LAUSR

5-methylcytosine is an enzymatically produced modified cytosine base that was first identified about 70 years ago. This modification is generally understood to be incompatible with gene expression when found in regulatory regions including gene promoters and enhancers. Oxidized 5-methylcytosine bases, in the form of its hydroxyl, formyl and carboxyl derivatives, have been known for about 10 years. Their biological functions in development and in human diseases are not yet clearly defined. Human diseases including cancer and developmental and neurological disorders have been linked to mutations of enzymes that produce these modifications (e.g., DNMT3A, DNMT3B, TET2) and to proteins that recognize 5-methylcytosine (MECP2) attesting to the clinical relevance of modified cytosines and the pathways they are involved in.