Four‐dimensional analysis of nucleogenesis of the pontine nucleus in the hindbrain

Abstract

Nuclei in the central nervous system are 3D aggregates of neurons that have common physiological properties, functionalities, and connectivities. To form specific nuclei, neurons migrate from their birthplace towards the presumptive nuclear region where they change their dynamics to aggregate and rearrange into a distinct 3D structure, a process that we term nucleogenesis. Nuclei, together with the laminar structure, form the basic cytoarchitectonic unit for information processing. However, in contrast to much-studied laminar structures, the neuronal dynamics that contribute to the aggregation process to form nuclei are poorly understood. Here, we analyze nucleogenesis by observing the mouse precerebellar pontine nucleus (PN), and provide the first 4D view of nucleogenesis by tracking neuronal behaviors along the three spatial axes over time. Early- and late-born PN neurons were labeled by in utero electroporation and their behaviors on cultured brain slices were recorded by time-lapse imaging. We find that when PN neurons migrate medially into the nuclear region, many of them switch to migrate radially and laterally, to populate the dorsal and lateral PN regions, respectively. The tendency to switch to radial migration is much less in later-born neurons, whereas that to switch to lateral migration is comparable between the two groups. In contrast to the radial and mediolateral axes, very few PN neurons switch to migrate rostrocaudally. These results could thus provide a framework for understanding the mechanisms that regulate this complex yet important process.

H3.3K27M Cooperates with Trp53 Loss and PDGFRA Gain in Mouse Embryonic Neural Progenitor Cells to Induce Invasive High-Grade Gliomas

“…We tested whether two drivers, transposable H3.3 K27M and Trp53 loss using a non-transposable gRNA/Cas9 targeting the Trp53 locus (K27M-P, 2-hit), were sufficient to induce tumorigenesis in either hindbrain or cortex. Hindbrain IUE was performed at E12.5 and forebrain IUE was performed at E13.5, in order to introduce mutant H3.3 K27M at the peak of cortical or pontine neurogenesis, respectively (Finlay and Darlington, 1995; Shinohara et al, 2013). Neoplastic transformation occurred with 100% penetrance in both hindbrain (Figure 1B and 1C) and cortex (Figure 1D), 6 and 8 months following surgery, respectively (Table S1).…”

The Long Journey of Pontine Nuclei Neurons: From Rhombic Lip to Cortico-Ponto-Cerebellar Circuitry

“…During this process PN neurons form a 3-dimensional aggregate bulging out of the ventral pons. In mice, PN nucleogenesis occurs between E14.5, when the first neurons arrive at their final destination, and E18.5, when nucleogenesis is close to completion (Shinohara et al, 2013). Various studies done in rodents provide a detailed analysis of the movement of neurons during nucleogenesis; however, the molecular mechanisms involved in the regulation of this process are poorly understood.…”

“…Early born-early arriving neurons switch their migration mode from tangential to radial near the ventral midline (Watanabe and Murakami, 2009; Shinohara et al, 2013). Depending on the cellular behavior of neurons, this switch can be categorized into two types (Figure 6).…”

“…This switch between tangential to radial migration is most apparent at E15.5 (Kawauchi et al, 2006). Interestingly, the ability to switch between tangential to radial migration was only seen in early born-early arriving PN neurons (Watanabe and Murakami, 2009; Shinohara et al, 2013). Late born PN neurons instead stack ventrally to early arriving neurons (Altman and Bayer, 1987d; Shinohara et al, 2013) resulting in an inside-out lamellae-like structure of the PN (Figures 6B, 7A).…”

“…Interestingly, the ability to switch between tangential to radial migration was only seen in early born-early arriving PN neurons (Watanabe and Murakami, 2009; Shinohara et al, 2013). Late born PN neurons instead stack ventrally to early arriving neurons (Altman and Bayer, 1987d; Shinohara et al, 2013) resulting in an inside-out lamellae-like structure of the PN (Figures 6B, 7A). Because early born PN neurons are able to migrate dorsally and late born PN neurons are mostly located more ventrally, it was hypothesized that the RTN is populated mostly by early born neurons, whereas BPN is formed of both early and late born PN neurons (Altman and Bayer, 1987d; Shinohara et al, 2013).…”