Progenitor Hyperpolarization Regulates the Sequential Generation of Neuronal Subtypes in the Developing Neocortex

Abstract

During corticogenesis, ventricular zone progenitors sequentially generate distinct subtypes of neurons, accounting for the diversity of neocortical cells and the circuits they form. While activity-dependent processes are critical for the differentiation and circuit assembly of postmitotic neurons, how bioelectrical processes affect nonexcitable cells, such as progenitors, remains largely unknown. Here, we reveal that, in the developing mouse neocortex, ventricular zone progenitors become more hyperpolarized as they generate successive subtypes of neurons. Experimental in vivo hyperpolarization shifted the transcriptional programs and division modes of these progenitors to a later developmental status, with precocious generation of intermediate progenitors and a forward shift in the laminar, molecular, morphological, and circuit features of their neuronal progeny. These effects occurred through inhibition of the Wnt-beta-catenin signaling pathway by hyperpolarization. Thus, during corticogenesis, bioelectric membrane properties are permissive for specific molecular pathways to coordinate the temporal progression of progenitor developmental programs and thus neocortical neuron diversity.

Apical progenitors remain multipotent throughout cortical neurogenesis

“…To test this possibility, we performed FT labeling at E15.5 and waited 10 hours before collection to allow daughter IPs to differentiate (Telley et al, 2016; Govindan et al, 2018). At this stage, > 75% of FT + cells have differentiated into IPs, as revealed by co-expression of TBR2 and the proliferation marker KI67 (Vitali et al, 2018) (Fig. 4c, Fig.…”

“…In utero electroporations were performed as previously described (Vitali et al, 2018). Briefly, a 1.5 µg/µl DNA solution containing 1:2 transposon pPB-CAG-EmGFP and hyperactive piggyBac transposase (pRP-Puro-CAGG-Pbase) (Chen and LoTurco, 2012) was prepared in sterile PBS containing 0.01 mg/mL fast green.…”

“…The temporal resetting in V m values identified here may contribute to the reassignment in AP identity and regulate sensitivity to extracellular signals (Vitali et al, 2018). Such temporally dynamic environmental factors may include cell-cell interactions (Mutch et al, 2009; Okamoto et al, 2016), metabolic supplies, neurotransmitter-mediated feedback from newborn neurons or nearby axons (Seuntjens et al, 2009; Toma et al, 2014), as well as the protein and ion composition of the neurogenic niche and cerebrospinal fluid (Lehtinen et al, 2011), which together may be involved in AP re-specification.…”

“…(2) Resting membrane potential . Progression of AP neurogenic competence is regulated by a progressive hyperpolarization of the resting membrane potential (V m ) in a Wnt-dependent manner (Vitali et al, 2018). Since the Wnt pathway regulator Tcf7l1 was re-induced in AP 15→12 (Fig.…”

An Electric Take on Neural Fate and Cortical Development

“…While bioelectric properties of neurons are known to be key to their excitability and therefore neural transmission, membrane potential has not typically been associated with neurodevelopment. However, recent work from Vitali et al (2018) and Smith et al (2018) demonstrate an important role for bioelectrical properties in neural fate determination and neuronal migration that is independent of its role in neuronal excitability, opening up new directions of study in brain development.…”