Delayed degradation and impaired dendritic delivery of intron-lacking EGFP-Arc/Arg3.1 mRNA in EGFP-Arc transgenic mice

Oswald Steward, Kelly Matsudaira Yee, Shannon Farris, Patricia S. Pirbhoy, Paul F Worley, Kohji Okamura, Hiroyuki Okuno, Haruhiko Bito

Research output: Contribution to journalArticle

Abstract

Arc is a unique immediate early gene (IEG) whose expression is induced as synapses are modified during learning. Newly-synthesized Arc mRNAis rapidly transported throughout dendrites and localizes near recently activated synapses. Arc mRNA levels are regulated by rapid degradation, which is accelerated by synaptic activity in a translation-dependent process. One possible mechanism is nonsense-mediated mRNA decay (NMD), which depends on the presence of a splice junction in the 3 UTR. Here, we test this hypothesis using transgenic mice that express EGFP-Arc. Because the transgene was constructed fromArc cDNA, it lacks intron structures in the 3 UTR that are present in the endogenous Arc gene. NMD depends on the presence of proteins of the exon junction complex (EJC) downstream of a stop codon, so EGFP-Arc mRNA should not undergo NMD. Assessment of Arc mRNA rundown in the presence of the transcription inhibitor actinomycin-D confirmed delayed degradation of EGFP-Arc mRNA. EGFP-Arc mRNA and protein are expressed at much higher levels in transgenic mice under basal and activated conditions but EGFP-Arc mRNA does not enter dendrites efficiently. In a physiological assay in which cycloheximide (CHX) was infused after induction of Arc by seizures, there were increases in endogenous Arc mRNA levels consistent with translation-dependent Arc mRNA decay but this was not seen with EGFP-Arc mRNA. Taken together, our results indicate: (1) Arc mRNA degradation occurs via a mechanism with characteristics of NMD; (2) rapid dendritic delivery of newly synthesized Arc mRNA after induction may depend in part on prior splicing of the 3 UTR.

Original languageEnglish (US)
Article number435
JournalFrontiers in Molecular Neuroscience
Volume10
DOIs
Publication statusPublished - Jan 31 2018

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Keywords

  • Dendrite
  • Dendritic mRNA
  • Dendritic spines
  • Immediate early gene
  • LTP
  • Nonsense-mediated decay
  • Protein synthesis
  • Synaptic plasticity

ASJC Scopus subject areas

  • Molecular Biology
  • Cellular and Molecular Neuroscience

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