Cytogenetic and molecular analysis of the satellite DNA of the genusCtenomys (Rodentia Octodontidae) from Uruguay

Abstract

The genus of subterranean rodents Ctenomys presents the widest range of variability in diploid number among mammals (from 2n = 10 to 2n = 70). In Uruguay, this variability is observed in karyotypes with 2n = 44, 50 or 58 and two geographically isolated populations with 70 chromosomes but different karyotypic structure. The last three populations were analyzed in the present study. They present a satellite DNA, which was isolated from genomic DNA after AluI digestion. In situ hybridization showed that this satellite DNA is located in the centromeric region of a few chromosomes, coincident with Hoechst 33258 staining and C-banding patterns. A similar satellite DNA was detected in Argentinian species of this genus. We established that, in spite of differences in number of positive heterochromatic blocks per karyotype, the C value is the same in the three populations studied. The nature and possible evolutionary path of this repeated DNA is discussed.

Karyotypic and molecular polymorphisms in Ctenomys torquatus (Rodentia: Ctenomyidae): taxonomic considerations

“…Finally, we must take into account the combined action of chance events and selection, since the population structure of Ctenomys shows a wide variability, from small deme subdivision to colonies (Villar et al 2005). Nevertheless, one of the striking facts in Ctenomys karyotypic evolution is the conservation of DNA content (Ruedas et al 1992;Novello et al 1996), in spite of the variation in chromosome number. The stability of DNA content could reflect the maintenance of the same genome in different chromosomes, in order to maintain linkage groups, since Robertsonian rearrangements are the main changes observed in Ctenomys evolution (Villar et al 2005).…”

“…Population structure characteristics are frequently invoked to explain the origin of chromosome rearrangements in subterranean rodents, through the action of genetic drift (Nevo et al 1994;Novello et al 1996). However, no direct evidence of such events has been presented (but see Nevo et al 1997).…”

G-banding patterns of the genusCtenomysfrom Uruguay (Rodentia Ctenomydae): high karyotype variation but chromosome arm conservation

“…Chromosomal differentiation in this genus also includes a high degree of variation in the amount and localization of heterochromatin, ranging from positive C-bands in the centromeric area of few chromosomes, to karyotypes showing heterochromatic short arms in the whole chromosomes (Rossi et al 1995;Novello et al 1996). These patterns were confirmed in Uruguayan populations.…”

“…The major satellite DNA of tuco-tucos, named RPCS (repetitive PuvII Ctenomys sequence), is organized in long arrays of 348 bp monomer units (Novello et al 1988;Rossi et al 1990). In situ hybridization showed that RPCS mainly localizes in different chromosomal regions positive for C-banding: whole arms and pericentromeric blocks, as well as telomeric and interstitial bands (Rossi et al 1993;Novello et al 1996) in mitotic and meiotic cells (Novello and Villar 2006).…”

High levels of polymorphism found through cross-amplification of microsatellite loci in a Ctenomys pearsoni (Rodentia, Ctenomyidae) population

“…Typically, these animals prefer living along the banks or near the mouths of rivers (Altuna, 1983;Lessa and Langguth, 1983;Altuna et al, 1999). Moreover, this species is characterized by having the highest levels of karyotypic variation at intra-and inter-population levels (Reig et al, 1990;Novello et al, 1990Novello et al, , 1996Villar et al, 2005) that is incongruent with the low levels of morphological and molecular variation observed among populations (D'Anatro and D'Elía, 2011).…”