miRNAs in Mammalian Adult Olfactory Neurogenesis

Neuronal plasticity in the adult mammalian olfactory system is sustained by continuous supply of new interneurons throughout life. This ongoing neurogenesis needs to be tightly controlled at the molecular level in order to produce adequate interneuron subtypes in the correct proportions. Furthermore, genetic regulators of olfactory neurogenesis must insure both stability of the neurogenic sequence and adaptability to environmental inputs. In addition to transcriptional control by coding mRNAs, recent reports have shown that micro-RNAs (miRNAs) play an important role in fine-tuning neurogenic processes at different levels, from regionalization and maintenance of the stem-cell niche to neuronal subtype fate specification and synaptic integration and plasticity. Here, we provide an overview and critical discussion of the emerging literature dealing with the involvement of miRNAs in olfactory neurogenesis, focusing more closely on miR-124, miR-125, miR-132, and miR-7. We highlight the current technical limitations and discuss state-of-the-art approaches to identify new important miRNAs and investigate their functions in vivo.