title: Long-term channelrhodopsin-2 (ChR2) expression can induce abnormal axonal morphology and targeting in cerebral cortex.
abstract: Long-term expression of optogenetic proteins including channelrhodopsin-2 (ChR2) is widely used to study neural circuit function, but whether ChR2 expression itself perturbs circuits is not known. We expressed a common construct, CAG::ChR2 (H134R)-EYFP-WPRE, in L2/3 pyramidal cells in rat somatosensory cortex via in utero DNA electroporation (IUE). L2/3 pyramidal cells expressed ChR2-EYFP, but histology revealed abnormal morphology and targeting of ChR2-EYFP expressing axons, beginning at postnatal day (P) 33 and increasing with age. Axonal abnormalities included cylinders that enveloped pyramidal cell proximal apical dendrites, and spherical, calyx-like structures that surrounded neuronal cell bodies, including in L4. These are abnormal subcellular and laminar targets for L2/3 pyramidal cell synapses. Abnormalities did not occur in cells expressing GFP instead of ChR2, or in intermixed ChR2-negative axons. Long-term viral-mediated expression (80 d) did not cause axonal abnormalities when the CAG promoter was used, but produced some abnormalities with the stronger αCaMKII promoter (albeit much less than with in utero electroporation). Thus, under some circumstances high-level, long-term expression of ChR2-EYFP can perturb the structural organization of cortical circuits.
authors: Department of Molecular and Cellular Biology, Helen Wills Neuroscience Institute, University of California Berkeley Berkeley, CA, USA.
authors: Toshio
authors: T
authors: Miyashita
authors: Yu R
authors: YR
authors: Shao
authors: Jason
authors: J
authors: Chung
authors: Olivia
authors: O
authors: Pourzia
authors: Daniel E
authors: DE
authors: Feldman
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001369:Axons / Q000378:metabolism* / Q000473:pathology; D000075402:Channelrhodopsins; D018274:Electroporation / Q000379:methods; D005260:Female; D005786:Gene Expression Regulation; D018390:Gene Targeting / Q000379:methods; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000235:genetics; D062308:Optogenetics / Q000379:methods*; D011247:Pregnancy; D051381:Rats; D020318:Rats, Long-Evans; D013003:Somatosensory Cortex / Q000254:growth & development / Q000378:metabolism* / Q000473:pathology*; D013997:Time Factors
chemical_list: D000075402:Channelrhodopsins; D009419:Nerve Tissue Proteins
keywords: axon development; circuit; in utero electroporation; optogenetics
references: Neuron. 2009 Jan 29;61(2):301-16
references: 19186171
references: Neuron. 2010 Jan 28;65(2):230-45
references: 20152129
references: Gene. 1991 Dec 15;108(2):193-9
references: 1660837
references: Cereb Cortex. 2008 Jul;18(7):1588-603
references: 17998276
references: Neuroscience. 2004;128(1):209-16
references: 15450368
references: Proc Natl Acad Sci U S A. 2004 Dec 28;101(52):18206-11
references: 15608064
references: J Biol Chem. 2012 Feb 17;287(8):6014-24
references: 22187434
references: Eur J Neurosci. 2010 Feb;31(3):410-24
references: 20105242
references: J Neurosci. 2007 Jun 20;27(25):6760-70
references: 17581963
references: Annu Rev Neurosci. 2011;34:389-412
references: 21692661
references: Brain Res. 2006 Aug 4;1103(1):1-12
references: 16806119
references: Nat Neurosci. 2008 Aug;11(8):901-7
references: 18622400
references: Nature. 2010 Apr 22;464(7292):1155-60
references: 20414303
references: Nature. 2009 Feb 26;457(7233):1142-5
references: 19151697
references: Dev Biol. 2001 Dec 1;240(1):237-46
references: 11784059
references: Cereb Cortex. 2010 Jan;20(1):229-40
references: 19447860
references: Proc Natl Acad Sci U S A. 2003 Nov 25;100(24):13940-5
references: 14615590
references: Mol Ther. 2009 Oct;17(10):1692-702
references: 19638961
references: Nat Neurosci. 2003 Mar;6(3):291-9
references: 12577061
references: J Neurosci. 2010 Feb 24;30(8):3082-92
references: 20181605
references: Trends Cogn Sci. 2011 Dec;15(12):592-600
references: 22055387
references: J Physiol. 2006 Sep 1;575(Pt 2):583-602
references: 16793907
references: Brain Struct Funct. 2007 Jul;212(1):3-17
references: 17717695
references: J Comp Neurol. 2004 Nov 1;479(1):1-14
references: 15389616
references: J Neurosci. 2007 Oct 17;27(42):11334-42
references: 17942728
references: J Comp Neurol. 2007 Dec 10;505(5):526-38
references: 17924571
references: Nature. 2008 Jan 3;451(7174):61-4
references: 18094685
references: Nat Rev Neurosci. 2007 Aug;8(8):577-81
references: 17643087
references: Eur J Neurosci. 2010 Jun;31(12):2221-33
references: 20550566
references: Neuroscience. 2001;103(4):865-72
references: 11301197
references: Neurosci Res. 2006 Jun;55(2):105-15
references: 16542744
references: Science. 1996 Dec 6;274(5293):1678-83
references: 8939850
references: J Neurosci. 2009 Mar 11;29(10):3172-81
references: 19279254
references: Br J Pharmacol. 2011 Aug;163(8):1626-38
references: 21410464
references: J Neurosci. 2007 May 9;27(19):5224-35
references: 17494709
references: Nat Rev Neurosci. 2011 Apr;12(4):191-203
references: 21386859