@phdthesis{Muench2023,
  author    = {M{\"u}nch, Luca},
  title     = {Die Rolle transposabler Elemente in der Genese des malignen Melanom im Fischmodell Xiphophorus},
  doi       = {10.25972/OPUS-28922},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-289228},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2023},
  abstract  = {Der Name der transposablen Elemente beruht auf ihrer F{\"a}higkeit, ihre genomische Position ver{\"a}ndern zu k{\"o}nnen. Durch Chromosomenaberrationen, Insertionen oder Deletionen k{\"o}nnen ihre genomischen Transpositionen genetische Instabilit{\"a}t verursachen. Inwieweit sie dar{\"u}ber hinaus regulatorischen Einfluss auf Zellfunktionen besitzen, ist Gegenstand aktueller Forschung ebenso wie die daraus resultierende Frage nach der Gesamtheit ihrer biologischen Signifikanz. Die Weiterf{\"u}hrung experimenteller Forschung ist unabdingbar, um weiterhin offenen Fragen nachzugehen. Das Xiphophorus-Melanom-Modell stellt hierbei eines der {\"a}ltesten Tiermodelle zur Erforschung des malignen Melanoms dar. Durch den klar definierten genetischen Hintergrund eignet es sich hervorragend zur Erforschung des b{\"o}sartigen schwarzen Hautkrebses, welcher nach wie vor die t{\"o}dlichste aller bekannten Hautkrebsformen darstellt. Die hier vorliegende Arbeit besch{\"a}ftigt sich mit der Rolle transposabler Elemente in der malignen Melanomgenese von Xiphophorus.},
  subject      = {Transposon},
  language  = {de}
}
@phdthesis{Liu2022,
  author    = {Liu, Ruiqi},
  title     = {Dynamic regulation of the melanocortin 4 receptor system in body weight homeostasis and reproductive maturation in fish},
  doi       = {10.25972/OPUS-20653},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-206536},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {Puberty is an important period of life with physiological changes to enable animals to reproduce. Xiphophorus fish exhibit polymorphism in body size, puberty timing, and reproductive tactics. These phenotypical polymorphisms are controlled by the Puberty (P) locus. In X. nigrensis and X. multilineatus, the P locus encodes the melanocortin 4 receptor (Mc4r) with high genetic polymorphisms. Mc4r is a member of the melanocortin receptors, belonging to class A G-protein coupled receptors. The Mc4r signaling system consists of Mc4r, the agonist Pomc (precursor of various MSH and of ACTH), the antagonist Agrp and accessory protein Mrap2. In humans, MC4R has a role in energy homeostasis. MC4R and MRAP2 mutations are linked to human obesity but not to puberty. Mc4rs in X. nigrensis and X. multilineatus are present in three allele classes, A, B1 and B2, of which the X-linked A alleles express functional receptors and the male-specific Y-linked B alleles encode defective receptors. Male body sizes are correlated with B allele type and B allele copy numbers. Late-maturing large males carry B alleles in high copy number while early-maturing small males carry B alleles in low copy number or only A alleles. Cell culture co-expression experiments indicated that B alleles may act as dominant negative receptor mutants on A alleles. In this study, the main aim was to biochemically characterize the mechanism of puberty regulation by Mc4r in X. nigrensis and X. multilineatus, whether it is by Mc4r dimerization and/or Mrap2 interaction with Mc4r or other mechanisms. Furthermore, Mc4r in X. hellerii (another swordtail species) and medaka (a model organism phylogenetically close to Xiphophorus) were investigated to understand if the investigated mechanisms are conserved in other species. In medaka, the Mc4r signaling system genes (mc4r, mrap2, pomc, agrp1) are expressed before hatching, with agrp1 being highly upregulated during hatching and first feeding. These genes are mainly expressed in adult brain, and the transcripts of mrap2 co-localize with mc4r indicating a function in modulating Mc4r signaling. Functional comparison between wild-type and mc4r knockout medaka showed that Mc4r knockout does not affect puberty timing but significantly delays hatching due to the retarded embryonic development of knockout medaka. Hence, the Mc4r system in medaka is involved in regulation of growth rather than puberty. In Xiphophorus, expression co-localization of mc4r and mrap2 in X. nigrensis and X. hellerii fish adult brains was characterized by in situ hybridization. In both species, large males exhibit strikingly high expression of mc4r while mrap2 shows similar expression level in the large and small male and female. Differently, X. hellerii has only A-type alleles indicating that the puberty regulation mechanisms evolved independently in Xiphophorus genus. Functional analysis of Mrap2 and Mc4r A/B1/B2 alleles of X. multilineatus showed that increased Mrap2 amounts induce higher cAMP response but EC50 values do not change much upon Mrap2 co-expression with Mc4r (expressing only A allele or A and B1 alleles). A and B1 alleles were expressed higher in large male brains, while B2 alleles were only barely expressed. Mc4r A-B1 cells have lower cAMP production than Mc4r A cells. Together, this indicates a role of Mc4r alleles, but not Mrap2, in puberty onset regulation signaling. Interaction studies by FRET approach evidenced that Mc4r A and B alleles can form heterodimers and homodimers in vitro, but only for a certain fraction of the expressed receptors. Single-molecule colocalization study using super-resolution microscope dSTORM confirmed that only few Mc4r A and B1 receptors co-localized on the membrane. Altogether, the species-specific puberty onset regulation in X. nigrensis and X. multilineatus is linked to the presence of Mc4r B alleles and to some extent to its interaction with A allele gene products. This is reasoned to result in certain levels of cAMP signaling which reaches the dynamic or static threshold to permit late puberty in large males. In summary, puberty onset regulation by dominant negative effect of Mc4r mutant alleles is a special mechanism that is found so far only in X. nigrensis and X. multilineatus. Other Xiphophorus species obviously evolved the same function of the pathway by diverse mechanisms. Mc4r in other fish (medaka) has a role in regulation of growth, reminiscent of its role in energy homeostasis in humans. The results of this study will contribute to better understand the biochemical and physiological functions of the Mc4r system in vertebrates including human.},
  subject      = {Japank{\"a}rpfling},
  language  = {en}
}
@article{AdamMauelerSchartl1991,
  author    = {Adam, Dieter and Maueler, Winfried and Schartl, Manfred},
  title     = {Transcriptional activation of the melanoma inducing Xmrk oncogene in Xiphophorus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-87584},
  year      = {1991},
  abstract  = {The melanoma inducing locus of Xiphophorus encodes a tumorigenic version of a novel putative receptor tyrosine kinase (Xmrk). To elucidate the mechanism of oncogenic activation of Xmrk, we compared the structure and expression of two oncogenic loci with the corresponding proto-oncogene. Only minor structural alterations were found to be specific for the oncogenic Xmrk genes. Marked overexpression of the oncogene transcripts in melanoma, which are approximately 1 kb shorter than the proto-oncogene transcript, correlates with the malignancy of the tumors. The tumor transcripts are derived from an alternative transcription start site that is used only in the oncogenic loci. Thus, oncogenic activation of the melanoma inducing Xmrk gene appears primarily to be due to novel transcriptional control and overexpression.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}
@article{SchartlWittbrodtMaeueleretal.1993,
  author    = {Schartl, Manfred and Wittbrodt, J. and M{\"a}ueler, W. and Raulf, F. and Adam, D. and Hannig, G. and Telling, A. and Storch, F. and Andexinger, S. and Robertson, S. M.},
  title     = {Oncogenes and melanoma formation in Xiphoporus (Teleostei: Poeciliidae)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-87149},
  year      = {1993},
  abstract  = {In Xiphophorus melanoma formation has been attributed by classical genetic findings to the overexpression of a cellular oncogene (Tu) due to elimination of the corresponding regulatory gene locus in hybrids. We have attempted to elucidate this phenomenon on the molecular biological level. Studies on the structure and expression of known proto-oncogenes revealed that several of these genes, especially the c-src gene of Xiphophorus, may act as effectors in establishing the neoplastic phenotype of the melanoma cells . However, these genes appear more to participate in secondary steps of tumorigenesis. Another gene, being termed Xmrk, which represents obviously a so far unknown proto-oncogene but with a cons iderably high similarity to the epidermal growth-factorreceptor gene, was mapped to the Tu-containing region of the chromosome. This gene shows features with respect to its structure and expression that seem to justify it to be regarded as a candidate for a gene involved in the primary processes leading to neoplastic transformation of pigment cells in Xiphophorus.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}
@article{MeyerSchartl1979,
  author    = {Meyer, Manfred K. and Schartl, Manfred},
  title     = {Eine neue Xiphophorus-Art aus Vera Cruz, Mexiko : (Pisces: Poeciliidae)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-87124},
  year      = {1979},
  abstract  = {Xiphophorus andersi n. sp. from the Rio Atoyac, Vera Cruz, Mexico is described: lang head, moderately slender body, large dark black spar at the basis of the anal fin; adult male with short sword-like caudal appendage; rip of ray 5a of gonopodium without a developed claw. Xiphophorus andersi n. sp. differs by the combination of distinct characters from all the other species of the genus known so far. The new species shows features of both the so-called platyfish species group and the so-called swordtail species group.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}
@article{WinklerHongWittbrodtetal.1992,
  author    = {Winkler, Christoph and Hong, Yunhan and Wittbrodt, Joachim and Schartl, Manfred},
  title     = {Analysis of heterologous and homologous promoters and enhancers in vitro and in vivo by gene transfer into Japanese medaka (Oryzias latipes) and Xiphophorus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86796},
  year      = {1992},
  abstract  = {Efficient expression systems are required for analysis of gene regulation and function in teleost fish. To develop such systems, a nurober of inducible or constitutive promoter and enhancer sequences of fish or higher vertebrate origin were tested for activity in a variety of fish celllines andin embryos of the Japanese medaka fish (Oryzias latipes) and Xiphophorus. The activity of the different promoterenhancer combinations were quantitated. Considerable differences were found for some constructs if tested in vitro or in vivo. From the data obtained, a set of expression vectors for basic research as weH as for aquaculture purposes were established.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}
@article{RaulfMaeuelerRobertsonetal.1989,
  author    = {Raulf, Friedrich and M{\"a}ueler, Winfried and Robertson, Scott M. and Schartl, Manfred},
  title     = {Localization of cellular src mRNA during development and in the differentiated bipolar neurons of the adult neural retina in Xiphophorus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86703},
  year      = {1989},
  abstract  = {The expression of the c-src gene in embryonie and adult tissue of the teleost fish Xiphophorus helleri was analyzed by in-situ hybridization. The highly conserved fish c-src gene was found to be expressed at high levels in midterm embryos, where c-src mRNA was localized in developing neurons of the sensory layer of the differentiating retina and in the developing brain. In adult tissues the expression of c-src was found to persist in certain cell types of the brain and the neural retina, especially in the bipolar cells of the inner nuclear layer, which are postmitotic, fully differentiated mature neurons. Thus c-src in Xiphophorus appears to be a developmentally regulated proto-oncogene which is important for neuronal differentiation during organogenesis, but whose persistence of expression in certain terminally differentiated neurons strongly suggests a particular maintenance function for c-src in these cells as well.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}
@article{SchartlSchartlAnders1982,
  author    = {Schartl, A. and Schartl, Manfred and Anders, F.},
  title     = {Promotion and regression of neoplasia by testosterone-promoted cell differentiation in Xiphophorus and Girardinus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86684},
  year      = {1982},
  abstract  = {No abstract available.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}
@inproceedings{SchartlSchartlAnders1981,
  author    = {Schartl, A. and Schartl, Manfred and Anders, F.},
  title     = {Phenotypic conversion of malignant melanoma to benign melanoma and vice versa in Xiphophorus},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86662},
  year      = {1981},
  abstract  = {No abstract available.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}
@inproceedings{AndersSchollSchartl1981,
  author    = {Anders, F. and Scholl, E. and Schartl, Manfred},
  title     = {Environmental and hereditary factors in the causation of neoplasia, based on studies of the Xiphophorus fish melanoma system},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86402},
  year      = {1981},
  abstract  = {Neoplasia in Xiphophorus can be classified into: a) a Jarge group triggered by carcinogens; b) a large group triggered by promoters; and c) a small group that develops "spontaneously" according to Mendelian Jaw. The process leading to susceptibility for neoplasia is represented by the disintegration of gene systems that normally protect the fish from neoplasia. Interpopulational arid interracial hybridization is the most effective process that Ieads to disintegration of the protective gene systems. Environmental factors may complete disintegration in somatic cells and thus may trigger neoplasia. The applications of the findings on Xiphophorus to humans are discussed.},
  subject      = {Schwertk{\"a}rpfling},
  language  = {en}
}