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First published online May 20, 2009
doi: 10.1242/10.1242/jcs.043257
Research Article |
Department of Cancer Biology, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
* Author for correspondence (e-mail: jhmccarty{at}mdanderson.org)
Accepted 17 February 2009
Central nervous system (CNS) neurovascular units are multicellular complexes consisting of neural cells, blood vessels and a milieu of extracellular matrix (ECM) proteins. ECM-mediated adhesion and signaling events within neurovascular units probably contribute to proper CNS development and physiology; however, the molecular mechanisms that control these events remain largely undetermined. Previous studies from our group and others showed that ablation of the ECM receptor,
vβ8 integrin, in neural progenitor cells (NPCs) of the embryonic mouse brain results in severe developmental neurovascular pathologies and premature death. Here, we have investigated the functions for this integrin in the adult brain by studying mice harboring a homozygous-null β8 gene mutation generated on an outbred background that permits survival for several months. We show that adult β8–/– mice display widespread defects in neurovascular unit homeostasis, including increased numbers of intracerebral blood vessels with pronounced perivascular astrogliosis. Furthermore, in neurogenic regions of the adult brain, where NPCs cluster around blood vessels in neurovascular niches, β8 integrin is essential for normal control of NPC proliferation and survival. Analysis of NPCs cultured ex vivo reveals that the growth and survival defects correlate, in part, with diminished integrin-mediated activation of latent transforming growth factor β1 (TGFβ1), which is an ECM protein ligand for
vβ8 integrin. Collectively, these data identify essential functions for β8 integrin in regulating neurovascular unit physiology in the post-natal mouse brain.
Key words: Tgfβ,
vβ8 integrin, Angiogenesis, Blood-brain barrier, Extracellular matrix, Neural stem cell
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