Functional analysis of cortical neuron migration using miRNA silencing

Abstract

MicroRNAs (miRNAs) are endogenous, single-stranded ~21-nucleotide-long noncoding RNAs that have emerged as key fine-tuning posttranscriptional regulators of gene expression. The validation of miRNA-target interactions in animal model systems is not trivial, especially in the developing cerebral cortex. Induction of miRNAs loss-of-function is the ideal way to study their physiological role in vivo. Although it has been accepted that the dramatic brain phenotype of the Dicer conditional knockout mouse resulted from loss of mature miRNAs, functional connections to individual miRNAs need to be carried out. In this chapter, we compare three methods that are currently used to promote the loss-of-function of selected miRNAs in the developing cerebral cortex: genetic knockouts, small molecule inhibitors, and miRNA sponges. As an example, we are presenting some data obtained with different miRNA-loss of function approaches that support a role for miR-22 and miR-124 in radial migration and multipolar–bipolar transition of cortical projection neurons. These distinct loss of function methods provide complementary information and results indicate that, depending of the scientific question, one can choose between these methods to analyze the role of selected miRNAs in cortical development.