that the proportion of mutants with multilocus deletions increased with the number of particle traversals. These data provide direct evidence that a single a particle traversing a nucleus will have a high probability of resulting in a mutation and highlight the need for radiation protection at low doses.

Heavy ion mutagenesis: linear energy transfer effects and genetic linkage

We have characterized a series of 69 independent mutants at the endogenous hprt locus of human TK6 lymphoblasts and over 200 independent S1-deficient mutants of the human x hamster hybrid cell line AL arising spontaneously or following low-fluence exposures to densely ionizing Fe ions (600 MeV/amu, linear energy transfer = 190 keV/microns). We find that large deletions are common. The entire hprt gene (> 44 kb) was missing in 19/39 Fe-induced mutants, while only 2/30 spontaneous mutants lost the entire hprt coding sequence. When the gene of interest (S1 locus = M1C1 gene) is located on a nonessential human chromosome 11, multilocus deletions of several million base pairs are observed frequently. The S1 mutation frequency is more than 50-fold greater than the frequency of hprt mutants in the same cells. Taken together, these results suggest that low-fluence exposures to Fe ions are often cytotoxic due to their ability to create multilocus deletions that may often include the loss of essential genes. In addition, the tumorigenic potential of these HZE heavy ions may be due to the high potential for loss of tumor suppressor genes. The relative insensitivity of the hprt locus to mutation is likely due to tight linkage to a gene that is required for viability.

A fine-structure deletion map of human chromosome 11p: analysis of J1 series hybrids

Deletion analysis offers a powerful alternative to linkage and karyotypic approaches for human chromosome mapping. A panel of deletion hybrids has been derived by mutagenizing J1, a hamster cell line that stably retains chromosome 11 as its only human DNA, and selecting for loss of MIC1, a surface antigen encoded by a gene in band 11p13. A unique, self-consistent map was constructed by analyzing the pattern of marker segregation in 22 derivative cells lines; these carry overlapping deletions of 11p13, but selectively retain a segment near the 11p telomere. The map orders 35 breakpoints and 36 genetic markers, including 3 antigens, 2 isozymes, 12 cloned genes, and 19 anonymous DNA probes. The deletions span the entire short arm, dividing it into more than 20 segments and define a set of reagents that can be used to rapidly locate any newly identified marker on 11p, with greatest resolution in the region surrounding MIC1. The approach we demonstrate can be applied to map any mammalian chromosome. To test the gene order, we examined somatic cell hybrids from five patients, whose reciprocal translocations bisect band 11p13; these include two translocations associated with familial aniridia and two with acute T-cell leukemia. In each patient, the markers segregate in telomeric and centromeric groups as predicted by the deletion map. These data locate the aniridia gene (AN2) and a recurrent T-cell leukemia breakpoint (TCL2) in the marker sequence, on opposite sides of MIC1. To provide additional support, we have characterized the dosage of DNA markers in a patient with Beckwith-Wiedemann syndrome and an 11p15-11pter duplication. Our findings suggest the following gene order: TEL - (HRAS1, MER2, CTSD, TH/INS/IGF2, H19, D11S32) - (RRM1, D11S1, D11S25, D11S26) - D11S12 - (HBBC, D11S30) - D11S20 - (PTH, CALC) - (LDHA, SAA, TRPH, D11S18, D11S21) - D11S31 - D11S17 - HBVS1 - (FSHB, D11S16) - AN2 - MIC1 - TCL2 - delta J - CAT - MIC4 - D11S9 - D11S14 - ACP2 - (D11S33, 14L) - CEN. We have used the deletion map to show the distribution on 11p of two centromeric repetitive elements and the low-order interspersed repeat A36Fc. Finally, we provide evidence for an allelic segregation event in the hamster genome that underlies the stability of chromosome 11 in J1. The deletion map provides a basis to position hereditary disease loci on 11p, to distinguish the pattern of recessive mutations in different forms of cancer and, since many of these genes have been mapped in other mammalian species, to study the evolution of a conserved syntenic group.

Molecular cloning of MER-2, a human chromosome-11-encoded red blood cell antigen, using linkage of cotransfected markers

We report the molecular cloning of a human gene MER-2 located on chromosome 11 that encodes a cell surface antigen which is polymorphic on red blood cells. An essential element of the cloning strategy was cotransfection-induced linkage of pSV2-neo, which encodes resistance to the antibiotic G418, to the human MER-2 gene. An important feature of the pSV2-neo construct is that the same gene (the transposon, Tn5) that encodes G418 resistance in eukaryotic cells confers neomycin resistance in bacteria. Chinese hamster ovary (CHO) cells were cotransfected with pSV2-neo and genomic DNA from a CHO X human cell hybrid containing a single human chromosome (chromosome 11). Transfectants expressing both the human MER-2 gene and G418 resistance were isolated by selection in the antibiotic G418, followed by indirect immunofluorescence using the monoclonal antibody 1D12, which recognizes the MER-2 antigen, manual enrichment, and single-cell cloning. Genomic DNA from a primary transfectant positive for MER-2 expression and G418 resistance was used to construct a cosmid library and cosmid clones able to grow in neomycin were isolated. Of 150,000 cosmid clones screened, 90 were resistant to neomycin and of these, 11 contained human repetitive sequences. Five neomycin-resistant cosmid clones containing human repetitive DNA were able to transfect CHO cells for G418 resistance and MER-2 expression.

Expression of human chromosome 11-encoded cell-surface antigens by DNA-mediated transfectants

DNA-mediated transfectants were isolated that expressed two of the cell-surface antigens encoded by human chromosome 11. These tranfectants were used to analyze monoclonal antibodies selected to recognize human cell-surface antigens expressed by a somatic cell hybrid containing 11 as its only human chromosome. Analysis of the transfectants, deletion hybrids, and mutants showed that the monoclonal antibodies recognized at least five different antigens, one of which we had not identified previously. A majority of the monoclonal antibodies recognized the a1 antigen. The use of cells from higher primates demonstrated that the a1-specific monoclonal antibodies recognize at least two epitopes.

Assignment of the gene coding for the T3-delta subunit of the T3-T-cell receptor complex to the long arm of human chromosome 11 and to mouse chromosome 9

The gene encoding the 20-kDa glycoprotein of the T3-T-cell receptor complex (T3-delta chain) has been mapped to human chromosome 11 by hybridization of a T3-delta cDNA clone (pPGBC#9) to DNA from a panel of human-rodent somatic cell hybrids. In Southern blotting experiments with DNAs of somatic cell hybrids that contained segments of chromosome 11, we were able to assign the T3-delta gene to the distal portion of the long arm of human chromosome 11 (11q23-11qter). By use of a newly developed cDNA clone (pPEM-T3 delta) that codes for the murine T3-delta chain, the mouse T3-delta gene was mapped on chromosome 9. The importance of the T3-delta map position and its relationship to the other genes on the long arm of human chromosome 11 and to those on mouse chromosome 9 is discussed.

Wilms' tumor-aniridia association: segregation of affected chromosome in somatic cell hybrids, identification of cell surface antigen associated with deleted area, and regional mapping of c-Ha-ras-1 oncogene, insulin gene, and beta-globin gene

Fusion of an auxotrophic mutant hamster cell with the skin fibroblasts of a child with the Wilms' tumor-aniridia association produced clones which, on the one hand, contained the child's normal chromosome 11 and, on the other, the chromosome 11 with the 11p13 deletion associated with the syndrome. Both hybrids were positive for human LDH-A by enzymatic assay. Clones containing the normal human chromosome 11 were killed by a cytotoxic monoclonal antibody to a cell surface antigen previously mapped to the 11p13----11pter region of chromosome 11. Clones with the abnormal 11 were not killed. Thus, we have produced hybrids from the same patient distinct from each other on the basis of their chromosome 11. These hybrids have been used to map the locus for a cell surface antigen to the deleted region on chromosome 11 of a patient with the Wilms tumor-aniridia association. The linkage between this antigen and the syndrome should be helpful in further study of the genetics of this disease. In addition, we have found that the c-Ha-ras-1 oncogene is distal to the p13 region of chromosome 11 and the position of insulin and beta-globin on the chromosome. Finally, by producing segregants of the hybrids containing the abnormal chromosome 11, we have provided evidence that chromosome 11-associated c-Ha-ras-1 is syntenic with chromosome 11 and not moved to a different portion of the genome.

Relationships between genes on human chromosome 11 encoding cell-surface antigens

Genes encoding seven monoclonal antibody-defined cell-surface antigens have been regionally mapped on human chromosome 11, and compared to those of the AL complex defined by polyclonal antibodies using mutational analysis. MIC1, encoding W6/34 antigen, is probably identical to S1, previously mapped to 11pter-p13. MDU1 and MIC8, encoding 4F2 and TRA-1.10 antigens, respectively, are probably identical to S2(a4) and map to 11q13-q22. MIC9, which governs expression of 4D12 and 2E2 antigens, and maps to 11q22-qter, is not related to any of the five AL genes. MIC4 and MIC11, both mapping to 11pter-p13, may have some relationship to S3 and S1, respectively, but identity has not been proven.

Human chromosome 11 carries at least four genes controlling expression of cell-surface antigens

We have mapped two new genes to chromosome 11 which control the cell-surface expression of two distinct antigens defined by monoclonal antibodies. One of the antigens has a general tissue distribution and is associated with a molecular complex of two polypeptides of 80,000 dalton and 40,000 dalton molecular weight. The second antigen has a restricted tissue distribution and is carried on a polypeptide of 100,000 daltons. We have used a combination of genetic and biochemical techniques to demonstrate that these new markers are distinct from the antigens defined by the monoclonal antibodies F10.44.2 and W6/34 which are also encoded by genes on chromosome 11. It is concluded that human chromosome 11 carries at least four distinct genes controlling cell-surface antigen expression.

Further studies on a hybrid cell-surface antigen associated with human chromosome 11 using a monoclonal antibody

A monoclonal antibody has been obtained that recognizes an antigen encoded by human chromosome 11. We present evidence that this monoclonal antibody recognizes the same or a similar antigenic activity as that previously called a1. Genetic information necessary for a1 expression and recognition by the monoclonal antibody both map to 11p13 leads to 11pter. Mutants that have lost a1 are no longer recognized by the monoclonal antibody. The macroglycolipid fraction of human erythrocyte membranes which contains the a1 antigenic activity is able to convert antigen-negative Chinese hamster ovary cells into cells which are killed by the monoclonal antibody plus complement.

Expression of human myeloid-associated surface antigens in human-mouse myeloid cell hybrids

Hybrid cell lines were obtained after fusion of mouse myeloid cells (WEHI-TG) with leukocytes from two patients with chronic myeloid leukemia. A third fusion was carried out with leukocytes from a patient with acute lymphocytic leukemia. All three patients carried the Philadelphia chromosome (Ph1) in the leukemia cell population. Cytochemical analysis confirmed the myelo-monocytic nature of the hybrid cell lines. The presence of Ph1 translocation products could be established in most hybrids derived from the two chronic myeloid leukemic patients, which confirms that indeed human myeloid cells were fused. Several of these hybrid lines showed reactivity with monoclonal antibodies known to be specific for human myeloid cells, whereas interlineage Chinese hamster fibroblast-human chronic myeloid leukemia hybrids failed to react with these antibodies. Five independently obtained monoclonal antibodies--MI/NI, UJ-308, VIM-D5, FMC-10, and B4.3--showed very similar reactivity patterns when tested on the hybrid clones. This result substantiates the evidence obtained from other studies, that these five antibodies are directed against the same myeloid-associated antigen. The gene(s) for expression of the latter antigen could be assigned to human chromosome 11.

Chromosome mapping of human cell surface molecules: monoclonal anti-human lymphocyte antibodies 4F2, A3D8, and A1G3 define antigens controlled by different regions of chromosome 11

Monoclonal antibodies 4F2, A3D8, and A1G3, directed against cell surface antigens present on subsets of human cells, were used to identify the human chromosome regions that code for the antigenic determinants. Human fibroblasts expressed all three antigens, and no cross-reactivity with Chinese hamster or mouse cells was found. Fourteen rodent X human somatic cell hybrids, derived from six different human donors and from two different Chinese hamster and one mouse cell line, were studied simultaneously for human chromosome content and for antibody binding as detected by indirect immunofluorescence. Concordancy with binding of all three antibodies was observed only for human chromosome 11. All other chromosomes were excluded by three or more discordant hybrid clones. Data from six hybrids containing three different regions of chromosome 11 indicate that it is the long arm of chromosome 11 which is both necessary and sufficient for expression of the human antigen defined by 4F2 while the antigen(s) defined by A3D8 and A1G3 map to short arm.

Assignment of gene coding for cell surface glycoprotein with a molecular weight of 75,000 to human chromosome 11

The gene for a cell surface glycoprotein recognized by a mouse monoclonal antibody (Mab 4), has been assigned to human chromosome 11 by the study of mouse-human lymphocyte hybrids. The antigen is present on all human peripheral blood leukocytes, on human fibroblasts, and on human lymphoid and erythroid cell lines, but not on erythrocytes. Immunoprecipitation and polyacrylamide slab gel electrophoresis of both human cells and mouse-human hybrid clones carrying human chromosome 11 show that the apparent molecular weight of this glycoprotein is 75,000.

Genetic and biochemical characterization of a human surface determinant on somatic cell hybrids: the 4F2 antigen

We have mapped the gene which codes the species-specific determinant defined by monoclonal antibody 4F2 to human chromosome 11. All human chromosomes, except Y, were included in a group of four human-mouse hybrid lines. Hybrids heterogeneous for 4F2 antigen expression were sorted using the fluorescence-activated cell sorter (FACS) to yield populations homogeneous with respect to the presence or absence of this determinant. Isozyme analysis indicated corresponding genetic selection for or against human chromosome 11. This map assignment was confirmed using a hybrid line which contained only human chromosome 11. Immunoprecipitation of the 4F2 determinant from the 11 only hybrid resulted in a heavy subunit of molecular weight (Mr) = 100,000 and a light subunit of Mr = 41,000. This contrasts with results obtained from nonhybrid human cells of different lineages. These results demonstrate the importance of FACS techniques in the rapid mapping of genes which code human cell surface antigens.

Human transferrin receptor: expression of the receptor is assigned to chromosome 3

Human chromosome 3 has been identified as responsible for expression of the transferrin receptor in mouse-human lymphocyte hybrids. The receptor was detected by immunoprecipitation with anti-human receptor antibody of 125I-labeled cells. This method also detected a similar 94,000-dalton protein in mouse cells. A radioimmunoassay developed for the human transferrin receptor measured 10% crossreactivity with the mouse protein. The two proteins were distinguished by NaDodSO4/polyacrylamide gel patterns of partial proteolytic digests of the immunoprecipitated proteins. Mouse-human hybrids were generated by fusing a mouse thymoma (BW5147) cell line to either concanavalin A- or pokeweed mitogen-activated human peripheral blood lymphocytes or a mouse myeloma (NS-1) to uncultured human peripheral blood lymphocytes. Each hybrid was karyotyped with respect to both mouse and human chromosomes. In every case, expression of the human transferrin receptor correlated only with human chromosome 3.

Demonstration, by somatic cell genetics, of coordinate regulation of genes for two enzymes of purine synthesis assigned to human chromosome 21

A method for determining coordinate genetic regulation is proposed for mammalian cells. The method involves (i) isolation of a set of mutants defective in the relevant pathway; (ii) complementation analysis of these mutants to determine dominance and to categorize the mutants into various different complementation groups; (iii) determination of the biochemical blocks in the mutants; (iv) identification of individual mutants that fail to complement the members of at least two distinct complementation groups that complement each other, such mutants being said to show coordinate regulation of the affected functions; (v) biochemical and reversion analysis of the relevant cell types to confirm the basis for the observed coordinate regulation; (vi) assignment of the individual genes to particular human chromosomes; (vii) mapping of the genes to determine contiguity on the genome; and (viii) examination of the structure of the relevant gene products. This method has allowed the demonstration of coordinate regulation between the gene coding for phosphoribosylglycineamide synthetase [5-phosphoribosylamine:glycine ligase (ADP-forming), EC 6.3.4.13], defective in our Ade-C mutants, and the gene coding for phoshoribosylaminoimidazole synthetase [5'-phosphoribosylformylglycinamidine cyclo-ligase (ADP-forming), EC 6.3.3.1], defective in our Ade-G mutants. Moreover, both genes can be assigned to human chromosome 21. Because at least two genes for purine biosynthesis have now been assigned to chromosome 21, and because patients with trisomy 21 (Down syndrome) show increased levels of serum purines, it may be that cells of these patients overproduce purines and that this overproduction may be relevant to the pathology of the syndrome.

Immunochemical analysis of anti-HLA-A2, HLA-A3, and HLA-B27 xenoantisera elicited with hybrids between human and murine cells

Rabbits were immunized with hybrids constructed with human and murine cells. Serological and immunochemical studies showed that xenoantiserum 1595 is operationally specific for HLA-A2, xenoantisera 0806 and 0746 for HLA-A3 and xenoantiserum 0745 for HLA-B27. The Fab2 blocking assay suggests a spatial relationship between allotypic determinants recognized by the xenoantisera and those reacting with the HLA-A, B-specific monoclonal antibodies (MoAb) Q1/28, 6/31, Q6/64, and CR-1 and the anti-beta 2-microglobulin (beta 2-mu) MoAb NAMB-1.