miRNA-Dependent and Independent Functions of the Microprocessor in the Regulation of Neural Stem Cell Biology

The gene regulatory capacity and diversity of microRNAs (miRNAs) is critical in the central nervous system where constant and rapid adaptation to environmental changes is needed, both during development and in the adult. Here, we will discuss how miRNA biogenesis is modulated to sustain a variety of neural phenomena, including embryonic and adult neurogenesis. Moreover, we will present the newly discovered miRNA-independent function of the microprocessor where mRNA regulation is achieved through direct site-specific cleavage by the RNAse III Drosha. Noncanonical functions of the microprocessor have striking effects on neural stem cells (NSCs), directly repressing the stability of mRNAs that encode proteins crucial for stem cell activity. We will discuss and compare different mechanisms through which the microprocessor regulates NSC maintenance and differentiation during embryonic and adult neurogenesis.