Evolutionary Molecular Cytogenetics of Catarrhine Primates: Past, Present and Future

Abstract

The catarrhine primates were the first group of species studied with comparative molecular cytogenetics. Many of the fundamental techniques and principles of analysis were initially applied to comparisons in these primates, including interspecific chromosome painting, reciprocal chromosome painting and the extensive use of cloned DNA probes for evolutionary analysis. The definition and importance of chromosome syntenies and associations for a correct cladistics analysis of phylogenomic relationships were first applied to catarrhines. These early chromosome painting studies vividly illustrated a striking conservation of the genome between humans and macaques. Contemporarily, it also revealed profound differences between humans and gibbons, a group of species more closely related to humans, making it clear that chromosome evolution did not follow a molecular clock. Chromosome painting has now been applied to more that 60 primate species and the translocation history has been mapped onto the major taxonomic divisions in the tree of primate evolution. In situ hybridization of cloned DNA probes, primarily BAC-FISH, also made it possible to more precisely map breakpoints with spanning and flanking BACs. These studies established marker order and disclosed intrachromosomal rearrangements. When applied comparatively to a range of primate species, they led to the discovery of evolutionary new centromeres as an important new category of chromosome evolution. BAC-FISH studies are intimately connected to genome sequencing, and probes can usually be assigned to a precise location in the genome assembly. This connection ties molecular cytogenetics securely to genome sequencing, assuring that molecular cytogenetics will continue to have a productive future in the multidisciplinary science of phylogenomics.

The genome of the vervet (Chlorocebus aethiops sabaeus)

“…The vervet karyotype contains seven additional autosomes compared to the inferred ancestral catarrhine karyotype (Finelli et al 1999;Stanyon et al 2012). To discern whether vervets also display more frequent smaller-scale rearrangements, we first conducted a comparative analysis of total interspersed repeats, then performed detailed comparisons of synteny between the vervet genome and those of human and rhesus macaque.…”

“…A previous report used chromosome painting to compare the human karyotype with those of several catarrhine species, including vervet (Stanyon et al 2012). We conducted a higher resolution molecular cytogenetic comparison of the vervet, rhesus macaque, and human karyotypes, narrowing each breakpoint region through reiterative FISH experiments.…”

“…The Old World monkey (OWM) ancestor had 46 chromosomes; several rearrangements have increased the vervet diploid chromosome count to 60 (Stanyon et al 2012). A detailed summary of the recent evolutionary history of each vervet chromosome with respect to rhesus macaque and human is included at http://www.biologia.uniba.it/ vervet/.…”

“…ENCs are typically discovered while performing chromosomal marker order comparison, usually by FISH, among closely related species (Stanyon et al 2012). Nine ENCs were reported as shared by all OWM species and are OWMspecific, based on human and rhesus macaque studies (Ventura et al 2007).…”

“…The vervet genome differs from most other primate genomes in its higher chromosome number (2n = 60), which mainly reflects chromosome breakages (Finelli et al 1999;Jasinska et al 2007). Seven chromosome fission events resulted in 29 vervet autosomes, compared to 21 or 22 in most other catarrhines (Stanyon et al 2012). With few exceptions, such as the gibbon (Carbone et al 2014) and owl monkey (Ruiz-Herrera et al 2005), primate chromosomes reveal little change from the inferred ancestral karyotype.…”