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Extracellular matrix-inducing Sox9 orchestrates basal progenitor proliferation and gliogenesis in developing neocortex

ABSTRACT: Neocortex expansion is largely based on the proliferative capacity of basal progenitors (BPs), which is increased by extracellular matrix (ECM) components via integrin signaling. Here we show that Sox9 drives expression of ECM components and that laminin 211 increases BP proliferation in embryonic mouse neocortex. Examination of Sox9 expression reveals that Sox9 is expressed in BPs of developing ferret and human, but not mouse neocortex. Functional studies by conditional Sox9 expression in the mouse BP lineage demonstrate increased BP proliferation, reduced Tbr2 and induction of Olig2 expression, indicative of premature gliogenesis. Conditional Sox9 expression also results in cell non-autonomous stimulation of BP proliferation followed by increased production of upper-layer neurons. Collectively, our findings demonstrate that Sox9 exerts concerted effects on transcription, BP proliferation, neuron production, and neurogenic as well as gliogenic BP cell fate, suggesting that Sox9 acts a master regulator in the subventricular zone to promote neocortical expansion.

ORGANISM(S): Mus musculus

PROVIDER: GSE134162 | GEO | 2020/03/27

REPOSITORIES: GEO

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Project description:Vascular calcification and increased extracellular matrix (ECM) stiffness are hallmarks of vascular ageing. Sox9 (SRY-Box Transcription Factor 9) is a master regulator of chondrogenesis, also expressed in the vasculature, that has been implicated in vascular smooth muscle cell (VSMC) osteo-chondrogenic conversion. Here, we investigated the relationship between vascular ageing, calcification and Sox9-driven ECM regulation in VSMCs. Immunohistochemistry in human aortic samples showed that Sox9 was not spatially associated with vascular calcification but correlated with the senescence marker p16. Analysis of Sox9 expression in vitro showed it was mechanosensitive with increased expression and nuclear translocation in senescent cells and on stiff matrices. Manipulation of Sox9 via overexpression and depletion, combined with atomic force microscopy (AFM) and proteomics, revealed that Sox9 regulates ECM stiffness and organisation by orchestrating changes in collagen expression and reducing VSMC contractility, leading to the formation of an ECM that mirrored that of senescent cells. These ECM changes promoted phenotypic modulation of VSMCs whereby senescent cells plated onto ECM synthesized from cells depleted of Sox9 returned to a proliferative state, while proliferating cells on a matrix produced by Sox9 expressing cells showed reduced proliferation and increased DNA damage, reiterating features of senescent cells. Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3 (LH3) was identified as a Sox9 target, and key regulator of ECM stiffness. LH3 is packaged into extracellular vesicles (EVs) and Sox9 promoted EV secretion, leading to increased LH3 deposition within the ECM. These findings identify cellular senescence and Sox9 as a key regulators of ECM stiffness during VSMC ageing and highlight a crucial role for ECM structure and composition in regulating VSMC phenotype. We identify a positive feedback cycle whereby cellular senescence and increased ECM stiffening promote Sox9 expression which drives further ECM modifications that act to accelerate vascular stiffening and cellular senescence.

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Extracellular matrix-inducing Sox9 orchestrates basal progenitor proliferation and gliogenesis in developing neocortex

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