There is substantial interest and speculation in the role of the “sixth DNA base,” 5-hydroxymethylcytosine (5-hmC), although its precise function has not yet been elucidated. Since its discovery in neuronal Purkinje, granule and ES cells, studies of this new modified DNA base have been limited by the lack of high-quality, validated tools and technologies that discriminate hydroxy-methylation from methylation in regulating genome expression. Obtaining a specific assay for 5-hmC is particularly important since standard bisulfite sequencing cannot distinguish between these two types of methylation.
