Are molecular cytogenetics and bioinformatics suggesting diverging models of ancestral mammalian genomes?

Author(s): Froenicke, Lutz; Caldes, Montserrat Garcia; Graphodatsky, Alexander; Muller, Stefan; Lyons, Leslie A; Robinson, Terence J; Volleth, Marianne; Yang, Fengtang; Wienberg, Johannes | Abstract: "Excavating" ancestral genomes The recent release of the chicken genome sequence (Hillier et al. 2004Go) provided exciting news for the comparative genomics community as it allows insights into the early evolution of the human genome. A bird species can now be used as an outgroup to model early mammalian genome organization and reshuffling. The genome sequence data have already been incorporated in a computational analysis of chicken, mouse, rat, and human genome sequences for the reconstruction of the ancestral genome organization of both a mammalian ancestor as well as a murid rodent ancestor (Hillier et al. 2004Go; Bourque et al. 2005Go). This bioinformatic effort joins a molecular cytogenetic model (Richard et al. 2003Go; Yang et al. 2003Go; Robinson et al. 2004Go; Svartman et al. 2004Go; Wienberg 2004Go; Froenicke 2005Go) as the second global approach to explore the architecture of the ancestral eutherian karyotype—a fundamental question in comparative genomics. Since both models use the human genome as reference, they are readily comparable. Surprisingly, however, they share few similarities. Only two small autosomes and the sex chromosomes of the hypothesized ancestral karyotypes are common to both. Unfortunately, given its significance, neither the extent of these differences nor their impact on comparative genomics have been discussed by Bourque and colleagues (2005Go). In an attempt to redress this, we compare the two methods of ancestral genome reconstruction, verify the resulting models, and discuss reasons for their apparent divergence.