The Ews-ERG Fusion Protein Can Initiate Neoplasia from Lineage-Committed Haematopoietic Cells

The EWS-ERG fusion protein is found in human sarcomas with the chromosomal translocation t(21;22)(q22;q12), where the translocation is considered to be an initiating event in sarcoma formation within uncommitted mesenchymal cells, probably long-lived progenitors capable of self renewal. The fusion protein may not therefore have an oncogenic capability beyond these progenitors. To assess whether EWS-ERG can be a tumour initiator in cells other than mesenchymal cells, we have analysed Ews-ERG fusion protein function in a cellular environment not typical of that found in human cancers, namely, committed lymphoid cells. We have used Ews-ERG invertor mice having an inverted ERG cDNA cassette flanked by loxP sites knocked in the Ews intron 8, crossed with mice expressing Cre recombinase under the control of the Rag1 gene to give conditional, lymphoid-specific expression of the fusion protein. Clonal T cell neoplasias arose in these mice. This conditional Ews gene fusion model of tumourigenesis shows that Ews-ERG can cause haematopoietic tumours and the precursor cells are committed cells. Thus, Ews-ERG can function in cells that do not have to be pluripotent progenitors or mesenchymal cells

Untersuchungen zur Beteiligung zellulärer und genetischer Mechanismen bei Immunregulation und -modulation

Durch Immunregulation und -modulation sorgt das Immunsystem dafür, daß von außen in den Organismus gelangende Agentien nicht zu dauerhaften Schäden führen. Wesentliche Funktionen des Immunsystems stützen sich dabei auf die zelluläre Immunität. Gerät dieses komplizierte Regelwerk aus dem Gleichgewicht, können schwere Erkrankungen autoimmuner oder atopischer Genese resultieren. Der erste Teil der Arbeit befaßt sich mit zwei Aspekten der zellulären Immunantwort. Allergische Immunantworten sind durch die Typ 2 T Zellantwort charakterisiert. Für die Induktion einer Typ 2 Antwort wird Interleukin-4 benötigt, dessen Herkunft nicht geklärt ist. NK1.1 positive T Zellen als Quelle des initialen IL-4 konnten durch in vivo und in vitro Messung von allergie-spezifischen Parametern ausgeschlossen werden. Der MHC-Komplex präsentiert T Zellen Antigene in Form von Peptiden. Pathologische T Zellantworten können durch fortwährende Antigenpräsentation unterhalten werden. Durch Untersuchungen zur molekularen Charakteristik der MHC - Peptid Interaktion ließen sich Bindungsmotive so verfeinern, daß Peptide mit sehr starker Bindung an den MHC ohne gleichzeitige Erkennungssequenz für den T Zellrezeptor entwickelt werden konnten. Peptide dieser Art könnten zur Blockierung einer pathologischen T Zellantwort genutzt werden. Für viele immunologische Erkrankungen ist die Beteiligung genetischer Faktoren beschrieben worden. Der zweite Teil der Arbeit befaßt sich mit der Bedeutung genetischer Disposition bei Allergien im Mausmodell. Homozygote Inzuchtstämme konnten als High- und Low-Responder für den Phänotyp "allergische Soforttypreaktion der Haut" gegenüber Birkenpollenextrakt definiert werden. Die Phänotypisierung der F1 Generation wies auf dominante Vererbung hin, die informative Rückkreuzung auf die Beteiligung von mindestens zwei Genen für die Ausprägung des Merkmals. Wie die Analyse MHC congener Mäuse zeigte, entspricht einer dieser Loci dem MHC Komplex. Durch eine genomweite Kartierung mit Mikrosatelliten wurde als weiterer Kandidat der IL-5 Rezeptor identifiziert. Die detaillierte Analyse des Gens in High-und Low-Respondern weist auf eine Anzahl funktionell bedeutsamer Polymorphismen hin. Dabei imponiert das Low-Responder Allel als Suszeptibilitätsallel. Die Unterschiede haben Auswirkung auf Transkription/Translation und Spleißvorgänge, die zu quantitativer Differenz der Genprodukte führt. Die Daten weisen damit auf einen regulatorischen Mechanismus hin, da die Proteinstruktur des Rezeptors bei High- und Low-Respondern identisch ist.Immune deviations can lead to serious autoimmune or atopic disorders. Two possible candidates for such pathological immune responses have been investigated: (i) the MHC class I allele HLA-B27, which is strongly linked to ankylosing spondylitis and reactive arthritis. Its presentation of potentially pathogenic peptides and therapeutical modifications of peptidic ligands have been studied. (ii) Interleukin-4 (IL-4), which is the key player in the induction and maintenance of allergic immune responses. A subpopulation of natural killer (NK1.1) cells have been discussed as a source of initial IL-4. Through experiments with NK1.1 deficient mice we could demonstrate, that such immune resonses are not dependent on the presence of NK1.1 cells. Both, autoimmunity and atopy belong to the large group of multifactorial diseases, i. e. genetic and environmental factors influence the expression of the various phenotypes. To dissect the genetics of allergic diseases systematically, a mouse model of immmediate cutaneous hypersensitivity (ICHS) upon birch pollen sensitization has been etablished. Phenotyping of the F1 progeny of high- and low-responder mice revealed ICHS as a dominant trait with incomplete penetrance. Mice from a backcross to the low-responder strain did split into the three classes of high-, intermediate and low-response. Genotyping of these mice revealed a strong candidate gene on chromosome 6: the interleukin-5 receptor (IL-5R). Analysis of the IL-5R gene resulted in the detection of genetic variance of the high- and low-responder allele in non-coding regions with functional relevance. Additional regulatory variance is implicated through differential alternative splicing of the three receptor isoforms. A second gene cluster contributes to the expression of the allergic phenotype: MHC class II alleles, as has been demonstrated for other immunologic disorders in mice and humans

Panel of Microsatellite Markers for Whole-Genome Scans and Radiation Hybrid Mapping and a Mouse Family Tree

To facilitate whole-genome scan experiments, we selected a panel of 128 microsatellite markers on the basis of spacing and polymorphism in the strains DBA/2, BALB/c, AKR, C57BL/6, C57BL/10, A/J, C3H, 129/J, SJL/J, JF1, and PWB. Many of the primer pairs were redesigned for better performance. The last four strains were not characterized previously using these markers. JF1 and PWB are particularly interesting for intersubspecific crosses offering high polymorphism. We provide allele size data for the markers on these strains and add them to the emerging radiation hybrid framework map, which is not continuous except for chromosome 17 and 13. Information on the interrelationships of strains is useful both because of the importance of polymorphism in designing crosses and the background in assessing phenotypes. Microsatellites offer a widely dispersed, selectively neutral set of characters that lends itself conceptually to parsimony methods of analysis. The microsatellite allele size data were recoded as binary discrete characters in such a way that adjacent sizes differ by one step. Trees were generated using a Wagner parsimony method. As expected, the non-Mus domesticus strains, PWB (musculus) and JF1 (molossinus), are excluded from the domesticus strains. Among the domesticus strains, C57BL/6 and C57BL/10 (derived from the same founding pair) form a strongly supported group, as do C3H, A/J, and BALB/c (derived from the Bagg albino stock). No unique branching order for SJL/J, AKR, and DBA/2 is strongly supported, which may reflect a complicated history. Strain 129/J is clearly placed as the most deeply diverged of the domesticus strains represented

Mll fusions generated by Cre-loxP-mediated de novo translocations can induce lineage reassignment in tumorigenesis

Chromosomal translocations are primary events in tumorigenesis. Those involving the mixed lineage leukaemia (MLL) gene are found in various guises and it is unclear whether MLL fusions can affect haematopoietic differentiation. We have used a model in which chromosomal translocations are generated in mice de novo by Cre-loxP-mediated recombination (translocator mice) to compare the functionally relevant haematopoietic cell contexts for Mll fusions, namely pluripotent stem cells, semicommitted progenitors or committed cells. Translocations between Mll and Enl or Af9 cause myeloid neoplasias, initiating in pluripotent stem cells or multipotent myeloid progenitors. However, while Mll-Enl translocations can also cause leukaemia from T-cell progenitors, no tumours arose with Mll-Af9 translocations in the T-cell compartment. Furthermore, Mll-Enl translocations in T-cell progenitors can cause lineage reassignment into myeloid tumours. Therefore, a permissive cellular environment is required for oncogenicity of Mll-associated translocations and Mll fusions can influence haematopoietic lineage commitment

Spontaneous B cell hyperactivity in autoimmune-prone MRL mice

The MRL-lpr/lpr mouse strain is a commonly used model of the human autoimmune disease systemic lupus erythematosus (SLE). Although much is known about the contribution of the lpr Fas mutation to B cell tolerance breakdown, the role of the genetic background of the MRL strain itself is less well explored. In this study, we use the MD4 anti-hen egg lysozyme Ig (IgHEL) transgenic system to explore B cell function in MRL+/+ and non-autoimmune mice. We demonstrate that MRL IgHEL B cells show spontaneous hyperactivity in the absence of self-antigen, which is associated with low total B cell numbers but an expansion of the marginal zone B cell population. However, B cell anergy is normal in the presence of soluble lysozyme [soluble hen egg lysozyme (sHEL)], and MRL IgHEL B cells undergo normal elimination in the presence of sHEL when competing with a polyclonal C57BL/6 B cell repertoire. We conclude that B cell hyperactivity may contribute to the autoimmune phenotype of MRL+/+ and MRL-lpr/lpr strains when it initiates antibody responses to rare or sequestered antigens that are below the threshold for tolerance induction, but that there is no B cell intrinsic defect in anergy in MRL mice

B and T Cells Express the Ews-ERG Fusion RNA

<p>A 96-d-old mouse with both <i>Ews-ERG</i> and <i>Rag1-Cre</i> alleles was used as a source of spleen and thymus cells. Single cell suspensions of spleen cells were labelled with anti-B220 or with anti-Thy1.2 and were purified using a MoFlo preparative flow cytometer. Estimated purities were achieved of greater than 95%. cDNA was prepared from RNA extracted from sorted cells or from aliquots of unsorted populations and RT-PCR (approximately 3,400 B220+ or 6,400 Thy1.2+ cell equivalents per PCR reaction) carried out with specific <i>Pax5</i> (A), <i>CD3</i> (B) or <i>Ews-ERG</i> (C) primers. PCR reaction products were fractionated on 1% agarose gels and either stained with ethidium bromide and photographed (A and B) or gel blotted and hybridised with an <i>Ews-ERG</i> probe (C)</p