Comparative genome maps of the pangolin, hedgehog, sloth, anteater and human revealed by cross-species chromosome painting: further insight into the ancestral karyotype and genome evolution of eutherian mammals

To better understand the evolution of genome organization of eutherian mammals, comparative maps based on chromosome painting have been constructed between human and representative species of three eutherian orders: Xenarthra, Pholidota, and Eulipotyphla, as well as between representative species of the Carnivora and Pholidota. These maps demonstrate the conservation of such syntenic segment associations as HSA3/21, 4/8, 7/16, 12/22, 14/15 and 16/19 in Eulipotyphla, Pholidota and Xenarthra and thus further consolidate the notion that they form part of the ancestral karyotype of the eutherian mammals. Our study has revealed many potential ancestral syntenic associations of human chromosomal segments that serve to link the families as well as orders within the major superordinial eutherian clades defined by molecular markers. The HSA2/8 and 7/10 associations could be the cytogenetic signatures that unite the Xenarthrans, while the HSA1/19p could be a putative signature that links the Afrotheria and Xenarthra. But caution is required in the interpretation of apparently shared syntenic associations as detailed analyses also show examples of apparent convergent evolution that differ in breakpoints and extent of the involved segments.