Beta1 integrin maintains integrity of the embryonic neocortical stem cell niche.

Karine Loulier,Turhan Coksaygan,Srinivasulu Chigurupati,Sung-Chun Tang,Holly Colognato,Mahendra S Rao,Mark P Mattson,Veronique Marthiens,Mohamed R Mughal,Peter E Hall,Bruce Patton,Jenne Relucio,Justin D Lathia,Tarik F Haydar,Charles Ffrench-Constant

doi:10.1371/journal.pbio.1000176

Abstract

Author SummaryThe developing cerebral cortex contains bipolar neural stem cells that span the cortical layers between the inner ventricular surface and the outer pial surface of the embryonic brain. The nuclei of these cells remain near the ventricular cavity, a microenvironment or niche thought to provide vital signals. It is not known how this inner end of the bipolar stem cell is held in place, or what would happen if its attachment to the inner surface were lost. Genetic manipulation can be used to disrupt candidate molecules involved in this adhesion, but this will affect all adhesion points and complicate the results. We have therefore developed an approach to target the stem cell attachments specifically at the ventricular surface by placing blocking antibodies directly into the ventricles of mouse embryos and then expressing fluorescent markers in the stem cells to see the effects of losing this attachment in living tissue. We examined laminins and integrins, whose expression and properties make them excellent candidates. Blocking integrin signalling by antibody application caused the inner end of the stem cells to rapidly detach and then undergo aberrant cell division. We also showed that a transient block of integrins (for <2 hours) resulted in permanent malformations of the cortical layers and disrupted neuronal migration.

Highlights

The cues responsible for maintaining the physical and molecular architecture of the stem cell niche of the developing mammalian brain are not well known
The high level of b1 integrin continues into the cortical subventricular zone (SVZ) as marked by the second layer of phospho histone 3 (PH3)+ cells, and b1 integrin is highly expressed at the pial surface and in blood vessels (Figure 1A and 1B)
At E16, as large numbers of neurons begin to differentiate in the cortex, the level of b1 integrin remains high in the VZ/SVZ but decreases in the neuronal layers (Figure 1C and 1D)

Summary

Introduction

The cues responsible for maintaining the physical and molecular architecture of the stem cell niche of the developing mammalian brain are not well known. The radial glia neural stem cells (NSC) that generate neurons are bipolar and have a radial morphology that spans the developing neocortical wall [1,2] These NSC have their soma located within the ventricular zone (VZ) adjacent to the ventricle, and their apical and basal processes make contact with the ventricular surface and the pial basement membrane, respectively [3,4]. The developing cerebral cortex contains bipolar neural stem cells that span the cortical layers between the inner ventricular surface and the outer pial surface of the embryonic brain The nuclei of these cells remain near the ventricular cavity, a microenvironment or niche thought to provide vital signals. We showed that a transient block of integrins (for ,2 hours) resulted in permanent malformations of the cortical layers and disrupted neuronal migration

Methods

Results

Conclusion