Pumilio2 regulates synaptic plasticity via translational repression of synaptic receptors in mice
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Hongxin Dong1, Mengyi Zhu2, Liping Meng1, Yan Ding2, Ding Yang2, Shanshan Zhang1, Wenan Qiang3, Daniel W. Fisher4 and Eugene Yujun Xu2
1Departments of Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
2State Key Laboratory of Reproductive Medicine, Nanjing Medical University, Nanjing, 211166, P. R. China
3Department of Obstetrics and Gynecology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
4Department of Neurology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611, USA
Eugene Yujun Xu, email: firstname.lastname@example.org
Hongxin Dong, email: email@example.com
Keywords: Pumilio (PUM); RNA binding protein; dendrite; synapse; glutamate receptor 2 (GLUR2)
Received: August 23, 2017 Accepted: January 13, 2018 Epub: January 30, 2018 Published: August 14, 2018
PUMILIO 2 (PUM2) is a member of Pumilio and FBF (PUF) family, an RNA binding protein family with phylogenetically conserved roles in germ cell development. The Drosophila Pumilio homolog is also required for dendrite morphogenesis and synaptic function via translational control of synaptic proteins, such as glutamate receptors, and recent mammalian studies demonstrated a similar role in neuronal culture with associated motor and memory abnormalities in vivo. Importantly, transgenic mice with PUM2 knockout show prominent epileptiform activity, and patients with intractable temporal lobe epilepsy and mice with pilocarpine-induced seizures have decreased neuronal PUM2, possibly leading to further seizure susceptibility. However, how PUM2 influences synaptic function in vivo and, subsequently, seizures is not known. We found that PUM2 is highly expressed in the brain, especially in the temporal lobe, and knockout of Pum2 (Pum2–/–) resulted in significantly increased pyramidal cell dendrite spine and synapse density. In addition, multiple proteins associated with excitatory synaptic function, including glutamate receptor 2 (GLUR2), are up-regulated in Pum2–/– mice. The expression of GLUR2 protein but not mRNA is increased in the Pum2–/– mutant hippocampus, Glur2 transcripts are increased in mutant polysome fractions, and overexpression of PUM2 led to repression of reporter expression containing the 3′Untranslated Region (3′UTR) of Glur2, suggesting translation of GLUR2 was increased in the absence of Pum2. Overall, these studies provide a molecular mechanism for the increased temporal lobe excitability observed with PUM2 loss and suggest PUM2 might contribute to intractable temporal lobe epilepsy.
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