Chromosomal evolution in Rattini (Muridae, Rodentia)

Abstract

The Rattini (Muridae, Murinae) includes the biologically important model species Rattus norvegicus (RNO) and represents a group of rodents that are of clinical, agricultural and epidemiological importance. We present a comparative molecular cytogenetic investigation of ten Rattini species representative of the genera Maxomys, Leopoldamys, Niviventer, Berylmys, Bandicota and Rattus using chromosome banding, cross-species painting (Zoofluorescent in situ hybridization or FISH) and BAC-FISH mapping. Our results show that these taxa are characterised by slow to moderate rates of chromosome evolution that contrasts with the extensive chromosome restructuring identified in most other murid rodents, particularly the mouse lineage. This extends to genomic features such as NOR location (for example, NORs on RNO 3 are present on the corresponding chromosomes in all species except Bandicota savilei and Niviventer fulvescens, and the NORs on RNO 10 are conserved in all Rattini with the exception of Rattus). The satellite I DNA family detected and characterised herein appears to be taxon (Rattus) specific, and of recent origin (consistent with a feedback model of satellite evolution). BACmapping using clones that span regions responsible for the morphological variability exhibited by RNO 1, 12 and 13 (acrocentric/submetacentric) and their orthologues in Rattus species, demonstrated that the differences are most likely due to pericentric inversions as exemplified by data on Rattus tanezumi. Chromosomal characters detected using R. norvegicus and Maxomys surifer whole chromosome painting probes were mapped to a consensus sequencebased phylogenetic tree thus allowing an objective assessment of ancestral states for the reconstruction of the putative Rattini ancestral karyotype. This is thought to have comprised 46 chromosomes that, with the exception of a single pair of metacentric autosomes, were acrocentric in morphology.

Recombination Rates and Genomic Shuffling in Human and Chimpanzee—A New Twist in the Chromosomal Speciation Theory

“…Termed hemiplasy (Avise and Robinson 2008), this hypothesis suggests that derived chromosomal rearrangements may have persisted as polymorphisms across multiple speciation nodes (Robinson et al 2008; Robinson and Ropiquet 2011). This has been the case for chiropteran and afrotherian species (Robinson et al 2008), Perissodactyla (Trifonov et al 2008), Rodentia (Badenhorst et al 2011), Bovidae (Robinson and Ropiquet 2011), and this is also probably true for Primates (Dutrillaux and Couturier 1981; Rumpler et al 2008). Incomplete lineage sorting (when a gene tree is topologically inconsistent with the species tree) has been detected in the human–chimpanzee–gorilla species phylogeny in genome-wide studies (Chen and Li 2001; Patterson et al 2006; Hobolth et al 2011; Scally et al 2012).…”

A High-Resolution Comparative Chromosome Map of <b><i>Cricetus cricetus </i></b>and <b><i>Peromyscus eremicus </i></b>Reveals the Involvement of Constitutive Heterochromatin in Breakpoint Regions

“…On the other hand, paint probes from R. norvegicus have only been used for comparative studies in few Muridae species [Badenhorst et al, 2011;Chaves et al, 2012;Romanenko et al, 2012]. In the present study, both paint probes (MMU and RNO) were used in the construction of the comparative maps for the Cricetidae species C. cricetus and P. eremicus .…”

Chromosomal polymorphism in mammals: an evolutionary perspective

“…In similar fashion, the two Sumatran and Bornean orang‐utan species display the same variability in centromere position on chromosome 12 (see Section ), suggesting that the shared polymorphism may be ∼350–400 kyr old (Locke et al ., ). Other examples may be found in Rodentia with the Asian Rattini showing two fusion/fission polymorphisms that date back minimally to 1.5 and 3.2 Myr, respectively (Badenhorst et al ., ). Moreover, Rattus exulans , R. tanezumi and R. losea were unambiguously shown to share a pericentric inversion polymorphism (Badenhorst et al ., , , and references therein) leading to suggestions that this floating polymorphism has persisted for ∼2.2 Myr (Robins et al ., ; Pagès et al ., ).…”