Exploring evolution in Ceboidea (Platyrrhini, Primates) by Williams-Beuren probe (HSA 7q11.23) chromosome mapping

The ancestral platyrrhine karyotype was characterised by a syntenic association (that is whole chromosomal homology) of human 5 and a small segment of human 7 orthologues. This large syntenic association has undergone numerous rearrangements in various phylogenetic lines. We used a locus-specific molecular cytogenetic approach to study the chromosomal evolution of the human 7q11.23 orthologous sequences (William- Beuren syndrome, WS) in various Ceboidea (Platyrrhini) species. The fluorescent in situ hybridisation of the WS probe revealed a two-way pattern of chromosomal organization that suggests various evolutionary scenarios. The first pattern (seen in Callimico and Saimiri) includes a fairly simple disruption of the 7/5 syntenic association by a chromosome fission. The second pattern (seen in Atelinae, Alouattinae and in Callicebus) is characterised by an increasing complexity in the 7/5 association as a consequence of a series of inversions and translocations resulting in different syntenic associations. These data support recent proposals for phylogenomic groupings of New World monkeys. The study also illustrates how single-locus probe hybridisations can reveal intrachromosomal rearrangements.