Delayed Degradation and Impaired Dendritic Delivery of Intron-Lacking EGFP-Arc/Arg3.1 mRNA in EGFP-Arc Transgenic Mice

Frontiers in Molecular Neuroscience

Oswald Steward¹  Shannon Farris²  Kelly Matsudaira Yee²  Patricia S. Pirbhoy³  Haruhiko Bito⁴  Kohji Okamura⁵  Paul Worley⁶  Hiroyuki Okuno⁷ 

[1] Center for the Neurobiology of Learning and Memory, University of California, Irvine, Irvine, CA, United States;Department of Anatomy and Neurobiology, University of California, Irvine, Irvine, CA, United States;Department of Neurobiology and Behavior, University of California, Irvine, Irvine, CA, United States;Department of Neurochemistry, University of Tokyo Graduate School of Medicine, Tokyo, Japan;Department of Systems BioMedicine, National Research Institute for Child Health and Development, Tokyo, Japan;Johns Hopkins School of Medicine, Baltimore, MD, United States;Medical Innovation Center, Kyoto University Graduate School of Medicine, Kyoto, Japan;Reeve-Irvine Research Center, University of California, Irvine, Irvine, CA, United States;

关键词: LTP;    synaptic plasticity;    protein synthesis;    dendrite;    dendritic mRNA;    dendritic spines;   

DOI  :  10.3389/fnmol.2017.00435

来源: DOAJ

【 摘 要 】

Arc is a unique immediate early gene (IEG) whose expression is induced as synapses are modified during learning. Newly-synthesized Arc mRNA is 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 from Arc 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.

【 授权许可】

Unknown