RESUMO
With 82 species currently described, the genus Leptodactylus is the most diverse and representative one in the family Leptodactylidae. Concerning chromosomal organization, this genus represents an interesting and underexplored group since data from molecular cytogenetics are incipient, and little is known about the organization and distribution of repetitive DNA elements in the karyotypes. In this sense, this study aimed at providing a comparative analysis in 4 Leptodactylus species (L. macrosternum, L. pentadactylus, L. fuscus, and Leptodactylus cf. podicipinus), combining conventional cytogenetics (Giemsa staining, C-banding, and AgNOR staining) and mapping of molecular markers (18S rDNA, telomeric and microsatellite probes), to investigate mechanisms underlying their karyotype differentiation process. The results showed that all species had karyotypes with 2n = 22 and FN = 44, except for Leptodactylus cf. podicipinus which presented FN = 36. The 18S rDNA was observed in pair 8 of all analyzed species (corresponding to pair 4 in L. pentadactylus), coinciding with the secondary constrictions and AgNOR staining. FISH with microsatellite DNA probes demonstrated species-specific patterns, as well as an association of these repetitive sequences with constitutive heterochromatin blocks and ribosomal DNA clusters, revealing the dynamics of microsatellites in the genome of the analyzed species. In summary, our data demonstrate an ongoing process of genomic divergence inside species with almost similar karyotype, driven most likely by a series of pericentric inversions, followed by differential accumulation of repetitive sequences.
Assuntos
Anuros/genética , Cromossomos/ultraestrutura , DNA Ribossômico/genética , Cariotipagem , Repetições de Microssatélites , Animais , Bandeamento Cromossômico , Inversão Cromossômica , Análise Citogenética , Citogenética , Sondas de DNA , Feminino , Geografia , Heterocromatina/metabolismo , Hibridização in Situ Fluorescente , Cariótipo , Masculino , Meiose , Mitose , Região Organizadora do Nucléolo , Filogenia , Especificidade da EspécieRESUMO
Basic and molecular cytogenetic techniques were carried out in 3 Neotropical region populations of catfishes, two of Trachelyopterus galeatus (one from the marshlands of Paraguay River basin and another from Lago Catalão, Amazon River basin) and one of Trachelyopterus porosus, a sympatric population to T. galeatus from the Amazon River basin. This study aimed to describe and understand the structure and evolution of Trachelyopterus B chromosomes, mainly through physical mapping of repetitive elements. A diploid number of 58 chromosomes was found for all individuals, as well as the presence of B chromosomes. For T. porosus this is the first report of a supernumerary. The sympatric species of T. galeatus and T. porosus from Amazon River had 1-3 B chromosomes and T. galeatus from Paraguay River had 1-2 B chromosomes, all of them showed intra- and interindividual numerical variation. Two females of T. porosus exhibited a new variant B chromosome (B2), previously not seen in Auchenipteridae, which might have originated from B1 chromosomes. All B chromosomes were entirely heterochromatic. In contrast to all complement A and B2 chromosomes, in which the telomeric sequences were found in the telomeric regions, B1 chromosomes of all populations were totally marked by (TTAGGG)n probes. (GATA)n sequence sites were found through all complement A chromosomes, but B1 and B2 chromosomes exhibited only a clustered block in one of the chromosome arms. The most frequent B chromosomes (B1) in all populations/species, including those previously studied in Auchenipteridae catfishes, share the following characteristics: totally heterochromatic, small, metacentric, with accumulation of repetitive (TTAGGG)n sequences, and a low number of (GATA)n copies, which might suggest a common ancient origin in Trachelyopterus species/populations.
Assuntos
Peixes-Gato/genética , Cromossomos/ultraestrutura , Animais , Brasil , Mapeamento Cromossômico , Análise Citogenética , Citogenética , Diploide , Feminino , Cariótipo , Masculino , Repetições de Microssatélites , Paraguai , Sequências Repetitivas de Ácido Nucleico , Telômero/ultraestruturaRESUMO
Proechimys species are remarkable for their extensive chromosome rearrangements, representing a good model to understand genome evolution. Herein, we cytogenetically analyzed 3 different cytotypes of Proechimys gr. goeldii to assess their evolutionary relationship. We also mapped the transposable element SINE-B1 on the chromosomes of P. gr. goeldii 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 P. gr. goeldii, 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 Proechimys karyotypes.
Assuntos
Cromossomos/ultraestrutura , Rearranjo Gênico , Roedores/genética , Elementos Nucleotídeos Curtos e Dispersos , Animais , Bandeamento Cromossômico , Evolução Molecular , Feminino , Genoma , Heterocromatina/química , Hibridização in Situ Fluorescente , Cariótipo , Masculino , Cromossomos Sexuais , América do SulRESUMO
The family Aspredinidae comprises a clade of complex systematic relationships, both from molecular and morphological approaches. In this study, conventional and molecular cytogenetic studies coupled with nucleotide sequencing were performed in 6 Aspredininae species (Amaralia hypsiura, Bunocephalus cf. aloikae, Bunocephalus amaurus, Bunocephalus aff. coracoideus, Bunocephalus verrucosus, and Platystacus cotylephorus) from different locations of the Amazon hydrographic basin. Our results showed highly divergent diploid numbers (2n) among the species, ranging from 49 to 74, including the occurrence of an XX/X0 sex chromosome system. A neighbor-joining phylogram based on the cytochrome c oxidase I (COI) showed that Bunocephalus coracoideus is not a monophyletic clade, but closely related to B. verrucosus. The karyotypic data associated with COI suggest an ancestral karyotype for Aspredinidae with a reduced 2n, composed of bi-armed chromosomes and a trend toward chromosomal fissions resulting in higher diploid number karyotypes, mainly composed of acrocentric chromosomes. Evolutionary relationships were discussed under a phylogenetic context with related species from different Siluriformes families. The karyotype features and chromosomal diversity of Aspredinidae show an amazing differentiation, making this family a remarkable model for investigating the evolutionary dynamics in siluriforms as well as in fish as a whole.
Assuntos
Peixes-Gato/genética , Cromossomos/genética , Animais , Evolução Biológica , Brasil , Peixes-Gato/classificação , Cromossomos/ultraestrutura , Código de Barras de DNA Taxonômico , DNA Ribossômico/genética , Diploide , Evolução Molecular , Feminino , Hibridização in Situ Fluorescente , Cariotipagem , Masculino , Filogenia , RNA Ribossômico 18S/genética , RNA Ribossômico 5S/genética , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico , Cromossomos Sexuais/genética , Cromossomos Sexuais/ultraestrutura , Especificidade da EspécieRESUMO
The hyline tribe Lophyohylini includes 87 species of treefrogs, of which cytogenetics aspects have been studied in less than 20% of them. In order to evaluate the evolution of some of its chromosome characters (NOR position, C-bands, and DAPI/CMA3 bands), we studied the karyotypes of 21 lophyohylines, 16 of them for the first time, and analyzed them in a phylogenetic context. Most species showed similar karyotypes regarding chromosome number (2n = 24) and morphology (FN = 48), excepting Phyllodytes edelmoi and Osteocephalus buckleyi with 2n = 22 (FN = 44) and 2n = 28 (FN = 50), respectively. The NOR location was variable among species and provided valuable phylogenetic information. This marker was located in pair 11 in all species of Trachycephalus, Itapotihyla langsdorffii, and Nyctimantis arapapa, representing the plesiomorphic condition of Lophyohylini. Besides, other apomorphic states were recovered for the clades comprising N. rugiceps and N. siemersi (NOR in pair 5), and Dryaderces pearsoni, Osteocephalus, and Osteopilus (NOR in pair 9). Phyllodytes presented variation for NORs position; they were in pair 2 in P. edelmoi, pair 7 in P. melanomystax, and pair 8 in P. gyrinaethes and P. praeceptor. Polymorphisms in size, number, and activity of this marker were observed for N. siemersi, Osteocephalus fuscifacies, and some species of Trachycephalus. Remarkably, in N. siemersi NORs were detected on a single chromosome in the two specimens studied by this technique, raising the question of how this complex polymorphism is maintained. Interstitial telomeric sequences were found in P. edelmoi, P. melanomystax, and Osteocephalus buckleyi, and their presence seems to be not related to the chromosome reorganization events. Finally, some species showed spontaneous rearrangements, possibly as a consequence of an uncommon phenomenon in anuran cytogenetics: the presence of fragile sites or secondary constrictions not associated with NORs. We propose that this rare feature would have played an important role in the evolution of this group of frogs. From the evidence obtained in this and previous studies, we conclude that Lophyohylini presents a complex chromosome evolution.
Assuntos
Anuros/genética , Cromossomos/genética , Animais , Anuros/classificação , Bandeamento Cromossômico , Sítios Frágeis do Cromossomo/genética , Cromossomos/ultraestrutura , Análise Citogenética , Evolução Molecular , Feminino , Cariótipo , Masculino , Região Organizadora do Nucléolo/genética , Região Organizadora do Nucléolo/ultraestrutura , Filogenia , Polimorfismo Genético , América do Sul , Especificidade da Espécie , Telômero/genéticaRESUMO
Single-celled eukaryote genomes predominantly replicate through multiple origins. Although origin usage during the S-phase has been elucidated in some of these organisms, few studies have comparatively approached this dynamic. Here, we developed a user-friendly website able to calculate the length of the cell cycle phases for any organism. Next, using a formula developed by our group, we showed a comparative analysis among the minimum number of replication origins (MO) required to duplicate an entire chromosome within the S-phase duration in trypanosomatids (Trypanosoma cruzi, Leishmania major, and Trypanosoma brucei) and yeasts (Saccharomyces cerevisiae and Schizosaccharomyces pombe). Using the data obtained by our analysis, it was possible to predict the MO required in a situation of replication stress. Also, our findings allow establishing a threshold for the number of origins, which serves as a parameter for genome approaches that map origins. Moreover, our data suggest that when compared to yeasts, trypanosomatids use much more origins than the minimum needed. This is the first time a comparative analysis of the minimum number of origins has been successfully applied. These data may provide new insight into the understanding of the replication mechanism and a new methodological framework for studying single-celled eukaryote genomes.
Assuntos
Cromossomos/genética , Leishmania major/genética , Origem de Replicação , Saccharomyces cerevisiae/genética , Schizosaccharomyces/genética , Trypanosoma brucei brucei/genética , Trypanosoma cruzi/genética , Ciclo Celular , Cromossomos/ultraestrutura , Cromossomos Fúngicos/genética , Cromossomos Fúngicos/ultraestrutura , Replicação do DNA , DNA Fúngico/genética , DNA de Protozoário/genética , Internet , Leishmania major/crescimento & desenvolvimento , Especificidade da Espécie , Trypanosoma cruzi/crescimento & desenvolvimentoRESUMO
We show that an inhomogeneous Bernoulli site percolation process running upon a fullerene's dual [Formula: see text] can be used for representing bivalents attached to the nuclear envelope in mouse Mus M. Domesticus 2n = 40 meiotic spermatocytes during pachytene. It is shown that the induced clustering generated by overlapping percolation domains correctly reproduces the probability distribution observed in the experiments (data) after fine tuning the parameters.
Assuntos
Cromossomos/genética , Meiose , Modelos Genéticos , Espermatócitos/ultraestrutura , Animais , Cromossomos/ultraestrutura , Simulação por Computador , Heterocromatina/genética , Heterocromatina/ultraestrutura , Masculino , Conceitos Matemáticos , Meiose/genética , Camundongos , Membrana Nuclear/genética , Membrana Nuclear/ultraestrutura , Estágio Paquíteno/genética , Complexo Sinaptonêmico/genética , Complexo Sinaptonêmico/ultraestruturaRESUMO
The Neacomys genus (Rodentia, Sigmodontinae) is distributed in the Amazon region, with some species limited to a single endemic area, while others may occur more widely. The number of species within the genus and their geographical boundaries are not known accurately, due to their high genetic diversity and difficulties in taxonomic identification. In this work we collected Neacomys specimens from both banks of the Tapajós River in eastern Amazon, and studied them using chromosome painting with whole chromosome probes of Hylaeamys megacephalus (HME; Rodentia, Sigmodontinae), and molecular analysis using haplotypes of mitochondrial genes COI and Cytb. Chromosome painting shows that Neacomys sp. A (NSP-A, 2n = 58/FN = 68) and Neacomys sp. B (NSP-B, 2n = 54/FN = 66) differ by 11 fusion/fission events, one translocation, four pericentric inversions and four heterochromatin amplification events. Using haplotypes of the concatenated mitochondrial genes COI and Cyt b, Neacomys sp. (2n = 58/FN = 64 and 70) shows a mean divergence of 6.2% for Neacomys sp. A and 9.1% for Neacomys sp. B, while Neacomys sp. A and Neacomys sp. B presents a medium nucleotide divergence of 7.4%. Comparisons were made with other published Neacomys data. The Tapajós and Xingu Rivers act as geographic barriers that define the distribution of these Neacomys species. Furthermore, our HME probes reveal four synapomorphies for the Neacomys genus (associations HME 20/[13,22]/4, 6a/21, [9,10]/7b/[9,10] and 12/[16,17]) and demonstrate ancestral traits of the Oryzomyini tribe (HME 8a and 8b, 18 and 25) and Sigmodontinae subfamily (HME 15 and 24), which can be used as taxonomic markers for these groups.
Assuntos
Biodiversidade , Mapeamento Cromossômico , Cromossomos/ultraestrutura , Roedores/genética , Animais , Teorema de Bayes , Brasil , Coloração Cromossômica , Citocromos b/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Variação Genética , Geografia , Haplótipos , Hibridização in Situ Fluorescente , Cariotipagem , Funções Verossimilhança , Masculino , Mitocôndrias/genética , Filogenia , Roedores/classificaçãoRESUMO
BACKGROUND: Brazilian gas station workers are chronically exposed to benzene, toluene, xylene (BTX) during their working time. Describe below two cases of latin female gas station workers with benzene poisoning symptoms and miscarriage history. CASE PRESENTATION: In both cases were identified complex chromosomal rearrangements (CCR) with fluorescence in situ hybridization, applied to whole chromosome paints by chromosomes 1, 2 and 4. The lower natural killer cell (NK) cells have also been observed in cases correspondents, especially the rare type of NK (NKbright) in their peripheral blood cells. CONCLUSIONS: It is known that acquired chromosomal aberrations are positively correlated with cancer and reproductive risk. In concordance, lower NK cytotoxicity increases the risk for cancer, as well. Thus, this is the first study providing hints on a possible causative relation of lower NK cytotoxicity and increase rates of chromosomal rearrangements including CCRs.
Assuntos
Benzeno/intoxicação , Exposição Ocupacional/efeitos adversos , Aborto Espontâneo , Adulto , Aberrações Cromossômicas , Coloração Cromossômica , Cromossomos/ultraestrutura , Feminino , Rearranjo Gênico , Humanos , Hibridização in Situ Fluorescente , Células Matadoras Naturais/citologia , Fatores de Tempo , Tolueno/intoxicação , Xilenos/intoxicaçãoRESUMO
Tyrannidae is the largest family of Passeriformes in the Neotropical region. However, despite an interesting chromosomal diversity, there are only few cytogenetic studies of this family, and most of these are based on conventional cytogenetics. Hence, we analyzed here the chromosomal diversity and karyotypical evolution of this group by chromosome painting in 3 different species - Pitangus sulphuratus, Serpophaga subcristata, and Satrapa icterophrys - and make comparisons with previous data. In addition to chromosome painting with Gallus gallus (GGA) and Leucopternis albicollis (LAL) probes, karyotypes were analyzed by conventional staining, C-banding, and FISH with 18S rDNA and telomeric probes. Although this family is characterized by extensive chromosomal variation, we found similar karyotypes and diploid numbers ranging from 2n = 80 in P. sulphuratus to 2n = 82 in S. subcristata and S. icterophrys. Constitutive heterochromatin was located centromerically in all 3 species. Clusters of 18S rDNA were present in 1 pair of microchromosomes, except in S. subcristata, where 2 pairs of microchromosomes were labeled. No interstitial telomeric sequences were detected. GGA and LAL whole-chromosome probes revealed the occurrence of fissions and both paracentric and pericentric inversions commonly seen in other Passeriformes. In general terms, tyrants show the typical karyotype found in Passeriformes, suggesting that the observed rearrangements occurred before the division of the suborders Oscines and Suboscines.