Several scientists are undertaking new researches on the 5-hydroxymethylcytosine (5-hmC), a cytosine with a methylene and a hydroxyl group. 5-hmC has a global role in human development, memory, and cancer. The researchers believe that there's a high probability that the 5-hmC modification helps supervise which genes are expressed in one cell type and locked in deep storage in another because the modified cytosine is often found inside genes. Nathaniel Heintz, a molecular biologist at New York's Rockefeller University and his postdoc Skirmantas Kriaucionis from Oxford University were trying to figure out whether the nuclei of meganeurons, Purkinje cells, were unusually bulky because of substantial DNA methylation. It has been observed that brain cell DNA has the most 5-hmC and some 0.3 to 0.7% of the bases in brain DNA are 5-hmC. Heart and kidney cells possess a medium amount of 5-hmC, while liver, testes, and stem cells have the lowest levels.