Normal and oncogenic roles for microRNAs in the developing brain.

MicroRNAS (miRNAs) are small endogenous non-coding RNAs that play important roles in many different biological processes including proliferation, differentiation and apoptosis through silencing of target genes. Emerging evidence indicates that miRNAs are key players in mammalian development that, when altered, contribute to tumorigenesis. However, only a few studies to date have focused on the role of miRNAs in medulloblastoma, the most common malignant pediatric brain tumor. These tumors arise in the cerebellum and may attribute their origins to deregulated proliferation of neural progenitor cells during development. Understanding the interplay between normal brain development and medulloblastoma pathogenesis is necessary in order for more efficient, less toxic targeted therapies to be developed and implemented. MiRNA expression profiling of both mouse and human medulloblastomas has led to the identification of signatures correlating with the molecular subgroups of medulloblastoma, tumor diagnosis and response to treatment, as well as novel targets of potential clinical relevance. This review summarizes the recent miRNA literature in both medulloblastoma and normal brain development.