5-Carboxylcytosine is localized to euchromatic regions in the nuclei of follicular cells in axolotl ovary

Abstract

5-Methylcytosine (5-mC) is an epigenetic modification associated with gene repression. Recent studies demonstrated that 5-mC can be enzymatically oxidised into 5-hydroxymethylcytosine and further into 5-formylcytosine (5-fC) and 5-carboxylcytsine (5-caC). 5-caC has been found in embryonic stem cells and in mouse pre-implantation embryos but no detectable levels of this modification have been reported for somatic tissues to date. Whereas it has been suggested that 5-caC can serve as an intermediate in the process of active demethylation, the function of this form of modified cytosine remains obscure. Here we show that 5-caC is immunochemically detectable in somatic cells of axolotl ovary. We demonstrate that both 5-hmC and 5-caC are localized to the euchromatin in the nuclei of axolotl follicular cells with similar patterns of spatial distribution. Our results suggest that 5-carboxylcytosine may play a distinct functional role in certain biological contexts.

Keywords: :

• epigenetics
• 5-hydroxymethylcytosine
• 5-carboxylcytosine
• DNA methylation
• active demethylation

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

We thank Lorrain Young (University of Nottingham) for support. We would like to acknowledge Denise Christie, Advanced Microscopy Unit, School of Biomedical Sciences, University of Nottingham for her contribution to the preparation of histological samples used in this study.