Biology subjects

Vaslin, C.

Publications and source records attributed to Vaslin, C..

3 recordsLinked to original sources

bioRxiv2020

Dynamic extrinsic pacing of the HOX clock in human axial progenitors controls motor neuron subtype specification

SUMMARYRostro-caudal patterning of vertebrates depends on the temporally progressive activation of HOX genes within axial stem cells that fuel axial embryo elongation. Whether HOX genes sequential activation, the “HOX clock”, is paced by intrinsic chromatin-based timing mechanisms or by temporal changes in extrinsic cues remains unclear. Here, we studied HOX clock pacing in human pluripotent stem cells differentiating into spinal cord motor neuron subtypes which are progenies of axial progenitors. We show that the progressive activation of caudal HOX genes in axial progenitors is controlled by a dynamic increase in FGF signaling. Blocking FGF pathway stalled induction of HOX genes, while precocious increase in FGF alone, or with GDF11 ligand, accelerated the HOX clock. Cells differentiated under accelerated HOX induction generated appropriate posterior motor neuron subtypes found along the human embryonic spinal cord. The HOX clock is thus dynamically paced by exposure parameters to secreted cues. Its manipulation by extrinsic factors alleviates temporal requirements to provide unprecedented synchronized access to human cells of multiple, defined, rostro-caudal identities for basic and translational applications.View Full Text

developmental biology↗

bioRxiv2019

Direct readout of neural stem cell transgenesis with an integration-coupled gene expression switch

SUMMARYStable genomic integration of exogenous transgenes is critical for neurodevelopmental and neural stem cell studies. Despite the emergence of tools driving genomic insertion at high rates with DNA vectors, transgenesis procedures remain fundamentally hindered by the impossibility to distinguish integrated transgenes from residual episomes. Here, we introduce a novel genetic switch termed iOn that triggers gene expression upon insertion in the host genome, enabling simple, rapid and faithful identification of integration events following transfection with naked plasmids accepting large cargoes. In vitro, iOn permits rapid drug-free stable transgenesis of mouse and human pluripotent stem cells with multiple vectors. In vivo, we demonstrate accurate cell lineage tracing, assessment of regulatory elements and mosaic analysis of gene function in somatic transgenesis experiments that reveal new aspects of neural progenitor potentialities and interactions. These results establish iOn as an efficient and widely applicable strategy to report transgenesis and accelerate genetic engineering in cultured systems and model organisms.

developmental biology↗

bioRxiv2019

BMP4 patterns Smad activity and generates stereotyped cell fate organisation in spinal organoids

Bone Morphogenetic Proteins (BMP) are secreted regulators of cell fate in several developing tissues. In the embryonic spinal cord, they control the emergence of the neural crest, roof plate and distinct subsets of dorsal interneurons. Although a gradient of BMP activity has been proposed to determine cell type identity in vivo, whether this is sufficient for pattern formation in vitro is unclear. Here, we demonstrate that exposure to BMP4 initiates distinct spatial dynamics of BMP signalling within the self-emerging epithelia of both mouse and human pluripotent stem cells derived spinal organoids. The pattern of BMP signalling results in the stereotyped spatial arrangement of dorsal neural tube cell types and concentration, timing and duration of BMP4 exposure modulate these patterns. Moreover, differences in the duration of competence time-windows between mouse and human account for the species specific tempo of neural differentiation. Together the study describes efficient methods to generate patterned subsets of dorsal interneurons in spinal organoids and supports the conclusion that graded BMP activity orchestrates the spatial organization of the dorsal neural tube cellular diversity in mouse and human.

developmental biology↗