Genetic studies on human lymphoblastoid lines: isozyme analysis on cell lines from forty-one different individuals and on mutants produced following exposure to a chemical mutagen

The lymphoblast beta-adrenergic receptor in bipolar depressed patients: characterization and down-regulation

beta-Adrenergic receptor binding and adenylyl cyclase activity were examined in lymphoblast cell lines established from 12 patients with bipolar disorder and 10 unrelated healthy control subjects. No significant differences were found in [125I]iodocyanopindolol binding affinity or capacity or in isoprenaline-stimulated cAMP response. Incubation of lymphoblasts with isoprenaline (1 nM) for 24 h prior to assay reduced both receptor number and adenylyl cyclase activity. The extent of receptor down-regulation was significantly less in cells of bipolar disorder patients (20 +/- 5%) compared to controls (40 +/- 4%). Desensitization of adenylyl cyclase, however, was reduced to a similar degree in bipolar (65 +/- 14%) and control (68 +/- 20%) subjects. We conclude that basal beta-adrenergic receptor characteristics are not altered in bipolar disorder but that agonist down-regulation of receptor number may be less efficient than in control cells. The functional implications of this effect are discussed.

The expression of human glycerol-3-phosphate dehydrogenase in human/rodent somatic-cell hybrids

Our previous studies using rodent/human somatic-cell hybrids suggested that the expression of human mitochondrial glycerol-3-phosphate dehydrogenase (GPDM) is dependent on the presence of human mitochondria. This has now been tested directly by analysis of GPDM activity in a series of nine hybrid-cell lines, four segregating human chromosomes and five losing rodent chromosomes (reverse segregants). The chromosome composition of the hybrids was deduced from analysis of biochemical markers and examination of G- and G11-banded metaphase spreads and the mitochondrial content was determined by Southern blot analysis, using cloned mouse and human mtDNA sequences as probes. We found that the mtDNA species present in these hybrids correlated exactly with the pattern of chromosome segregation such that the conventional hybrids contained rodent mtDNA and the reverse segregants human mtDNA. However, the pattern of GPDM expression was not directly correlated with the species of chromosomes or mitochondria present: all the hybrids showed strong rodent GPDM activity and two from each class of hybrid also showed human GPDM activity but the other hybrids were negative for human GPDM. We conclude that rodent GPDM readily integrates into human mitochondria, that the expression of rodent GPDM is not dependent on the presence of rodent mitochondria, and that GPDM is not coded by mtDNA. Human GPDM either is not capable of being inserted into the rodent mitochondrial membrane or is regulated in some way in the hybrid cells by an unidentified rodent factor.

Isoenzyme studies in human leukemia-lymphoma cell lines--1. Carboxylic esterase

The isoenzyme patterns of carboxylic esterase (E.C. 3.1.1.1) were studied in 74 proven human leukemia-lymphoma and 12 normal B-lymphoblastoid cell lines. These cell lines have been extensively phenotyped using poly- and monoclonal antibodies. Esterase isoenzymes were separated by isoelectric focusing and visualized by histo-cytochemical techniques. No leukemia-specific or (except for monocytes) blood cell type-specific isoenzyme or isoenzyme pattern could be detected. The monocytic element in some cell lines was characterized by a strong isoenzyme band which could be selectively and completely inhibited by sodium fluoride. The enzyme phenotypes were stably expressed in all subcultures of a given cell line and did not appear to have any cell cycle dependency. The leukemia-lymphoma cell lines have been subclassified into four major groups according to immunological parameters: T-cell, B-cell, myelomonocytic and non-T, non-B-cell. On the basis of immunological data the T-cell lines were assigned to five stages of differentiation. The number and staining intensity of the isoenzymes increased with differentiation of the T-cells paralleling the expression of immunological markers. The B-cell leukemia-lymphoma cell lines were divided into pre B-, B-, Burkitt lymphoma, multiple myeloma and hairy cell leukemia cell lines. Substantial variability among the isoenzyme patterns was detected ranging from immature profiles of pre B-cell lines to complete isoenzyme repertoires of multiple myeloma cell lines. No significant difference was seen between the isoenzymes of mature B-cell lines and normal B-lymphoblastoid cell lines. The most prominent feature seen in myelomonocytic cell lines was the monocytic band indicating a monocytic origin and separating the 'monocytoid' from the 'pure myeloid' cell lines. Considerable heterogeneity in the isoenzyme patterns was observed in the non-T, non-B cell groups which comprised erythroleukemia cell lines and cell lines arrested at a very early stage of lymphoid differentiation. These latter cell lines together with some T- and B-cell lines shared the common characteristics of positivity for cALLA, TdT and Ia antigens and an immature, incomplete isoenzyme profile. The results support the notions of maturation arrest and normal gene expression in leukemic cell populations. Furthermore, the importance of biochemical studies as part of the multiple marker analysis could be demonstrated.

Tumorigenicity of human lymphoblastoid cell lines, acquired during in vitro culture and associated with chromosome gains

Tumorigenicity of human lymphoma and lymphoblastoid B-cell lines was assessed by their ability to form growing and transplantable masses on subcutaneous inoculation into neonatally thymectomized, Ara-C-protected, total-body-irradiated mice. By these criteria, 12 lines of known malignant origin were tumorigenic, 11 lymphoblastoid lines, tested after less than one year of in vitro growth, were non-tumorigenic and 8/18 long-established lymphoblastoid lines produced transplantable tumours. All of the long-established lines had acquired karyotypic changes on prolonged culture, the predominant characteristic being a gain of whole chromosomes or of major chromosome segments. None showed the classical 8:14 translocation associated with Burkitt's lymphoma. Comparisons with nontumorigenic precursors (recovered from liquid nitrogen storage) and with other non-tumorigenic but chromosomally abnormal, lymphoblastoid lines suggest that imbalance of the dosage of genes carried on chromosomes 7,8 and 9 may be important in determining the tumorigenic phenotype.

Beta-adrenoceptor binding defects in cell lines from families with manic-depressive disorder

Binding of 125I-iodohydroxybenzylpindolol to beta-adrenoceptors has been examined in lymphoblastoid cell lines from members of 5 families affected by manic-depressive disorder. Cell lines from 6 manic-depressives, 7 unaffected relatives and 11 non-psychiatric controls were examined. Binding was reduced to less than half of control values in cell lines from 4 out of 6 manic-depressives and only 1 out of 18 unaffected relatives or controls. All the cell lines with reduced beta-adrenoceptor binding came from 3 families; members of the remaining 2 families showed normal binding. These findings suggest that genetic heterogeneity is present in manic-depressive disorder and that a beta-adrenoceptor defect may influence genetic susceptibility to the disorder.

High frequency of beta-hexosaminidase deficiency in lymphoblastoid cell lines

The activity of seven lysosomal enzymes was determined in 25 lymphoblastoid cell lines. These lines included normal controls transformed with Epstein-Barr virus, Burkitt's lymphomas and other lymphomas with or without EBV genome. Four lines were deficient in total beta-hexosaminidase activity. The deficiency was as severe as that of the variant O (Sandhoff's disease) of clinical beta-hexosaminidase deficiency. The electrophoretic pattern was also similar to that observed in Sandhoff's disease. The possible mechanisms explaining the high frequency of beta-hexosaminidase deficiency in lymphoblastoid cell lines are discussed.

Differentiation in vitro of human-mouse teratocarcinoma hybrids

The mouse embryonal carcinoma (EC) line, PCC4, was used to construct a series of somatic cell hybrids which contain a single or a few human chromosomes. The hybrids all retained the EC phenotype as determined by morphology, expression of SSEA-1, lack of cell surface H-2 antigen and cytokeratin filaments, high alkaline phosphatase levels, the ability to form EC tumors ectopically in nude mice, and the ability to differentiate in response to retinoic acid. Constitutively differentiated cloned lines were derived from retinoic acid-treated hybrid cultures. Several derived lines had a phenotype indistinguishable from that of parietal endoderm cells, which includes synthesis of large amounts of laminin, type IV procollagen, and plasminogen activator. One differentiated line showed a fibroblast-like morphology. The differentiated lines derived from two of the hybrids, MCP6 and GEOC4, stably maintained the sole human chromosomal component present in the EC progenitors. These EC hybrids therefore provide a system to study developmental regulation of the introduced and stably maintained human genetic material derived from a variety of cell types.

Differentiation in vitro of human-mouse teratocarcinoma hybrids

The mouse embryonal carcinoma (EC) line, PCC4, was used to construct a series of somatic cell hybrids which contain a single or a few human chromosomes. The hybrids all retained the EC phenotype as determined by morphology, expression of SSEA-1, lack of cell surface H-2 antigen and cytokeratin filaments, high alkaline phosphatase levels, the ability to form EC tumors ectopically in nude mice, and the ability to differentiate in response to retinoic acid. Constitutively differentiated cloned lines were derived from retinoic acid-treated hybrid cultures. Several derived lines had a phenotype indistinguishable from that of parietal endoderm cells, which includes synthesis of large amounts of laminin, type IV procollagen, and plasminogen activator. One differentiated line showed a fibroblast-like morphology. The differentiated lines derived from two of the hybrids, MCP6 and GEOC4, stably maintained the sole human chromosomal component present in the EC progenitors. These EC hybrids therefore provide a system to study developmental regulation of the introduced and stably maintained human genetic material derived from a variety of cell types.

Electrophoretically detectable mutations induced in CHO cells by varying doses of ultraviolet radiation

Chinese hamster ovary (CHO) cells were subjected to ultraviolet radiation (UV) at doses resulting in 100% (no irradiation), 50-30%, 20-10% and approximately 1% survival. 2 divisions after UV exposure surviving cells were cloned and clones expanded for electrophoretic analysis of the products of approximately 40 enzyme loci. 4 different classes of variants (electrophoretic shifts, nulls, enzyme re-expression and enzyme modification) were detected in 29 of 1329 clones analyzed and proven mutants by subclone analysis. The frequency of mutants in the irradiated groups (28/38391 loci screened or 7.3 X 10(-4) was significantly higher than controls. The frequency of shift mutants at 10-20% survival was higher than shifts at 30-50% survival and was significantly higher than shifts at approximately 1% survival. The frequency of nulls increased with dose. 12 of the 28 mutants obtained in the irradiated groups were at only 3 of the mean 41 loci screened/clone. These results indicated that shift mutants could be detected more efficiently than nulls at lower dose and that loci varied widely with respect to their susceptibility to UV mutagenesis. Multiple null mutants at 2 loci, isocitrate dehydrogenase 2 and hexokinase 2, indicated they may be hemizygous in CHO cells.

Mutagenicity testing on non-selectively cloned Chinese hamster ovary cells with the protein-mapping method

Chemical mutagenesis was studied on Chinese hamster ovary cells by protein mapping. Cell cultures were treated with methylnitrosourea and the cells were cloned in non-selective media. The proteins of single clones were separated by 2-dimensional electrophoresis and analysed for qualitative (electrophoretic mobility) and quantitative (staining intensity; presence/absence) changes in the protein patterns. The investigation included 26 clones derived from treated cells and 26 control clones. The total number of gene loci tested was calculated from the number of protein spots analysed: it amounted to about 33 800. The protein patterns revealed 2 alterations defined as qualitative variant proteins. No alteration of this type was found in the control group. The frequency of quantitative variant proteins was increased by more than 100% compared with the control group. Our results and theoretical considerations suggest that the cellular concentration of single proteins offers a sensitive parameter for mutagenicity testing.

Introduction of a human X-6 translocation chromosome into a mouse teratocarcinoma: investigation of control of HLA-A, B, C expression

We have developed an approach to human developmental biology which exploits somatic cell genetics. With this system we have examined the production of the HLA-A,B,C antigens, A human-mouse somatic cell hybrid was constructed which contained a human X-7 chromosome translocation carrying the HLA region; this hybrid was used as a donor of the X-6 translocation in the technique of microcell transfer. The X-6 chromosome recipient was the mouse embryonal carcinoma cell line PCC4. The microcell hybrid MCP-6 retained the embryonal carcinoma phenotype as judged by shape and absence of H-2 expression. Nonetheless, the expression of the HLA-A,B,C genes was not extinguished. HLA-A,B,C antigen production of the cell surface, however, was not detected because this hybrid apparently could not make beta 2-microglobulin.

cDNA clones coding for the heavy chain of human HLA-DR antigen

Two cDNA clones, pDRH1 and pDRH2, containing sequences specific for human HLA-DR antigens were isolated from a bank of cDNA clones made from partially purified HLA-DR mRNA from the human lymphoblastoid cell line Maja. The clones were specific for the Mr 34,000 HLA-DR antigen glycoprotein chain. The identity of these clones was established by (i) their ability to hybridize specifically to HLA-DR mRNA in a positive selection assay; (ii) mRNA species hybridizing to the cDNA clones were expressed in B-cell but not in T-cell or fibroblast cell cultures; and (iii) a nucleotide sequence in the longer clone, pDRH2, could be translated into an amino acid sequence that is identical to the limited NH2-terminal amino acid sequence available for the purified HLA-DR antigen Mr 34,000 chain. Analysis of DNA from human, mouse, and human--mouse somatic cell hybrid lines by Southern transfer of restriction endonuclease digests indicated that the HLA-DR heavy chain is encoded in chromosome 6. This finding is compatible with the location of at least one of the HLA-D/DR heavy chain genes within the HLA region. In addition, the sequences coding for HLA-DR heavy chain appear to be present in only one or a few copies in the genome and to be relatively simple in structure.

Human mitochondrial glycerol phosphate dehydrogenase (GPDm) isozymes

1. A hydrophobic/phospholipid electrophoretic system has been devised which makes possible the analysis of human mitochondrial glycerol phosphate dehydrogenase (E.C. 1.1.99.5. GPDM). 2. GPDM has a wide tissue distribution in both adult and foetal life and is active in cultured lymphoblastoid cells and fibroblasts but is absent from red cells. 3. The solubilization procedure does not significantly alter the kinetic properties of the enzyme (Km alpha-glycerophosphate = 0.04-0.07 M, Km PMS = 0.19-0.35 mM) but the soluble form is less thermostable. 4. Comparisons of physicochemical characteristics, tissue distribution and coenzyme requirement point to a separate genetic determination and low level of evolutionary relatedness between GPDM and its cytosolic counterpart GPDS.

Evidence for a relationship between longevity of mammalian species and life spans of normal fibroblasts in vitro and erythrocytes in vivo

The replicative life spans of mammalian fibroblasts in vitro were studied in a number of cell cultures representing eight species. Emphasis was placed on determining the population doubling level at which phase III (a period of decrease in the rate of proliferation) and chromosomal alterations occur. All the cell cultures studied went through a growth crisis, a period of apparent growth cessation lasting for at least 2 weeks. In most cultures, the crisis represented the end of their replicative capacities, but in some cultures cell proliferation was resumed after the crisis. A predominantly diploid chromosome constitution (more than 75%) was demonstrated prior to the growth crisis. In cultures in which cell proliferation was resumed after the crisis, a nondiploid constitution prevailed in all cases except the rat (with 90% or more diploid cells all the time). The growth crisis occurred at population doubling levels that were characteristic for the species and was shown to be related to the species' maximal life span by a strict power law, being proportional to the square root of the maximal life span. Based on data in the literature, the same relationship was also valid for the lifespans of circulating mammalian erythrocytes in vivo. These results may indicate the prevalence of a common functional basis regulating the life span of fibroblasts and erythrocytes and thus operating in replicative as well as postmitotic cells in vitro and in vivo.

Human succinate dehydrogenase: biochemical and genetic characterization

A simple procedure for the preparation of soluble human succinate dehydrogenase is described. These preparations have proved suitable for analysis by zone electrophoresis, using a specific stain to detect activity after separation. In a survey of succinate dehydrogenase from various tissues and different individuals, no evidence for genetic heterogeneity due to the expression of either multiple loci or alternative alleles at the succinate dehydrogenase locus was found. However, epigenetic heterogeneity in both molecular size and charge was seen and various explanations for the occurrence of the isoenzymes are explored. Estimates of molecular size (93,300 +/- 9100) suggest that the smallest active unit of succinate dehydrogenase accounts for the major part of the solubilized activity. Kinetic studies have shown that the apparent Km values for succinate (0.9 mM) and PMS (0.4 mM) are comparable to those previously described for the beef heart enzyme, and these parameters were not significantly altered when the enzyme was removed from the membrane milieu. However a marked non-succinate-dependent activation of the membrane-associated enzyme at 38 C is apparently lost on solubilization, and this observation may have some bearing on earlier reports of an apparent decrease in Vmax on solubilization of succinate dehydrogenase.

NADH cytochrome b5 reductase activity in lymphoid cell lines. Expression of the defect in epstein Barr virus transformed lymphoblastoid cell lines from patients with recessive congenital methemoglobinemia

Recessive congenital methemoglobinemia (RCM) is due to the homozygous deficiency of NADH-cytochrome b5 reductase (EC 1.6.2.2.). In type I disease, in which the patients are only methemoglobinemic, the enzyme defect is fully expressed in the erythrocytes, whereas the leukocytes are much less affected. In type II disease, in which the patients are, in addition, mentally retarded, the defect is generalized to all the tissues including cultured fibroblasts. In the present study we have investigated Epstein-Barr virus (EBV) transformed lymphoid cell lines (LCL) derived from patients with both types of cytochrome b5 reductase deficiency and from nondeficient individuals. The total cytochrome b5 reductase activity of the control LCL was found to be similar whatever the LCL origin, except for one lymphoma line (Daudi). The enzyme from the control LCL (c 252/B 95) was found to be immunologically related to the human soluble erythrocyte cytochrome b5 reductase, indicating that it is the product of the same gene: the DIA1 (diaphorase) locus. The LCL derived from one patient with the type I disease and two patients with the type II disease were investigated.l In the former the defect was expressed to a lesser degree than in the cases with mental retardation in which the defect was much pronounced, and involved both the mitochondrial and the microsomal fraction. This indicated that all the subcellular forms of the cytochrome b5 reductase are under the same genetic control. Altogether, these data show that the LCL are a favorable material for studying both types of cytochrome b5 reductase deficiency and for investigating in depth the molecular aspects of this metabolic disease.

Deficiency of malic enzyme: a possible marker for malignancy in lymphoid cells

Soluble malic enzyme (MEs) has been examined in long-term human lymphoid cell lines cultured from 101 individuals. In 65 out of 66 lines derived from people without lymphoreticular malignancy the enzyme was very active. Lines established from 35 individuals with various forms of lymphoreticular malignancy were also examined, including in some cases more than 1 line derived from the same patient. In all cases where the cell line was thought to be derived from normal cells MEs was active, but in 27 out of 29 lines thought to be derived from malignant cells (from 25 patients) MEs was not detected. In the case of two patients with chronic lymphatic leukaemia 'normal' lines active for malic enzyme, and 'leukaemic' lines lacking malic enzyme, had been cultured from the same individual. Preliminary investigations of the lack of malic enzyme in somatic cell hybrids derived from lymphoma and leukaemia cell lines are compatible with an alteration at the level of the structural locus MEs on chromosome 6. However, the restoration of MEs activity in one line by fusion with mouse teratocarcinoma cells suggests that the alteration may be of a regulatory nature.

Mapping by gene dosage, using aneuploid human lymphoid cell lines

Human lymphoblastoid cell lines evolve in vitro by the emergence of successive waves of clones which are often chromosomally marked. This offers the opportunity to compare tissue samples of the same genetic origin but differing in certain defined parts of the karyotype. Using selected sets of lines in which the members of genetically matched pairs differed in the number of copies of 8p or of 12p, levels of GSR and LDH B respectively have been shown to correlate with the specific chromosome aberrations, supporting existing data on the regional assignment of these two structural loci. This approach represents a useful addition to established methods for human gene mapping.

Differences in genetic stability between human cell lines from patients with and without lymphoreticular malignancy

Isoenzymes determined by 11 loci have been examined in 137 human lymphoblastoid lines of various origins with a view to determining their phenotypic stability in culture. Lines of normal origin are stable and at these loci are phenotypically identical to the individuals from whom they are derived. Lymphomas and some lines from patients with leukaemias show a tendency to increased apparent homozygosity, presumably resulting from loss of expression of one or other allele during culture. Taken together with the cytogenetic evidence this suggests that progressive loss of functional parts of the genome with time in culture is a characteristic of lines derived from malignant lymphoid cells.

A molecular approach to the identification and individualization of human and animal cells in culture: isozyme and allozyme genetic signatures

The electrophoretic resolution of a group of genetically monomorphic gene-enzyme systems that are developmentally and biologically ubiquitous has been used to provide a species-specific and type-specific biochemical characterization of various cultured cells. The relative mobilities of gene-enzyme systems representing nine distinct gene products from cell cultures of 25 species from Drosophila to man are presented. These isoenzymes effectively discriminate interspecies cell-to-cell contamination and almost invariably serve to identify the contaminating species. The resolution of eight polymorphic gene-enzyme systems in human cell cultures provides a virtually unique allozyme genetic signature as a monitor of intraspecies cellular contamination. The genetic signatures of 47 commonly used human cells are presented. Included in the test were seven putative HeLa (human cervical carcinoma) contaminants each of which expressed a signature identical with that of HeLa. The probability that an unrelated human cell line will have a signature identical to a typed cell is computed for each line from the genotypic frequencies at each locus in a population of cultured human cells. The gene frequencies of this cell population are comparable to the same frequencies in natural human populations. The most common human signature has a frequency (and therefore a probability) of 0.02. The majority of the 17,010 possible signatures are far less probable. A calculation of the theoretical incidence of chance matching of signatures within test groups of two or more individuals is presented. The probability of a chance match between any two randomly selected individuals is 0.004 and among five randomly selected individuals is 0.034. The allozyme genetic signature represents a definitive monitor of cell identity and is presented as a standard of cell and tissue identification for a variety of biological studies.

Isozymes of amino acid naphthylamidase in human haematopoietic cell lines

The occurrence of isozymes of the proteolytic enzyme amino acid naphthylamidase was investigated in a panel of 44 neoplastic and non-neoplastic haematopoietic cell lines by polyacrylamide gel electrophoresis. Two isozymes (A and C) were common for all lines, whereas different forms of a third isozyme with intermediate electrophoretic mobility (B) appeared in nine lines. Isozyme A seemed to be associated with cell proliferation and was not a marker for malignancy. The appearance of different B isozymes not present in normal peripheral blood lymphocytes, occurred in some Burkitt lymphoma lines and in two non-malignant lines maintained for a long time in culture. In three lines derived from myeloid leukaemia a variant of isozyme B seemed to be a marker for cell origin.

A method for testing the growth activity of tissue culture media using suspension lymphoblastoid cells

A new rapid method for testing the growth activity of tissue culture media using the 'Raji' and 'Simpson' strains of lymphoblastoid cells grown in suspension is described. This method has advantages for rapidly assessing the quality of a culture medium.

Triplex gene dosage effect of TPI and G3PD in a human lymphoblastoid cell line with partial trisomy 12p13 and 18p

The EBV-induced lymphoblastoid line established from a patient carrying a duplication of the distal part of chromosome 12 short arm (12p13) retained the original partial trisomy and displayed the same triplex gene dosage effect for TPI and G3PD as found in the patient's RBC and WBC.

Lysosomal acid hydrolases in established lymphoblastoid cell lines, transformed by Epstein-Barr virus, from patients with genetic lysosomal storage diseases

Lysosomal acid hydrolases were determined in established lymphoblastoid cell lines, transformed in vitro by Epstein-Barr virus (EBV) from lymphocyte-rich cell populations isolated from the peripheral blood of patients with genetic lysosomal storage diseases--Hurler syndrome, Scheie syndrome, GM1-gangliosidosis type 1 and type 2, Tay-Sachs disease, and I-cell disease--and from obligate heterozygotes for these diseases. The respective enzyme activity was undectectable in lymphoblastoid cells from the patients, but not from controls. Obligate heterozygotes could not always be distinguished from controls in lymphoblastoid cells as well as in leukocytes. These results suggest that established lymphoblastoid cell lines are useful material for the enzymatic study of genetic lysosomal storage diseases.

Lysosomal enzymes in human lymphoblastoid lines: unusual characteristics of RAJI and DAUDI

The lysosomal enzymes N-acetyl hexosaminidase, alpha-galactosidase and alpha-mannosidase vary in electrophoretic mobility in different human lymphoblastoid (lymphoid) lines. The relative mobilities of these three enzymes and three out of four other lysosomal enzymes tested correlate well with each other. The patterns appear to be relatively stable characteristics of each line. The lines RAJI and DAUDI show a strikingly fast electrophoretic mobility for all of these enzymes. N-acetyl hexosaminidase is also markedly deficient in DAUDI.

The deficiency of a lysosomal acid hydrolase in two clones derived from the human lymphoblastoid line F137 after mutagen treatment

Two clones (out of a total of 181 clones tested) derived from the human lymphoblastoid (lymphoid) line F137 after mutagen treatment were found to be deficient in a lysosomal acid hydrolase. The clone N32 derived from EMS-treated F137 is deficient in N-acetyl hexosaminidase A and B but contains normal levels of N-acetyl hexosaminidase C and low levels of an enzyme resembling N-acetyl hexosaminidase S. Thus the enzyme deficiency in this clone appears to resemble the so-called Sandhoff variant of Tay-Sachs disease, a disease inherited as an autosomal recessive condition. The clone G3 derived from MNNG treated F137 is deficient in alpha-galactosidase A. This clone resembles the situation in X-linked Fabry's disease. Karyotype analysis of the clones failed to reveal any chromosome rearrangement or losses of chromosomal material that might have accounted for the mutations and it is suggested that a single point mutation might in each case account for the loss of enzyme activity. No storage of the natural substrates of the two enzymes could be demonstrated in the clones.

Spontaneous and induced patterns of the Epstein-Barr virus (EBV) cycle in a new set of somatic cell hybrids

A somatic cell hybrid line and its subclones obtained by fusing two Burkitt lymphoma lines (Raji and Namalwa) were examined for the expression of EBV-specific antigens both spontaneously and after induction. The hybrids retained spontaneous early antigen (EA) production at the level characteristic of Raji. Similarly the more permissive Raji pattern dominated the induction of EA by IUDR treatment or P3HR-1 virus superinfection. These findings accord with our previous results on independently derived Raji/Namalwa hybrids. Virus capsid antigen was induced in the hybrids by P3HR-1 virus superinfection though at a lower level than in the Raji parental cell.

Double immunoglobulin production in cloned somatic cell hybrids between two human lymphoid cell lines

Several clones of independently established somatic cell hybrids between two human lymphoid cell lines, Raji and Namalwa, were examined for surface immunoglobulin expression. Double-antibody radioimmunoassays were established for kappa and lambda light chains. Immunoglobulins were detergent-extrated by Triton X-100 and quantified by radioimmunoassay. The Raji parent expressed small amounts of kappa chains on its surface, and the Namalwa parent a 10 fold greater amount of lambda chains. We show that the majority of the hybrid clones co-express both parental phenotypes.

Enzyme polymorphisms as genetic signatures in human cell cultures

The electrophoretic resolution of seven relatively polymorphic human gene-enzyme systems expressed in tissue culture cells can be used as a sensitive genetic monitor for intraspecific cell contamination. An identical genotype at each of the same allozyme loci provides a 95% (or greater) confindence estimate of the identity of two cultured lines, on the basis of the allelic frequencies of the seven enzyme loci in natural populations and in populations of independently derived cultured cells. Of 27 commonly used human cell lines examined, only one of 351 pairwise comparisons proved genetically indistinguishable.

Prospects for evaluating genetic damage in mammalian cells in culture

Starting from some general considerations on cultured mammalian cells as a biological material for the detection of genetic changes, information is given on cell lines and genetic markers that have been the subject of extensive research. The experimental variables of mutation assays are then considered, with special reference to those involved in the system resistant to 8-azaguanine. Work now in progressin the field of environmental mutagenesis is mentioned at the end of the article.

Characterization and tissue distribution of N-acetyl hexosaminidase C: suggestive evidence for a separate hexosaminidase locus

1. An electrophoretic system in which N-acetyl hexosaminidase C (HEX(C)) MIGRATES LESS ANODALLY THAN N-acetyl hexosaminidase A (HEX(A)) is described. 2. HEX(C) is shown to differ from HEX(A) and HEX(B) in substrate specificity, molecular size and affinity for Concanavalin-A. 3. HEX(C) is present in a wide range of adult and foetal tissues and in tissues from patients with Tay-Sachs and Sandhoff's diseases. It is particularly prominent in brain, testis, thymus and lymphoblastoid cell extracts and in several foetal tissues. 4. It is suggested that HEX(C) is coded at a separate gene locus from HEX(A) and HEX(B).

The selection of somatic cell hybrids between human lymphoma cell lines

Somatic cell hybrids have been selected between three pairs of established human lymphoid cell lines producing pure lines of proliferating hybrid cells: Raji/Namalwa, Raji/Daudi, and Raji/BJAB. The hybrid cell lines have been characterized with respect to isozyme pattern, volume, and karyotype.

Selection of biochemically variant clones of human lymphoid cells

Two established clones of human lymphoid cells, Raji and P3HRI, could be cloned in semi-solid agarose-containing medium at high efficiency. Several other human lymphoid cell lines examined cloned poorly if at all under these conditions. Variant clones of Raji and P3HRI resistant to 6-thioguanine, and in the case of Raji also to either 8-azaadenine or 5-bromo-2'-deoxyuridine, were selected and characterized.

Production by EBV infection of an EBNA-positive subline from an EBNA-negative human lymphoma cell line without detectable EBV DNA

A continuous lymphoma cell line, BJAB, derived from the tumour of an exceptional African case of Burkitt's lymphoma, has previously been described. Unlike 97% of African BL cases studied, neither the original tumour cells nor the cell line contained detectable amounts of EBV (Epstein-Barr virus) DNA, nor did they express the EBV-determined nuclear antigen EBNA. The cells of the established line had the characteristics of B-type lymphocytes and they carried receptors for EBV. EBNA was induced in the majority of BJAB cells after EBV infection. Usually the cells died within 10 days of infection, but it was possible to establish a permanent EBNA-positive variant (GC-BJAB) of BJAB. The patient from whose tumour the original BJAB line was established was seropositive for EBV antigens, indicating previous exposure to and continuing presence of the virus; yet the tumour had not become infected by EBV. This evidence shows that EBV is not readily "picked up" by the lymphoma.

Genetic studies on human lymphoblastoid cell lines: isozyme and cytogenetic heterogeneity in a cell line, with evidence for localization of the Pep A locus in man

One hundred and thirty-three clones (60 mutagen treated, 73 controls) of the human male lymphoblastoid cell line F 137 have been examined for the electrophoretic pattern of more than 30 enzymes. In nine instances there was loss of activity of one allele of an X-linked or heterozygous autosomal locus. Seven of these involved the Pep A locus, and in every case the change was from the Pep A 2-1 phenotype to Pep A 2. Cytogenetic analysis of the parent line revealed a number of variants on the modal karyotype. On cloning, there appeared to be some selection for survival of non-modal cells. The proportions of the cytogenetically distinct populations within the bulk culture varied over a period of many months. There was a strong correlation in individual clones between loss of activity of the product of the Pep A1 allele and the presence in the cells of a 9/18 translocation. In addition there was one clone of phenotype Pep A 2 with a deletion of part of the long arm of chromosome 18. The data confirms the assignment of the Pep A structural locus to the distal half of the long arm of chromosome 18 and localizes it with some precision to the qter region. The Pep A 2 phenotype of the clones containing the 9/18 translocation could be the result of a small deletion eliminating the Pep A1 allele but not large enough to be detected cytogenetically. Alternatively inactivation of the Pep A1 allele may have occurred as a position effect resulting from the close association of heterochromatin from the centromere of 9 with the qter region of 18.

Studies of the linkage relationship of beta-2-microglobulin in man-mouse somatic cell hybrids

Beta-2-microglobulin (beta2mu) production has been studied in 33 primary man-mouse hybrid clones and in 26 secondary man-mouse hybrid clones. These clones have also been examined for the presence of 15 human enzyme phenotypes. Karyotypic analyses have been carried out on clones. From these studies the following conclusions can be drawn: (1) Gene(s) determining human beta2mu production in humans are apparently syntenic with the MPI gene on chromosome 15. (2) Long-term fibroblast lines may be of limited use in mapping studies as chromosomal rearrangements frequently occur in these lines. (3) The gene(s) determining beta2mu production in humans segregate independently of chromosome 6. If the assignment of the genes determining HL-A alloantigens to chromosome 6 is correct, our results imply that beta2mu and HL-A alloantigens are determined by genes carried on different chromosomes, despite the fact that beta2mu forms an integral part of the HL-A molecule.

Glutaraldehyde and human T cell rosettes

Blood mononuclear cells from ten healthy donors and cells from fifty cultured human lymphoblastoid lines were tested for the capacity to form rosettes with sheep erythrocytes. The effect of adding glutaralhehyde before scoring rosettes and the effect of substituting glutaraldehyde-fixed for fresh sheep cells were both examined. The results suggest that glutaraldehyde increases the apparent proportion of rosette-forming cells by altering the sheep erythrocytes in such a way that they will adhere to some B lymphocytes. Although a small number of cells carry both surface immunoglobulins and receptors for fresh sheep erythrocytes, the rosette test with fresh sheep cells identifies T lymphocytes more accurately in the absence of glutaraldehyde than in its presence.

Detection of homozygotes and heterozygotes for metachromatic leukodystrophy in lymphoid cell lines and peripheral leukocytes

Assays of arylsulphatase A have been performed on peripheral leukocytes and lymphoid cell lines from normal subjects and heterozygotes and homozygotes for metachromatic leukodystrophy (MLD) by utilizing an improved procedure based on the removal of excess protein from the final digest. No overlap of arylsulphatase A activity was observed between peripheral leukocytes obtained from 11 normal donors, 8 heterozygotes and 5 homozygotes for MLD. Absence of enzyme activity was demonstrated in the patients' leukocytes, when the modified assay procedure was employed. Arylsulphatase A activity (mean +/- S.D.) in 30 lymphoid lines and sublines established from 18 normal donors, 2 heterozygotes and 1 homozygote for MLD was 54-5 +/- 23-1, 24-1 +/- 3-2 and 0-9, respectively. The enzymic activity of arylsulphatase A and B remained stable over a period of several months. These findings indicate that long-term lymphoid lines express the genotype of the donor and maintain enzyme stability over long periods in culture. Moreover, it appears that peripheral leukocytes are a reliable system for the identification of the carrier state of MLD.

A method for the storage and retrieval of laboratory data on human lymphoblastoid cell lines

A computer-based system has been developed for the handling and retrieval of data on long-term human lymphoblastoid cell lines. It permits accurate recording of a wide range of genetic markers and other defined characteristics for the donor of each culture and for individual aliquots of any cell line. The data is recorded in relation to the in vitro age of each aliquot studied and the programme is designed to permit both the sequential examination of a single cell line and the comparison of lines of different origins. It is hoped that, by the application of this type of system, the confusion which has arisen in relation to other long-term cell lines (and which threatens to develop in relation to human lymphoblastoid cell lines) may be avoided and that the exchange of information between laboratories may be facilitated.