The Evolution of Human Chromosome 7 Syntenies in Eutheria, with Special Attention to Primates

Genetic and cytogenetic comparison in between man and non-human primates has largely contributed to the knowledge of the evolution of the Order Primates, and in particular of man. Recently, the “Chromosome painting” approach indicated a strong conservation of syntenies in Eutheria. At present, a more precise identification of breakpoints and evolutionary related rearrangements can be obtained by BAC and locus specific in situ hybridisation. In spite to this situation the evolutionary history of different human autosomes remains a dilemma; at the same time, high resolution banded chromosome analysis confirms to be a valuable tool for the preliminary detection of fine rearrangements. This review critically describes current information concerning the evolution of human chromosome 7 orthologous in several Eutherian groups. Included in this analysis are data on species belonging to 11 orders. Nevertheless, this study has been mainly focused on Primates were we considered data from 9 species of Prosimians, 25 species of Platirrhinae, and 51 species of Catarrhinae. Chromosome 7 synteny appeared in a mammalian ancestor in a dual form, generally described as 7a and 7b forms. These chromosomes underwent to several linespecific rearrangements in the different orders. A particular complexity in chromosome rearrangements has been highlighted in Primates. A chronologically fossil-tuned dynamic of the synteny is proposed, starting from classical and molecular cytogenetics specific landmarks which appeared throughout evolution.