Determination of the presence of 5-methylcytosine in Paramecium tetraurelia

PLoS One. 2018 Oct 31;13(10):e0206667. doi: 10.1371/journal.pone.0206667. eCollection 2018.


5-methylcytosine DNA methylation regulates gene expression and developmental programming in a broad range of eukaryotes. However, its presence and potential roles in ciliates, complex single-celled eukaryotes with germline-somatic genome specialization via nuclear dimorphism, are largely uncharted. While canonical cytosine methyltransferases have not been discovered in published ciliate genomes, recent studies performed in the stichotrichous ciliate Oxytricha trifallax suggest de novo cytosine methylation during macronuclear development. In this study, we applied bisulfite genome sequencing, DNA mass spectrometry and antibody-based fluorescence detection to investigate the presence of DNA methylation in Paramecium tetraurelia. While the antibody-based methods suggest cytosine methylation, DNA mass spectrometry and bisulfite sequencing reveal that levels are actually below the limit of detection. Our results suggest that Paramecium does not utilize 5-methylcytosine DNA methylation as an integral part of its epigenetic arsenal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5-Methylcytosine / analysis*
  • DNA Methylation
  • DNA, Protozoan
  • Genome, Protozoan
  • Paramecium tetraurelia / chemistry*


  • DNA, Protozoan
  • 5-Methylcytosine

Grants and funding

This research was supported by grants from the European Research Council (ERC) (260358 “EPIGENOME” and 681178 “G-EDIT”), the Swiss National Science Foundation (31003A_146257 and 31003A_166407), and from the National Center of Competence in Research (NCCR) RNA and Disease. Daniel J. Hogan is employed by Tocagen Incorporated. Alan G. Hendrick is employed by Storm Therapeutics Limited. Tocagen Incorporated and Storm Therapeutics Limited provided support in the form of salaries for authors [DJH and AGH], but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.