How can a single-celled organism like the ciliated protozoan Tetrahymena provide insight into epigenetics?
TAVERNA: There is a common misconception that epigenetics isn’t at play in single-celled organisms but some of the first evidence for non-Mendelian inheritance was in single-celled ciliated protozoa. Tetrahymena, in particular, turns out to be well suited for epigenetics studies. It maintains two separate nuclei at the same time: one contains the germline genome, a full copy of its DNA that gets passed down to the next generation, and the other contains the somatic genome, the DNA that gets transcribed. When Tetrahymena are “born,” they inherit germline DNA from their parents, but the somatic nucleus then differentiates from a germline nucleus in an epigenetic process that is directed in part by the parent’s somatic genomes. To do this, the somatic genome goes through a period of heterochromatin formation and gene silencing during which they get rid of DNA they don’t express. We can synchronize the life cycle of Tetrahymena so that they undergo this process of gene silencing at the sam
