Non-telomeric sites as evidence of chromosomal rearrangement and repetitive (TTAGGG)_narrays in heterochromatic and euchromatic regions in four species of <i>Akodon</i> (Rodentia, Muridae)

Abstract

Comparative studies among four species – Akodonazarae (2n = 38), A. lindberghi (2n = 42), A. paranaensis (2n = 44) and A. serrensis (2n = 46) – employing classic cytogenetics (C- and G-bands) and fluorescence in situ hybridization with telomeric (TTAGGG)_n sequencesare reported here. Non-telomeric signals in addition to the regular telomeric sites were detected in three species:A. azarae, A. lindberghi and A. serrensis. One interstitial telomeric site (ITS) was observed proximally at the long arm of chromosome 1 of A. azarae. The comparison of G-banding patterns among the species indicated that the ITS was due to a tandem fusion/fission rearrangement. Non-telomeric signals of A. lindberghi and A. serrensis were not related to chromosomal rearrangements; instead, the sequences co-localized with (i) heterochromatic regions of all chromosomes in A. serrensis; (ii) some heterochromatic regions in A. lindberghi, and (iii) both euchromatic and heterochromatic regions in the metacentric pair of A. lindberghi. These exceptional findings revealed that ITS in Akodon can be related to chromosomal rearrangements and repetitive sequences in the constitutive heterochromatin and that the richness of TTAGGG-like sequences in the euchromatin could be hypothesized to be a result of amplification of the referred sequence along the chromosome arms.

Discrimination of 2n = 60 <i>Spalax leucodon</i> cytotypes (Spalacidae, Rodentia) in Turkey by means of classical and molecular cytogenetic techniques

“…However, disclosing of large blocks of telomeric sequences within C-negative pericentromeric regions of acrocentric chromosomes is evidence for the occurrence of co-localization of the telomeric sequences with euchromatin material. A similar phenomenon has been described for chromosomes of Brazilian rodents of the genus Akodon and was explained by the presence of TTAGGG-like sequences in such euchromatin regions (Ventura et al, 2006).…”

Comparison of the Chromosome Structures between the Chicken and Three Anserid Species, the Domestic Duck (<i>Anas platyrhynchos</i>), Muscovy Duck (<i>Cairina moschata</i>), and Chinese Goose (<i>Anser cygnoides</i>), and the Delineation of their Karyotype Evolution by Comparative Chromosome Mapping

“…These non-telomeric sites of (TTAGGG)n repeats and the colocalization of telomeric repeats and satellite DNA sequences are most likely the result of chromosome rearrangements involving the chromosome ends (including inversions, centric fusion, and telomere-to-telomere fusion) (Go et al, 2000;Li et al, 2000;Lear, 2001;Hartmann and Scherthan, 2004;Ventura et al, 2006;Tsipouri et al, 2008). In addition, sequence analysis of ITSs revealed that the interstitial arrays of (TTAGGG)n repeats could be inserted at intrachromosomal sites through double-strand breaks in ancient chromosomes (Azzalin et al, 2001;Nergadze et al, 2004).…”

Localization of Telomeric Sequences in the Chromosomes of Three Species of Calomys (Rodentia, Sigmodontinae)

“…Concerning sigmodontine rodents, no ITS reflect the remarkable rearrangements that relate Akodon cursor and A. montensis (Fagundes et al 1997b), or this species and the more distant Bolomys lasiurus (Fagundes and Yonenaga-Yassuda 1998), nor show ITS the chromosomes that result from tandem fusions in Nectomys (Silva and Yonenaga-Yassuda 1998). On the other hand, the homeologous telocentric first pairs of A. azarae and A. boliviensis, which present a noticeable proximal IT (Viera et al 2004, Ventura et al 2006, correspond to pairs 1 plus 20 of A. paranaensis and A. serrensis (Ventura et al 2006).…”