New occurrence of a macro B-chromosome in Astyanax scabripinnis paranae (Pisces, Characiformes, Characidae)

Cytogenetic studies performed on 17 specimens (11 females and six males) of Astyanax scabripinnis paranae from the Cascatinha stream showed that this population has 2n = 50 chromosomes (8M + 22SM + 10ST + 10A), two chromosome pairs with NORs and conspicuous C-band positive blocks in the terminal position of the long arm of five chromosome pairs. Three females presented 2n = 51 chromosomes and the extra chromosome was a large metacentric similar in size and morphology to the first chromosome pair in the karyotype. This accessory chromosome was entirely heterochromatic in C-banded metaphases, which permitted its classification as a supernumerary chromosome. Some aspects related to the morphology of such macro B-chromosomes are discussed.

First cytogenetic description of the species Rhamdella microcephala (Pisces, Hepapteridae)

Cytogenetic studies were carried out on Rhamdella microcephala collected from the headwaters of the Machado river, a tributary of the Sapucaí river, Minas Gerais, Brazil. Sixteen specimens exhibited 2n=56 chromosomes, with 18 metacentrics, 30 submetacentrics and 8 subtelocentric-acrocentrics (FN=84). The nucleolar organizing regions (NORs) were identified in the interstitial position on the long arm of a submetacentric pair (pair 12). Chromomycin A3 staining evidenced only the NOR-bearing segments. Positive C-band segments were identified in a pericentromeric position in most of the chromosomes and the NOR-bearing segments were also C-band positive. Some aspects related to the chromosomal characteristics of Rhamdella microcephala are discussed.

Short interspersed repetitive elements (SINEs) from the cichlid fish, Oreochromis niloticus, and their chromosomal localization by fluorescent in situ hybridization

In the present study, we describe the cloning and characterization of a new SINE-like element from O. niloticus (ROn-2) and show the distribution of this SINE and a previously isolated SINE, ROn-1, in the chromosomes of O. niloticus. The ROn-2 element is 359 base pairs (bp) in length, contains short direct terminal repeats, a tRNA-related region similar to tRNA Val and tRNA Arg, a tRNA-unrelated region, and a poly-A tail. Analysis of the chromosomal distribution of ROn-1 and ROn-2 by fluorescent in situ hybridization showed that both SINE sequences are present in all chromosomes of tilapia, and organized in small clusters. The only exception was a large cluster of ROn-1 repeats found in the middle of the long arm of chromosome 1. In view of our data we discuss the hypothesis that the absence of large clusters of SINE sequences and the structural composition of these sequences may explain the absence of base-specific fluorochrome bands in the chromosomes of tilapia.

Chromosome localization of the ribosomal genes 18S and 5S in four stocks of rainbow trout (Oncorhynchus mykiss) from cultivated and naturalized stocks in Brazil

In the present study, fluorescence in situ hybridization (FISH) was employed to determine the chromosomal location of genes 18S rDNA and 5S rDNA in four rainbow trout stocks. In specimens from the stocks of Núcleo Experimental de Salmonicultura de Campos do Jordão and Gavião river, 18S genes were located at a subterminal position in the long arms of two submetacentric chromosomes, whereas in specimens from stocks of Mount Shasta and Teresópolis they were found in the short arms. In all analyzed stocks, 5S genes were located in two chromosome pairs. In a subtelocentric pair, 5S genes were present in the short arms and, in the other submetacentric pair, 5S genes were at an interstitial position. In the latter, 18S and 5S genes were contiguous. Taking into account that both 18S and 5S rDNA genes have been localized in the short arm of a submetacentric chromosome in almost all rainbow trout samples so far studied, the presence of such genes in the long arm, as seen in the samples from Núcleo Experimental de Salmonicultura de Campos do Jordão and Gavião river, supports the hypothesis of a pericentric inversion involving this chromosome segment in the ancestor line of these stocks. The observed polymorphism allowed the identification of a very useful genomic marker, and may therefore constitute an important tool in the genetic management of rainbow trout stocks.

First chromosome characterization in the neotropical eel, Gymnothorax ocellatus (Pisces, Muraenidae)

Cytogenetics studies in 12 specimens of Gymnothorax ocellatus reveled a diploid chromosome number of 2n=42 (16 metacentrics, 18 submetacentrics and 8 acrocentrics). The nucleolar organizer regions were located in a terminal position on the long arm of the chromosome pair number fifteen. Conspicuous blocks of constitutive heterochromatin were observed in the centromeric and pericentromeric regions of some chromosome pairs. The results obtained are similar to those previously described for others species of this family. However, the cytogenetic informations may be useful in the identification of a possible variety of this species in Brazilian coast and contribute to the understanding of relationships among the species and the process of diversification which occurred in this group. © 2005 The Japan Mendel Society.

The karyotype of Scoloplax distolothrix (Teleostei: Siluriformes: Scoloplacidae)

The karyotype of a fish species belonging to the family Scoloplacidae, Scoloplax distolothrix, is described for the first time. Cytogenetic studies showed that this species has 2n=50 chromosomes, 18 metacentrics, 18 submetacentrics, 10 subtelocentrics and 4 acrocentrics. The Ag-NORs are restricted to a single large metacentric pair in the interstitial position on the long arm. © 2006 The Japan Mendel Society.

Chromosomes of Crossopriza lyoni (Blackwall 1867), intraindividual numerical chromosome variation in Physocyclus globosus (Taczanowski 1874), and the distribution pattern of NORs (Araneomorphae, Haplogynae, Pholcidae)

Pholcidae (Haplogynae) encompasses 967 described species, of which only 14 have been cytogenetic analyzed. Several chromosomal features have already been described including presence of meta- and sub-metacentric chromosomes and sex determination chromosome system (SDCS) of the X, X1X2Y, and X1X2 types, which contrast with the telo- and acrocentric chromosomes and SDCS of the X1X2 type typical of entelegyne spiders. To obtain further cytogenetic information for the family, we examined two pholcid species, Crossopriza lyoni (Blackwall 1867) and Physocyclus globosus (Taczanowski 1874) using both conventional staining and silver staining techniques. Crossopriza lyoni exhibited 2n = 23 = 22 + X in males and 2n = 24 = 22 + XX in females, while P. globosus showed 2n = 15 = 14 + X and 4n = 30 = 28 + 2X, both in male adults, 2n = 16 = 14 + XX in female adults and embryos, and 2n = 15 = 14 + X in male embryos. Both species revealed predominately metacentric and submetacentric chromosomes and a SDCS of the X/XX type. The cytogenetic data obtained in this work and those already recorded for C. lyoni indicate interpopulational and intraspecific numerical chromosome variation, suggesting the presence of chromosomal races or cytotypes in this species. The intraindividual numerical chromosome variation observed in male adult specimens of P. globosus may be explained by the presence of cytoplasmatic bridges between germ cells. The use of the silver staining technique to reveal the nucleolar organizer region (NOR) showed that chromosome pairs 4 and 6 and the X chromosome in C. lyoni are telomeric NOR-bearers, and that the chromosome pair 2 in P. globosus possesses a proximal NOR in the long arm.

Subtelomeric region of chromosome 2 in patients with autism spectrum disorders

Autism spectrum disorders are severe psychiatric diseases commonly identified in the population. They are diagnosed during childhood and the etiology has been much debated due to their variations and complexity. Onset is early and characterized as communication and social interaction disorders and as repetitive and stereotyped behavior. Austistic disorders may occur together with various genetic and chromosomal diseases. Several chromosomal regions and genes are implicated in the predisposition for these diseases, in particular those with products expressed in the central nervous system. There are reports of autistic and mentally handicapped patients with submicroscopic subtelomeric alterations at the distal end of the long arm of chromosome 2. Additionally, there is evidence that alterations at 2q37 cause brain malformations that result in the autistic phenotype. These alterations are very small and not identified by routine cytogenetics to which patients are normally submitted, which may result in an underestimation of the diagnosis. This study aimed at evaluating the 2q37 region in patients with autistic disorders. Twenty patients were studied utilizing the fluorescence in situ hybridization technique with a specific probe for 2q37. All of them were also studied by the GTC banding technique to identify possible chromosomal diseases. No alterations were observed in the 2q37 region of the individuals studied, and no patient presented chromosomal diseases. This result may be due to the small sample size analyzed. The introduction of routine analysis of the 2q37 region for patients with autistic disorders depends on further studies. ©FUNPEC-RP.

Are NORs Always Located on Homeologous Chromosomes? A FISH Investigation with rDNA and Whole Chromosome Probes in Gymnotus Fishes (Gymnotiformes)

Gymnotus (Gymnotiformes, Gymnotidae) is the most diverse known Neotropical electric knife fish genus. Cytogenetic studies in Gymnotus demonstrate a huge karyotypic diversity for this genus, with diploid numbers ranging from 34 to 54. The NOR are also variable in this genus, with both single and multiple NORs described. A common interpretation is that the single NOR pair is a primitive trait while multiple NORs are derivative. However this hypothesis has never been fully tested. In this report we checked if the NOR-bearing chromosome and the rDNA site are homeologous in different species of the genus Gymnotus: G. carapo (2n = 40, 42, 54), G. mamiraua (2n = 54), G. arapaima (2n = 44), G. sylvius (2n = 40), G. inaequilabiatus (2n = 54) and G. capanema (2n = 34), from the monophyletic group G. carapo (Gymnotidae-Gymnotiformes), as well as G. jonasi (2n = 52), belonging to the G1 group. They were analyzed with Fluorescence in situ hybridization (FISH) using 18S rDNA and whole chromosome probes of the NOR-bearing chromosome 20 (GCA20) of G. carapo (cytotype 2n = 42), obtained by Fluorescence Activated Cell Sorting. All species of the monophyletic G. carapo group show the NOR in the same single pair, confirmed by hybridization with CGA20 whole chromosome probe. In G. jonasi the NORs are multiple, and located on pairs 9, 10 and 11. In G. jonasi the GCA20 chromosome probe paints the distal half of the long arm of pair 7, which is not a NOR-bearing chromosome. Thus these rDNA sequences are not always in the homeologous chromosomes in different species thus giving no support to the hypothesis that single NOR pairs are primitive traits while multiple NORs are derived. The separation of groups of species in the genus Gymnotus proposed by phylogenies with morphologic and molecular data is supported by our cytogenetic data. © 2013 Milhomem et al.

Comparative cytogenetic analysis of some species of the Dendropsophus microcephalus group (Anura, Hylidae) in the light of phylogenetic inferences

Background: Dendropsophus is a monophyletic anuran genus with a diploid number of 30 chromosomes as an important synapomorphy. However, the internal phylogenetic relationships of this genus are poorly understood. Interestingly, an intriguing interspecific variation in the telocentric chromosome number has been useful in species identification. To address certain uncertainties related to one of the species groups of Dendropsophus, the D. microcephalus group, we carried out a cytogenetic analysis combined with phylogenetic inferences based on mitochondrial sequences, which aimed to aid in the analysis of chromosomal characters. Populations of Dendropsophus nanus, Dendropsophus walfordi, Dendropsophus sanborni, Dendropsophus jimi and Dendropsophus elianeae, ranging from the extreme south to the north of Brazil, were cytogenetically compared. A mitochondrial region of the ribosomal 12S gene from these populations, as well as from 30 other species of Dendropsophus, was used for the phylogenetic inferences. Phylogenetic relationships were inferred using maximum parsimony and Bayesian analyses.Results: The species D. nanus and D. walfordi exhibited identical karyotypes (2n = 30; FN = 52), with four pairs of telocentric chromosomes and a NOR located on metacentric chromosome pair 13. In all of the phylogenetic hypotheses, the paraphyly of D. nanus and D. walfordi was inferred. D. sanborni from Botucatu-SP and Torres-RS showed the same karyotype as D. jimi, with 5 pairs of telocentric chromosomes (2n = 30; FN = 50) and a terminal NOR in the long arm of the telocentric chromosome pair 12. Despite their karyotypic similarity, these species were not found to compose a monophyletic group. Finally, the phylogenetic and cytogenetic analyses did not cluster the specimens of D. elianeae according to their geographical occurrence or recognized morphotypes.Conclusions: We suggest that a taxonomic revision of the taxa D. nanus and D. walfordi is quite necessary. We also observe that the number of telocentric chromosomes is useful to distinguish among valid species in some cases, although it is unchanged in species that are not necessarily closely related phylogenetically. Therefore, inferences based on this chromosomal character must be made with caution; a proper evolutionary analysis of the karyotypic variation in Dendropsophus depends on further characterization of the telocentric chromosomes found in this group. © 2013 Medeiros et al.; licensee BioMed Central Ltd.

Análise citogenética e molecular do gene FOXO3 em síndrome mielodisplásica

Pós-graduação em Genética - IBILCE

Origem, herança e estrutura dos cromossomos supranumerários no gênero Prochilodus (Characiformes, Prochilodontidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estrutura molecular e citogenética de cromossomos B em Astyanax paranae (Characiformes, Characidae)

Pós-graduação em Ciências Biológicas (Genética) - IBB

A rare non-Robertsonian translocation involving chromosomes 15 and 21

CONTEXTO:Translocações robertsonianas (TR) estão entre os rearranjos estruturais balanceados mais comuns em humanos e compreendem a fusão da cromatina completa do braço longo de dois cromossomos acrocêntricos. No entanto, são raras as translocações não Robertsonianas envolvendo esses cromossomos.RELATO DE CASO:Nós descrevemos uma translocação não balanceada de novo envolvendo os cromossomos 15 e 21. A recém-nascida era filha de uma mãe de 29 anos e de um pai de 42 anos, casal não consanguíneo. Os achados clínicos levaram ao diagnóstico de síndrome de Down (SD) com defeitos cardíacos congênitos graves (persistência do canal arterial e defeito do septo atrioventricular completo), além de baixos comprimento e peso ao nascimento (< 5o e < 10o percentil em curvas de medidas específicas para SD, respectivamente). A análise citogenética convencional revelou o cariótipo 46,XX,der(15)(15pter→15q26.2

Chromosomal mapping of two Mariner-like elements in the grasshopper Abracris flavolineata (Orthoptera: Acrididae) reveals enrichment in euchromatin

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