scholarly journals Extensive Chromosomal Reorganization in Apistogramma Fishes (Cichlidae, Cichlinae) Fits the Complex Evolutionary Diversification of the Genus

2019 ◽  
Vol 20 (17) ◽  
pp. 4077 ◽  
Author(s):  
Gideão Wagner Werneck Félix da Costa ◽  
Marcelo de Bello Cioffi ◽  
Thomas Liehr ◽  
Eliana Feldberg ◽  
Luiz Antonio Carlos Bertollo ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Tandem Repeats ◽  
5S Rdna ◽  
Unknown Origin ◽  
South American ◽  
Biogeographic Patterns ◽  
Evolutionary Diversification ◽  
Species Complexes ◽  
Chromosomal Changes

Neotropical cichlid fishes are one of the most diversified and evolutionarily successful species assemblages. Extremely similar forms and intraspecific polychromatism present challenges for the taxonomy of some of these groups. Several species complexes have a largely unknown origin and unresolved evolutionary processes. Dwarf cichlids of the genus Apistogramma, comprising more than a hundred species, exhibit intricate taxonomic and biogeographic patterns, with both allopatric and sympatric distributions. However, karyotype evolution and the role of chromosomal changes in Apistogramma are still unknown. In the present study, nine South American Apistogramma species were analyzed using conventional cytogenetic methods and the mapping of repetitive DNA sequences [18S rDNA, 5S rDNA, and (TTAGGG)n] by fluorescence in situ hybridization (FISH). Our results showed that Apistogramma has unique cytogenetic characteristics in relation to closely related groups, such as a reduced 2n and a large number of bi-armed chromosomes. Interspecific patterns revealed a scenario of remarkable karyotypic changes, including a reduction of 2n, the occurrence of B-chromosomes and evolutionary dynamic of rDNA tandem repeats. In addition to the well-known pre-zygotic reproductive isolation, the karyotype reorganization in the genus suggests that chromosomal changes could act as postzygotic barriers in areas where Apistogramma congeners overlap.

scholarly journals Composition and Nature of Heterochromatin in the Electrical Fish (Knifefishes) Gymnotus (Gymnotiformes: Gymnotidae)

2021 ◽  
Author(s):  
Maelin da Silva ◽  
Daniele Aparecida Matoso ◽  
Vladimir Pavan Margarido ◽  
Eliana Feldberg ◽  
Roberto Ferreira Artoni
Keyword(s):  
Dna Sequences ◽  
5S Rdna ◽  
Chromosome Mapping ◽  
South American ◽  
Sequence Specificity ◽  
Satellite Sequences ◽  
Rdna Sites ◽  
Close Relationship ◽  
Heterochromatic Sequence ◽  
South American Continent

Fishes of the genus Gymnotus have been suggested as a good model for biogeographic studies in the South American continent. In relation to heterochromatin, species of this genus have blocks preferably distributed in the centromeric region. The content of these regions has been shown to be variable, with description of transposable elements, pseudogenes of 5S rDNA and satellite sequences. In G. carapo Clade, although geographically separated, species with 2n = 54 chromosomes share the distribution of many 5S rDNA sites, a unique case within the genus. Here, repetitive DNA sequences from G. sylvius (2n = 40) and G. paraguensis (2n = 54) were isolated and mapped to understand their constitution. The chromosome mapping by FISH showed an exclusive association in the centromeres of all chromosomes. However, the cross-FISH did not show positive signs of interspecific hybridization, indicating high levels of heterochromatic sequence specificity. In addition, COI-1 sequences were analyzed in some species of Gymnotus, which revealed a close relationship between species of clade 2n = 54, which have multiple 5S rDNA sites. Possibly, the insertion of retroelements or pseudogenization and dispersion of this sequence occurred before the geographic dispersion of the ancestor of this clade from the Amazon region to the hydrographic systems of Paraná-Paraguay, a synapomorphy for the group.

The Organization of Repetitive DNA in the Genomes of Amazonian Lizard Species in the Family Teiidae

2015 ◽  
Vol 147 (2-3) ◽  
pp. 161-168 ◽  
Author(s):  
Natalia D.M. Carvalho ◽  
Vanessa S.S. Pinheiro ◽  
Edson J. Carmo ◽  
Leonardo G. Goll ◽  
Carlos H. Schneider ◽  
...  
Keyword(s):  
Repetitive Dna ◽  
Dna Sequences ◽  
Genome Organization ◽  
Repetitive Sequences ◽  
5S Rdna ◽  
Distinct Pattern ◽  
Structural Function ◽  
Mitotic Chromosomes ◽  
Lizard Species ◽  
Evolutionary Diversification

Repetitive DNA is the largest fraction of the eukaryote genome and comprises tandem and dispersed sequences. It presents variations in relation to its composition, number of copies, distribution, dynamics, and genome organization, and participates in the evolutionary diversification of different vertebrate species. Repetitive sequences are usually located in the heterochromatin of centromeric and telomeric regions of chromosomes, contributing to chromosomal structures. Therefore, the aim of this study was to physically map repetitive DNA sequences (5S rDNA, telomeric sequences, tropomyosin gene 1, and retroelements Rex1 and SINE) of mitotic chromosomes of Amazonian species of teiids (Ameiva ameiva, Cnemidophorus sp. 1, Kentropyx calcarata, Kentropyx pelviceps, and Tupinambis teguixin) to understand their genome organization and karyotype evolution. The mapping of repetitive sequences revealed a distinct pattern in Cnemidophorus sp. 1, whereas the other species showed all sequences interspersed in the heterochromatic region. Physical mapping of the tropomyosin 1 gene was performed for the first time in lizards and showed that in addition to being functional, this gene has a structural function similar to the mapped repetitive elements as it is located preferentially in centromeric regions and termini of chromosomes.

scholarly journals Comparative cytogenetics among Leporinus friderici and Leporellus vittatus populations (Characiformes, Anostomidae): focus on repetitive DNA elements

2019 ◽  
Vol 13 (2) ◽  
pp. 105-120 ◽  
Author(s):  
Thais Aparecida Dulz ◽  
Carla Andrea Lorscheider ◽  
Viviane Demetrio Nascimento ◽  
Rafael Bueno Noleto ◽  
Orlando Moreira-Filho ◽  
...  
Keyword(s):  
Repetitive Dna ◽  
Dna Sequences ◽  
Chromosomal Rearrangements ◽  
5S Rdna ◽  
Neotropical Fish ◽  
Comparative Cytogenetics ◽  
Fish Family ◽  
Telomere Sequence ◽  
Dna Elements ◽  
Chromosomal Changes

Anostomidae are a neotropical fish family rich in number of species. Cytogenetically, they show a conserved karyotype with 2n = 54 chromosomes, although they present intraspecific/interspecific variations in the number and chromosomal location of repetitive DNA sequences. The aim of the present study was to perform a comparative description of the karyotypes of two populations of Leporinusfriderici Bloch, 1794 and three populations of Leporellusvittatus Valenciennes, 1850. We used conventional cytogenetic techniques allied to fluorescence in situ hybridization, using 18S ribosomal DNA (rDNA) and 5S rDNA, a general telomere sequence for vertebrates (TTAGGG)n and retrotransposon (RTE) Rex1 probes. The anostomids in all studied populations presented 2n = 54 chromosomes, with a chromosome formula of 32m + 22sm for L.friderici and 28m + 26sm for L.vittatus. Variations in the number and location of the 5S and 18S rDNA chromosomal sites were observed between L.friderici and L.vittatus populations and species. Accumulation of Rex1 was observed in the terminal region of most chromosomes in all populations, and telomere sequences were located just on all ends of the 54 chromosomes in all populations. The intraspecific and intergeneric chromosomal changes occurred in karyotype differentiation, indicating that minor chromosomal rearrangements had present in anostomid species diversification.

DNA methylation in satellite repeats disorders

2019 ◽  
Vol 63 (6) ◽  
pp. 757-771 ◽  
Author(s):  
Claire Francastel ◽  
Frédérique Magdinier
Keyword(s):  
Dna Methylation ◽  
Human Genome ◽  
Repetitive Dna ◽  
Dna Sequences ◽  
Satellite Repeats ◽  
Tremendous Progress ◽  
Genes Encoding ◽  
Dna Elements ◽  
Near Future

Abstract Despite the tremendous progress made in recent years in assembling the human genome, tandemly repeated DNA elements remain poorly characterized. These sequences account for the vast majority of methylated sites in the human genome and their methylated state is necessary for this repetitive DNA to function properly and to maintain genome integrity. Furthermore, recent advances highlight the emerging role of these sequences in regulating the functions of the human genome and its variability during evolution, among individuals, or in disease susceptibility. In addition, a number of inherited rare diseases are directly linked to the alteration of some of these repetitive DNA sequences, either through changes in the organization or size of the tandem repeat arrays or through mutations in genes encoding chromatin modifiers involved in the epigenetic regulation of these elements. Although largely overlooked so far in the functional annotation of the human genome, satellite elements play key roles in its architectural and topological organization. This includes functions as boundary elements delimitating functional domains or assembly of repressive nuclear compartments, with local or distal impact on gene expression. Thus, the consideration of satellite repeats organization and their associated epigenetic landmarks, including DNA methylation (DNAme), will become unavoidable in the near future to fully decipher human phenotypes and associated diseases.

Role of Transcriptional Read-Through in PRE Activity in Drosophila melanogaster

Acta Naturae ◽  
2016 ◽  
Vol 8 (2) ◽  
pp. 79-86 ◽  
Author(s):  
P. V. Elizar’ev ◽  
D. V. Lomaev ◽  
D. A. Chetverina ◽  
P. G. Georgiev ◽  
M. M. Erokhin
Keyword(s):  
Dna Sequences ◽  
Cell Types ◽  
Transcription Terminator ◽  
Response Elements ◽  
Polycomb Response Elements ◽  
The Individual ◽  
Multicellular Organisms ◽  
Different Cell Types ◽  
Main Factor

Maintenance of the individual patterns of gene expression in different cell types is required for the differentiation and development of multicellular organisms. Expression of many genes is controlled by Polycomb (PcG) and Trithorax (TrxG) group proteins that act through association with chromatin. PcG/TrxG are assembled on the DNA sequences termed PREs (Polycomb Response Elements), the activity of which can be modulated and switched from repression to activation. In this study, we analyzed the influence of transcriptional read-through on PRE activity switch mediated by the yeast activator GAL4. We show that a transcription terminator inserted between the promoter and PRE doesnt prevent switching of PRE activity from repression to activation. We demonstrate that, independently of PRE orientation, high levels of transcription fail to dislodge PcG/TrxG proteins from PRE in the absence of a terminator. Thus, transcription is not the main factor required for PRE activity switch.

Arterite de Takayasu em Gestante: Relato de Caso / Takayasu Arteritis in Pregnancy: Case Report

1970 ◽  
Vol 5 (4) ◽  
pp. 61-66
Author(s):  
Patrícia Resende Penido ◽  
Rhanna Junqueira Westin de Carvalho ◽  
Roger Willian Moraes Mendes
Keyword(s):  
Case Report ◽  
Takayasu Arteritis ◽  
Imaging Techniques ◽  
Unknown Origin ◽  
Pregnant Patient ◽  
Immunosuppressive Drugs ◽  
Clinical Treatment ◽  
Satisfactory Outcome

RESUMOIntrodução: A Arterite de Takayasu (AT) consiste em uma vasculopatia de origem indefinida, sendo de caráter crônico, que afeta a aorta e seus ramos principais. Em gestantes é uma condição complexa, em que o tratamento clínico é realizado com restrições. A utilização de corticoides tem sido favorável no controle inflamatório, principalmente naqueles casos em que antes da gravidez se fazia uso de imunossupressores. Casuística: Foi relatado um caso de uma gestante portadora de AT, através da análise de prontuário e de exames complementares, sendo realizado o pré-natal pelas equipes de Obstetrícia e Reumatologia, onde foi realizado tratamento clínico com corticoides, mostrando uma evolução satisfatória, ocorrendo apenas uma hospitalização que foi seguida de uma cesárea na trigésima sexta semana de gravidez, com recém nato saudável de 3.810g. Discussão: A AT pode estar associada a várias etiologias, sendo a gênese pouco conhecida. O diagnóstico na maioria das vezes é demorado, pela dificuldade da suspeita clínica, além de demandar o uso de técnicas de imagem mais sofisticadas. A gestação associada é fenômeno raro, já que as portadoras são orientadas a evitarem a gravidez. O controle clínico permitiu uma gestação sem grandes complicações e serviu como meio para levar a gestação até praticamente o fim do terceiro trimestre. Conclusão: Deve-se ressaltar o papel do acompanhamento clínico, especialmente com esta pan-arterite, mostrando os medicamentos que podem ser utilizados nesse grupo, especialmente quando se usava imunossupressores antes da gravidez. Palavras chave: Arterite de Takayasu, Gravidez, Vasculite. ABSTRACT:Introduction: Takayasu's arteritis (TA) consists of a vascular disease of unknown origin and chronic nature, which affects the aorta and its main branches. In pregnant women it is a complex condition, in which the clinical treatment is performed with restrictions. The use of corticosteroids has been favorable to control inflammation, especially in those cases when immunosuppressant had been used before pregnancy. Case Report: A case of a pregnant patient with TA has been reported through the analysis of medical records and laboratory tests. The Obstetrics and Rheumatology staff performed the prenatal care, and clinical treatment with corticosteroids was done showing a satisfactory outcome. There was only one hospitalization of the patient, which was followed by a cesarean in the thirty sixth week of pregnancy.  The newborn was a healthy one, weighing 3.810g. Discussion: TA may be associated with several etiologies, and the genesis is little known. The diagnosis most often takes time due to the difficulty of clinical suspicion, and requires the use of more sophisticated imaging techniques. The pregnancy is rare phenomenon, since the carriers are advised to avoid pregnancy. The clinical management allowed a pregnancy without major complications and served as a means to carry the pregnancy to almost the end of the third quarter. Conclusion: The role of the clinical follow-up should be noticed especially with this pan-arteritis, showing the drugs that can be used in this group, especially when there is use of immunosuppressive drugs before pregnancy. Keywords: Takayasu Arteritis, Pregnancy, Vasculitis.

scholarly journals Involvement of Very Short DNA Tandem Repeats and the Influence of the RAD52 Gene on the Occurrence of Deletions in Saccharomyces cerevisiae

Genetics ◽  
2000 ◽  
Vol 156 (2) ◽  
pp. 549-557 ◽  
Author(s):  
Anne J Welcker ◽  
Jacky de Montigny ◽  
Serge Potier ◽  
Jean-Luc Souciet
Keyword(s):  
Fusion Proteins ◽  
Tandem Repeats ◽  
Chromosomal Rearrangements ◽  
Reversion Rate ◽  
Wild Type ◽  
Recombination Mechanism ◽  
Nonhomologous Recombination ◽  
Deletion Rate ◽  
Dna Tandem Repeats

Abstract Chromosomal rearrangements, such as deletions, duplications, or Ty transposition, are rare events. We devised a method to select for such events as Ura+ revertants of a particular ura2 mutant. Among 133 Ura+ revertants, 14 were identified as the result of a deletion in URA2. Of seven classes of deletions, six had very short regions of identity at their junctions (from 7 to 13 bp long). This strongly suggests a nonhomologous recombination mechanism for the formation of these deletions. The total Ura+ reversion rate was increased 4.2-fold in a rad52Δ strain compared to the wild type, and the deletion rate was significantly increased. All the deletions selected in the rad52Δ context had microhomologies at their junctions. We propose two mechanisms to explain the occurrence of these deletions and discuss the role of microhomology stretches in the formation of fusion proteins.

SINE-B1 Distribution and Chromosome Rearrangements in the South American Proechimys gr. goeldii (Echimyidae, Rodentia)

2021 ◽  
pp. 1-8
Author(s):  
Naiara P. Araújo ◽  
Radarane S. Sena ◽  
Cibele R. Bonvicino ◽  
Gustavo C.S. Kuhn ◽  
Marta Svartman
Keyword(s):  
Transposable Element ◽  
Genome Evolution ◽  
Significant Role ◽  
Sex Chromosomes ◽  
Chromosomal Rearrangements ◽  
Evolutionary Relationship ◽  
Chromosome Rearrangements ◽  
South American ◽  
Gross Chromosomal Rearrangements

<i>Proechimys</i> species are remarkable for their extensive chromosome rearrangements, representing a good model to understand genome evolution. Herein, we cytogenetically analyzed 3 different cytotypes of <i>Proechimys</i> gr. <i>goeldii</i> to assess their evolutionary relationship. We also mapped the transposable element SINE-B1 on the chromosomes of <i>P.</i> gr. <i>goeldii</i> in order to investigate its distribution among individuals and evaluate its possible contribution to karyotype remodeling in this species. SINE-B1 showed a dispersed distribution along chromosome arms and was also detected at the pericentromeric regions of some chromosomes, including pair 1 and the sex chromosomes, which are involved in chromosome rearrangements. In addition, we describe a new cytotype for <i>P.</i> gr. <i>goeldii</i>, reinforcing the significant role of gross chromosomal rearrangements during the evolution of the genus. The results of FISH with SINE-B1 suggest that this issue should be more deeply investigated for a better understanding of its role in the mechanisms involved in the wide variety of <i>Proechimys</i> karyotypes.

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