Genomic Imprinting: A New Epigenetic Perspective of Sleep Regulation
Fig 1
Evolution of REM sleep and genomic imprinting.
The timeline (expressed as millions of years ago, MYA) on the horizontal axis maps geological and glacial periods and the evolutionary divergence that occurred among reptiles, birds, and mammals (monotremes, eutherians, and marsupials). The red line delineates the presence of genomic imprinting in therians. A description of REM sleep according to different species is annotated on the right.
