Origin and function of olfactory bulb interneuron diversity

Abstract

In adult rodents, subventricular zone (SVZ) astrocytes (B cells) function as primary progenitors in the generation of new neurons that migrate to the olfactory bulb (OB), where they differentiate into multiple types of interneurons. It has been generally considered that individual adult SVZ stem cells are capable of generating different types of neurons and glial cells. However, recent studies indicate that these adult SVZ primary progenitors are heterogeneous and predetermined to generate specific types of neurons. Surprisingly, OB interneurons are generated by stem cells not only in the walls of the lateral ventricle facing the striatum but also in the rostral migratory stream and walls of the lateral ventricle facing the cortex and the septum. SVZ B cells in different locations within this extensive germinal region generate different kinds of interneurons. General physiological characteristics of major classes of OB interneurons have begun to emerge, but the functional contribution of each subtype remains unknown. The mosaic organization of the SVZ offers a unique opportunity to understand the origin of interneuron diversity and how this assortment of neurons contributes to plasticity of postnatal olfactory circuits.

NeuroD1 induces terminal neuronal differentiation in olfactory neurogenesis

“…In addition, we have shown that ectopic expression of NeuroD1 is sufficient to induce instant and widespread neuronal differentiation in the periventricular area, a region that is specialized in the maintenance of stem cells (4,5,30). Overexpression of the determination factor Pax6 did not induce a comparable phenotype, demonstrating the specificity of the observed phenotype.…”

“…Here, stem cell populations first located in the ventricular zone and after the establishment of an ependymal layer positioned in subventricular zone (SVZ) generate migratory neuroblasts throughout life (4). These perform long-distance chain migration via the rostral migratory stream (RMS) into the olfactory bulb (OB), where they migrate into the granule cell layer (GCL) and the glomerular layer (GL) to differentiate into GABA-and dopaminergic neurons (4,5). Thus, in this system, generation of neurons is permanent and the consecutive steps in the neurogenic sequence are spatially separated.…”

A Critical Time Window for the Recruitment of Bulbar Newborn Neurons by Olfactory Discrimination Learning

“…Along with the dentate gyrus (DG) of the hippocampal formation, the olfactory bulb (OB) is a region of the mammalian brain in which there is a continued supply of newly generated neurons (Abrous et al, 2005;Lledo et al, 2008). Olfactory adult-born neurons originate from the periventricular region, and then migrate tangentially through the rostral migratory stream to reach the OB.…”

Retrograde monosynaptic tracing reveals the temporal evolution of inputs onto new neurons in the adult dentate gyrus and olfactory bulb

“…Similarly, the subependymal zone (SEZ) harbors aNSCs, which give rise to neuroblasts that migrate tangentially along the rostral migratory stream (RMS) to the OB. There, the neuroblasts migrate radially and differentiate into various types of interneurons populating both the granule cell layer (GCL) and the glomerular layer (17,18). We therefore adapted the RABV-based monosynaptic tracing technique to target adult-generated neurons for primary RABV infection.…”