By Carla Mellough
Continuing on with our recent focus on microRNA (miRNA) and induced pluripotency (see ‘Reprogramming the methods that induce pluripotency’), a recent article published in the September advance issue of Nucleic Acids Research from David Wu’s group (WJWU and LYNN Institute for Stem Cell Research) in California may shed light on the mechanisms that govern somatic cell reprogramming. In this article Lin et al. uncover a regulatory mechanism that controls global DNA demethylation and histone methylation, a requirement for the reprogramming of somatic cells. Global demethylation is an event largely associated with early zygote development and is key for the establishment of stem cell pluripotency, but how cell stemness is reset in somatic cells during reprogramming is not yet clearly understood. Of the four Yamanaka factors, two (Oct3/4 and Sox2) are essential for reprogramming to occur and both of these were recently shown to be crucial for expression of the miRNA Mir-302. MiRNAs are a class of non-coding RNAs that suppress the translation of target messenger RNAs. Mir-302 expression, encoded for within a region of chromosome 4 that is associated with longevity, is high in both human embryonic stem cells (hESC) and induced pluripotent stem cells (iPSC) with mir-302 downregulation accompanying cell differentiation>. This suggests a role for mir-302 in the regulation of stemness and pluripotency (alongside other stem cell-associated miRNAs) and therefore also the reversion of lineage restricted cells to a pluripotent state.