RESUMO
Viviparity evolved independently about 150 times in vertebrates and more than 20 times in fish. Several lineages added to the protection of the embryo inside the body of the mother, the provisioning of nutrients, and physiological exchange. This often led to the evolution of a placenta. Among fish, one of the most complex systems serving the function of the placenta is the embryonal trophotaenia/ovarian luminal epithelium of the goodeid fishes. For a better understanding of this feature and others of this group of fishes, high-quality genomic resources are essential. We have sequenced the genome of the darkedged splitfin, Girardinichthys multiradiatus The assembly is chromosome level and includes the X and Y Chromosomes. A large male-specific region on the Y was identified covering 80% of Chromosome 20, allowing some first inferences on the recent origin and a candidate male sex determining gene. Genome-wide transcriptomics uncovered sex-specific differences in brain gene expression with an enrichment for neurosteroidogenesis and testis genes in males. The expression signatures of the splitfin embryonal and maternal placenta showed overlap with homologous tissues including human placenta, the ovarian follicle epithelium of matrotrophic poeciliid fish species and the brood pouch epithelium of the seahorse. Our comparative analyses on the evolution of embryonal and maternal placenta indicate that the evolutionary novelty of maternal provisioning development repeatedly made use of genes that already had the same function in other tissues. In this way, preexisting modules are assembled and repurposed to provide the molecular changes for this novel trait.
Assuntos
Ciprinodontiformes , Placentação , Animais , Biologia , Ciprinodontiformes/genética , Ciprinodontiformes/metabolismo , Feminino , Genoma , Masculino , Placentação/genética , Gravidez , Cromossomos Sexuais/genéticaRESUMO
In humans, the CDKN2A locus encodes two transcripts, INK4A and ARF. Inactivation of either one by mutations or epigenetic changes is a frequent signature of malignant melanoma and one of the most relevant entry points for melanomagenesis. To analyze whether cdkn2ab, the fish ortholog of CDKN2A, has a similar function as its human counterpart, we studied its action in fish models for human melanoma. Overexpression of cdkn2ab in a Xiphophorus melanoma cell line led to decreased proliferation and induction of a senescence-like phenotype, indicating a melanoma-suppressive function analogous to mammals. Coexpression of Xiphophorus cdkn2ab in medaka transgenic for the mitfa:xmrk melanoma-inducing gene resulted in full suppression of melanoma development, whereas CRISPR/Cas9 knockout of cdkn2ab resulted in strongly enhanced tumor growth. In summary, this provides the first functional evidence that cdkn2ab acts as a potent tumor suppressor gene in fish melanoma models.
Assuntos
Inibidor p16 de Quinase Dependente de Ciclina/genética , Ciprinodontiformes/genética , Genes Supressores de Tumor , Melanócitos/metabolismo , Melanoma Experimental/genética , Oryzias/genética , Animais , Carcinogênese/genética , Carcinogênese/patologia , Evolução Molecular , Regulação Neoplásica da Expressão Gênica , Técnicas de Inativação de Genes , Melanócitos/patologia , Família Multigênica , Fenótipo , FilogeniaRESUMO
Aberrations in gene expression are a hallmark of cancer cells. Differential tumor-specific transcript levels of single genes or whole sets of genes may be critical for the neoplastic phenotype and important for therapeutic considerations or useful as biomarkers. As an approach to filter out such relevant expression differences from the plethora of changes noted in global expression profiling studies, we searched for changes of gene expression levels that are conserved. Transcriptomes from massive parallel sequencing of different types of melanoma from medaka were generated and compared to microarray datasets from zebrafish and human melanoma. This revealed molecular conservation at various levels between fish models and human tumors providing a useful strategy for identifying expression signatures strongly associated with disease phenotypes and uncovering new melanoma molecules.
Assuntos
Melanoma/genética , Oryzias/genética , Transcriptoma , Animais , Linhagem Celular Tumoral , Humanos , Sistema de Sinalização das MAP Quinases/genética , Melanoma/patologia , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologia , Neoplasias Uveais/genética , Neoplasias Uveais/patologiaRESUMO
Melanoma is a tumor with a very low cure rate once metastasized. Although many genes important for melanoma induction, transformation, and metastasis have been identified, the process of melanomagenesis is only partly understood. Melanoma mediators are easiest to investigate in cell culture models, but animal models are required to evaluate their importance in the context of the whole organism. Here, we describe a transgenic melanoma model in medaka. The oncogenic receptor tyrosine kinase, Xmrk, responsible for melanoma formation in Xiphophorus, was stably expressed under the control of a pigment cell-specific promoter. The transgenic fish developed pigment cell tumors with a penetrance of 100%. The model was used for monitoring the in vivo relevance of several apoptosis and differentiation genes, and for induction of melanoma-relevant signal transduction pathways. We found that Stat5 activation, and Mitf and Bcl-2 levels correlated with a more aggressive stage of the malignancy. Interestingly, different types of pigment cell tumors occurred depending on the genetic background, namely invasive melanoma, uveal melanoma, or exophytic and less aggressive pigment cell tumors called xanthoerythrophoroma. Furthermore, on p53 mutant background, the expression of xmrk led to the appearance of giant focal pigment cell tumors, whereas tumor onset was unchanged compared with wild-type medaka.
Assuntos
Ciprinodontiformes/genética , Proteínas de Peixes/genética , Melanoma/genética , Oryzias/genética , Receptores Proteína Tirosina Quinases/genética , Neoplasias Cutâneas/genética , Animais , Animais Geneticamente Modificados , Modelos Animais de Doenças , Feminino , Doenças dos Peixes/genética , Proteínas de Peixes/metabolismo , Proteínas Inibidoras de Apoptose/genética , Masculino , Melanoma/metabolismo , Melanoma/secundário , Fator de Transcrição Associado à Microftalmia/genética , Proteínas Proto-Oncogênicas c-bcl-2/genética , Receptores Proteína Tirosina Quinases/metabolismo , Fatores de Transcrição SOXE/genética , Transdução de Sinais/fisiologia , Neoplasias Cutâneas/metabolismo , Neoplasias Cutâneas/patologiaRESUMO
The Xmrk oncogene involved in melanoma formation in the fish Xiphophorus was formed relatively recently by duplication of the epidermal growth factor co-orthologue egfrb. In the platyfish X. maculatus, Xmrk is located close to the major sex-determining locus in a subtelomeric region of the X and Y sex chromosomes that frequently undergoes duplications and other rearrangements. This region accumulates repetitive sequences: more than 80% of the 33-kb region 3' of Xmrk is constituted by retrotransposable elements. The high degree of nucleotide identity between X- and Y-linked sequences and the rarity of gonosome-specific rearrangements indicated that the instability observed was not a manifestation of gonosome-specific degeneration. Seven other duplicated genes were found, all corresponding, in contrast to Xmrk, to pseudogenes (nonfunctionalization). Functional persistence of Xmrk in a highly unstable region in divergent Xiphophorus species suggests a beneficial function under certain conditions for this dispensable and potentially injurious gene.
Assuntos
Ciprinodontiformes/genética , Proteínas de Peixes/genética , Oncogenes , Receptores Proteína Tirosina Quinases/genética , Animais , Sequência de Bases , Elementos de DNA Transponíveis , Feminino , Duplicação Gênica , Biblioteca Genômica , Hibridização Genética , Masculino , Dados de Sequência Molecular , Regiões Promotoras Genéticas , Sequências Repetitivas de Ácido Nucleico , Cromossomo X/genética , Cromossomo Y/genéticaRESUMO
The microphthalmia-associated transcription factor (MITF) exists in at least four isoforms. These are generated in higher vertebrates using alternative 5' exons and promoters from a single gene. Two separate genes (mitf-m and mitf-b), however, are present in different teleost fish species including the poeciliid Xiphophorus, the pufferfishes Fugu rubripes and Tetraodon nigroviridis, and the zebrafish Danio rerio. Fish proteins MITF-m and MITF-b correspond at both the structural and the expression levels to one particular bird/mammalian MITF isoform. In the teleost lineage subfunctionalization of mitf genes after duplication at least 100 million years ago is associated with the degeneration of alternative exons and, probably, regulatory elements and promoters. For example, a remnant of the first exon specific for MITF-m is detected within the pufferfish gene encoding MITF-b. Retracing the evolutionary history of mitf genes in vertebrates uncovered the differential recruitment of new introns specific for either the teleost or the bird/mammalian lineage.
Assuntos
Processamento Alternativo , Ciprinodontiformes/genética , Proteínas de Ligação a DNA/genética , Éxons , Duplicação Gênica , Tetraodontiformes/genética , Fatores de Transcrição/genética , Sequência de Aminoácidos , Animais , Evolução Molecular , Fator de Transcrição Associado à Microftalmia , Dados de Sequência Molecular , Filogenia , Alinhamento de SequênciaRESUMO
The appearance of vertebrate species that reproduce without genetic recombination has been explained by their origin from a rare hybridization event between members of two distantly related species. For the first recognized vertebrate unisexual, the Amazon molly Poecilia formosa, mostly morphological and biochemical genetic information has been available so far with respect to its evolutionary origin. DNA sequence analyses of transcribed portions of the genome (tyrosine kinase proto-oncogenes) demonstrated its hybrid state unequivocally. Both alleles can be traced in a DNA sequence-based phylogenetic tree to extant species that represent the parental species or that are closely related to the corresponding extinct forms, namely P. mexicana limantouri and a so far taxonomically ill-defined north Mexican subspecies of the P. latipinna/P. velifera complex. A rough estimate from the mutation rates dates the hybridization event further back than would have been predicted on the basis of "Muller's ratchet" for an ecologically successful species.
