Abnormal levels of Gadd45alpha in developing neocortex impair neurite outgrowth

PLoS One. 2012;7(9):e44207. doi: 10.1371/journal.pone.0044207. Epub 2012 Sep 6.

Abstract

To better understand the short and long-term effects of stress on the developing cerebral cortex, it is necessary to understand how early stress response genes protect or permanently alter cells. One family of highly conserved, stress response genes is the growth arrest and DNA damage-45 (Gadd45) genes. The expression of these genes is induced by a host of genotoxic, drug, and environmental stressors. Here we examined the impact of altering the expression of Gadd45alpha (Gadd45a), a member of the Gadd45 protein family that is expressed throughout the developing cortices of mice and humans. To manipulate levels of Gadd45a protein in developing mouse cortex, we electroporated cDNA plasmids encoding either Gadd45a or Gadd45a shRNA to either overexpress or knockdown Gadd45a levels in the developing cortices of mice, respectively. The effects of these manipulations were assessed by examining the fates and morphologies of the labeled neurons. Gadd45a overexpression both in vitro and in vivo significantly impaired the morphology of neurons, decreasing neurite complexity, inducing soma hypertrophy and increasing cell death. Knockdown of Gadd45a partially inhibited neuronal migration and reduced neurite complexity, an effect that was reversed in the presence of an shRNA-resistant Gadd45a. Finally, we found that shRNA against MEKK4, a direct target of Gadd45a, also stunted neurite outgrowth. Our findings suggest that the expression of Gadd45a in normal, developing brain is tightly regulated and that treatments or environmental stimuli that alter its expression could produce significant changes in neuronal circuitry development.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Differentiation / genetics
  • Gene Expression Regulation, Developmental
  • Gene Knockdown Techniques
  • HeLa Cells
  • Humans
  • MAP Kinase Kinase Kinase 4 / metabolism
  • Mice
  • Neocortex / embryology*
  • Neocortex / metabolism*
  • Neocortex / pathology
  • Neurites / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism

Substances

  • Cell Cycle Proteins
  • GADD45A protein, human
  • Gadd45a protein, mouse
  • Nuclear Proteins
  • RNA, Messenger
  • MAP Kinase Kinase Kinase 4

Grant support

This work was supported by funds from the McKnight Brain Research Foundation and the Evelyn F. and William L. McKnight Brain Institute at the University of Florida (to M.R.S.) and a University of Florida Opportunity Fund Award (to M.R.S.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.