Conserved chromosomal positions of dual domains of the ets protooncogene in cats, mice, and humans

A Beautiful Life: High Risk-High Payoff in Genetic Science

This narrative is a personal view of adventures in genetic science and society that have blessed my life and career across five decades. The advances I enjoyed and the lessons I learned derive from educational training, substantial collaboration, and growing up in the genomics age. I parse the stories into six research disciplines my students, fellows, and colleagues have entered and, in some cases, made an important difference. The first is comparative genetics, where evolutionary inference is applied to genome organization, from building gene maps in the 1970s to building whole genome sequences today. The second area tracks the progression of molecular evolutionary advances and applications to resolve the hierarchical relationship among living species in the silence of prehistory. The third endeavor outlines the birth and maturation of genetic studies and application to species conservation. The fourth theme discusses how emerging viruses studied in a genomic sense opened our eyes to host-pathogen interaction and interdependence. The fifth research emphasis outlines the population genetic-based search and discovery of human restriction genes that influence the epidemiological outcome of abrupt outbreaks, notably HIV-AIDS and several cancers. Finally, the last arena explored illustrates how genetic individualization in human and animals has improved forensic evidence in capital crimes. Each discipline has intuitive and technological overlaps, and each has benefitted from the contribution of genetic and genomic principles I learned so long ago from Drosophila. The journey continues.

The transcription factor ETS1 in lymphomas: friend or foe?

ETS1 is a member of the ETS family of transcription factors, which contains many cancer genes. ETS1 gene is mapped at 11q24.3, a chromosomal region that is often the site of genomic rearrangements in hematological cancers. ETS1 is expressed in a variety of cells, including B and T lymphocytes. ETS1 is important in various biological processes such as development, differentiation, proliferation, apoptosis, migration and tissue remodeling. It acts as an oncogene controlling invasive and angiogenic behavior of malignant cells in multiple human cancers. In particular, ETS1 deregulation has been reported in diffuse large B-cell lymphoma, in Burkitt lymphoma and in Hodgkin lymphoma. Here, we summarize the function of ETS1 in normal cells, with a particular emphasis on lymphocytes, and its possible role as an oncogene or tumor suppressor gene in the different mature B cell lymphomas.

Allelic variation of Ets1 does not contribute to NK and NKT cell deficiencies in type 1 diabetes susceptible NOD mice

The NOD mouse is a well characterized model of type 1 diabetes that shares several of the characteristics of Ets1-deficient targeted mutant mice, viz: defects in TCR allelic exclusion, susceptibility to a lupus like disease characterized by IgM and IgG autoantibodies and immune complex-mediated glomerulonephritis, and deficiencies of NK and NKT cells. Here, we sought evidence for allelic variation of Ets1 in mice contributing to the NK and NKT cell phenotypes of the NOD strain. ETS1 expression in NK and NKT cells was reduced in NOD mice, compared to C57BL/6 mice. Although NKT cells numbers were significantly correlated with ETS1 expression in both strains, NKT cell numbers were not linked to the Ets1 gene in a first backcross from NOD to C57BL/6 mice. These results indicate that allelic variation of Ets1 did not contribute to variation in NKT cell numbers in these mice. It remains possible that a third factor not linked to the Ets1 locus controls both ETS1 expression and subsequently NK and NKT cell phenotypes.

ETS family of genes in leukemia and Down syndrome

The human ETS2 and ERG genes are members of the ETS gene family, with sequence homology to the viral ets gene of the avian erythroblastosis retrovirus, E26. These genes are located on chromosome 21 and molecular genetic analysis of Down syndrome (DS) patients with partial trisomy 21 suggested that ETS2 may be a gene within the minimal DS genetic region. We have, in fact, been able to confirm the presence of the ETS2 gene dosage in triplicate occurring in occult human 21 chromosome abnormalities. It is known that ERG and ETS2 gene translocations occur in certain specific leukemias associated with defined chromosome rearrangements [e.g., t(8;21)]. Moreover, it is known that DS individuals are at greater risk for leukemic disease than their normal familial cohorts, implying that trisomy of that region of human chromosome 21 may play a role in the development of this type of neoplasia. The human ETS genes, first identified in our laboratory, are highly conserved, being found from lower organisms, like Drosophila and sea urchin, to humans. In mammals, the ETS genes are structurally distinct, located on separate chromosomes; they are transcriptionally active and differentially regulated. The ETS2 protein is phosphorylated and turns over with a half-life of approximately 20 min. After activation with the tumor promoter, TPA, the level of ETS2 elevates 5- to 20-fold. The properties of the ETS2 protein, such as nuclear localization, phosphorylation, rapid turnover, and response to protein kinase C, indicate that this protein belongs to a group of oncogene proteins thought to have regulatory functions in the nucleus. In the mouse thymus ets-1 and ets-2 are 8-10-fold higher, respectively, in the CD4+ subset than in other subsets examined, suggesting a role in T-cell development for these genes. Cells transfected with the cellular ets-2 gene, expressing higher levels of ets-2 products, showed a stimulated proliferation response, abolished their serum requirement and formed colonies in soft agar that could induce tumors in nude mice. Collectively, these data suggest that this family of genes might play a role in controlling specific steps of the signaling transduction pathway. Thus, the ETS genes, as other genes with homology to viral oncogenes, might be instrumental in regulating cellular growth and differentiation, as well as organismal development.

Ets and retroviruses - transduction and activation of members of the Ets oncogene family in viral oncogenesis

Studies of retroviral-induced oncogenesis in animal systems led to the initial discovery of viral oncogenes and their cellular homologs, and provided critical insights into their role in the neoplastic process. V-ets, the founding member of the ETS oncogene family, was originally identified as part of the fusion oncogene encoded by the avian acute leukemia virus E26 and subsequent analysis of virus induced leukemias led to the initial isolation of two other members of the ETS gene family. PU.1 was identified as a target of insertional activation in the majority of tumors induced by the murine Spleen Focus Forming virus (SFFV), while fli-1 proved to be the target of Friend murine leukemia virus (F-MuLV) in F-MuLV induced erythroleukemia, as well as that of the 10A1 and Graffi viruses. The common features of the erythroid and myeloid diseases induced by these viruses provided the initial demonstration that these and other members of the ETS family play important roles in hematopoietic development as well as disease. This review provides an overview of the role of ETS genes in retrovirally induced neoplasia, their possible mechanisms of action, and how these viral studies relate to current knowledge of the functions of these genes in hematopoiesis.

A role for both Ets and C/EBP transcription factors and mRNA stabilization in the MAPK-dependent increase in p21 (Cip-1/WAF1/mda6) protein levels in primary hepatocytes

In primary hepatocytes and HepG2 hepatoma cells, prolonged activation of the p42/44 mitogen-activated protein kinase (MAPK) pathway is associated with a reduction in DNA synthesis, mediated by increased expression of the cyclin-dependent kinase inhibitor protein p21 (Cip-1/WAF1/mda6) (p21). This study was performed to evaluate the contribution of transcriptional and post-transcriptional regulation in this response. Prolonged activation of the MAPK pathway in wild-type or p21 null hepatocytes caused a large decrease and increase, respectively, in DNA synthesis. Prolonged activation of the MAPK pathway in either wild-type or p21 antisense HepG2 cells also caused large decreases and increases, respectively, in DNA synthesis. MAPK signaling increased the phosphorylation of the transcription factors Ets2, C/EBPalpha, and C/EBPbeta, and rapidly increased transcription from the p21 promoter via multiple Ets- and C/EBP-elements within the enhancer region. Eight hours after MAPK activation, loss of C/EBPbeta or Ets2 function significantly reduced MAPK-stimulated transcription from the p21 promoter and abolished increased p21 protein expression. At this time, MAPK signaling increased both p21 mRNA and p21 protein stabilities that were also demonstrated to be essential for a profound increase in p21 protein levels. Thirty-six hours after MAPK activation, transcription from the p21 promoter was still significantly reduced in cells without either C/EBPbeta or Ets2 function; however, these cells were now capable of exhibiting a partial increase in p21 protein expression. In contrast, loss of C/EBPalpha function modestly reduced MAPK-stimulated transcription from the p21 promoter but strongly inhibited the ability of prolonged MAPK activation to increase protein levels of p21. This data suggested that prolonged enhancement of p21 protein levels may be under posttranscriptional control. In agreement with this hypothesis, prolonged MAPK signaling further increased p21 mRNA stability at 36 h, compared with the 8-h time point. Our data argue that MAPK signaling increased p21 promoter activity via multiple transcription factors, which alone were insufficient for a robust prolonged increase in p21 protein levels in primary hepatocytes, and that to increase p21 protein levels also required enhanced stabilization of p21 mRNA and p21 protein. Collectively, these data suggest that loss of transcription factor and mRNA/protein stabilization functions correlates with an inability of MAPK signaling to cause growth arrest versus proliferation in primary hepatocytes.

Expression of human papilloma virus E7 protein causes apoptosis and inhibits DNA synthesis in primary hepatocytes via increased expression of p21(Cip-1/WAF1/MDA6)

The impact of human papilloma virus (HPV16) E7 proteins and retinoblastoma (RB) antisense oligonucleotides upon mitogen-activated protein kinase (MAPK)-mediated inhibition of DNA synthesis via p21(Cip-1/WAF1/MDA6) (p21) was determined in primary hepatocytes. Prolonged activation of the MAPK pathway in p21(+/+) or p21(-/-) hepatocytes caused a large decrease and increase, respectively, in DNA synthesis. Either transfection with RB antisense oligonucleotides, expression of wild type E7, or RB binding mutant E7 (C24S) proteins increased p21 levels and reduced DNA synthesis in p21(+/+) hepatocytes. RB antisense oligonucleotides and E7 proteins increased apoptosis in p21(+/+), but not p21(-/-), hepatocytes. Expression of wild type E7 increased DNA synthesis above control levels in p21(-/-) cells, which was additive with prolonged MAPK activation. In contrast, expression of mutant E7 did not alter DNA synthesis above control levels in p21(-/-) cells and was supra-additive with prolonged MAPK activation. Antisense ablation of RB in p21(-/-) hepatocytes had a weak stimulatory effect upon DNA synthesis itself but enhanced the capacity of mutant E7 protein to stimulate DNA synthesis to the same level observed using wild type E7. The ability of prolonged MAPK activation to stimulate DNA synthesis in the presence of mutant E7 and antisense RB was additive. Collectively, the present data demonstrate that loss of RB function together with loss of p21 function plays an important role in the E7- and MAPK-dependent modulation of apoptosis and DNA synthesis in primary hepatocytes.

Transcription factors Ets1, Ets2, and Elf1 exhibit differential localization in human endometrium across the menstrual cycle and alternate isoforms in cultured endometrial cells

To better understand the transcriptional regulation of human endometrial remodeling, the localization of three members of the Ets family of transcription factors was examined at different stages of the menstrual cycle. Elf1 was found by immunohistochemistry to be predominantly localized to the glandular epithelium. In contrast, Ets1 and Ets2 were found at lower intensities in both glandular epithelial and stromal cells. Low expression during the menstrual phase of the cycle, and high expression and intensity of staining in decidualized stromal cells of the late secretory phase were common to Ets1, Ets2, and Elf1. These localization patterns were confirmed in cultured human endometrial stromal and epithelial cells by Western blotting, which also demonstrated different isoforms and phosphorylation products of Ets1 and Ets2 in the two cell types. This study has shown for the first time that members of the Ets family of transcription factors, previously found predominantly during development and in hematopoietic cells, are expressed in the human endometrium and display cell and cycle-stage specificity. Expression of Elf1 predominantly in the glandular epithelium may indicate that Elf1 plays a unique role in epithelium-specific gene regulation in the endometrium.

Regulation of urokinase expression in the developing avian heart: a role for the Ets-2 transcription factor

During heart development, cells of the endocardial cushions undergo an epithelial-mesenchymal transformation and migrate into the surrounding extracellular matrix. This event is required for the normal formation of valves and chamber septation. Coincident with this phenotypic change is the expression of the serine protease urokinase by the mesenchymal cells. This protease plays an important role in remodeling of the matrix, promotion of cell migration by regulating cell-matrix interactions, and the activation of growth factors. To understand the mechanisms underlying the expression of urokinase during heart development, studies were designed to analyze the role of the Ets transcription factors in the regulation of the avian urokinase gene promoter. Deletion or mutagenesis of the Ets consensus sites significantly decreased the activity of the promoter in isolated cushion tissue cells. Proteins were identified by electrophoretic mobility shift analysis and UV-crosslinking which bound to a specific region of the promoter shown to be required for full transcriptional activity. Analyses based upon protein molecular weight and interaction with specific antibodies suggest a role for the Ets-2 protein in promoter binding and activity. The expression of Ets-2 in the cushion tissue cells was confirmed by RT-PCR analysis and in situ hybridization. The mRNA levels and the DNA binding activity of the Ets-2 protein were found to change during development paralleling the increase in urokinase activity. Overexpression of the full-length Ets-2 protein or a dominant-negative form of the protein altered the activity of the promoter and significantly affected the production of urokinase in these cells. The results from these studies suggest an important role for the Ets-2 protein in heart development and may contribute to a better understanding of the inductive factors present in the heart which facilitate the normal morphogenesis of this organ.

A mouse model for Down syndrome exhibits learning and behaviour deficits

Trisomy 21 or Down syndrome (DS) is the most frequent genetic cause of mental retardation, affecting one in 800 live born human beings. Mice with segmental trisomy 16 (Ts65Dn mice) are at dosage imbalance for genes corresponding to those on human chromosome 21q21-22.3--which includes the so-called DS 'critical region'. They do not show early-onset of Alzheimer disease pathology; however, Ts65Dn mice do demonstrate impaired performance in a complex learning task requiring the integration of visual and spatial information. The reproducibility of this phenotype among Ts65Dn mice indicates that dosage imbalance for a gene or genes in this region contributes to this impairment. The corresponding dosage imbalance for the human homologues of these genes may contribute to cognitive deficits in DS.

Genetic instability of chromosome 3 in HPV-immortalized and tumorigenic human keratinocytes

The HPV-1811 cell line is derived from primary human foreskin keratinocytes that have been transfected with human papilloma virus type 18. At late passage, these cells produce invasive squamous cell carcinomas when injected into nude mice. A striking, but unstable, aberration of chromosome 3 occurs very early after establishment of the culture; a consistent rearrangement is observed concomitant with tumorigenicity. Using molecular cytogenetic techniques, we characterized the complex development of this aberration. A whole chromosome probe to this chromosome was made by linker-adapter PCR amplification of a single flow-sorted chromosome. Hybridization of this probe to normal metaphase chromosomes revealed the der (3) to be composed of chromosome 3, distal 13q, and 21q22. Hybridization of a 3q subtelomeric probe and a glycoprotein V probe which maps to 3qter indicated that this locus is duplicated in the final form of the chromosome, but that much instability occurs prior to its establishment. The ETS2 oncogene, which maps to 21q22, is translocated to the der(3) when the cell line becomes tumorigenic, but not prior to this time. Early-passage cells which have been induced to become tumorigenic by exposure to the carcinogen nitrosomethylurea also have the localization of the ETS2 at 3qter.

A NotI restriction map of the entire long arm of human chromosome 21

A variety of maps of the human genome have been constructed, including cloned DNA maps. We have isolated 40 of the 42 NotI sites that exist on the long arm of human chromosome 21, as NotI linking clones and constructed a complete NotI restriction map spanning the entire region. This map, which provides the most reliable ordering and distance estimation in the region from a pericentromeric locus to the terminus, demonstrates the usefulness of linking clone mapping for analysing human chromosomes.

The ets multigene family is conserved throughout the Metazoa

This study provides the first empirical evidence for the conservation of the ets proto-oncogene transcription factor family throughout the Metazoa. Using the polymerase chain reaction with degenerate primers corresponding to conserved sequences within the ETS DNA-binding domain, we have detected ets genes in a range of lower metazoans, including sponges, ctenophores, anemones, flatworms and nematodes, and in several higher invertebrate metazoans. Many of these sequences are significantly divergent from the original v-ets-1 oncogene, although most can be aligned with recently defined groups within the ets gene family. Multiple ETS domain sequences were detected in a number of the lower metazoan species, providing evidence for the existence of an ets multigene family at the earliest stages of metazoan evolution. In contrast, we were unable to detect any ETS sequences in fungal, plant or several protozoan DNAs. Our findings suggest that the duplication and divergence of ets proto-oncogenes responsible for generating the multigene family occurred concomitantly with the development of metazoan animals. In addition, these data corroborate other recent molecular evidence in providing strong support for the monophyletic origin of all multicellular animals, including sponges.

Chromosomal localization of glutamate receptor genes: relationship to familial amyotrophic lateral sclerosis and other neurological disorders of mice and humans

Receptors for the major excitatory neurotransmitter glutamate may play key roles in neurodegeneration. The mouse Glur-5 gene maps to chromosome 16 between App and Sod-1. The homologous human GLUR5 gene maps to the corresponding region of human chromosome 21, which contains the locus for familial amyotrophic lateral sclerosis. This location, and other features, render GLUR5 a possible candidate gene for familial amyotrophic lateral sclerosis. In addition, dosage imbalance of GLUR5 may have a role in the trisomy 21 (Down syndrome). Further characterization of the murine glutamate receptor family includes mapping of Glur-1 to the same region as neurological mutants spasmodic, shaker-2, tipsy, and vibrator on chromosome 11; Glur-2 near spastic on chromosome 3; Glur-6 near waltzer and Jackson circler on chromosome 10; and Glur-7 near clasper on chromosome 4.

Localization of growth arrest-specific genes on mouse Chromosomes 1, 7, 8, 11, 13, and 16

Growth arrest in NIH3T3 cells is associated with increased expression of a variety of mRNAs, several of which have been isolated as cDNA clones. Six of these growth arrest-specific (Gas) genes were mapped by following the inheritance of DNA restriction fragment length variants (RFLVs) associated with them in panels of recombinant inbred (RI) strains of mice and in the progeny of backcrosses both between laboratory mouse strains and between a laboratory strain and Mus spretus. The six genes are unlinked. Gas-1 maps to Chromosome (Chr) 13, Gas-2 to Chr 7, Gas-3 to Chr 11, Gas-4 to Chr 16, Gas-6 to Chr 8, and Gas-10 to Chr 1.

Localization of the HST/FGFK gene with regard to 11q13 chromosomal breakpoint and fragile site

The HST/FGFK gene, a member of the fibroblast growth factor gene family and a protooncogene, is localized on chromosomal band 11q13. Genes in this region are frequently involved in hematopoietic and solid tumors. Here we show that the HST gene lies telomeric to the BCL1 gene, the t(11;14)(q13;q32) breakpoint, and the FRA11A rare fragile site.

Molecular localization of the t(11;22)(q24;q12) translocation of Ewing sarcoma by chromosomal in situ suppression hybridization

Chromosome translocations are associated with a variety of human leukemias, lymphomas, and solid tumors. To localize molecular markers flanking the t(11;22) (q24;q12) breakpoint that occurs in virtually all cases of Ewing sarcoma and peripheral neuroepithelioma, high-resolution chromosomal in situ suppression hybridization was carried out using a panel of cosmid clones localized and ordered on chromosome 11q. The location of the Ewing sarcoma translocation breakpoint was determined relative to the nearest two cosmid markers on 11q, clones 23.2 and 5.8, through the analysis of metaphase chromosome hybridization. By in situ hybridization to interphase nuclei, the approximate physical separation of these two markers was determined. In both Ewing sarcoma and peripheral neuroepithelioma, cosmid clone 5.8 is translocated from chromosome 11q24 to the derivative chromosome 22 and a portion of chromosome 22q12 carrying the leukemia inhibitory factor gene is translocated to the derivative chromosome 11. The physical distance between the flanking cosmid markers on chromosome 11 was determined to be in the range of 1000 kilobases, and genomic analysis using pulsed-field gel electrophoresis showed no abnormalities over a region of 650 kilobases in the vicinity of the leukemia inhibitory factor gene on chromosome 22. This approach localizes the Ewing sarcoma breakpoint to a small region on chromosome 11q24 and provides a rapid and precise technique for the molecular characterization of chromosomal aberrations.

Identification of a common viral integration region in Cas-Br-E murine leukemia virus-induced non-T-, non-B-cell lymphomas

The Cas-Br-E murine leukemia virus is a nondefective retrovirus that induces non-T-, non-B-cell lymphomas in susceptible NIH/Swiss mice. By using a DNA probe derived from Cas-Br-E provirus-flanking sequences, we identified a DNA region, originally called Sic-1, rearranged in 16 of 24 tumors analyzed (67%). All proviruses were integrated in a DNA segment smaller than 100 bp and were in the same 5'-to-3' orientation. Ecotropic as well as mink cell focus-forming virus types were found integrated in that specific DNA region. On the basis of Southern blot analysis of somatic cell hybrids and progeny of an interspecies backcross, the Sic-1 region was localized on mouse chromosome 9 near the previously described proto-oncogenes or common viral integration sites: Ets-1, Cbl-2, Tpl-1, and Fli-1. Restriction map analysis shows that this region is identical to the Fli-1 locus identified in Friend murine leukemia virus-induced erythroleukemia cell lines and thus may contain sequences also responsible for the development of mouse non-T-, non-B-cell lymphomas.

Comparison of interspecific to intersubspecific backcrosses demonstrates species and sex differences in recombination frequency on mouse chromosome 16

One hundred fourteen progeny from an interspecific backcross between laboratory mice and M. spretus were typed for six markers spanning most of mouse Chromosome (Chr) 16. Additional maps of 9-10 markers of this chromosome were derived from analysis of over 500 progeny from four backcrosses between inbred laboratory strains and members of the Mus musculus group, M.m. musculus and M.m. molossinus (subspecies). The results of these analyses confirmed the gene order: (CEN)-Prm-1/Prm-2-Igl-1-Smst-Mtv-6-Gap43-Pit-1(dw)- D21S16h-App-Sod-1-Ets-2-Mx. Maps produced from these five crosses were of similar lengths, but recombination in several regions was affected by sex of the F1 parent or by the combination of strains used in the cross. As reported previously, recombination frequencies were elevated significantly at the distal end of the chromosome in a cross using F1 males. The male map showed significant compression in the interval Smst to Gap43. Both male and female intersubspecific maps were expanded near the proximal and distal ends of the chromosome relative to the interspecific cross. The spretus cross was compressed in the proximal interval, Prm-1-Igl-1-Smst, and was slightly expanded in the Smst-Gap43 interval, relative to intersubspecific crosses using F1 females. Female intersubspecific maps were expanded about 50% near the distal end of the chromosome when compared to the interspecific cross. The expansion or compression of maps using different strain or sex combinations has implications for the efficient production of high resolution recombinational maps of the mouse genome.

Evidence for the evolutionary origin of human chromosome 21 from comparative gene mapping in the cow and mouse

To determine the extent of conservation between bovine syntenic group U10, human chromosome 21 (HSA 21), and mouse chromosome 16 (MMU 16), 11 genes were physically mapped by segregation analysis in a bovine-hamster hybrid somatic cell panel. The genes chosen for study span MMU 16 and represent virtually the entire q arm of HSA 21. Because the somatostatin gene (SST), an HSA 3/MMU 16 locus, was previously shown to be in U10, the transferrin gene (TF), an HSA 3/MMU 9 marker, was also mapped to determine whether U10 contains any HSA 3 genes not represented on MMU 16. With the exception of the protamine gene PRM1 (HSA 16/MMU 16), all of the genes studied were syntenic on bovine U10. Thus, all homologous loci from HSA 21 that have been studied in the cow are on a single chromosome. The bovine homolog of HSA 21 also carries several HSA 3 genes, two of which have homologous loci on MMU 16. The syntenic association of genes from the q arm of HSA 3 with HSA 21 genes in two mammalian species, the mouse and the cow, indicates that HSA 21 may have that contained genes now residing on HSA 3. Additionally, the syntenic association of TF with SST in the cow permits the prediction that the rhodopsin gene (RHO) is proximal to TF on HSA 3q.

Requirement of ets-2 expression for Xenopus oocyte maturation

A molecular clone of the Xenopus laevis ets-2 gene was isolated from an oocyte complementary DNA library. The amount of messenger RNA (mRNA) in each oocyte or embryo was almost constant during oogenesis and was maintained until the blastula stage of embryonic development, indicating that the observed 3.2-kilobase transcript is a maternal message. The only normal adult tissue in which ets-2 mRNA was detected was the ovary. Injection of antisense oligonucleotides homologous to the ets-2 sequence into oocytes led to degradation of the mRNA and blocked hormone-induced germinal vesicle breakdown. The ets-2 product is thus required for the meiotic maturation of Xenopus oocytes.

Monoclonal antibodies specific to human ETS-2 oncoprotein: recognition of epitopes clustered on the B domain

Six monoclonal antibodies were prepared from mice immunized with a bacterially expressed human ets-2 protein. These antibodies specifically recognize the two human ets-2-encoded proteins p56 and p54 but failed to react with chicken, mouse, rat, bovine, or monkey proteins, suggesting that the antibodies recognize epitopes specific to the human ets-2 protein. Differential reactivities of these monoclonal antibodies with the peptide fragments generated by partial proteolytic digestion of the bacterially expressed ets-2 protein indicated that the six antibodies recognize at least three distinct epitopes in the B domain of the ets-2 protein. Immunoprecipitation experiments comparing native and denaturing conditions suggested that the ets-2 domain detected by the monoclonal antibodies is masked in the native condition by either protein folding or interacting proteins. The biochemical analysis of the ets-2 protein will be facilitated by the development of these monoclonal antibodies, which may be useful as both domain-specific probes and tools for specifically detecting the human ets-2 protein in heterologous expression systems.

Reciprocal expression of human ETS1 and ETS2 genes during T-cell activation: regulatory role for the protooncogene ETS1

The expression of the protooncogenes ETS1 and ETS2 has been studied in purified human T cells activated either by cross-linking of the T-cell receptor-CD3 complex on their cell surface or by direct stimulation with phorbol esters and ionomycin. Our results show that resting T cells express high levels of ETS1 mRNA and protein, while expression of ETS2 is undetectable. Upon T-cell activation, ETS2 mRNA and proteins are induced, while ETS1 gene expression decreases to very low levels. Late after stimulation, ETS1 mRNA is reinduced and maintained at a high level, while ETS2 gene expression decreases to undetectable levels. Therefore, it appears that in human T cells, ETS2 gene products are associated with cellular activation and proliferation, while ETS1 gene products are preferentially expressed in a quiescent state.

Slot blot method for the quantification of DNA sequences and mapping of chromosome rearrangements: application to chromosome 21

As an alternative to the methods of gene dosage based on either RFLP studies or Southern blots using specific and reference probes, we designed a "slot blot" method for the evaluation of the copy number of unique chromosome 21 sequences. Varying amounts of denatured DNA from a normal control, a trisomy 21 patient, and the subject to be analyzed were loaded on the same membrane. Successive hybridizations with reference probes and chromosome 21 probes were then carried out. Intensities of the signals on autoradiograms were quantified by densitometric scanning. Graphic and statistical analysis of the linear regressions between reference and chromosome 21 probe signals were performed, and the conclusion that the DNA from the studied subject had two or three copies for a given chromosome 21 sequence was assessed by statistical comparison of the slopes. As a test for the validation of this method, 10 coded blood DNAs from five normal controls and from five trisomy 21 patients were analyzed, by using two reference (COL1A1 and COL1A2) and two chromosome 21 (D21S11 and D21S17) probes. Among the 10 DNAs analyzed, it was possible to diagnose, with 100% accuracy, normal controls and trisomic 21 individuals. Application of this methodology to the mapping of partial chromosome 21 rearrangements is presented.

Molecular and functional characterization of the promoter of ETS2, the human c-ets-2 gene

The 5' end of the human c-ets-2 gene, ETS2, was cloned and characterized. The major transcription initiation start sites were identified, and the pertinent sequences surrounding the ETS2 promoter were determined. The promoter region of ETS2 does not possess typical "TATA" and "CAAT" elements. However, this promoter contains several repeat regions, as well as two consensus AP2 binding sites and three putative Sp1 sites. There is also a palindromic region similar to the serum response element of the c-fos gene, located 1400 base pairs (bp) upstream from the first major transcription initiation site. A G + C-rich sequence (GC element) with dyad symmetry can be seen in the ETS2 promoter, immediately following an unusually long (approximately 250-bp) polypurine-polypyrimidine tract. A series of deletion fragments from the putative promoter region were ligated in front of the bacterial chloramphenicol acetyltransferase gene and tested for activity following transfection into HeLa cells. The 5' boundary of the region needed for maximum promoter activity was found to be 159 bp upstream of the major initiation site. This region of 159 bp contains putative binding sites for transcription factors Sp1 and AP2 (one for each), the GC element, one small forward repeat, one inverted repeat, and half of the polypurine-pyrimidine tract. The promoter of ETS2 (within the polypyrimidine tract) serves to illustrate an alternative structure that may be present in genes with "TATA-less" promoters.

Loss of heterozygosity on chromosomes 1 and 11 in sporadic pheochromocytomas

Molecular genetic analysis was performed with 20 oncogene probes and 32 polymorphic DNA probes on tumor DNA samples from seven pheochromocytomas; namely, one multiple endocrine neoplasia type 2B, and two familial and four sporadic pheochromocytomas. No amplification or rearrangement of the oncogenes was detected in any of the tumors. However, loss of heterozygosity on chromosome 1p, 11p or 11q was detected in these cases. In addition, a locus related to ETS1 was deleted in two of the sporadic tumors. These results suggest that pheochromocytomas may be genetically heterogeneous, and that inactivation of unknown genes on chromosome 1p, 11p or 11q may contribute to their development.

Defects of skeletal morphology, density, and structure in mouse fetuses with trisomy 16

Skeletal anomalies present in trisomy 16 in the mouse--an animal model of human trisomy 21--are described. Altogether 27 fetuses with trisomy 16 and 118 chromosomally balanced siblings were examined radiographically and by alizarin staining on day 20 of gestation; the radiographs were analyzed by computer-aided densitometry and structural differentiation. Extensive asymmetry or abnormal fusion of the vertebral centers and alterations of the vertebral arches were observed along with rib malformations (rib-vertebra syndrome). The skull primarily exhibited anomalies of the occipital bone. Ossification of the humerus, femur, and tibia was characterized by reduced mineralization. Typical, fracture-like alterations affecting only the tibia were also observed. Measurement of the lengths of the humeri of fetuses of comparable weight revealed a growth retardation not correlatable with the degree of mineralization. The significance of these skeletal abnormalities with regard to the trisomy 21 syndrome is discussed.

Expression of the human ETS-2 oncogene in normal fetal tissues and in the brain of a fetus with trisomy 21

The expression of the ETS-2 proto-oncogene, located on chromosome 21, in normal fetal tissues and in neural tissue of a fetus affected by Down syndrome has been investigated. The results show that the ETS-2 proto-oncogene is expressed in almost all the tissues examined and that it is transcribed at constant levels in neural tissue between the 13th and 24th weeks. ETS-2 expression appeared to be slightly increased in Down syndrome brain compared with that of normal controls of the same gestational age.

c-ets-2 protooncogene has mitogenic and oncogenic activity

An expression vector containing the murine c-ets-2 protooncogene cDNA was introduced into NIH 3T3 cells by DNA transfection. The cells transfected with this construct showed foci of densely growing, morphologically altered cells, when grown either in low-serum (0.05%) or in serum-free medium. The c-ets-2-derived foci contained additional copies of the c-ets-2 gene, Northern blot analysis demonstrated overexpression of a c-ets-2-specific 2.5-kilobase RNA, and ets-specific antiserum recognized a 56-kDa protein. Overexpression of the c-ets-2-encoded protein stimulated cell proliferation and abolished their serum requirement. The c-ets-2 transfected cells formed colonies in semisolid medium and induced tumors in nude mice, indicating that c-ets-2 can be a transforming gene when overexpressed in these cells. This work demonstrates that a member of the c-ets gene family has transforming and mitogenic activity. In addition, the role of c-ets-2 in cell proliferation and its location in the minimal Down syndrome region on chromosome 21 implicates its involvement in the phenotypic changes associated with Down syndrome.

Physical mapping of complex genomes by cosmid multiplex analysis

A rapid and powerful approach for linking individual clones of a cosmid library and the assembly of a large physical map is presented, which depends on the simultaneous analysis of many cosmid clones for overlapping regions. This method uses cosmid vectors that contain endogenous bacteriophage T3 and T7 promoters to allow for the identification of overlapping clones through the synthesis of end-specific RNA probes. A genomic library is constructed and organized as an ordered matrix such that each clone is assigned an identifying coordinate. DNA from mixtures of cosmid clones is pooled such that each pool contains only one common member with any other pool, RNA probes are prepared from mixtures of cosmid clones, and groups of clones overlapping with the constituents of the mixtures are determined by hybridization. Pooled probes are most simply prepared by grouping clones according to the rows and columns of the library matrix. The pairwise comparison of data generated by the hybridization of mixed probes can be decoded by using simple algorithms that predict the order and linkage of all clones in the collection and organize them into predicted contigs. To demonstrate the feasibility of multiplexed analysis of cosmids, a genomic library was prepared from a mouse-human somatic cell hybrid that contains a portion of the long arm of human chromosome 11. Preparation, arrangement on a matrix, and analysis of pooled cosmid clones from this collection resulted in the detection of 1099 linked pairs of cosmids, which could be assembled into 315 contigs. Thus, with a minimal amount of effort, a substantial portion of this genomic region has been linked in multiple overlapping contigs. This method may have practical applications in the large-scale mapping and sequencing of mammalian genomes.

elk, tissue-specific ets-related genes on chromosomes X and 14 near translocation breakpoints

The myb-ets-containing acute leukemia virus, E26, transforms myeloblasts and erythroblasts in culture and causes a mixed erythroid and myeloid leukemia in chicks. Genes (ets-1, ets-2, and erg) with variable relatedness to the v-ets oncogene of the E26 virus have been identified, cloned, and characterized in several species. Two new members (elk-1 and elk-2) of the ets oncogene superfamily have now been identified. Nucleotide sequence analysis of the elk-1 cDNA clone revealed that this gene encodes a 428-residue protein whose predicted amino acid sequence showed 82% similarity to the 3' region of v-ets. The elk or related sequences appear to be transcriptionally active in testis and lung. The elk cDNA probe detects two loci in the human genome, elk-1 and elk-2, which map to chromosome regions Xp11.2 and 14q32.3, respectively. These loci are near the translocation breakpoint seen in the t(X;18) (p11.2;q11.2), which is characteristic of synovial sarcoma, and the chromosome 14q32 breakpoints seen in ataxia telangiectasia and other T cell malignancies. This suggests the possibility that rearrangements of elk loci may be involved in pathogenesis of certain tumors.

The IL-4 and IL-5 genes are closely linked and are part of a cytokine gene cluster on mouse chromosome 11

The murine IL-4 and IL-5 genes encode hemopoietic growth factors involved in the stimulation, proliferation, and differentiation of cells of the T lymphocyte, B lymphocyte, and granulocyte lineages. We have mapped the Il-4 and Il-5 loci representing the structural genes for IL-4 and IL-5, respectively, to mouse chromosome 11 using Chinese hamster x mouse and rat x mouse somatic cell hybrids. Physical linkage studies of the IL-4 and IL-5 genes by pulsed field gel electrophoresis have shown that they are closely linked, being 110-180 kb apart. Since the Il-5 locus maps to the interface of bands A5 and B1 in the same location as the genes for IL-3 and GM-CSF, this places these three cytokine genes, as well as the IL-4 gene, within a region of about 5000-10,000 kb. The present physical linkage studies indicate that the IL-4 and IL-5 genes are a minimum of 600 kb apart from the closely linked IL-3 and GM-CSF genes. The gene clustering, together with similarities in gene structure, regulation, and biological function, raises the possibility that the four genes may be part of a distantly related cytokine gene family.

Detection of single-copy genes by nonisotopic in situ hybridization on human chromosomes

A technique of in situ hybridization on metaphase chromosomes with biotinylated DNA probes is described. This technique was used to localize unique DNA sequences on chromosomes and allowed a localization of two probes 1.8 and 1.3 kb long. The hybridization signal appears like two, twin, spots on the two sister chromatids, allowing a clear distinction from the background. Moreover a chromosomal localization is possible by counting a relatively small number of mitoses compared with the technique using 3H-labeled DNA probes.

A short-lived nuclear phosphoprotein encoded by the human ets-2 proto-oncogene is stabilized by activation of protein kinase C

The human ets-2 gene is a homolog of the v-ets oncogene of the E26 virus and codes for a 56-kilodalton nuclear protein. The ets-2 protein is phosphorylated and has a rapid turnover, with a half-life of 20 min. When human lymphocytic CEM cells were treated with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA), the level of the ets-2 protein was quickly elevated 5- to 20-fold. This effect of TPA was mimicked by a synthetic diacylglycerol, 1-oleoyl-2-acetyl glycerol, and was blocked by the protein kinase C inhibitor H7, indicating that protein kinase C is involved in the induction. The increase in the ets-2 protein was due to stabilization of the protein, because the protein had a half-life of more than 2 h in the presence of TPA and the ets-2 mRNA level did not increase significantly upon TPA treatment. The protein synthesis inhibitor cycloheximide enhanced the effect of TPA on the ets-2 protein and could itself slow turnover of the protein. Properties of the ets-2 protein, such as nuclear localization, phosphorylation, rapid turnover, and response to protein kinase C, indicate that this protein belongs to a group of oncogene proteins which are generally thought to have regulatory functions in the nucleus (e.g., myc, fos, myb, and p53). Our results suggest that protein kinase C, either directly or indirectly, regulates the level of the ets-2 protein by posttranslational mechanisms.

Properties of a murine retroviral recombinant of avian acute leukemia virus E26: a murine fibroblast assay for v-ets function

A replication-defective murine retroviral construct, termed pME26, was generated by inserting avian gag-myb-ets sequences derived from the cloned avian acute leukemia virus E26 into an Abelson murine leukemia virus-derived retroviral vector. ME26 virus can be rescued efficiently from transfected NIH 3T3 cells by replicating murine leukemia viruses. Either pME26-transfected nonproducers or ME26 virus-infected NIH 3T3 cells expressed a 135-kilodalton fusion protein (p135) which was detectable by immunoprecipitation with antiserum directed against avian leukemia virus p27gag, myb or ets oncogene protein, or murine leukemia virus p15gag and was principally localized in the nucleus. NIH 3T3 cells infected with ME26 exhibited morphological alterations and increased proliferation in reduced serum and formed small colonies in agar suspension. Discrete foci could be readily recognized in cells maintained in a defined medium containing 0.03 to 0.1% calf serum. In newborn NFS/N mice, ME26 induced a significantly higher mortality and incidence of erythroid and myeloid leukemias. Analysis of a series of mutants affecting the expression of various portions of p135 indicated that the v-ets gene acts to mitogenically stimulate the proliferation of NIH 3T3 fibroblasts and reduces or abolishes their serum dependence. These properties provide an assay system to study functions of the ets gene family.