Telomeric sequences localization and G-banding patterns in the identification of a polymorphic chromosomal rearrangement in the rodent Akodon cursor (2n=14, 15 and 16)

Departamento de Biologia, Instituto de Biociências, Universidade de São Paulo, Brazil.
Chromosome Research (Impact Factor: 2.48). 07/1997; 5(4):228-32. DOI: 10.1023/A:1018463401887
Source: PubMed


Akodon cursor is an exceptional example of high chromosomal variability, displaying diploid numbers from 14 to 16 and fundamental numbers (FN) from 18 to 26 as the result of a complex rearrangement in par 1 and pericentric inversions in three autosomal pairs. The difference in the diploid number is due to the presence of a large metacentric pair 1 in the 2n=14 karyotype, a large metacentric 1 and two different submetacentrics (1a and 1b) in 2n=15 and 1a and 1b submetacentric pairs in homozygosis in the 2n = 16 karyotype. Chromosomes 1a and 1b share homology with the short and long arms of the large metacentric 1 respectively. In this paper, evidence based on fluorescence in situ hybridization (FISH) with telomeric sequences and G-banding indicates that pericentric inversions and fusion of chromosomes 1a and 1b are the probable rearrangements giving rise to the large metacentric 1.

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Available from: Valéria Fagundes, Apr 27, 2014
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    • "Additionally, telomeric repeat sequences were also present at nontelomeric sites (interstitial telomeric sequences, ITSs). Interstitial telomeric signals were present in 12 pericentromeric regions, coinciding with CBG bands, in P. lamarum and in pair 4 of Phyllomys sp. 4. The origin of ITs is still debated, but it seems that they may reflect components of the satellite DNA, as described in rodents of the genus Microtus (Rovatsos et al. 2011) or remnants of ancestral chromosome rearrangements, such as inversions and centric or tandem fusions (Meyne et al. 1990; Lee et al. 1993; Fagundes et al. 1997; Svartman and Vianna-Morgante 1998; Pellegrino et al. 1999; Bolzán and Bianchi 2006; Ruiz-Herrera et al. 2008). Only three species of Echimyidae (Proechimys gr. "
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    ABSTRACT: Phyllomys (Echimyidae, Rodentia) is a genus of Neotropical rodents with available cytogenetic data restricted to six out of 13 species, mainly based on simple staining methods, without detailed analyses. In this work, we present new karyotypes for Phyllomys lamarum (diploid number 2n = 56, fundamental number or number of autosomal arms FN = 102) and Phyllomys sp. (2n = 74, FN = 140) from the state of Minas Gerais, southeastern Brazil. We provide the first GTG- and CBG-banding patterns, silver-staining of the nucleolar organizer regions (Ag-NORs), and fluorescence in situ hybridization (FISH) with telomeric and 45S rDNA probes of Phyllomys. In addition to examining their chromosomes and phenotypic characters, we sequenced mitochondrial DNA from the specimens analyzed to confirm their taxonomic identification. The comparison of the distinctive chromosome complements of our specimens with those of other species of Phyllomys already published allowed us to conclude that chromosome data may be very useful for the taxonomy of the genus, as no two species analyzed presented the same diploid and fundamental numbers (2n and FN).
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    • "The ITS sites at centromeres have been described in many different taxonomic groups (Meyne et al. 1990). In some lineages, they were shown to result from retaining the ancestor telomeres after, for example, Robertsonian or tandem fusion/fission (Ventura et al. 2006) or more complex (Fagundes et al. 1997) rearrangements. On the other hand, telomere-like sequences are often present in chromosomes as a component of the satellite DNA (Garrido-Ramos et al. 1998). "
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    • "It is assumed that bulk of interstitial telomeric repeats could be generated by mechanisms such as mutation, unequal crossing-over, transposition, or amplification from intrachromosomal short telomeric sequences (Wiley et al. 1992; Vermeesch et al. 1996; Garagna et al. 1997; Sharma and Sharma 1998). Also, ITSs are considered remnants of chromosomal rearrangements , such as, inversions, centric, or tandem fusions, that occurred during the species' karyotype evolution (Lee et al. 1993; Fagundes et al. 1997; Pellegrino et al. 1999). Recent studies provided evidences that s-ITSs could be produced during the process of DNA double strand breaks repair. "
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