A Short Introduction to Cytogenetic Studies in Mammals with Reference to the Present Volume

Abstract

Genome diversity has long been studied from the comparative cytogenetic perspective. Early workers documented differences between species in diploid chromosome number and fundamental number. Banding methods allowed more detailed descriptions of between-species rearrangements and classes of differentially staining chromosome material. The infusion of molecular methods into cytogenetics provided a third revolution, which is still not exhausted. Chromosome painting has provided a global view of the translocation history of mammalian genome evolution, well summarized in the contributions to this special volume. More recently, FISH of cloned DNA has provided details on defining breakpoint and intrachromosomal marker order, which have helped to document inversions and centromere repositioning. The most recent trend in comparative molecular cytogenetics is to integrate sequencing information in order to formulate and test reconstructions of ancestral genomes and phylogenomic hypotheses derived from comparative cytogenetics. The integration of comparative cytogenetics and sequencing promises to provide an understanding of what drives chromosome rearrangements and genome evolution in general. We believe that the contributions in this volume, in no small way, point the way to the next phase in cytogenetic studies.

Tracing the evolution of amniote chromosomes

“…However, in the study of mammal chromosome evolution, most effort has been placed into determining how the genomes of the karyotypically diverse eutherian mammals have changed since their radiation approximately105 MYA. This is because comparisons with the other two mammalian lineages were impossible using cross-species chromosome painting (Graphodatsky et al 2012). As a consequence, most studies have focused on reconstructing the eutherian or boreoeutherian ancestral karyotype, rather than on that of the ancestor to all mammals.…”

“…Such comparisons have shown that some of the associated segments revealed by chromosome painting amongst eutherian species represent an ancestral organization present in marsupials and even in chicken and the green anole. These associations include the association of segments from human chromosomes 4/8, 12/22, 14/15 and 16/19 (Graphodatsky et al 2012). The initial attempts made to reconstruct ancestral karyotypes purely from genome sequence comparisons for just a few eutherian species and using chicken as an outgroup, resulted in ‘mammalian’ ancestral karyotypes consisting of 2 n  = 42 (Bourque et al 2005; International Chicken Genome Sequencing C 2004).…”

“…For instance, chromosome paints generated from eutherian species (e.g. humans) fail to detect homology with marsupial or monotreme chromosomes (Graphodatsky et al 2012) and therefore, ancestral karyotype reconstructions based solely on eutherian chromosome painting data are restricted to the eutherian lineage. Interestingly, a greater evolutionary depth is possible in the reptilian lineage, with chromosome probes derived from chicken able to detect homology to crocodile, turtle and lizard species (Kasai et al 2012; Pokorna et al 2012; Pokorna et al 2011), which last shared a common ancestor over 200 million years ago (MYA).…”

Comparative Chromosome Painting in Genets (Carnivora, Viverridae, <b><i>Genetta</i></b>), the Only Known Feliforms with a Highly Rearranged Karyotype

“…Those will contribute to clarify unresolved taxonomic problems in genets, allow reconstructing the chromosomal phylogeny of Genetta , and enable to assess some of the findings and hypotheses in this study. Further surveys should combine comparative chromosome painting with whole-genome sequencing, which permits more refined genome comparisons [Graphodatsky et al, 2012;Le Scouarnec and Gribble, 2012;Warren et al, 2015].…”

Chromosomes of Iberian Leuciscinae (Cyprinidae) Revisited: Evidence of Genome Restructuring in Homoploid Hybrids Using Dual-Color FISH and CGH

“…Linking cytogenetic to genetic data was greatly enhanced after cytogenetics became a molecular science, allowing looking for the 'signature' of evolutionary processes in the 'chromosomics' era sensu Claussen [2005]. This role was reaffirmed with the culmination of genetic-based approaches and next generation sequencing technologies [Speicher and Carter, 2005;Dobigny and Yang, 2008;Graphodatsky et al, 2012]. Fish biologists, however, have seldom engaged in multidimensional studies including cytogenetic examination to address similar questions [e.g.…”