王軍利,許映龍,許珉
siRNA真核表達(dá)載體對大鼠耳蝸前體細(xì)胞Notch3基因表達(dá)的影響
王軍利,許映龍,許珉
目的構(gòu)建Notch3基因的siRNA真核表達(dá)載體,探討其對大鼠耳蝸前體細(xì)胞中Notch3基因表達(dá)的影響。方法機(jī)械分離并胰酶消化新生大鼠耳蝸感覺上皮,懸浮培養(yǎng)基培養(yǎng)耳蝸前體細(xì)胞。根據(jù)Notch3基因序列設(shè)計并合成2對siRNA,插入pSilencer4.1-CMV neo載體,進(jìn)行酶切及測序鑒定。采用脂質(zhì)體法向大鼠耳蝸前體細(xì)胞轉(zhuǎn)染重組質(zhì)粒,采用Real time-PCR和Western blotting法檢測重組質(zhì)粒對Notch3基因的干擾效果。結(jié)果經(jīng)前體細(xì)胞標(biāo)記物Abcg2染色鑒定證實(shí)原代培養(yǎng)的細(xì)胞球?yàn)槎伹绑w細(xì)胞。酶切及測序鑒定證實(shí)成功構(gòu)建了siRNA真核表達(dá)載體pSilencer-Notch3-S1和pSilencer-Notch3-S2。Real-time PCR和Western blotting檢測結(jié)果顯示所構(gòu)建的Notch3基因真核表達(dá)載體成功地干擾了目的基因的表達(dá)。與空白對照組比較,轉(zhuǎn)染pSilencer-Notch3-S1和pSilencer-Notch3-S2的細(xì)胞Notch 3 mRNA和蛋白表達(dá)量均有明顯減少,而轉(zhuǎn)染空質(zhì)粒的細(xì)胞與空白對照組比較無顯著差異。結(jié)論成功構(gòu)建了大鼠Notch3基因的RNAi真核表達(dá)載體,該載體在大鼠耳蝸前體細(xì)胞中對Notch3基因的表達(dá)可發(fā)揮抑制作用。
Notch3;小分子干擾;耳蝸; 前體細(xì)胞
感音神經(jīng)性聾嚴(yán)重影響著人們的健康和生存質(zhì)量,其主要病變部位位于耳蝸毛細(xì)胞和螺旋神經(jīng)元[1]。近年研究發(fā)現(xiàn),新生哺乳動物耳蝸中存在一定數(shù)量的具有成體干細(xì)胞特點(diǎn)的前體細(xì)胞,是細(xì)胞移植治療感音神經(jīng)性聾極佳的種子細(xì)胞[2-4]。Notch信號通路是一個在進(jìn)化中高度保守的反映細(xì)胞間通訊機(jī)制的通路,調(diào)控細(xì)胞的增殖、分化和凋亡,在胚胎發(fā)育和細(xì)胞命運(yùn)的決定中發(fā)揮著重要作用[2-3]。本研究構(gòu)建針對Notch3基因的siRNA真核表達(dá)載體,以抑制大鼠耳蝸前體細(xì)胞中Notch3基因的表達(dá),為進(jìn)一步研究Notch3在耳蝸前體細(xì)胞分化過程中的作用奠定基礎(chǔ)。
1.1實(shí)驗(yàn)動物 新生3d的SD大鼠[SCXK (陜)2007-001],由西安交通大學(xué)醫(yī)學(xué)院實(shí)驗(yàn)動物中心提供。實(shí)驗(yàn)由西安交通大學(xué)動物實(shí)驗(yàn)管理委員會批準(zhǔn),符合美國國立衛(wèi)生研究院(NIH)發(fā)布的實(shí)驗(yàn)動物應(yīng)用和保護(hù)指南。
1.2主要試劑 增殖培養(yǎng)液和分化培養(yǎng)液[2]:DMEM/F12(97ml)、B27(2ml)、N2(1ml)購自美國Gibco公司,EGF(20ng/ml)、bFGF(10ng/ml)購自美國PeproTech公司;氨芐霉素(50μg/ml)購自美國Amresco公司。多克隆兔抗Abcg2一抗和鼠抗GAPDH購自美國Santa Cruz公司,Notch3大鼠抗體購自美國Cell Signaling公司,二抗(Cy3標(biāo)記山羊抗兔IgG和FITC標(biāo)記山羊抗小鼠IgG)購自美國Jackson Immuno Research公司,4,6-二脒基-2-苯基吲哚(4,6-diamidino-2-phenylindole,DAPI)購自美國Sigma公司,pSilencer 4.1-CMV neo質(zhì)粒購自美國Ambion公司,限制性內(nèi)切酶BamH Ⅰ、HindⅢ及T4DNA連接酶購自美國NEB公司,質(zhì)粒抽提試劑盒購自天為時代公司,膠回收試劑盒購自廣州美津生物公司,LipofectamineTM2000轉(zhuǎn)染試劑盒購自美國Invitrogen公司,大腸埃希菌DH5α,Real-Time PCR試劑盒SYBR? Premix Ex TaqTMⅡ (Perfect Real Time) DRR081S和反轉(zhuǎn)錄試劑盒 PrimeScript? RT Master Mix DRR036S購自大連寶生物公司。
1.3針對Notch3基因的siRNA cDNA的制備根據(jù)Gen Bank報道的Notch3基因核苷酸序列NM_020087.2,應(yīng)用美國Ambion公司在線設(shè)計軟件選取Notch3的干擾位點(diǎn),共設(shè)計2對4條干擾序列:根據(jù)RNA干涉載體pSilencer 4.1-CMV neo的要求分別于上、下游引入BamH Ⅰ和HindⅢ的酶切位點(diǎn)。siRNA設(shè)計由北京奧科鼎盛生物科技有限公司合成。兩對干擾序列如下:Notch3-S1,5'-GATCCCTGCCGAAGCGACATAGATTTCAAG AGAATCTATGTCGCTTCGGCAGTTA-3';5'-AG CTTAACTGCCGAAGCGACATAGATTCTCTTGA AATCTATGTCGCTTCGGCAGG-3';Notch3-S2,5'-GATCCGCCTACCCTGCACGGAGGCTTCAAGA GAGCCTCCGTGCAGGGTAGGCTTA-3';5'-AGC TTAAGCCTACCCTGCACGGAGGCTCTCTTGAA GCCTCCGTGCAGGGTAGGC G-3'。
1.4Notch3-siRNA表達(dá)載體的構(gòu)建及鑒定 將以上2條干擾序列分別退火,形成帶有黏端的雙鏈,用T4連接酶連接插入pSilencer 4.1-CMV neo質(zhì)粒BamH Ⅰ及HindⅢ位點(diǎn)之間,參照Ambion公司說明書,連接產(chǎn)物轉(zhuǎn)化DH5α感受態(tài)細(xì)胞,LB平板篩選陽性克隆。轉(zhuǎn)化后挑取單個白色菌落,接種于5ml 100μg/ml Amp LB培養(yǎng)液,37℃振蕩過夜培養(yǎng),提取質(zhì)粒,用BamH Ⅰ及Hind Ⅲ雙酶切鑒定,送北京奧科鼎盛生物科技有限公司測序。
1.5原代耳蝸前體細(xì)胞的培養(yǎng) 無菌環(huán)境下獲取新生3d大鼠的耳蝸感覺上皮[1],加入0.25%胰酶/ EDTA 37℃消化5min,期間吹打40~50次,加入含5%胎牛血清的DMEM/F12液終止消化。1000r/min離心5min,棄上清,添加增殖培養(yǎng)基液重懸,接種于4孔懸浮細(xì)胞培養(yǎng)板中(美國Nunc公司)。置入37℃、5%CO2孵箱。
1.6免疫細(xì)胞化學(xué)染色 4%多聚甲醛(pH 7.4)室溫固定細(xì)胞20min;PBS洗滌,加入0.2% Triton X-100溶液20min;PBS洗滌,以2%BSA封閉非特異性結(jié)合位點(diǎn)30min;加一抗孵育,4℃過夜;PBS洗滌,加入二抗室溫避光孵育2h,PBS洗滌。采用0.2% DAPI進(jìn)行細(xì)胞核染色,熒光顯微鏡下觀察。
1.7瞬時轉(zhuǎn)染 采用增殖培養(yǎng)基懸浮培養(yǎng)3d,吸出所獲細(xì)胞球并種植在預(yù)先用鼠尾膠原包被處理過的6孔板中,加分化液,置于37℃、5%CO2孵箱貼壁培養(yǎng)2d,光學(xué)顯微鏡下觀察貼壁良好且融合率達(dá)到80%左右的細(xì)胞進(jìn)行轉(zhuǎn)染。轉(zhuǎn)染步驟按照LipofectamineTM2000試劑說明書操作。實(shí)驗(yàn)共分4組,空白對照組:未進(jìn)行轉(zhuǎn)染的細(xì)胞;pSilencer-C組:pSilencer空載體轉(zhuǎn)染;pSilencer-Notch3-S1干擾組和pSilencer-Notch3-S2干擾組:分別接受pSilencer-Notch3-S1干擾質(zhì)粒和pSilencer-Notch3- S2質(zhì)粒轉(zhuǎn)染。
1.8Real-time PCR法檢測干涉效果 瞬時轉(zhuǎn)染72h后,收集各組細(xì)胞,參照Trizol Reagent說明提取細(xì)胞總RNA。用PrimeScript? RT Master Mix DRR036S試劑盒將提取的RNA反轉(zhuǎn)錄合成cDNA。以GAPDH作為內(nèi)參照。Notch 3,F(xiàn): GGCTACCTTGGCTCTGCTGAA;R:AGCAGCTTGGCAGCCTCATA,產(chǎn)物114bp;GAPDH,F(xiàn):GGCACAGTCAAGGCTGAGAATG;R:ATGGTGGTGAAGACGCCAGTA,產(chǎn)物143bp。Real-time PCR采用美國Applied Biosystems公司StepOneTM實(shí)時熒光定量PCR系統(tǒng),采用StepOneTMSoftware V2.1分析。Real-Time PCR反應(yīng)的擴(kuò)增程序如下:95℃預(yù)變性30s;95℃ 5s,60℃ 31s,40個循環(huán)。
1.9Western blotting檢測干預(yù)效果 瞬時轉(zhuǎn)染48h后收獲細(xì)胞,約1×106個細(xì)胞加入100μl細(xì)胞裂解液進(jìn)行裂解,提取細(xì)胞總蛋白,取變性樣品進(jìn)行6%SDS-PAGE蛋白電泳,通過電轉(zhuǎn)儀將蛋白轉(zhuǎn)移至硝酸纖維素膜,5%脫脂奶粉封閉非特異性結(jié)合位點(diǎn)2h,將膜與相應(yīng)一抗4℃孵育12h,洗滌,二抗室溫孵育2h,洗滌,加入化學(xué)發(fā)光底物(super signal west dura extended duration substrate,PIERCE),暗室X光片曝光、顯影、定影,以GAPDH作為內(nèi)參照。采用NIH Image J軟件測量各條帶光密度值。半定量結(jié)果以樣品條帶的光密度值/GAPDH光密度值表示。
2.1獲取耳蝸前體細(xì)胞 經(jīng)機(jī)械分離及胰酶消化,獲取新生3d大鼠耳蝸感覺上皮細(xì)胞,并于懸浮培養(yǎng)基培養(yǎng)。獲得懸浮生長的細(xì)胞克隆稱為細(xì)胞球,經(jīng)前體細(xì)胞標(biāo)記物Abcg2染色鑒定該細(xì)胞球?yàn)槎伹绑w細(xì)胞(圖1)。
圖1 Abcg2在大鼠耳蝸前體細(xì)胞的表達(dá)Fig.1 Expression of Abcg2 in cochlear progenitor cellsA. Images of cochlear progenitor spheres; B. Nuclei labeled with DAPI (blue); C. Expression of Abcg2, progenitor cell marker, on the sphere (red)
2.2siRNA干涉載體構(gòu)建鑒定 DNA測序結(jié)果證實(shí),2個載體都成功插入了干擾片段,堿基順序符合所設(shè)計的siRNA序列。將測序正確的成功插入干擾片段的質(zhì)粒分別命名為pSilencer-Notch3-S1和pSilencer-Notch3-S2(圖2)。備用于后續(xù)實(shí)驗(yàn)。
圖2 pSilencer-Notch3- siRNA重組質(zhì)粒酶切測序峰圖Fig.2 Sequencing of pSilencer-Notch3- siRNA
2.3Real-time PCR結(jié)果 Real-time PCR半定量結(jié)果顯示,空白對照組、pSilencer-C組、pSilencer-Notch3-S1干擾組和pSilencer-Notch3-S2干擾組的相對表達(dá)量分別為:1(ΔΔCt 0)、0.920024 (ΔΔCt 0.120256)、0.403224 (ΔΔCt 1.190088749)和0.503461(ΔΔCt 0.990049)。由結(jié)果可見,pSilencer-Notch3-S1和pSilencer-Notch3-S2組Notch3mRNA表達(dá)水平明顯降低。
2.4Western blotting檢測結(jié)果 pSilencer-Notch3-S1和pSilencer-Notch3-S2組Notch3蛋白表達(dá)水平明顯減少,與空白對照組比較分別減少了67.5%和51.6%,pSilencer-C組無顯著變化(圖3)。各組細(xì)胞中GAPDH蛋白表達(dá)量基本一致。
圖3 轉(zhuǎn)染細(xì)胞Notch3蛋白表達(dá)情況(Western blotting)Fig. 3 Expression of Notch3 in the transfected cochlear progenitor cells (Western blotting)1. Blank; 2. pSilencer-C; 3. Negative control; 4. pSilencer-Notch3-S1; 5. pSilencer-Notch3-S2
在鳥類和許多低等脊椎動物中可以觀察到毛細(xì)胞損傷后,一部分支持細(xì)胞重新進(jìn)入細(xì)胞周期并分化產(chǎn)生新的毛細(xì)胞和支持細(xì)胞[3]。但是在哺乳動物的耳蝸毛細(xì)胞損傷后卻沒有這種再生現(xiàn)象[5-6]。近年研究發(fā)現(xiàn)新生哺乳動物耳蝸感覺上皮細(xì)胞可以分離出耳蝸前體細(xì)胞,并可形成能自我更新、增殖的懸浮細(xì)胞球,貼壁生長后可分化為毛細(xì)胞樣細(xì)胞[3]。
Abcg2蛋白是細(xì)胞表面轉(zhuǎn)運(yùn)蛋白ABC(ATP binding cassette)超家族成員之一[4],被認(rèn)為是干細(xì)胞/前體細(xì)胞的通用標(biāo)志[7]。2007年Savary等[8]利用Abcg2蛋白作為標(biāo)記物,成功分選出耳蝸前體細(xì)胞。本研究經(jīng)機(jī)械分離和胰酶消化新生大鼠耳蝸感覺上皮,獲取了Abcg2表達(dá)陽性的耳蝸前體細(xì)胞。
耳蝸前體細(xì)胞的分化受多種因素調(diào)節(jié),其中Notch信號通路在細(xì)胞的增殖、分化過程中起著重要調(diào)控作用。在哺乳動物中Notch受體的同源分子有4種,分別是Notch1、Notch2、Notch3和Notch4。Notch信號的活性受到諸多因素的調(diào)節(jié),不同Notch蛋白可激活不同的Notch信號通路[9]。有研究認(rèn)為在耳蝸前體細(xì)胞的分化過程中,正在分化為耳蝸毛細(xì)胞的前體細(xì)胞可通過激活其相鄰細(xì)胞的Notch1,抑制Math1的表達(dá),相鄰細(xì)胞即無法向毛細(xì)胞方向分化而分化為支持細(xì)胞,同時該細(xì)胞反過來激活毛細(xì)胞的Notch3來抵消毛細(xì)胞內(nèi)Notch1的作用,也就是說Notch1活化可抑制細(xì)胞分化,Notch3活化可以拮抗Notch1的作用,也可能是引發(fā)細(xì)胞分化的作用,但這一模式尚未得到完全證實(shí)[10]。
目前針對Notch3的研究相對較少,Notch3在耳蝸前體細(xì)胞分化過程中的作用尚不明確。為此本研究構(gòu)建了Notch3基因的RNA干擾質(zhì)粒,用RNAi技術(shù)封閉大鼠耳蝸前體細(xì)胞Notch3基因的表達(dá)。RNAi不僅可抑制體外細(xì)胞特定基因的表達(dá),而且也可抑制體內(nèi)特定基因的表達(dá),具有高效性和高特異性[11-12]。
DNA測序證實(shí),本研究所構(gòu)建的針對Notch3基因的pSilencer-Notch3-S1和pSilencer-Notch3-S2表達(dá)載體都成功插入了干擾片段。但用干擾載體通過脂質(zhì)體瞬時轉(zhuǎn)染新生大鼠耳蝸前體細(xì)胞是一個較為棘手的問題。一般來說,懸浮生長的具有干細(xì)胞特性的原代前體細(xì)胞脂質(zhì)體轉(zhuǎn)染效率比較低,為此本研究將懸浮培養(yǎng)5d的耳蝸前體細(xì)胞球種植在預(yù)先用鼠尾膠原包被處理過的培養(yǎng)板上,誘導(dǎo)其貼壁,短暫貼壁培養(yǎng)36h,既保證了前體細(xì)胞不發(fā)生分化,又提高了轉(zhuǎn)染效率。同時經(jīng)過反復(fù)摸索轉(zhuǎn)染條件,得出脂質(zhì)體和質(zhì)粒DNA的最佳使用量均為脂質(zhì)體轉(zhuǎn)染說明建議用量的一半,這樣既能保證轉(zhuǎn)染效率較高,又減少了脂質(zhì)體對細(xì)胞的損傷。轉(zhuǎn)染成功后該載體在CMV啟動子調(diào)控下表達(dá)siRNA。
為了檢驗(yàn)RNA干擾的效率,本研究首先從干擾效應(yīng)的第一個環(huán)節(jié)mRNA水平進(jìn)行檢測。Real time-PCR結(jié)果表明,pSilencer-Notch3-S1和pSilencer-Notch3-S2實(shí)驗(yàn)組Notch3基因的mRNA表達(dá)受到了明顯抑制。第二步,從蛋白水平檢測Notch3蛋白的表達(dá)水平,與mRNA水平相對應(yīng),Western blotting結(jié)果證實(shí)pSilencer-Notch3-S1和pSilencer-Notch3-S2實(shí)驗(yàn)組的Notch3蛋白表達(dá)明顯下降,說明在RNA干擾開始發(fā)揮作用后,由于mRNA結(jié)構(gòu)的破壞,無論缺失起始密碼子或終止密碼子都將導(dǎo)致翻譯不能正常進(jìn)行。
本研究所構(gòu)建的針對Notch3基因的siRNA真核表達(dá)載體對新生大鼠耳蝸前體細(xì)胞中Notch3基因的表達(dá)有明顯的抑制作用,表明所構(gòu)建的siRNA成功地發(fā)揮了干涉效應(yīng),從而為進(jìn)一步研究Notch3基因以及整個Notch通路在耳蝸前體細(xì)胞分化過程中的作用奠定了基礎(chǔ)。
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Blocking effect of vector-based siRNA on Notch3 gene expression in rat cochlear progenitor cells
WANG Jun-li, XU Ying-long, XU Min*
Department of Otolaryngology-HNS, Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710004, China
*
E-mail: ent551205@163.com
ObjectiveTo explore the blocking effect of siRNA on the expression of Notch3 gene in rat cochlear progenitor cells using siRNA eukaryotic expression vector.MethodsThe sensory epithelial cells of neonatal rat cochlea were mechanically isolated, and then they underwent trypsin digestion and suspension culture to acquire cochlear progenitor cells. Immunfluorescence staining of Abcg2 expression was applied to confirm the acquired cochlear progenitor cells. Two siRNA cDNAs were synthesized according to the Notch3 gene sequence and cloned into the vector pSilencer4.1-CMV neo, namely pSilencer-Notch3-S1 and pSilencer-Notch3-S2 respectively, and they were further identified by restriction endonuclease digestion analysis and DNA sequencing. The cochlear progenitor cells were then transfected with pSilencer-Notch3-S1 and pSilencer-Notch3-S2. The interfering effect was detected by Real-time PCR and Western blotting.ResultsThe clonal growth cell spheres were acquired and identified to contain Abcg2 positive cochlear progenitor cells. The vectors were successfully constructed and confirmed by DNA sequencing restriction endonuclease digestion analysis. DNA sequencing showed that the two target segments were cloned into pSilencer4.1-CMV neo-vector respectively. Western blotting showed that the protein expression decreased significantly in pSilencer-Notch3-S1 transfected cochlear progenitor cells. Real-time PCR demonstrated a significant decrease in expression of Notch3 mRNA in both pSilencer-Notch3-S1 group and pSilencer-Notch3-S2 group.ConclusionThe vector-based siRNA on Notch3 gene can effectively inhibit the expression of Notch3 gene in rat cochlear progenitor cells.
Notch3;RNA interfering; cochlea; progenitor cells
R329.492
A
0577-7402(2013)05-0369-04
2013-01-22;
2013-03-28)
(責(zé)任編輯:李恩江)
國家自然科學(xué)基金(30973300)
王軍利,博士研究生。主要從事耳聾的基礎(chǔ)與臨床研究
710004 西安 西安交通大學(xué)第二附屬醫(yī)院耳鼻喉科(王軍利、許映龍、許珉)
許珉,E-mail:ent551205@163.com
This work was supported by the National Natural Science Foundation of China (30973300)