Evolutionary Changes in Vertebrate Genome Signatures with Special Focus on

With a remarkable increase in genomic sequencedataof awide rangeof species, novel tools areneeded for comprehensive analysesof thebig sequencedata. Self-organizingmap (SOM) is apowerful tool forclustering high-dimensionaldataononeplane. Foroligonucleotidecompositionshandledashigh-dimensionaldata,we have previously modified the conventional SOM for genome informatics: BLSOM. In the present study, we constructed BLSOMs for oligonucleotide compositions in fragment sequences (e.g. 100 kb) from a wide range of vertebrates, including coelacanth, and found that the sequenceswere clustered primarily according to species without species information. As one of the nearest living relatives of tetrapod ancestors, coela-canth is believed to provide access to the phenotypic and genomic transitions leading to the emergence of tetrapods. The characteristic oligonucleotide composition found for coelacanth was connected with the lowest dinucleotide CGoccurrence (i.e. the highest CG suppression) among fishes, whichwas rather equiva-lent to that of tetrapods. This evident CG suppression in coelacanth should reflect molecular evolutionary processes of epigenetic systems including DNA methylation during vertebrate evolution. Sequence of a de novo DNA methylase (Dntm3a) of coelacanth was found to be more closely related to that of tetrapods than that of other fishes. Key words: big data; epigenetic; SOM; DNA methylation; CG suppression 1