A Mouse Model for Conditional Secretion of Specific Single-Chain Antibodies Provides Genetic Evidence for Regulation of Cortical Plasticity by a Non-cell Autonomous Homeoprotein Transcription Factor

PLoS Genet. 2016 May 12;12(5):e1006035. doi: 10.1371/journal.pgen.1006035. eCollection 2016 May.

Abstract

During postnatal life the cerebral cortex passes through critical periods of plasticity allowing its physiological adaptation to the environment. In the visual cortex, critical period onset and closure are influenced by the non-cell autonomous activity of the Otx2 homeoprotein transcription factor, which regulates the maturation of parvalbumin-expressing inhibitory interneurons (PV cells). In adult mice, the maintenance of a non-plastic adult state requires continuous Otx2 import by PV cells. An important source of extra-cortical Otx2 is the choroid plexus, which secretes Otx2 into the cerebrospinal fluid. Otx2 secretion and internalization requires two small peptidic domains that are part of the DNA-binding domain. Thus, mutating these "transfer" sequences also modifies cell autonomous transcription, precluding this approach to obtain a cell autonomous-only mouse. Here, we develop a mouse model with inducible secretion of an anti-Otx2 single-chain antibody to trap Otx2 in the extracellular milieu. Postnatal secretion of this single-chain antibody by PV cells delays PV maturation and reduces plasticity gene expression. Induced adult expression of this single-chain antibody in cerebrospinal fluid decreases Otx2 internalization by PV cells, strongly induces plasticity gene expression and reopens physiological plasticity. We provide the first mammalian genetic evidence for a signaling mechanism involving intercellular transfer of a homeoprotein transcription factor. Our single-chain antibody mouse model is a valid strategy for extracellular neutralization that could be applied to other homeoproteins and signaling molecules within and beyond the nervous system.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antibody Specificity / genetics
  • Antibody Specificity / immunology*
  • Cerebral Cortex / immunology
  • Cerebral Cortex / metabolism
  • Disease Models, Animal
  • Gene Expression Regulation
  • Humans
  • Interneurons / immunology*
  • Mice
  • Neuronal Plasticity / immunology
  • Otx Transcription Factors / genetics
  • Otx Transcription Factors / immunology*
  • Parvalbumins / biosynthesis
  • Signal Transduction
  • Single-Chain Antibodies / genetics
  • Single-Chain Antibodies / immunology*
  • Visual Cortex / immunology
  • Visual Cortex / metabolism

Substances

  • Otx Transcription Factors
  • Otx2 protein, mouse
  • Parvalbumins
  • Single-Chain Antibodies

Grant support

The study was supported by ERC Advanced Grant HOMEOSIGN n°339379, ANR–11-BLAN-069467 BrainEver, Région Ile de France, Fondation Bettencourt Schueller and GRL program N°2009-00424. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.