Complement-mediated antiserum cytotoxic reactions to human chromosome 7 coded antigen(s): immunoselection of rearranged human chromosome 7 in human-mouse somatic cell hybrids

Murine Embryonic Stem Cells

Embryonic stem (ES) cells are derived from preimplantation stage mouse embryos at the time when they have reached the blastocyst stage. It is at this point that the first steps of differentiation take place during mammalian embryonic development. The individual blastomeres now start to organize themselves into three distinct locations, each encompassing a different cell type: outside epithelial cells, trophectoderm; cells at the blastocele surface of the inner cell mass (ICM), the primitive endoderm; and inside cells of the ICM, the primitive ectoderm. ES cells originate from the third population, the primitive ectoderm, which is a transiently existing group of cells in the embryo. Primitive ectoderm cells diminish within a day as the embryo is entering into the next steps of differentiation. ES cells, however, while retaining the property of their origin in terms of developmental potential, also have the ability to self-renew. It is hence important to realize that ES cells do not exist in vivo; they should be regarded simply as tissue culture artifact. Nevertheless, these powerful cells have the potential to differentiate into all the cells of the embryo proper and postnatal animal. Furthermore, they retain the limitation of their origin through their inability to contribute to the trophectoderm lineage (the trophoblast of the placenta) and the lineages of the primitive endoderm, the visceral and parietal endoderm. Due to these unique features, we must admit that even if we regard ES cells as products of in vitro culture and should not compare them to true somatic stem cells found in the adult organism, they certainly offer us a fantastic tool for genetic, developmental, and disease studies.

Epidermal growth factor receptor expression in a retinoic acid-treated human melanoma cell line

Treatment of a human cell line (HXG-2), established from a metastatic melanoma, with retinoic acid (RA) induced morphologic differentiation and eliminated its cloning capacity in soft agar. With the v-erb B oncogene as a probe, slot blot hybridization of genomic DNA from parental HXG-2 cells did not show epidermal growth factor (EGF) receptor gene amplification as compared with normal diploid fibroblasts. Analysis of RNA as well as EGF receptor determinations from HXG-2 and RA-treated HXG-2 cells showed essentially no differences, indicating that RA treatment does not modulate EGF receptor gene expression. Although enhanced EGF receptor expression is found in some advanced-stage melanomas, RA-induced changes in the transformation phenotype of cell line HXG-2 probably do not result from modulation of the EGF-mediated pathway.

Chromosomal localization of human genes required for G1 progression in mammalian cells

Specific probes derived from the human genes that complement the mutations of two independent temperature-sensitive (ts) mutants of the BHK-21 hamster cell line were used to determine the chromosomal locations of the loci in the human genome. The ts11 gene, which complements a mutation that blocks progression through the G1 phase of the cell cycle and which has now been identified as the structural gene for asparagine synthetase, is a member of a small gene/pseudogene family with four members. In a rodent-human somatic cell hybrid panel, the ts11 genomic locus from which the genomic probe derives segregates with human chromosome region 7cen----7q35, proximal to the TCR beta locus. In situ hybridization maps this locus more precisely to the q21-31 region of chromosome 7. Two other members of the gene family detected by the ts11 probe segregate concordantly with chromosome region 8pter----8q24 and chromosome region 21pter----21q22. Similar experiments using the same rodent-human hybrid panel conducted with a probe identifying the tsBN51 gene, which also encodes a function necessary for G1 progression, mapped this locus to human chromosome 8, proximal to the large amplification unit encompassing the c-myc gene of Colo320 cells. Chromosomal in situ hybridization of the tsBN51 probe confirmed the localization of this gene to chromosome 8, with the most likely location of the gene being 8q21.

Chromosome changes in metastatic human melanoma

Cytogenetic studies were performed on human malignant melanoma cells from eight metastatic lesions. Five tumors displayed near-triploid and three near-diploid chromosome numbers. Chromosomes #1, #6, #7, followed by #2 and #9, were found to be most frequently involved in structural aberrations. Aberrations involving chromosome #1, with deletions or translocations of 1p, involving region 1p12-1p22 in seven of eight breakpoints of the p arm were observed. Seven of nine breakpoints of 6q were located at region 6q15-6q21. Most of the breakpoints on chromosome #7 occurred near the centromeric region. All tumors had additional chromosome material involving 1q, chromosome #7 (7q in two tumors), and in five tumors an increased dose of chromosome #6 (6p in one tumor). The nonrandom breakpoints of these and other chromosomes involved diverse bands, including loci of oncogenes and fragile sites. The observation of nonrandom chromosomal changes in advanced malignant melanoma suggests that genes important in the progression of melanoma are located on chromosomes #1, #6, and #7.

Exclusion of catalytic and regulatory subunits of cAMP-dependent protein kinase as candidate genes for the defect causing cystic fibrosis

Cystic fibrosis (CF) is a common autosomal recessive disease with significant morbidity and mortality. Defects in cAMP control mechanisms are implicated in the pathophysiology of the disease. The mutation causing CF has been localized to chromosome 7q22-7q31.1. We have used (1) somatic-cell hybrids containing this region of the human genome in a mouse background and (2) segregation analysis in families to exclude both the genes coding for a catalytic subunit and three distinct regulatory subunits of cAMP-dependent protein kinase as candidates for the gene defect in CF. Two of these genes--those for the human homologue of the mouse type I regulatory subunit and the human homologue of the rat type II regulatory subunit--map to human chromosome 7.

Localization of the gene for the erythroid anion exchange protein, band 3 (EMPB3), to human chromosome 17

We have isolated genomic DNA clones which code for the human erythroid membrane protein band 3 (EMPB3). The identification of the gene has been confirmed by comparison of the amino acid sequence derived from the nucleotide sequence for two restriction fragments from the 5' end of the gene. Two exons have been identified. One exon encodes 20 amino acids which are identical to residues 36 to 56 of the band 3 protein, and the other encodes 44 amino acids homologous to residues 118 to 162. Southern analysis of genomic DNA derived from a panel of rodent-human somatic cell hybrids, which retain different complements of human chromosomes, with band 3 probes has allowed us to localize EMPB3 to human chromosome 17. The gene has been further localized between 17q21 and qter by analysis of DNA from somatic cell hybrids which carry derivative chromosomes from translocations involving chromosome 17 and either chromosome 15 or 21.

Biochemical and genetic exclusion of calmodulin as the site of the basic defect in cystic fibrosis

Recent physiological studies have shown a defective beta-adrenergic regulation of chloride transport and protein secretion in tissues affected by cystic fibrosis. The exact biochemical nature of this abnormality is unknown, but an intracellular second messenger may be involved. We have tested the hypothesis that calmodulin is the site of the basic defect in CF using biochemical and molecular genetic techniques. We report here that there is no gross structural abnormality in the calmodulin protein from CF submandibular glands, and that although there are at least three distinct sequences that cross-hybridise with a calmodulin cDNA probe in the human genome, none of these can be the locus of CF. A polymorphism at the locus of a calmodulin cross-hybridising sequence at human chromosome 7p2 is described.

A candidate for the cystic fibrosis locus isolated by selection for methylation-free islands

A genomic sequence close to the cystic fibrosis locus with the characteristics of an HTF island has been selectively cloned and characterized. Two markers flanking this sequence, which is conserved throughout mammalian evolution, show a very much greater disequilibrium than that found with any existing marker. A single mutational event accounts for most cases of cystic fibrosis. The sequence is expressed, and is a candidate for the cystic fibrosis gene.

Chromosomal localization of a human band 3-like gene to region 7q35----7q36

Band 3, the major transmembrane protein of erythrocytes, mediates the exchange of anions across the membrane and anchors the erythroid membrane skeleton. Proteins immunologically related to Band 3 have been detected in a variety of nonerythroid cells. We have isolated a human cDNA clone that encodes a protein related to but distinct from the erythroid form of Band 3, based on the comparison of the amino acid sequence for the two proteins. The presence of the gene for the Band 3-like protein in a panel of mouse-human somatic cell hybrids containing subsets of human chromosomes correlated with the presence of human chromosome 7. In situ hybridization analysis using the c-DNA for this nonerythroid Band 3 gene further localized the gene to region 7q35----7q36 of human metaphase chromosomes.

Karyotypic evolution in human malignant melanoma

Chromosome studies were performed on direct preparations, early passage cultures, and cell lines derived from melanocytic lesions of 37 patients. There were six congenital or common acquired nevi, six dysplastic nevi, one early primary melanoma (radial growth phase), three complex melanomas (RGP with foci of vertical growth phase), six advanced primary melanomas (VGP), and 26 metastases. The karyotype was normal in the six common nevi. A chromosomally abnormal clone with a single karyotypic alteration was found in two dysplastic nevi. All melanomas had clones with multiple cytogenetic changes. Nonrandom abnormalities involving translocations or deletions in the short arm of chromosome #1, either arm of chromosome #6, and/or extra copies of the short arm of chromosome #7 were present in all melanomas. These were not obviously associated with a particular stage of disease, except that the only nonrandom alteration in the early (RGP) melanoma involved chromosome #6. In four cases, cytogenetic data were available on both a primary melanoma and its metastases. In each instance there were common alterations (demonstrating the clonality of the disease), as well as additional changes in the metastases. Our findings indicate that demonstrable somatic genetic abnormalities increase in severity with clinical progression of melanocytic disease, but additional data are required to establish the significance of specific karyotypic changes (and the involved genes) in the clinical evolution of these disorders.

Location of gene for beta subunit of human T-cell receptor at band 7q35, a region prone to rearrangements in T cells

The T-cell receptor is formed by two chains, alpha and beta, for which specific clones were recently obtained. In this report the gene for the beta chain of the human T-cell receptor was located on the long arm of chromosome 7, band q35, by means of in situ hybridization. This chromosome region in T cells is unusually prone to develop breaks in vivo, perhaps reflecting instability generated by somatic rearrangement of T-cell receptor genes during normal differentiation in this cell lineage.

Expression of the receptor for epidermal growth factor correlates with increased dosage of chromosome 7 in malignant melanoma

Epidermal growth factor (EGF) receptor is expressed selectively by human melanoma cells which show the presence of an extra copy of chromosome 7. None of the cells of benign pigmented lesions (nevi) or radial growth phase (nonmetastatic) primary melanoma expressed EGF receptor and none of these cells showed an extra copy of chromosome 7. The results indicate that a single extra dose of a gene (for EGF receptor) may provide a selective advantage to cells in the late stages of tumorigenesis.

Cell surface glycoproteins mediate compaction, trophoblast attachment, and endoderm formation during early mouse development

Early mouse embryos undergo several morphogenetic processes, such as compaction, trophoblast attachment, and endoderm formation that can be studied in vitro. Several polyspecific and monospecific antisera have been used to perturb these processes in a nontoxic, reversible fashion. One of the antibody-defined molecules, cell CAM 120/80, promotes epithelial cell adhesion, embryo compaction, and endoderm formation. The results suggest the presence of another such molecule(s) involved in these same processes. Evidence is also presented that another set of antibody-defined molecules, GP 140, involved in attachment of somatic cells to the substrate, mediates trophoblast attachment of the mouse blastocyst. The possible role of these molecules in governing the processes leading to cell lineages in the mouse embryo is discussed.

Molecular cloning of a new transforming gene from a chemically transformed human cell line

Molecular cloning of the transforming gene from a chemically transformed human osteosarcoma-derived cell line enables the gene to be mapped to chromosome 7 (7p11.4-7qter) and by this criterion and by direct hybridization to be shown to be unrelated to known oncogenes.

Receptor modulating properties of an antibody directed against the epidermal growth factor receptor

A murine antiserum with specificity for the human epidermal growth factor (EGF) receptor was used to investigate EGF receptor function. The IgG fraction of this antiserum displayed no EGF-like mitogenic activity, even when cross-linking was ensured by sequential treatment with rabbit anti-(mouse IgG). The interaction of antibody with solubilized purified EGF receptor was characterized in detail. The binding of 125I-antibody to the receptor was not blocked by EGF, but the binding of 125I-EGF to the receptor was blocked by the immune IgG. Scatchard analysis of this reaction revealed a reduction in maximal EGF binding but an enhanced EGF binding affinity. In addition, at low concentrations, the immune IgG was found to enhance receptor kinase activity in the absence of EGF. The enhancement of kinase activity, as measured by receptor phosphorylation, was due to a decreased Km for ATP, and an increased V. These results suggest that the antibody is capable of altering conformations at receptor active sites by binding to non-active species-specific epitopes.

Diminished in vitro tyrosine kinase activity of the EGF receptor of senescent human fibroblasts

Fibroblastic cultures derived from normal human tissues undergo a finite number of population doublings when serially subcultivated in vitro (see refs 1, 2 for reviews). Epidermal growth factor (EGF) serves as a mitogen for early doubling level cultures of the human fetal lung-derived cell strain, WI-38, under serum-free conditions. The ability of cells from late doubling level cultures to respond mitogenically to EGF is lost, however, despite undiminished binding of EGF throughout the replicative lifespan. The ultimate effects of EGF, that is DNA synthesis and mitosis (see ref. 4 for review), occur after a sequence of events initiated by binding of ligand to specific cellular receptors. The receptor for EGF has been characterized as a 145,000-165,000 (145 K-165 K) molecular weight doublet, and, like the receptors for platelet-derived growth factor and insulin, and the transforming proteins of certain of the RNA tumour viruses, is a tyrosine-specific protein kinase with autophosphorylating activity. Moreover, several of the cellular target molecules of tyrosine phosphorylation have been found to be substrates for two or more of these kinases. The hypothesis that tyrosine phosphorylation underlies a common mechanism of growth control prompted us to ask whether the loss of responsiveness to EGF by late doubling level WI-38 cells is accompanied by altered expression of the EGF receptor, and specifically whether changes occur in the ability of receptors from populations of cells of various in vitro ages to catalyse tyrosine autophosphorylation. We show here that autophosphorylating activity is absent from the EGF receptor of cells which have lost their mitogenic responsiveness to EGF.

The eye and the chromosome

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

Identity of human epidermal growth factor (EGF) receptor with glycoprotein SA-7: evidence for differential phosphorylation of the two components of the EGF receptor from A431 cells

A 165-kilodalton (kDal) surface glycoprotein encoded by human chromosome 7 (SA-7) had been characterized by using antisera raised against human chromosome 7-containing somatic cell hybrids. We now present evidence that SA-7 is the human receptor for epidermal growth factor (EGF) and that these antisera recognize human-specific determinants. The gene coding for the human EGF receptor is localized to the p12 to p22 region of chromosome 7. We have characterized the 145-kDal/165-kDal EGF receptor doublet of A431 cells after immunoprecipitation of radiolabeled cell extracts with these antisera. We find that a protein with endogenous kinase activity copurifies with the A431 receptor doublet and that both components of the doublet contain phosphotyrosine and phosphothreonine and the 165-kDal component contains phosphoserine as well. Further, although each component of the receptor doublet has an average pI of 7, both display charge heterogeneity and appear to have unique charge isomers. The relationship between the two components of the A431 EGF receptor is discussed.

A human cell-surface antigen defined by a monoclonal antibody and controlled by a gene on chromosome 12

A murine monoclonal antibody 602-29, subclass IgG1, that recognizes an antigenic determinant expressed by most human cells is described. Immunoprecipitation and sodium dodecyl sulfate-gel electrophoresis analysis indicate that the antigenic determinant is carried by a protein with an apparent molecular weight of 21,000. The antigen is expressed by human-mouse somatic cell hybrids, and analysis of segregants that have lost human chromosomes indicates that the gene controlling expression of the 602-29 antigen is on chromosome 12.

Genetic analysis of epidermal growth factor action: assignment of human epidermal growth factor receptor gene to chromosome 7

Purified murine epidermal growth factor (EGF) binds to mouse and human cells. Two mouse transformed cell lines of different origins, PG19 and B82, were found to lack EGF receptors (EGFR). The defect in each of these two cell lines seems to be identical because they fail to complement each other. Somatic cell hybrids between these EGFR-deficient mouse cells and human cells expressing EGFR were produced. Several of these hybrids bound labeled EGF. Detailed cytogenetic analysis of these cell hybrids, followed by correlation of EGFR expression with human chromosomes revealed that EGFR presence correlated with human chromosome 7. The results suggest that the structural gene or a gene necessary for expression of the human EGF receptor is located on human chromosome 7.

Partial trisomy for the long arm of chromosome 7 due to familial balanced translocation

A partial trisomy for the distal segment of the long arm of chromosome 7 (bands q32 replaced by qter) was observed in a severely retarded child with somatic and CNS anomalies. The phenotypically normal father and paternal grandmother had a balanced reciprocal translocation between the long arm of a chromosome 2 and the long arm of a chromosome 7: 46,XX-XY,t(2;7) (q37;q32). The clinical features of the child at birth and at the ages of 5 months and 2 years are compared with those previously reported in cases of partial trisomy 7q.

Monoclonal antibody defining a stage-specific mouse embryonic antigen (SSEA-1)

A monoclonal antibody derived by fusion of mouse myeloma cells with spleen cells from a mouse immunized with F9 teratocarcinoma cells is described. This antibody, which reacts with embryonal carcinoma cells of mouse and human origin and with some preimplantation stage mouse embryos, defines an embryonic stage-specific antigen. This stage-specific antigen (SSEA-1) is first detected on blastomeres of 8-cell stage embryos. Trophectodermal cells are transitorily positive; however, each cell in the inner cell mass eventually expresses this antigen.

Genetic analysis of the human cell surface: antigenic marker for the human X chromosome in human-mouse hybrids

Somatic cell hybrids of human fibroblasts and mouse A9 cells, carrying only a portion of the human X chromosome in a mouse chromosome background, were injected into C3H mice. The resulting mouse anti-hybrid cell antisera contain antibodies found to be human specific and to react with only those hybrid cells carrying the human X chromosome, as confirmed by essentially perfect concordance between antibody binding assayed by indirect immunofluorescence and presence of the human X-linked enzyme hypoxanthine phosphoribosyl-transferase determined by autoradiographic assay of [3H] hypoxanthine utilization. Heterogeneous mixtures of hybrid cells may be analyzed into fluorescent (X plus) and nonfluorescent (X minus) subpopulations and fractionated viably by using a fluorescence-activated cell sorter.