Chromosomal Dynamics in Cercopithecini Studied by Williams-Beuren probe mapping

Chromosomal evolution in the tribe Cercopithecini and in related taxa is highly debated. Uncertainty in reconstruction is mainly related to the great genetic variability and polymorphism of the taxa. Recent molecular and karyological efforts individuate a split between genetically conservative, arbitrarily defined, "terrestrial" guenons and vervets, and genetically variable and derived "arboreal" guenons. We performed the mapping of WS loci probe (7q11.23) in order to verify the chromosomal dynamics of the genomes of three tree-dwelling species of the tribe: C. neglectus, C. mitis mitis, C. albogularis labiatus. Data from literature for the "ground-dwelling" Chlorocebus aethiops sabaeus has been compared with our results. The distribution of the WS probe showed a high genomic dynamics in the different species, with three different pattern of rearrangements. Starting from the ancestral synteny 7 found in Pongo pygmaeus (PPY), the present mapping demonstrates different location of the hybridizations signals. A parsimonious interpretation lead to the hypothesis that a pericentric inversion transformed the PPY orthologous in C. neglectus. The C. mitis and the strictly related C. a. labiatus demonstrate more complex, and derivative, rearrangements. According to the position of the WS signal, and to banding pattern analysis, C. mitis and C. albogoularis, underwent to the pericentric inversion, followed by a paracentric inversion and a successive interstitial fission that fragmented the synteny. Starting from the PPY like orthologous a single and independent event, a centric fission, that did not affect the WS position, occurred in Ch. aethiops producing a Gorilla gorilla like chromosome. Our results confirm the hypothesis that chromosomal dynamics in Cercopithecini proceed by fissions and inversions and indicate the usefulness of the locus specific mapping approach for the identification of intrachromosome rearrangements.