An induction gene trap screen in neural stem cells reveals an instructive function of the niche and identifies the splicing regulator sam68 as a tenascin-C-regulated target gene.
Neural stem cells (NSCs) reside in a niche that abounds in extracellular matrix (ECM) molecules. The ECM glycoprotein tenascin-C (Tnc) that occurs in more than 25 isoforms represents a major constituent of the privileged NSC milieu. To understand its role for NSCs, the induction gene trap technology was successfully applied to mouse embryonic NSCs, and a library of more than 500 NSC lines with independent gene trap vector integrations was established. Our pilot screen identified Sam68 as a target of Tnc signaling in NSCs. The Tnc-mediated downregulation of Sam68, which we found expressed at low levels in the niche along with Tnc, was independently confirmed on the protein level. Sam68 is a multifunctional RNA-binding protein, and its potential significance for cultured NSCs was studied by overexpression. Increased Sam68 levels caused a marked reduction in NSC cell proliferation. In addition, Sam68 is a signal-dependent regulator of alternative splicing, and its overexpression selectively increased the larger Tnc isoforms, whereas a mutated phosphorylation-deficient Sam68 variant did not. This emphasizes the importance of Sam68 for NSC biology and implicates an instructive rather than a purely permissive role for Tnc in the neural stem cell niche.
Moritz
Sören
S
Department for Cell Morphology and Molecular Neurobiology, NDEF 05/339, Universitaetsstrasse 150, D-44780 Bochum, Germany.
Lehmann
Stefanie
S
Faissner
Andreas
A
von Holst
Alexander
A
D048868:Adaptor Proteins, Signal Transducing / Q000096:biosynthesis* / Q000235:genetics; D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D051379:Mice; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D020033:Protein Isoforms / Q000502:physiology; D016601:RNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D015398:Signal Transduction; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D019063:Tenascin / Q000502:physiology*
D048868:Adaptor Proteins, Signal Transducing; C513253:Khdrbs1 protein, mouse; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D019063:Tenascin