Biology subjects

Bel-Vialar, S.

Publications and source records attributed to Bel-Vialar, S..

4 recordsLinked to original sources

bioRxiv2026

CDC25B couples ribosome biogenesis to cell cycle kinetics to promote spinal cord neurogenesis

During neurogenesis, neural progenitors undergo a tightly regulated transition from proliferation to differentiation, which requires precise coordination between cell cycle progression and molecular reprogramming. Although the role of CDC25B is well established in promoting G2/M transition through CDK1 activation, we previously showed that it is both necessary and sufficient to trigger neural progenitor differentiation, via CDK-dependent and CDK-independent mechanisms. However, the molecular networks underlying this neurogenic activity remain poorly understood. Here, using a gain-of-function approach in the chicken spinal cord combined with bulk RNA sequencing, we show that CDC25B overexpression upregulates transcripts encoding ribosomal proteins and enhances ribosome biogenesis (RiBi) in neural progenitors. Consistent with these findings, during normal development, RiBi increases in neurogenic progenitor domains expressing CDC25B. Notably, the increase in RiBi is not associated with an increase in translation in neural progenitors. Instead, it is followed by an increase in mTORC1 activity in neuronal precursors and subsequently by a rise in the global translation rate in differentiating neurons. Moreover, increasing mTORC1 activity is sufficient to trigger a premature transition of neuronal precursors to the next step of differentiation. Altogether, our data support a model in which CDC25B coordinates cell cycle progression with RiBi in neurogenic progenitors, thereby initiating a program that culminates in translation in differentiating neurons.

developmental biology↗

bioRxiv2021

Control of G2 phase duration by CDC25B modulates the switch from direct to indirect neurogenesis in the neocortex

During development, cortical neurons are produced in a temporally regulated sequence from apical progenitors, directly, or indirectly through the production of intermediate basal progenitors. The balance between these major progenitors types is determinant for the production of the proper number and types of neurons and it is thus important to decipher the cellular and molecular cues controlling this equilibrium. Here we address the role of a cell cycle regulator, the CDC25B phosphatase, in this process. We show that deleting CDC25B in apical progenitors leads to a transient increase of the production of TBR1+ neurons at the expense of TBR2+ basal progenitors in mouse neocortex. This phenotype is associated with lengthening of the G2 phase of the cell cycle, the total cell cycle length being unaffected. Using in utero electroporation and cortical slice cultures, we demonstrate that the defect in TBR2+ basal progenitor production requires interaction with CDK1 and is due to the G2 phase lengthening in CDC25B mutants. Altogether, this study identifies a new role for CDC25B and the length of the G2 phase in direct versus indirect neurogenesis at early stages of the cortical development.

developmental biology↗

bioRxiv2017

FGFs are orchestra conductors of Shh-dependent oligodendroglial fate specification in the ventral spinal cord

Most oligodendrocytes of the spinal cord originate from ventral progenitor cells of the pMN domain, characterized by expression of the transcription factor Olig2. A minority of oligodendrocytes is also recognized to emerge from dorsal progenitors during fetal development. The prevailing view is that generation of ventral oligodendrocytes depends on Sonic hedgehog (Shh) while dorsal oligodendrocytes develop under the influence of Fibroblast Growth Factors (FGFs). Using the well-established model of the chicken embryo, we evidence that ventral spinal progenitor cells activate FGF signaling at the onset of oligodendrocyte precursor cell (OPC) generation, as do they dorsal counterpart. Inhibition of FGF receptors at that time appears sufficient to prevent generation of ventral OPCs, highlighting that, in addition to Shh, FGF signaling is required also for generation of ventral OPCs. We further reveal an unsuspected interplay between Shh and FGF signaling by showing that FGFs serve dual essential functions in ventral OPC specification. FGFs are responsible for timely induction of a secondary Shh signaling center, the lateral floor plate, a crucial step to create the burst of Shh required for OPC specification. At the same time, FGFs prevent down-regulation of Olig2 in pMN progenitor cells as these cells receive higher threshold of the Shh signal. Finally, we bring arguments favoring a key role of newly differentiated neurons acting as providers of the FGF signal required to trigger OPC generation in the ventral spinal cord.

developmental biology↗

bioRxiv2017

Neurogenic decisions require a cell cycle independent function of the CD25B phosphatase

A fundamental issue in developmental biology and in organ homeostasis is understanding the molecular mechanisms governing the balance between stem cell maintenance and differentiation into a specific lineage. Accumulating data suggest that cell cycle dynamics plays a major role in the regulation of this balance. Here we show that the G2/M cell cycle regulator CDC25B phosphatase is required in mammals to finely tune neuronal production in the neural tube. We show that in chick neural progenitors, CDC25B activity is both required and sufficient to stimulate neurogenic divisions and to promote neuronal differentiation. We design a mathematical model showing that within a limited period of time, cell cycle length modifications cannot account for changes in the ratio of the mode of division. Using a CDC25B point mutation that cannot interact with CDK, we show that part of CDC25B activity on neurogenic divisions is independent of its action on the cell cycle.

developmental biology↗