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Abstract: Neural stem cells in the subventricular zone (SVZ) generate progenitors which in turn give rise to neuroblasts. These neuroblasts then migrate along the rostral migratory stream (RMS) in chains and reach the olfactory bulb (OB), where they mature into local interneurons. Interneurons in the OB are heterogeneous, which are mainly located in granular cell layer (GCL), external plexiform layer (EPL) and glomerular layer (GL). In this study, we show that green fluorescent protein-expressing (GFP+) cells in the SVZ and RMS of the 5HT3aR-BACEGFP transgenic mouse exclusively express transcription factor Sp8 which is expressed in lateral ganglionic embryonic eminence (LGE) and postnatal SVZ. These GFP+ neuroblasts of the 5HT3aR-BACEGFP transgenic mouse migrate along the RMS to the OB where they differentiate into calretinin+ (CR+), parvabumin+ (PV+), vasoactive intestinal peptide+ (VIP+), somatostatin+ (Som+) and tyrosine hydroxylase+ (TH+), but not calbindin+ (CB+) interneurons. These GFP+ interneurons continuously express Sp8 in the OB. Furthermore, these results suggest that GFP-expressing cells are derived from LGE, and this transgenic mouse line will be a useful tool for studying the development and function of interneurons in both neocortex and OB. [Copyright &y& Elsevier]

Highlights: [•] BIG1 is colocalized with synaptic marker synaptophysin in soma and partly in neurites. [•] BIG1 content increased with embryonic rat brain growth. [•] BIG1 siRNA inhibited neurite development in primary cultured cortical neuron. [•] Depletion or inhibition of BIG1 decreased the phosphorylation of PI3K–AKT and ERK. [•] We report a novel function of BIG1 in regulating neurite outgrowth. [Copyright &y& Elsevier]

Abstract: In the past several decades, tremendous progress has been achieved through developmental studies of the central nervous system structures such as the cerebral cortex. The septum, which receives reciprocal connections from a variety of brain structures, contains diverse projection neurons but few interneurons. However, the mechanisms underlying its development remain poorly understood. Here we show that the septum is organized into an onion skin-like structure composed of five groups of neurons. These neurons are parvalbumin, choline acetyltransferase, neuronal nitric oxide synthase, calretinin and calbindin immunoreactive. Using the BrdU birth-dating method, we found that these five groups of neurons in the septum are grossly generated following an outside-in pattern. Interestingly, the distinct molecular identities of these neuronal subtypes correspond to their heterogeneous subpallial origins. Using three specific transgenic mouse lines and focal in utero electroporation of Cre-reporter plasmid, we showed that septal neurons originate from not only local progenitor regions but also neighboring progenitor regions including the medial ganglionic eminence and preoptic area. Thus, the neuronal diversity of the septum is achieved through both temporal and spatial control. Our results also suggest that multiple neuronal subtypes arrive to the septum through both radial and tangential migration. Based on these findings, we proposed a novel developmental model involving multiple spatial–temporal origins of septal neurons. This study presents new perspectives for comprehensively exploring septal functions in brain circuits. [Copyright &y& Elsevier]