Package and identification of replication deficient recombinant adenovirus expression vector of channelrhodopsin-2

Abstract

Background Channelrhodopsin-2 (ChR2)is a cation channel isolated from the eyespot of Chlamydomonas algae and has been used to control neuron activity.The light stimulation is a more precise fashion whether space or time than that of electrical,magnetic and ultrasound stimulation. Objective This study was to construct a replication deficient recombinant adenovirus cxpression vector of ChR2 and to determine its function.Methods Human embryo kidney 293 (HEK293) cell line was cultured and passaged in DF12 medium containing 10％ fetal bovine serum(FBS).The ChR2 gene was cloned at the downstream of cytomegalovirus(CMV)promoter of the adenoviral shuttle plasmid pSB291 in sense direction,and the resultant recombinant plasmid pSB291-hChR2- GFP was transfected into HEK293 cell together with plasmid pBHG lox ( deltaE1,3 ) containing adenoviral genome,then small amounts replication deficient recombinant adenovirus expression vector of ChR2 (Ad-ChR2) was obtained.Through amplification gradient centrifugation and dialysis,pure Ad-ChR2 was obtained.Visual cortex cells derived from 4 1-day-old clean Long Evans rats were primary cultured with serum-free culture media and infected by AdChR2.When expressing green fluorescencc,those cells received the stimulated of blue light with 460 nm.Patch clamp technique was applied to record an action potential. Results After purification and concentration,the titer of AdhCHR2 reached 7.9×1010 PFU/ml.Twenty-four hours after transfect of Ad-ChR2,HEK293 cell membrane showed the green fluorescence for the recombinant plasmid with green fluorescence protein under the inversed fluorescence microscope.The HEK293 cells change their shape from flat to round 13 days after transfected.The primary cultured visual cortex cells exhibited the green fluorescence 3-5 days after infected by Ad-ChR2.The action potentials evoked by blue light stimulation were recorded with patch clamp on those cells expressing green fluorescence. Conclusions Ad-ChR2 expressing vector is constructed successfully in this study.It is verified that Ad-ChR2 expressing vector can infect visual cortex cells with visual function.This result is very important for visual plasticity study. Key words: Channelrhodopsin-2; Adenovirus; Patch clamp