Molecular cytogenetic analysis of heterochromatin in the chromosomes of tilapia, Oreochromis niloticus (Teleostei : Cichlidae)

The structure of the heterochromatic bands in mitotic chromosomes of the important tropical aquaculture species of tilapia, Oreochromis niloticus, was investigated by the combination of the C-banding technique, chromosomal digestion with two restriction endonucleases and fluorescence in situ hybridization (FISH) of two satellite DNAs (SATA and SATB). The tilapia chromosomes presented heterochromatic bands in the centromeres and in the short arms of almost all chromosomes that were differentially digested by the restriction endonucleases HaeIII and EcoRI. FISH of SATA showed that the satellite sequence is distributed in the centromeric region of all chromosomes of tilapia. FISH also revealed an intense hybridization signal for SATB in only one chromosome pair, but less intense signals were also present in several other pairs. The digestion of tilapia chromosomes by HaeIII and EcoRI was positively correlated with the position of SATA and SATB in chromosomes as revealed by FISH. The results obtained may be useful in future molecular and genetic studies of tilapias.

A tandemly repetitive centromeric DNA sequence of the fish Hoplias malabaricus (Characiformes : Erythrinidae) is derived from 5S rDNA

A substantial fraction of the eukaryotic genome consists of repetitive DNA sequences that include satellites, minisatellites, microsatellites, and transposable elements. Although extensively studied for the past three decades, the molecular forces that generate, propagate and maintain repetitive DNAs in the genomes are still discussed. To further understand the dynamics and the mechanisms of evolution of repetitive DNAs in vertebrate genome, we searched for repetitive sequences in the genome of the fish species Hoplias malabaricus. A satellite sequence, named 5SHindIII-DNA, which has a conspicuous similarity with 5S rRNA genes and spacers was identified. FISH experiments showed that the 5S rRNA bona fide gene repeats were clustered in the interstitial position of two chromosome pairs of H. malabaricus, while the satellite 5SHindIII-DNA sequences were clustered in the centromeric position in nine chromosome pairs of the species. The presence of the 5SHindIII-DNA sequences in the centromeres of several chromosomes indicates that this satellite family probably escaped from the selective pressure that maintains the structure and organization of the 5S rDNA repeats and become disperse into the genome. Although it is not feasible to explain how this sequence has been maintained in the centromeric regions, it is possible to hypothesize that it may be involved in some structural or functional role of the centromere organization.

Karyotype characterization of Mugil incilis Hancock, 1830 (Mugiliformes: Mugilidae), including a description of an unusual co-localization of major and minor ribosomal genes in the family

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic studies in three species of Lutjanus (Perciformes: Lutjanidae: Lutjaninae) from the Isla Margarita, Venezuela

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chromosome Evolution in African Cichlid Fish: Contributions from the Physical Mapping of Repeated DNAs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Characterisation of the chromosome fusions in Oreochromis karongae

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic Mapping of the Retroelements Rex1, Rex3 and Rex6 among Cichlid Fish: New Insights on the Chromosomal Distribution of Transposable Elements

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cytogenetic analysis in the incertae sedis species Astyanax altiparanae Garutti and Britzki, 2000 and Hyphessobrycon eques Steindachner, 1882 (Characiformes, Characidae) from the upper Parana river basin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Karyotype of the cricket, Zucchiella atlantica, with an overview of the chromosomes of the subfamily Nemobiinae

Few reports have been published on cytogenetics in crickets of the subfamily Nemobiinae. Within the Neotropical region the karyotypes of only two species are known, both of them belonging to the genus Phoremia. In the present paper, chromosomes of a third Neotropical species, Zucchiella atlanticaMello 1990 (Orthoptera: Trigonidiidae), have been studied and a cytological review of other species of that subfamily is presented. Zucchiella atlantica shows 2n male = 22 + XO and 2n female = 22 + XX which suggests an ancestral condition within the subfamily as the diploid number in all the species previously studied ranges from 2n male = 7 to 2n female = 21. In Orthoptera those species with high chromosome numbers tend to show reduction in their chromosomal numbers by means of centric fusions rather than to increase chromosomal numbers, due to difficulties in the availability of new centromeres. A structural polymorphism in one chromosome of pair 5 was observed as an intra-individual variation, suggesting differential activity of the genome from cell to cell.

Multiple nucleolus organizer regions in Leptodactylus mystacinus (Amphibia, Anura) and comments on its systematic position in the L fuscus group based on cytogenetic and molecular analyses

Specimens of Leptodactylus mystacinus from Brazil were karyotyped with conventional and differential staining. The 2n = 22 karyotype is similar to that found for the majority of the Leptodactylus, the karyotypic conservatism also confirmed by the similarity of the replication banding patterns with those previously described. L. mystacinus has a small amount of C-banded heterochromatin, located mainly at the centromeres, although telomeric or interstitial bands have also been noticed. With DA/CMA(3) some chromosome regions showed slightly bright fluorescence, and with DA/DAPI, no particular AT-rich repetitive region was observed. Silver staining showed an extensive inter- and intraindividual variation in the number and position of Ag-positive regions, in 1p, 4p, 8p, 8q, and 11p. Nevertheless, FISH using rDNA probes confirmed only the signals on the short arms of chromosomes 4 and 8 as true NORs. The remaining silver stained regions are probably due to the heterochromatin with some affinity to the Ag-staining. Phylogenetic analysis based on partial cytochrome b sequence revealed that L. mystacinus forms a basal branch, so that the presence of multiple NORs in pairs 4 and 8 in this species indicates an autapomorphy.

Karyotypic diversification and its contribution to the taxonomy of Eleocharis (Cyperaceae) from Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Chromosomal imbalances in successive moments of human bladder urothelial carcinoma

Objective: To understand developmental characteristics of urinary bladder carcinomas (UBC) by evaluating genomic alterations and p53 protein expression in primary tumors, their recurrences, and in the morphologically normal urothelium of UBC patients. Methods: Tumors and their respective recurrences, six low-grade and five high-grade cases, provided 19 samples that were submitted to laser microdissection capture followed by high resolution comparative genomic hybridization (HR-CGH). HR-CGH profiles went through two different analyses-all tumors combined or classified according to their respective histologic grades. In a supplementary analysis, 124 primary urothelial tumors, their recurrences, and normal urothelium biopsied during the period between tumor surgical resection and recurrence, were submitted to immunohistochemical analyses of the p53 protein. During the follow-up of at least 21 patients, urinary bladder washes citologically negative for neoplastic cells were submitted to fluorescence in situ hybridization (FISH) to detect copy number alterations in centromeres 7, 17, and 9p21 region. Results and Conclusions: HR-CGH indicated high frequencies (80%) of gains in 11p12 and losses in 16p12, in line with suggestions that these chromosome regions contain genes critical for urinary bladder carcinogenesis. Within a same patient, tumors and their respective recurrences showed common genomic losses and gains, which implies that the genomic profile acquired by primary tumors was relatively stable. There were exclusive genomic alterations in low and in high grade tumors. Genes mapped in these regions should be investigated on their involvement in the urinary bladder carcinogenesis. Successive tumors from same patient did not present similar levels of protein p53 expression; however, when cases were grouped according to tumor histologic grades, p53 expression was directly proportional to tumor grades. Biopsies taken during the follow-up of patients with history of previously resected UBC revealed that 5/15 patients with no histologic alterations had more than 25% of urothelial cells expressing the p53 protein, suggesting that the apparently normal urothelium was genomically unstable. No numerical alterations of the chromosomes 7, 17, and 9p21 region were found by FISH during the periods free-of-neoplasia. Our data are informative for further studies to better understand urinary bladder urothelial carcinogenesis. © 2013 Elsevier Inc.

Estrutura e evolução cariotípica de peixes ciclídeos sul americanos

Pós-graduação em Biologia Geral e Aplicada - IBB

Identificação e caracterização de sequências repetidas de DNA no genoma de peixes ciclídeos do gênero Cichla

Pós-graduação em Biologia Geral e Aplicada - IBB

Mapeamento cromossômico comparativo em peixes ciclícos utilizando sequências repetitivas de DNA

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)