Genetics of cell-surface antigens: regional mapping of three components of the human cell-surface antigen complex, AL, on chromosome 11

Genome sequencing-the dawn of a game-changing era

The development of genome sequencing technologies has revolutionized the biological sciences in ways which could not have been imagined at the time. This article sets out to document the dawning of the age of genomics and to consider the impact of this revolution on biological investigation, our understanding of life, and the relationship between science and society.

Measuring the spectrum of mutation induced by nitrogen ions and protons in the human-hamster hybrid cell line A(L)C

Astronauts can be exposed to charged particles, including protons, alpha particles and heavier ions, during space flights. Therefore, studying the biological effectiveness of these sparsely and densely ionizing radiations is important to understanding the potential health effects for astronauts. We evaluated the mutagenic effectiveness of sparsely ionizing 55 MeV protons and densely ionizing 32 MeV/nucleon nitrogen ions using cells of two human-hamster cell lines, A(L) and A(L)C. We have previously characterized a spectrum of mutations, including megabase deletions, in human chromosome 11, the sole human chromosome in the human-hamster hybrid cell lines A(L)C and A(L). CD59(-) mutants have lost expression of a human cell surface antigen encoded by the CD59 gene located at 11p13. Deletion of genes located on the tip of the short arm of 11 (11p15.5) is lethal to the A(L) hybrid, so that CD59 mutants that lose the entire chromosome 11 die and escape detection. In contrast, deletion of the 11p15.5 region is not lethal in the hybrid A(L)C, allowing for the detection of chromosome loss or other chromosomal mutations involving 11p15.5. The 55 MeV protons and 32 MeV/nucleon nitrogen ions were each about 10 times more mutagenic per unit dose at the CD59 locus in A(L)C cells than in A(L) cells. In the case of nitrogen ions, the mutations observed in A(L)C cells were predominantly due to chromosome loss events or 11p deletions, often containing a breakpoint in the pericentromeric region. The increase in the CD59(-) mutant fraction for A(L)C cells exposed to protons was associated with either translocation of portions of 11q onto a hamster chromosome, or discontinuous or "skipping" mutations. We demonstrate here that A(L)C cells are a powerful tool that will aid in the understanding of the mutagenic effects of different types of ionizing radiation.

Mutant yields and mutational spectra of the heterocyclic amines MeIQ and PhIP at the S1 locus of human-hamster AL cells with activation by chick embryo liver (CELC) co-cultures

Cooking meat and fish at high temperature creates heterocyclic amines (HA) including 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Several HA are mutagens in the Ames' S9/Salmonella assay. While PhIP is a substantial Ames' test mutagen, it is 1000-fold less active than the extraordinarily potent MeIQ. In contrast, MeIQ is significantly less mutagenic than PhIP in several mammalian cell assays, especially in repair-deficient Chinese hamster ovary (CHO) cells. HA are suspect human carcinogens on the basis of (i) epidemiological evidence, (ii) induction of tumors in rodents and monkeys, (iii) DNA adduct formation and (iv) mutagenic capacity. In this study, MeIQ and PhIP were significant mutagens at the S1 locus of co-cultivated human/hamster hybrid AL cells following metabolic activation by beta-napthoflavone (betaNF)-induced chick embryonic liver cultures (CELC). MeIQ was more mutagenic than PhIP in the CELC+AL cell assay. The mutant response curves increase with dose and then plateau (PhIP), or decrease (MeIQ). The inflections in these response curves coincide with dose-dependent decreases in cytochrome CYP1A1 activity. Molecular analysis of S1- mutants indicates that a substantial fraction, >65%, of the mutations induced by PhIP are deletions of 4.2 to 133 (Mbp); half are larger than 21 Mbp. Mutations induced by MeIQ were smaller, most (56%) being less than 5.7 Mbp. When appropriate metabolic activation is combined with a target locus, which can detect both small and large chromosomal mutations, both MeIQ and PhIP are significant mutagens and clastogens in repair proficient mammalian cells.

Molecular cytogenetics localizes two new breakpoints on 11q23.3 and 21q11.2 in myelodysplastic syndrome with t(11;21) translocation

Translocation t(11;21)(q24;q11.2) is a rare but recurrent chromosomal abnormality associated with myelodysplastic syndrome (MDS) that until now has not been characterized at the molecular level. We report here results of a molecular cytogenetic analysis of this translocation in a patient with refractory anemia. Using FISH with a panel of 11q and 21q cosmid/YAC probes, we localized the chromosome 11 breakpoint at q23.3 in a region flanked by CP-921G9 and CP-939H3 YACs, distal to the HRX/MLL locus frequently involved in acute leukemias. The chromosome 21 breakpoint was mapped in a 800-kb fragment inserted into the CP-145E3 YAC at 21q11.2, proximal to the AML1 gene. It is noteworthy that in all four cases with a t(11;21) reported until now, a second der(11)t(11;21) and loss of normal chromosome 11 could be observed either at diagnosis or during the course of the disease. Since in our case heteromorphism was detected by FISH on the centromeric region of the two der(11), the second der(11) chromosome could be the result of a mitotic recombination that had occurred on the long arm of chromosome 11, rather than of duplication of the original der(11). Constancy of secondary karyotypic changes resulting in an extra copy of the putative chimeric gene at der(11), loss of 11 qter sequences, and partial trisomy 21 suggest that neoplastic progression of MDS cases with a t(11;21) may be driven by the same mechanism(s).

Chromosomal mutations and chromosome loss measured in a new human-hamster hybrid cell line, ALC: studies with colcemid, ultraviolet irradiation, and 137Cs gamma-rays

Small mutations, megabase deletions, and aneuploidy are involved in carcinogenesis and genetic defects, so it is important to be able to quantify these mutations and understand mechanisms of their creation. We have previously quantified a spectrum of mutations, including megabase deletions, in human chromosome 11, the sole human chromosome in a hamster-human hybrid cell line AL. S1- mutants have lost expression of a human cell surface antigen, S1, which is encoded by the M1C1 gene at 11p13 so that mutants can be detected via a complement-mediated cytotoxicity assay in which S1+ cells are killed and S1- cells survive. But loss of genes located on the tip of the short arm of 11 (11p15.5) is lethal to the AL hybrid, so that mutants that have lost the entire chromosome 11 die and escape detection. To circumvent this, we fused AL with Chinese hamster ovary (CHO) cells to produce a new hybrid, ALC, in which the requirement for maintaining 11p15.5 is relieved, allowing us to detect mutations events involving loss of 11p15.5. We evaluated the usefulness of this hybrid by conducting mutagenesis studies with colcemid, 137Cs gamma-radiation and UV 254 nm light. Colcemid induced 1000 more S1- mutants per unit dose in ALC than in AL; the increase for UV 254 nm light was only two-fold; and the increase for 137Cs gamma-rays was 12-fold. The increase in S1- mutant fraction in ALC cells treated with colcemid and 137Cs gamma-rays were largely due to chromosome loss and 11p deletions often containing a breakpoint within the centromeric region.

Characterization of a cosmid library from flow-sorted chromosomes 11

A cosmid library specific for human chromosome 11 has been constructed from flow-sorted chromosomes. The flow-purified chromosomes were prepared from the hamster/human hybrid line J1 which contains chromosome 11 as the only human chromosome. Individual clones were sampled in 187 microtitre plates, resulting in a total of 17,952 colonies. Hybridization analysis revealed that 83.7% of these clones were of human and 10.4% of hamster origin. The average insert size was estimated at 33.6 kb, and only 2.4% of insert fragments appear to be rearranged. This should result in 494,487 kb of cloned human DNA representing 3.5 chromosome 11 equivalents. We have prepared high-density nylon membranes of the arrayed library containing 1,536 single colonies per filter. We have demonstrated the usefulness of the library in the molecular genetic analysis of human chromosome 11 by testing for the presence of possibly polymorphic simple repeat motifs, by identifying cosmids that contain inserts from the telomeric ends of chromosome 11 and by assessing the potential of the library for rapid chromosome walking.

Localization of the gene encoding R kappa B (NFRKB), a tissue-specific DNA binding protein, to chromosome 11q24-q25

Although NF (nuclear factor)-kappa B binds in vitro to several of the kappa B regulatory elements found in cellular and viral genes, another DNA binding protein, R kappa B, also binds to a related variant of the kappa B site that regulates interleukin-2 receptor alpha-chain gene expression, a critical event in T cell activation. Southern blot analysis of a human-mouse somatic cell hybrid panel and in situ hybridization using a fluorescent genomic R kappa B probe have allowed assignment of the R kappa B gene (NFRKB) to 11q24-q25. The NFRKB locus is in close proximity to the chromosomal breakpoint implicated in Ewing sarcoma, but it does not appear to span this region. Nonetheless, NFRKB may be particularly useful as the most telomeric marker thus far assigned to 11q.

The use of human repetitive DNA to target selectable markers into only the human chromosome of a human-hamster hybrid cell line (AL)

We used the plasmid BLUR-8 that contains an 800-base pair (bp) sequence of human repetitive Alu DNA in a cotransfection protocol to target the plasmids pSV2neo or EBO-pcD-leu-2 (hygro) into a single site of the sole human chromosome, number 11, of a Chinese hamster-human hybrid cell line (AL). The neo and hygro plasmids confer resistance to the antibiotics G418 and hygromycin, respectively. Of the 33 cotransfected clones with single-site insertions, 1/13 without BLUR-8 and 6/20 with BLUR-8 were only in human chromosome 11. A frequency of insertion of 1/13 is not different than expected by chance (rho = 0.3512). On the other hand, the probability that 6/20 insertions, as seen with BLUR-8, occurred by chance is low (rho = 0.0003). We suggest that the human DNA sequences contained in BLUR-8 targeted insertions into only the human chromosome.

Amino acid sequence analysis of proteins in the human corneal stromal cell membrane

Plasma membrane proteins from human corneal stromal fibroblasts were isolated and separated by two-dimensional polyacrylamide gel electrophoresis. Separated polypeptides were electroeluted onto polyvinylidene difluoride (PVDF) membranes and individual polypeptides were subjected to NH2-terminal amino acid sequence analysis. Of a total of 33 polypeptides sequenced, 26 were found to be blocked at their NH2-terminus. Seven major membrane polypeptides were sequenced and further analyzed. One polypeptide, designated #18, was determined to be homologous to the beta subunit of prolyl hydroxylase/protein disulfide isomerase/thyroid hormone-binding protein. The other six polypeptides were found to have no significant sequence homology with any known polypeptides, as revealed by a protein data base homology search. Polypeptide Bands #90, #102, and #103 were found to have the same NH2-terminal amino acid sequence and the same overall molecular weight, yet separated from one another according to pI. These three polypeptides probably arose from differential posttranslational modification of the same original protein. Synthetic peptides were prepared from the #18 and #19 sequence and antibodies were produced. Immunostaining of cultured human corneal stromal cells and frozen sections of corneas demonstrated that these membrane polypeptides were present in corneal keratocytes, both in vitro and in vivo. Antibody against #18 stained fixed cultured corneal fibroblasts in a very fibrous pattern, with more intense staining in the perinuclear region of the cell, while antibody against #19 stained the cell surface in a much more uniform pattern. In sections of human cornea, both antibodies stained only the keratocytes in the stroma, but they also appeared to stain epithelial cells.

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.

Gene for human CD59 (likely Ly-6 homologue) is located on the short arm of chromosome 11

The CD59 (MEM-43) antigen, which probably is a human homologue of mouse Ly-6 antigens, is a broadly expressed Mr 18,000-25,000 human leucocyte surface glycoprotein recognized by monoclonal antibody MEM-43. Ten mouse-human T-lymphocyte hybrids, carrying all mouse chromosomes and a limited number of human chromosomes, were analyzed for expression of CD59 by indirect immunofluorescence and immunoblotting with MEM-43 antibody. Karyotypic analysis of the tested clones showed that the presence of human chromosome 11 correlated with the expression of CD59 in all clones tested. Three other human chromosome 11-encoded antigens, 4F2 (Trop-4), Leu 7 (HNK-1, CD57), and lymphocyte homing receptor, were expressed concordantly with CD59. A more exact localization of the gene for CD59 was obtained by the study of Chinese hamster-human cell hybrids containing short or long arm deletions of human chromosome 11. CD59 segregated with hybrids containing part of the short arm of human chromosome 11, but not with the hybrids containing the long arm. Based on these studies we assign the gene for CD59 to region p14-p13 of the short arm of chromosome 11.

Analysis of human chromosome 11 by somatic cell genetics: reexamination of derivatives of human-hamster cell line J1

Through the fusion of a CHO cell population to a human cell population, a hybrid cell line which has lost all human chromosomes except chromosome 11 was derived. This cell line, J1, does not appear to segregate human chromosome 11 during growth. A series of deletion segregants were isolated from J1 which had lost a portion of either the long, short, or both arms of chromosome 11. This panel of deletion segregants was used for mapping a number of genetic markers on the short arm of chromosome 11. Karyotypic analysis led to the interpretation that derivatives of J1 selected for the loss of cell surface antigens encoded by genes on the short arm of the chromosome had simple terminal deletions of this chromosome arm. More recently, we have applied recombinant DNA and in situ hybridization techniques to the analysis of the structure of chromosome 11. In the course of this analysis, we have obtained data that indicate that all J1 deletion segregants retain a small chromosomal segment containing the structural genes for insulin and HRAS1. Analysis of in situ hybridization data indicates that in cell lines in which a chromosome 11 fragment cannot be identified by karyotype analysis, human DNA has been translocated to a Chinese Hamster chromosome. These results suggest that the original interpretation of the karyotypes of deletion segregants derived from J1 as simple terminal deletions is not correct. A reanalysis of gene localization studies based on these deletion segregants suggests that some assignments of genes to specific bands on chromosome 11 should be reconsidered. In particular, data on additional deletion segregants are consistent with localization of the beta-globin gene complex to band 11p15. The data presented here suggest that in several hybrid derivatives of J1, a continuous DNA segment of approximately 10(7) base pairs in length which includes the insulin and HRAS1 (cellular homolog of retroviral oncogene Harvey ras) genes has been isolated from the remainder of the human genome. We propose that the stability of chromosome 11 in the original hybrid was due to complementation of a genetic defect in the original CHO cell parent by a gene located in close physical proximity to the insulin and HRAS1 genes on chromosome 11. Data are presented which test and support this hypothesis.

Insertion of dominant selectable markers into the human genome

In the above discussion, I have outlined the current status of our efforts to use retroviral vectors to introduce selectable markers into the human genome and to use these markers for mapping specific chromosomal regions. I have not reviewed in detail the extensive characterization of the mouse H-2 region carried out by David Nelson and John Weis based on the insertion of a single retroviral element. This analysis has provided a model for the application of retroviral elements into various regions of the human genome. The prospects for increasing the resolution of the human genetic map and identifying many genes relevant to human health and development are likely to be enhanced by increasing the precision of this methodology.

Cytological localization of adenosine kinase, nucleoside phosphorylase-1, and esterase-10 genes on mouse chromosome 14

We have determined the regional locations on mouse chromosome 14 of the genes for mouse adenosine kinase (ADK), nucleoside phosphorylase-1 (NP-1), and esterase-10 (ES-10) by analysis of rearranged mouse chromosomes in gamma-irradiated Chinese hamster X mouse hybrid cell lines. Irradiated clones were screened for expression of the murine forms of these enzymes; segregant clones that expressed only one or two of the three markers were karyotyped. The patterns of enzyme expression in these segregants were correlated with the presence of rearranged chromosomes. The Adk gene was localized to bands A2 to B, Np-1 to bands B to C1, and Es-10 to bands D2 to E2.

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.

Somatic cell hybrid mapping panels

The recent advances in human gene mapping have been largely due to the development of interspecies cell hybrids containing human chromosomes and their fragments. The importance of characterized panels of these hybrid lines has grown exponentially with the application of recombinant DNA technologies to human genetics. In this article, we discuss current strategies employed in the construction of somatic cell hybrid mapping panels.

Localization of the structural gene for human apolipoprotein A-I on the long arm of human chromosome 11

Apolipoprotein A-I (apo A-I), the major apolipoprotein in human high density lipoproteins, is involved in the disease atherosclerosis. Cloned apo A-I cDNA (pA1-3) was used as a probe in chromosome mapping studies to detect the human apo A-I structural gene sequence in human-Chinese hamster cell hybrids. Southern blot analysis of 13 hybrids localized the gene to human chromosome 11. Confirmation of the chromosomal assignment was obtained by analysis of a hybrid (J1) containing a single human chromosome, no. 11. Regional mapping was achieved by using deletion subclones of J1 that localized the human apo A-I structural gene to the region 11q13 leads to qter. Since the human apolipoprotein C-III (apo C-III) structural gene is closely linked to apo A-I, it can be assigned to the same region on the long arm of chromosome 11. By extension of methods previously described, it now appears possible to carry out fine-structure analysis of this and related gene regions on chromosome 11 and to study the biochemical concomitants of these genes and of genes on other chromosomes for analysis of their role in atherosclerosis.

Molecular hybridization under conditions of high stringency permits cloned DNA segments containing reiterated DNA sequences to be assigned to specific chromosomal locations

Identifying the specific DNA sequences involved in the chromosomal abnormalities in developmental and neoplastic diseases may be essential to understanding the molecular biology of these disorders. The use of recombinant DNA techniques in conjunction with rodent-human hybrid cells makes it possible to assign chromosomal locations to specific DNA sequences. However, the ubiquitous presence of reiterated DNA species often complicates the application of straightforward molecular hybridization. To accelerate the mapping of cloned sequences to specific chromosomal locations, we investigated the possibility that cloned sequences containing reiterated DNA might be used without isolating unique sequences. By varying conditions of hybridization (specifically temperature) and using restricted DNA samples from human genomic DNA, Chinese hamster ovary-human chromosome 11 hybrids, and non-chromosome 11 hybrids, we have been able to assign cloned DNA sequences containing reiterated sequences to their chromosome of origin. By hybridization under the high-stringency condition of 55 degrees C, specific banding was produced with both human genomic DNA and the human-chromosome-containing hybrid from which the probe was prepared. Furthermore, using a panel of chromosome 11 deletion mutants, we have been able to assign a cloned sequence to a specific chromosomal location. We believe that this approach will accelerate gene mapping procedures and facilitate identification of DNA sequences involved in chromosomal abnormalities.

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.

Fluorescence-activated cell sorting of mouse-human hybrid cells aids in locating the gene for the Leu 7 (HNK-1) antigen to human chromosome 11

Leu 7 (HNK-1) is a membrane antigen expressed on human natural killer cells and some other lymphoid cells. Starting with two clones of mouse-human hybrid lymphoid cells that had 1.6% and 35% Leu 7-positive cells, respectively, we viably sorted Leu 7-positive and -negative cells using a fluorescence-activated cell sorter (FACS). Short-term progeny of the sorted cells were then karyotyped. Chromosome 11 was the only human chromosome that was absent from the Leu 7-negative population and present in nearly all of the progeny of the Leu 7-positive selected cells. Thus, we assigned the Leu 7 gene to 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.

Human ferritin gene is assigned to chromosome 19

Ferritin is the intracellular iron storage protein. Tissue ferritin stores are markedly increased in hemochromatosis, a disease of iron overload that has been linked to chromosome 6. In order to provide further information concerning the genetics of ferritin synthesis and to determine if the structural gene for ferritin was on chromosome 6, studies were performed to identify the human chromosome that contains the ferritin gene. Ferritin immunoassays were performed on extracts of Chinese hamster ovary somatic cells that were hybridized with human lymphocytes and fibroblasts and contained various human chromosomes in different combinations. None of the 13 cell lines that lacked immunoreactive human ferritin contained chromosome 19, and all 9 of the cell lines that produced human ferritin contained chromosome 19. No other human chromosome shared this association with human ferritin. In studies of subclones of ferritin-positive cell lines, immunoreactive ferritin consistently segregated only with chromosome 19. Immunoprecipitation studies performed on cells that had been incubated with 59Fe-containing transferrin indicated that chromosome 19-containing cells incorporated iron into intact and functional molecules of human ferritin. The necessary and exclusive association of chromosome 19 with human ferritin indicates that a defect in the structural gene for human ferritin cannot account for the abnormalities of hemochromatosis. Moreover, this hamster-human hybrid cell system should prove useful in further studies of regulation of ferritin concentration and composition.

Genetic fine-structure mapping in human chromosome 11 by use of repetitive DNA sequences

A method is described for mapping of the DNA fragments of a human chromosome produced by restriction enzyme treatment of the total DNA from a hybrid cell containing a single human chromosome. The method involves production and selection of somatic cell mutants containing deletions of the human chromosome and application of a hybridization probe consisting of an individual member copy of a repetitive human DNA family. A linear map has been constructed of 19 marker DNA fragments and 5 immunological and biochemical markers on human chromosome 11, selected as a model chromosome for these studies. This approach appears to be widely applicable, is independent of cytogenetic analysis, promises to be capable of revealing the existence of rearrangements as well as deletions, appears to be amenable to further increase in resolving power, and offers potential application in various human genetic problems.

Chromosome sorting and DNA sequence localization

This article focuses on current techniques and possible future developments in chromosome isolation and sorting, and DNA analysis of sorted chromosomes. The strategy of subchromosomal gene mapping by chromosome sorting is outlined and a list of cell lines containing translocated chromosomes is provided which may be used to map genes to a single chromosome with a standard fluorescence activated cell sorter. The usefulness of this and other gene mapping methods for localizing unique DNA sequences and characterizing recombinant DNA libraries constructed from sorted chromosomal DNA is also discussed.

The gene, MIC4, which controls expression of the antigen defined by monoclonal antibody F10.44.2, is on human chromosome 11

The monoclonal antibody, F10.44.2, is directed against a human antigenic determinant of restricted tissue distribution. In this report it is shown that this determinant is coded for by a gene, MIC4, which is on human chromosome 11, as shown by its reactivity with a panel of somatic cell hybrids. Synteny with an antigen recognized by another monoclonal antibody, W6/34, is demonstrated by hybrid and fluorescence-activated cell sorter analysis, although it is clear from absorption analysis that the determinants involved are on different molecules.

Assigning the polymorphic human insulin gene to the short arm of chromosome 11 by chromosome sorting

We have determined the subchromosomal location of the human insulin gene by analyzing DNA isolated from sorted human metaphase chromosomes. Metaphase chromosome suspensions were sorted into fractions according to relative Hoechst fluorescence intensity by the fluorescence activated chromosome sorter. The chromosomal DNA in each fraction was characterized by restriction endonuclease analysis. Initial sorts indicated that the insulin gene-containing fragment resided in a fraction containing chromosomes 9, 10, 11, and 12. Studies of cell lines that contained chromosome translocations permitted the assignment of the insulin gene to a derivative chromosome that contains portions of the short arm of chromosome II. Simultaneous sorting of the normal homolog from this small derivative chromosome separated the two different sized insulin gene-containing restriction fragments in this individual. These data indicate that the two restriction fragments represent insulin gene polymorphism and not duplicate gene loci.

Assignment of the gene coding for phosphoribosylglycineamide formyltransferase to human chromosome 14

Purine-requiring Chinese hamster ovary cell auxotrophs of the complementation class ade-E were hybridized with various human cells, and hybrids were isolated under selective conditions in which the retention of the complementing gene on the human chromosome is necessary for survival. Synteny analysis in 72 primary and secondary hybrid clones using isozyme, karyotypic, and biochemical methods provides evidence for an assignment of the gene for phosphoribosylglycineamide formyltransferase (GART, EC 2.1.2.2), deficient in ade-E mutants, to human chromosome 14. The importance of this gene assignment to the development of hypotheses regarding the organization, structure, and regulation of genes involved in the same biosynthetic pathway in mammalian cells is discussed.

Two-dimensional electrophoresis of human-CHO cell hybrids containing human chromosome 11

Two-dimensional electrophoresis-electrofocusing with polyacrylamide gels is described in which the pattern of peptide spots obtained from hybrid cells of CHO containing the single human chromosome 11 are compared with those from the hybrid which has undergone reversion so as to lose this chromosome. At least eight distinct spots unique to the cell containing chromosome 11 have been located on the electrophoretogram. Experiments are described demonstrating applicability of the method to hybrids containing specific deletion mutants of chromosome 11, an approach which makes possible regional mapping of the loci responsible for specific peptides. The methodology appears applicable to study of gene expression under the influence of hormones and other agents and to the comparison of normal and disease situations.

Isolation and localization of DNA segments from specific human chromosomes

Recombinant DNA techniques have been combined with somatic cell genetic methods to identify, isolate, and amplify fragments of human DNA localized at specific regions of human chromosome 11 selected as a model system. A library of genomic DNA segments has been constructed, in lambda Charon 4A bacteriophage, from the DNA of a somatic cell hybrid carrying a portion of human chromosome 11 on a Chinese hamster ovary cell background. Using a nucleic acid hybridization technique that distinguishes human and Chinese hamster interspersed, repetitive DNA, we have been able to distinguish recombinant phages carrying DNA segments of human origin from recombinant phages carrying DNA segments of Chinese hamster origin. We have isolated 50 human DNA segments thus far and have characterized 5 in detail. For each DNA segment characterized, a subsegment that carries no repetitive human DNA sequences has been identified. These segments have been used as hybridization probes in experiments that localize the DNA fragment on the chromosome. In each case an unequivocal chromosomal localization has been obtained with reference to a panel of hybrid cell clones each of which carries a deletion of a portion of the short arm of chromosome 11. At least one DNA segment has been identified which maps to each of the four regions on the short arm defined by the panel of hybrid cell clones used. The approaches described here appear to be general. They can be extended to produce a fine structure map of human chromosome 11 and other human chromosomes. This approach promises implications for human genetics generally, for the human genetic diseases, and possibly for understanding of gene regulation in normal and abnormal differentiation.

Human placental cell surface antigens:expression by cultured cells of diverse phenotypic origin

The present work examined the expression of cell surface glycoprotein antigens in cultured human cell lines. The set of glycoproteins studied was defined by their immunoreactivity with antiserum developed to Triton-solubilized extracts of placental brush border membranes. Studies were performed using cell lines of trophoblastic (BeWo, JEG-3) and nontrophoblastic (Chang liver cells) origin, as well as diploid fibroblast cell lines (WI-38, GM-38). Antiplacental brush border antiserum reacts with at least 19 distinct antigens present in placental membrane preparations, each of which can be resolved and identified in two-dimensional electrophoresis. The subunit molecular weight and isoelectric point for all components were defined by their positions in the two-dimensional matrix. Thirteen of these could be detected among the five cell lines examined by lactoperoxidase-catalyzed cell surface iodination. One of these 13 antigens has been identified as the placental isoenzyme of alkaline phosphatase (PAP). The expression of this component is limited to choriocarcinoma cells and Chang liver cells and it is not present in diploid fibroblasts. Under normal circumstances expression of PAP is unique to the differentiated placenta but has been frequently demonstrated in both trophoblastic and nontrophoblastic neoplasms. Two other antigens are variably expressed among the different cell types examined in the present study and their presence or absence was independent of the trophoblastic, epithelial nontrophoblastic, or fibroblastic origin of the cells. Ten surface antigens were expressed in all five cell lines. Six of these had previously been found common to membranes from three adult differentiated tissues, including liver and kidney, as well as placenta (Wada et al, J Supramol Struc 10(3): 287-305, 1979). The presence of this set of antigens in cultured cells as well extends the possibility that these are ubiquitously expressed on human cell surfaces. Two other antigens observed in all cultured cells had been found in both placental and either kidney or liver membranes and may represent common functions shared by many tissues which are also necessary for growth in vitro. The two remaining placental antigens seen in all cultured cells have previously been shown to be absent in adult tissues. Their presence in cultured cells but not in the membranes of resting differentiated tissues may signify the expression of glycoproteins characteristic of trophoblasts in all cells adapted to growth in culture.

Regional mapping of the gene for human lysosomal acid phosphatase (ACP2) using a hybrid clone panel containing segments of human chromosome 11

A clone panel containing various segments of human chromosome 11 has been selected and use for regional assignment of the gene for human lysosomal acid phosphatase (ACP2) to the short arm of chromosome 11, in the region 11p11 leads to 11p12. Further evidence has also been presented to update the regional assignment of the gene for lactate dehydrogenase A (LDHA) to 11p12 leads to 11p13, and to support a previous assignment of the genes for the two components of the human cell-surface antigens of the SA11 (previously designated AL) group, SA11-1 and SA11-3 (previously designated AL-a1 and AL-a3), to 11pter leads to 11p13. This regional clone panel will be useful for rapid regional mapping of other genes assigned to chromosome 11.

Induced segregation of human syntenic genes by 5-bromodeozyuridine + near-visible light

Chromosome-breaking agents have been used in two different procedures for promoting segregation of syntenic genes on human chromosome 12. In method A, a human-Chinese hamster cell hybrid containing the single human chromosome 12 was treated either with 5-bromodeoxyuridine BrdU + near-visible light or with X-rays. In method B, normal human fibroblasts were treated with BrdU + near-visible light followed by their fusion with a Chinese hamster glycine-requiring cell mutant CHO-K1/gly-A. Since the human complementing gene for serine hydroxymethyltransferase, an enzyme deficient in gly-A, lies on human chromosome 12, only those hybrids retaining that chromosome can survive the glycine-free medium. Clones isolated from both procedures were analyzed for the loss or retention of four other syntenic genes on chromosome 12, TPI, GAPD, LDH B, and PepB. The results demonstrate that method B is much more effective in generating clones with extensive marker losses. In addition, the segregation pattern and frequency obtained in this study provided information on the linear order of TPI and GAPD on chromosome 12.

Further studies on hybrid cell-surface antigens associated with human chromosome 11

A new human immunogenetic cell-surface activity associated with human chromosome 11 in the AL human-Chinese hamster ovary cell hybrid is described. Like a1, but not a2, it is present on the human erythrocyte. By mutagenesis and selection, specific, stable, variants of the AL hybrid have been prepared exhibiting various combinations of a1, a2, a3, and lactic dehydrogenase A activities. The antigens of the AL system can be demonstrated by the horseradish peroxidase system which offers a promising approach to scanning of tissue cells.