Chromosomal localization of telomeric sequences in three species of <i>Akodon</i> (Rodentia, Sigmodontinae)

Abstract

The distribution of the vertebrate telomeric sequence T₂AG₃ in three species of the rodent genus Akodon was examined by FISH with a peptide nucleic acid probe. In addition to the expected telomeric hybridization, non-telomeric signals were observed in the three species. In A. dolores, centromeric signals were visible in two of the four biarmed autosome pairs featuring Robertsonian polymorphism, indicating the retention of at least part of the telomeric sequences during the fusion process, and an interstitial signal of lower intensity was observed in the short arm of another. In A. boliviensis, a strong signal was observed near the centromeric end of the first chromosome pair. The first pair of A. azarae (homologous to the first pair of A. boliviensis) showed a similar but markedly amplified signal, and a subcentromeric signal in the X chromosome corresponding to a heterochromatic region; additionally, interstitial signals of lower intensity were present in one to four chromosomes in the majority of cells examined.

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

“…laucha specimens showed a complement of 64 chromosomes formed by 3 biarmed and 28 terminal or subterminal autosomal pairs (AFNϭ68), a submetacentric X and a subterminal Y chromosome, a karyotype basically corresponding to that observed in specimens from Córdoba ( Gardenal et al 1977, Lisanti et al 2004) and several localities of Uruguay and Argentina ( Brum-Zorrilla et al 1990). The metaphase cells of this species not only presented the expected marks at the telomeres, but also showed a remarkable set of signals at non-telomeric positions.…”

“…With respect to heterochromatin content, while C-bands cannot be detected in C. venustus (Lisanti et al 2004), conspicuous pericentric blocks are seen in C. musculinus autosomes and the X (Forcone et al 1980, Lisanti et al 1996, Corach et al 1988. Moderate centric C-bands are also noticed in C. laucha karyotype (Lisanti et al 2004).…”

“…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).…”

“…In Akodon dolores, with Rb polymorphisms of pairs 2 to 5 and another of pair 1 that resembles that of A. cursor (Bianchi et al 1979, Wittouck et al 1995, centromeric ITS are observed only in pairs 4 and 5 (Viera et al 2004). Similarly, 2 cytotypes of the Oryzomys subflavus complex, related by 4 Rb rearrangements, show ITS in only 2 of the 4 biarmed pairs (Andrades-Miranda et al 2002).…”

Chromatin Organization and Remodeling of Interstitial Telomeric Sites During Meiosis in the Mongolian Gerbil (Meriones unguiculatus)

“…The appearance of telomere sequences in inner positions of the chromosomes has been explained as a result of a complex karyotype evolution process, with chromosomal rearrangements such as Rb translocations and amplification of telomeric DNA repeats being the most plausible (Meyne et al 1990;Azzalin et al 2001;Viera et al 2004;Rovatsos et al 2011). The sequences found in the metacentric/submetacentric chromosomes of M. unguiculatus shown here would have probably arisen from Rb translocation events.…”