Evolutionary consequences of DNA methylation on the GC content in vertebrate genomes

The genomes of many vertebrates show a characteristic variation in GC content. To explain its origin and evolution mainly three mechanisms have been proposed, selection for GC content, mutation bias and GC-biased gene conversion. At present the mechanism of GC-biased gene conversion, i.e. short-scale, unidirectional exchanges between homologous chromosomes in the neighborhood of recombination-initiating double-strand breaks in favor for GC nucleotides, is the most widely accepted hypothesis. We here suggest that DNA methylation also plays an important role in the evolution of GC content in vertebrate genomes. To test this hypothesis we investigated one mammalian (human; GSE30340) and one avian (chicken) genome. We used bisulfite sequencing to generate a whole-genome methylation map of chicken sperm. Human processed data files (spermdonor1, #reads>=1) were downloaded from the NGSmethDB database (