Comparative Genomic In Situ Hybridization and the Possible Role of Retroelements in the Karyotypic Evolution of Three Akodontini Species

Abstract

South American Akodontini rodents are characterized by a large number of chromosome rearrangements. Among them, the genus Akodon has been extensively analyzed with classical and molecular cytogenetics, which allowed the identification of a large number of intra- and interspecific chromosomal variation due to Robertsonian rearrangements, pericentric inversions, and heterochromatin additions/deletions. In order to shed some light on the cause of these rearrangements, we comparatively analyzed the karyotypes of three Akodontini species, Akodon cursor (2n = 14, FN = 19), A. montensis (2n = 24, FN = 42), and Necromys lasiurus (2n = 34, FN = 34), after GTG- and CBG-banding. The karyotypes differed by Robertsonian rearrangements, pericentric inversions, centromere repositioning, and heterochromatin variation. Genome comparisons were performed through interspecific fluorescent in situ hybridization (FISH) with total genomic DNAs of each species as probes (GISH). Our results revealed considerable conservation of the euchromatic portions among the three karyotypes suggesting that they mostly differ in their heterochromatic regions. FISH was also performed to assess the distribution of telomeric sequences, long and short interspersed repetitive elements (LINE-1 and B1 SINE) and of the endogenous retrovirus mysTR in the genomes of the three species. The results led us to infer that transposable elements have played an important role in the enormous chromosome variation found in Akodontini.

SINE-B1 Distribution and Chromosome Rearrangements in the South American <b><i>Proechimys</i></b> gr. <b><i>goeldii</i></b> (Echimyidae, Rodentia)

“…GTG-and CBG-banding and silver-staining of the nucleolus organizer regions (Ag-NORs) were carried out according to Seabright [1971], Sumner [1972], and Howell and Black [1980], respectively. FISH with a biotinylated telomeric sequence (Invitrogen) and the R2 45S rDNA probe labeled by nick translation with digoxigenin-11-dUTP (DIG-Nick Translation mix, Roche Applied Science) was performed following Araújo et al [2017] and Araújo et al [2014], respectively. Immunodetection was carried out with neutravidin or anti-digoxigenin, both conjugated with rhodamine (Roche Applied Science).…”

“…SINE-B1 also represents a considerable fraction of the Rattus norvegicus genome [Gibbs et al, 2004]. Chromosome mapping of these elements also revealed their great abundance in some rodents of the Cricetidae family [Acosta et al, 2008;Araújo et al, 2017]. A functional SINE-B1 is approximately 150 bp long and is located in GC-rich regions of the M. musculus genome [Boyle et al, 1990;Mouse Genome Sequencing Consortium, 2002].…”

“…Despite their wide occurrence and importance in genome structure and evolution, the distribution patterns of transposable elements on rodent chromosomes have been poorly investigated [e.g., Boyle et al, 1990;Rinehart et al, 2005;Acosta et al, 2008;Araújo et al, 2017]. Data from chromosome mapping of SINE-B1 in Rodentia have been described in only a few species belonging to the families Cricetidae (genera Akodon, Chionomys, Microtus, and Necromys [Acosta et al, 2008;Araújo et al, 2017]) and Muridae (genus Mus [Boyle et al, 1990]). The few genera investigated are far from representing the huge variety of rodent species and their impressive karyotypic plasticity.…”

Insights into Emydid Turtle Cytogenetics: The European Pond Turtle as a Model Species

“…Karyotype numbering was done as described by Bickham and Baker [1976a]. Amplification of 18S rDNA probes labeled with digoxigenin-dUTP and telomere hybridizations were performed as reported in Kretschmer et al [2018] and Araújo et al [2017], respectively. CGH to test for the presence of a cryptic GSD system followed Badenhorst et al [2013].…”

Cytogenetic analyses in Trinomys (Echimyidae, Rodentia), with description of new karyotypes

“…GTG- and CBG-banding patterns and silver-staining of the nucleolar organizer regions (Ag-NORs) were performed according to Seabright (1971) , Sumner (1972) , and Howel & Black (1980) , respectively. FISH with a biotinylated telomeric sequence (Invitrogen, Carlsabad, CA, USA) and with the R2 45S rDNA probe labeled by nick translation with digoxigenin-11-dUTP (DIG-Nick Translation mix; Roche Applied Science, Penzberg, Germany), followed Araújo et al (2017) ; Araújo et al (2014) , respectively. Immunodetection was carried out with neutravidin and antidigoxigenin, both conjugated with rhodamine (Roche Applied Science).…”