Integrating large-scale phylogenetic datasets to dissect the ancient evolutionary history of vertebrate genome

- Evolutionary history of human HOX-paralogons was investigated.
- History of 63 gene-families by employing 4419 protein sequences from diverse animal species.
- Large-scale dataset exhibit that vertebrate genome evolved by small-scale duplication events.
- These regional duplications occurred at different time points in animal history.
- Results decisively reject the assumption that ancestral vertebrate genome was shaped by WGDs.

BackgroundThe vertebrate genome often contains closely spaced set of paralogous genes from distinct gene families on typically two, three or four different chromosomes (paralogons). This type of genome architecture is widely considered to be remnants of whole genome duplication events (WGD/2R).ResultsTaking advantage of the well-annotated and high-quality human genomic sequence map as well as the ever-increasing accessibility of large-scale genomic sequence data from a diverse range of animal species, we investigated the evolutionary history of potential quadruplicated regions residing on human HOX-cluster bearing chromosomes (chromosomes 2/7/12/17). For this purpose a detailed phylogenetic analysis was performed for those multigene families, including members of at least three of the four HOX-bearing chromosomes. Topology comparison approach categorized the members of 63 families into distinct co-duplicated groups. Distinct gene families belonging to a particular co-duplicated group, exhibit similar evolutionary history and hence have duplicated concurrently, whereas genes of two different co-duplicated groups do not share their history and have not duplicated in concert with each other.ConclusionsThese results based on large-scale phylogenetic dataset yielded no evidence in favor of polyploidization events; instead it appears that triplicated and quadruplicated genomic segments on the human HOX-bearing chromosomes arose by small-scale duplication events that occurred at widely different time points in animal evolution.