Evolution of the Human chromosome 7: new information from the mapping of William-Breuren locus on non human primates chromosomes.

Abstract

Human chromosome 7 (HSA7) derives, by a pericentric inversion and a paracentric inversion, from an ancestral chromosome homologous to chromosome 10 of Pongo pygmaeus (the Asiatic Orang-Utan). Nevertheless the genesis of this autosome during primates evolution is not clear. Even if chromosome painting shows that HAS 7 synteny is highly conserved, GTG-banding comparison in Hominoidea and Cercopithecoidea indicates the probable occurrence of complex rearrangements during the evolution. In this study we used a single locus FISH approach, a powerful tool to detect fine rearrangements, in order to investigate the evolution of HAS 7. We report the chromosome mapping of Williams-Beuren syndrome locus (WS - HSA 7q11.23) on Macaca fascicularis (MFA), Cercopithecus (Chlorocebus) aethiops (CAE) and Trachypithecus cristatus (TCR) (Cercopithecoidea, Primates). The probe hybridises on all species tested and demonstrates the occurrence of rearrangements like fusion, fission and pericentric plus paracentric inversions respectively in MFA, CAE and TCR. Together with the first chromosome mapping of WS locus in Cercopithecoidea, this study confirms that single locus mapping is a very efficacious tool for the analysis of chromosomal rearrangements as it gave the opportunity to have a fine molecular confirmation to proposed banding patterns homologies.