Invertebrate epigenomics: the brave new world of the spineless

摘要

Epigenetics was initially defined more than 50 years ago by Conrad Waddington as: ‘the branch of biology which studies the causal interactions between genes and their products which bring the phenotype into being’ [1, 2]. Whereas this original definition of epigenetics was used to describe a sequence of irrevocable developmental decisions undertaken by the cells in the embryo to narrow their developmental choices, the word epigenetics has since evolved to define various, often heritable, DNA sequenceindependent changes that can result in altered transcriptional outputs. More precise definitions of the word epigenetics were proposed throughout recent years [3, 4] even though a consensus on its precise meaning has not yet been reached. Nonetheless, Conrad Waddington was right in identifying that embryogenesis is governed by a series of signals that progressively define cell fate and shape the embryo. Nowadays, we know that such signals consist of regulatory mechanisms such as DNA methylation, histone modifications, long noncoding RNA and others.