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通讯作者:

袁庆新,E-mail:yqx@njmu.edu.cn

中图分类号:R714.25

文献标识码:A

文章编号:1007-4368(2022)07-921-11

DOI:10.7655/NYDXBNS20220703

参考文献 1
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参考文献 2
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参考文献 10
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参考文献 11
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参考文献 13
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参考文献 14
ZHANG Y,WU H,WANG F,et al.Long non ⁃ coding RNA MALAT1 expression in patients with gestational dia⁃ betes mellitus[J].Int J Gynaecol Obstet,2018,140(2):164-169
参考文献 15
AMARAL M E,CUNHA D A,ANHÊ G F,et al.Participa⁃ tion of prolactin receptors and phosphatidylinositol 3⁃ ki⁃ nase and MAP kinase pathways in the increase in pancre⁃ atic islet mass and sensitivity to glucose during pregnancy [J].J Endocrinol,2004,183(3):469-476
参考文献 16
LI J,YING H,CAI G,et al.Pre⁃eclampsia⁃associated re⁃ duction in placental growth factor impaired beta cell pro⁃ liferation through PI3k signalling[J].Cell Physiol Bio⁃ chem,2015,36(1):34-43
参考文献 17
HAKONEN E,USTINOV J,PALGI J,et al.EGFR signal⁃ ing promotes β⁃cell proliferation and survivin expression during pregnancy[J].PLoS One,2014,9(4):e93651
参考文献 18
DUAN M Y,LI M,TIAN H,et al.Down⁃regulation of ln⁃ cRNA NEAT1 regulated by miR⁃194⁃5p/DNMT3A facili⁃ tates acute myeloid leukemia[J].Blood Cells Mol Dis,2020,82:102417
参考文献 19
GREMLICH S,DAMNON F,REYMONDIN D,et al.The long non ⁃coding RNA NEAT1 is increased in IUGR pla⁃ centas,leading to potential new hypotheses of IUGR ori⁃ gin/development[J].Placenta,2014,35(1):44-49
参考文献 20
ZHAO K,YE Z,LI Y,et al.lncRNA FTX contributes to the progression of colorectal cancer through regulating miR⁃192⁃5p/EIF5A2 axis[J].Onco Targets Ther,2020,13:2677-2688
参考文献 21
YANG X,TAO L,ZHU J,et al.Long noncoding RNA FTX reduces hypertrophy of neonatal mouse cardiac myo⁃ cytes and regulates the PTEN/PI3K/Akt signaling path⁃ way by sponging microRNA⁃22[J].Med Sci Monit,2019,25:9609-9617
目录contents

    摘要

    目的:对正常孕鼠和宫内发育迟缓(intrauterine growth retardation,IUGR)小鼠孕期胰岛RNA进行高通量测序分析, 筛选出差异表达的长链非编码RNA(long non⁃coding RNA,lncRNA)和信使RNA(messenger RNA,mRNA),为深入探讨IUGR孕鼠胰岛功能障碍的发病机制提供理论基础。方法:提取IUGR成年后孕鼠和正常孕鼠胰岛RNA并进行高通量测序,筛选出差异表达的lncRNA和mRNA,进行lncRNA和mRNA关联分析,对lncRNA相关的靶mRNA进行GO功能注释分析、KEGG通路富集分析,重点关注高差异表达且可能影响孕期胰岛功能的lncRNA。结果:IUGR孕鼠和正常孕鼠差异表达的lncRNA 1007个, 其中483个上调,524个下调;差异表达的mRNA 50个,其中22个上调,28个下调。对差异lncRNA的靶mRNA和差异mRNA进行功能分析,GO分析示它们参与的生物学途径集中于细胞及组织过程、生物调节、代谢及应激过程;分子功能集中在整合、催化活性、转运活性、分子功能调节等方面;KEGG分析示它们主要集中在代谢、癌症、次生代谢产物的生物合成、PI3K⁃AKT及 MAPK 通路。对差异表达的lncRNA FTX 和Neat1进一步分析表明,IUGR 孕鼠和正常孕鼠的FTX 表达量分别较未孕时下降 (P < 0.001),而 Neat1上升(P < 0.01);FTX、Neat1表达量在IUGR孕鼠和正常孕鼠间有显著差异(P < 0.05),且表达量受糖浓度调节。lncRNA FTX与其靶mRNA均为反式(trans)作用,lncRNA Neat1与Frmd8为顺式(cis)作用,余为trans作用。结论:本研究筛选出IUGR孕鼠和正常孕鼠胰岛中差异表达的lncRNA和mRNA,lncRNA通过不同互作关系调控靶mRNA,调节糖代谢过程。

    Abstract

    Objective:High ⁃throughput sequencing analysis was performed in adult islets RNAs of normal mice and intrauterine growth retardation(IUGR)mice during pregnancy,which screened out differentially expressed long non ⁃coding RNA(lncRNA)and messenger RNA(mRNA)to provide a theoretical basis for further exploring the pathogenesis of islet dysfunction in pregnant mice born with IUGR. Methods:Islet RNAs were extracted from IUGR and normal pregnant mice for high⁃throughput sequencing analysis. The differentially expressed lncRNAs and mRNAs were screened and association analysis between them was performed. We conducted gene ontology(GO)analyisis,Kyoto encyclopedia of gene and genome(KEGG)enrichment analysis on taget mRNAs of differentially expressed lncRNAs. Emphasis was placed on the highly differentially expressed lncRNAs,especially those that may be involved in the regulation of islet function during pregnancy. Results:There were 1007 differentially expressed lncRNAs between IUGR pregnancy (IP)and normal pregnancy(NP),among which 483 were up⁃regulated and 524 were down⁃regulated. Fifty mRNAs were differentially expressed,of which 22 were up ⁃ regulated and 28 were down ⁃ regulated. The GO analysis of differentially expressed lncRNAs’target mRNAs and differentially expressed mRNAs showed that biological process(BP)mainly focused on cellular and tissue processes, biological regulation,metabolism and stress processes;molecular functions(MF)were concentrated in integration,catalytic activity, transport activity,molecular function regulation,etc. KEGG enrichment analysis highlighted the involvement of metabolic pathway, cancer pathway,biosynthesis of secondary metabolites,PI3K ⁃AKT pathway and MAPK pathway. We furether analysed lncRNA FTX and Neat1. The expression level of FTX in normal mice and IUGR mice during pregnancy decreased(P < 0.001),while lncRNA Neat1 increased(P < 0.01). FTX and Neat1 exhibited significantly difference in the expression between IP and NP(P < 0.05),and both were regulated by glucose concentration. The association between lncRNA FTX and its target mRNAs was trans ⁃ action. The association between lncRNA Neat1 and Frmd8 was cis⁃action,while the rest were trans⁃action. Conclusion:In this study,differentially expressed lncRNAs and mRNAs in adult islets of normal mice and intrauterine growth retardation(IUGR)mice during pregnancy were screened. Besides,lncRNAs can regulate target mRNAs through different interaction modes,thus influencing glucose metabolism.

  • 糖尿病受遗传因素和环境因素共同作用,随着健康与疾病发育起源理论的提出,“胎源性疾病”受到越来越多的重视,子宫内环境改变、胚胎宫内发育不良及表观遗传的变化,将影响其成年后代谢性疾病的发生,这些个体成年后怀孕又将出现进一步代谢异常,这种跨代效应导致糖尿病发病率不断增加,从胚胎发育及孕期入手探究糖尿病的发病机制是目前热点之一。

  • 宫内发育迟缓(intrauterine growth retardation, IUGR)是常见的胚胎发育异常形式,可以导致新生期个体的胰岛面积明显减少,胰岛素染色减弱,胰岛较正常少且松散,血清胰岛素含量低于正常,成年后容易发生糖耐量异常[1],这些IUGR雌性个体成年后,面对怀孕这一压力测试,可能出现进一步的代谢失衡、胰岛功能障碍。

  • 许多研究已证实正常妊娠期母体会经历一系列的生理变化,以满足自身和胎儿不断变化的营养需求,包括心血管系统、肾脏系统、血液系统、呼吸系统和内分泌系统的适应性改变。孕期雌激素、孕激素、胎盘催乳素、胎盘生长激素、脂联素、瘦素等水平的变化及碳水化合物代谢的增加,导致生理性胰岛素抵抗,胰岛β细胞团出现代偿性增殖,从而保证妊娠期母体的糖代谢平衡。IUGR雌性个体成年后妊娠期会出现怎样的代谢及胰岛功能改变,其可能机制如何,目前少有研究。

  • 文献表明,成年期的糖代谢异常可能是其生命早期环境印迹的“程序化”结果,表观遗传学在其中发挥着重要作用[2]。表观遗传主要包括DNA甲基化、组蛋白修饰、染色质重塑、非编码RNA等,是指基因的核苷酸序列不发生改变的情况下,基因表达发生可遗传的变化。非编码转录本依据其大小分为两类,具有200个或更少核苷酸的(nucleotide,nt) 为小非编码RNA,包括微小RNA(microRNA,miRNA)、与piwi蛋白作用的RNA(piwi ⁃ interacting RNA,piRNA)和小干扰RNA(small interference RNA, siRNA);超过200nt的非编码RNA为长链非编码RNA(long non ⁃coding RNA,lncRNA),不编码蛋白质,结构上与信使RNA(messenger RNA,mRNA)相似,但缺乏开放阅读框,位于细胞质或细胞核内,核lncRNA主要参与表观遗传基因调控或维持核结构,而细胞质lncRNA参与转录后基因调控[3]。在人胰岛和纯化的β细胞[4] 以及小鼠胰岛细胞[5] 已经发现有1 000多条lncRNA表达,部分参与胰岛β细胞的分化成熟过程,且表达受糖浓度调节。lncRNA的表达在时间和空间上都受到严格的调控,因此失调的表达谱是疾病或发育状态改变的重要标志。

  • 本研究首先通过孕期给予母鼠8%的低蛋白饮食获得IUGR新生小鼠,然后待新生小鼠成年后与同周龄雄鼠配繁,最后获得IUGR孕鼠。对IUGR孕鼠 (IUGR pregnancy,IP)和正常孕鼠(normal pregnancy, NP)胰岛RNA进行高通量测序分析,比较两者lncRNA和mRNA表达差异,对差异lncRNA的靶mRNA和差异mRNA进行功能注释和富集通路分析,为糖尿病的早期预防和诊治提供新思路。

  • 1 材料和方法

  • 1.1 材料

  • 8周龄C57BL/6雄性小鼠16只、雌性小鼠32只购自上海南方模式生物科技股份有限公司,动物饲养和实验均通过南京医科大学实验动物福利伦理委员会(IACUC)批准。小鼠胰岛β细胞系min6细胞来自南京医科大学第一附属医院内分泌科实验室。

  • RNA isolater Total RNA Extraction Reagent、 SYBR Green Master Mix(南京Vazyme公司);Primer⁃ ScriptTM RT Master Mix(TaKaRa公司,日本);RNA引物(上海Invitrogen公司);Histopaque1077(Sigma公司,美国)。PCR扩增仪(Eppendorf公司,美国);实时定量PCR仪(Thermo Fisher公司,美国);Nano Drop超微分光光度仪(Thermo Fisher公司,美国)。

  • 1.2 方法

  • 1.2.1 实验动物造模

  • 8周龄C57B6/L小鼠饲养在SPF级环境。待小鼠适应环境后,傍晚雄性与雌性以1∶2合笼,次日清晨以阴道有精栓且阴道涂片发现精子为确定妊娠。

  • NP组:自确定妊娠开始予以标准繁殖饲料(蛋白含量为20%)。IP组:①IUGR小鼠造模。孕鼠自确定妊娠开始予以低蛋白饲料(购自北京协同生物有限公司,等热量、8%的蛋白质含量)至新生小鼠出生;IUGR小鼠造模成功标准:新生鼠体重低于同胎龄同性别小鼠体重的第10百分位点以下;②IUGR雌小鼠8周成年后与同周龄雄鼠合笼,自受孕开始饲以标准繁殖饲料(蛋白含量为20%)。

  • 1.2.2 小鼠胰岛的提取

  • NP、IP孕鼠各3只,用1%戊巴比妥钠麻醉后固定,剖开腹腔,分离穿刺胆总管,注入冷胶原酶消化、过细胞筛网,收集胰岛,放入Histopaque1077中纯化。所有胰岛均在显微镜下手挑计数。

  • 1.2.3 差异RNA检测分析

  • 广州基迪奥生物科技有限公司使用RNA isolater Total RNA Extraction Reagent裂解胰岛细胞,提取总RNA后使用Nano Drop超微分光光度仪进行RNA质检。

  • 从总RNA中去除核糖体RNA,以最大限度地保留所有编码RNA(coding RNA)和非编码RNA (non⁃coding RNA,ncRNA)。得到的RNA随机打断成为短片段,再以片断化后的RNA为模板,用六碱基随机引物(random hexamers)合成cDNA第1链; 接着加入缓冲液、dNTPs(dUTP代替dTTP)、RNase H和DNA polymeraseⅠ合成cDNA第2链,经过QiaQuick PCR试剂盒纯化并加EB缓冲液洗脱经末端修复、加碱基A,加测序接头,然后通过UNG(uracil⁃N⁃ glycosylase)酶降解第2条链。用琼脂糖凝胶电泳进行片段大小选择,进行PCR扩增。最后建好的测序文库用Illumina⁃HiSeqTM 4000进行测序。

  • 对下机数据进行过滤得到clean data后,将reads用Tophat2(2.1.1)比对到小鼠参考基因组(ensemble104)上,并利用Cufflinks重构转录本,得到已知转录本与新转录本。利用CPC、CNCI等软件对新转录本进行编码能力预测,得到新预测的lncRNA。然后分别对样本中的mRNA、lncRNA进行表达量分析,并使用edgeR包对组间lncRNA和mRNA进行差异分析。|log2FC|>1,P< 0.05表示有差异。

  • 利用lncRNA与mRNA表达量的Pearson相关系数、RNAplex等预测lncRNA的靶mRNA,对靶基因进行基因本体论(gene ontology,GO)功能注释分析和京都基因与基因组百科全书数据库(Kyoto encyclopedia of genes and genomes,KEGG)通路富集分析。

  • 1.2.4 实时荧光定量PCR

  • 逆转录反应按照RT⁃PCR试剂盒说明书进行。将AceQ qPCR SYBR Green Master Mix(High ROX premixed)应用于StepOne Plus系统,进行qRT⁃PCR反应。反应体系20 μL:模板cDNA 1 μL,SYBR Green Master Mix 10 μL,上下游引物各0.4 μL,灭菌ddH2O 8.2 μL。引物序列如下,β⁃ actin:上游5′ ⁃ TGAGCTGCGTTTTACACCCT ⁃ 3′,下游5′ ⁃ TTTGG ⁃ GGGATGTTTGCTCCA⁃3′;Neat1:上游5′⁃CAAGAA⁃ ACAGCAACACCAGAAG ⁃ 3′,下游5′ ⁃ TAAGGTC ⁃ CCCATTCAAGTCAGT ⁃ 3′;FTX:上游5′ ⁃AAGATC ⁃ TCCGCTGCCAGATG⁃3′,下游5′⁃CTGCTCCTGTGC⁃ CACGAATA ⁃ 3′。反应条件:预变性95℃ 5min; 95℃ 10s,60℃ 30s,40个循环。根据熔解曲线判断引物的特异性及扩增效率,采用2-ΔΔCt法对基因相对表达量进行计算和分析。

  • 1.2.5 min6细胞的培养及不同糖浓度刺激

  • 小鼠胰岛细胞系min6细胞,其正常培养基 (糖浓度25mmol/L)的配制:84%的高糖DMEM (含4.5g/L葡萄糖),15%胎牛血清(FBS),1%双抗 (100U/mL青霉素和100 μg/mL链霉素),0.035%的2.5mmol/L β⁃巯基乙醇。细胞置于37℃、含5%CO2 培养箱中,每天更换新鲜培养基,融合度达80%左右进行传代。将高糖DMEM替换成低糖DMEM(含葡萄糖1g/L),余成分不变,此时低糖完全培养基的糖浓度为5.5mmol/L,然后在10mL低糖完全培养基中分别加入0.01、0.02、0.05g葡萄糖粉,得到11.1、 16.7、33.3mmol/L不同糖浓度的培养基。将min6细胞接种于6孔培养板中,待细胞贴壁后,加入无糖低血清(0.25%)培养基培养6~8h后弃去,分别加入不同糖浓度培养基2mL,标记好糖浓度,放入37℃、含5%CO2培养箱中,24h后收RNA。

  • 1.3 统计学方法

  • 使用Graphpad Prism 8.4.3软件绘制实验结果图,基因表达量以均值±标准差(x-±s)表示,两组间比较采用独立样本 t 检验,多组间比较采用单因素方差分析(one⁃way ANOVA)。P< 0.05为差异有统计学意义。

  • 2 结果

  • 2.1 lncRNA的组间差异

  • 在NP、IP中共鉴定出个30 426个lncRNA转录本,其中已知的转录本13 404(44%),新的转录本943个。使用edgeR软件对组间lncRNA的表达量进行差异分析,发现在NP和IP中有差异表达的lncRNA 1 007个,其中483个上调,524个下调。图1示差异表达lncRNA的火山图和热图。表1列举了10个高差异表达的lncRNA。

  • 2.2 mRNA分析

  • 2.2.1 mRNA的组间差异

  • 在NP、IP中共鉴定出66 652个mRNA转录本,其中已知的转录本43 034个(64.57%),新的转录本10 018个。使用edgeR软件对组间mRNA的表达量进行差异分析,发现在NP和IP中有差异表达的mRNA 50个,其中22个上调,28个下调。图2示差异表达的mRNA的火山图和热图。表2列举了10个高差异表达的mRNA。

  • 2.2.2 差异mRNA的GO/KEGG通路富集分析

  • 图3显示了差异mRNA的KEGG通路富集分析和GO功能注释分析。KEGG信号通路富集分析中,按基因数量从多到少排序,前5位分别是代谢通路 (metabolic pathways)(4个基因)、PI3K⁃Akt信号通路 (PI3K⁃Akt signaling pathway)(3个基因)、内质网中的蛋白质加工(protein processing in endoplasmic reticulum)(3个基因)、集落黏附(focal adhesiom) (3个基因)、AMPK信号通路(AMPK signaling pathway)(2个基因)(图3A)。GO功能注释分析中绿色表示下调基因,红色表示上调基因,按照参与GO富集条目下调基因的数量排序,生物学途径(biological process,BP)中前5位是细胞进程(cellular process) (18个基因)、单有机体过程(single⁃origanism process) (16个基因)、生物调节(biological regulation)(11个基因)、代谢过程(metabolic process)(11个基因)、刺激反应(response to stimulus)(9个基因);细胞组分(cellular component,CC)中前5位是细胞(cell) (22个基因)、细胞部分(cell part)(22个基因)、细胞器(organelle)(21个基因)、细胞器部分(organelle part)(13个基因)、细胞膜(membrane)(12个基因); 分子功能(molecular function,MF)中前4位是绑定 (binding)(18个基因)、催化活性(catalytic activity) (9个基因)、转运活性(transporter activity)(4个基因)、化学排斥物活性(chemorepellent activity)(1个基因)(图3B)。

  • 图1 正常孕鼠和IUGR孕鼠差异表达的lncRNA

  • Fig.1 Differentially expressed lncRNAs between normal pregnant and IUGR pregnant mice

  • 表1 差异表达的lncRNA

  • Table1 Differentially expressed lncRNAs

  • 图2 正常孕鼠和IUGR孕鼠差异表达的mRNA

  • Fig.2 Differentially expressed mRNAs between normal pregnant and IUGR pregnant mice

  • 表2 差异表达的mRNA

  • Table2 Differentially expressed mRNAs

  • 图3 正常孕鼠和IUGR孕鼠差异mRNA的KEGG和GO富集分析图

  • Fig.3 The KEGG and GO enrichment analysis of differentially expressed mRNAs between normal and IUGR pregnant mice

  • 2.3 lncRNA与mRNA的关联分析

  • lncRNA参与调控许多转录后进程。对mRNA的调控方式包括:反义(antisense)作用、顺式(cis)作用、反式(trans)作用。

  • 2.3.1 antisense作用

  • antisense作用指一部分反义lncRNA与正义的mRNA结合而调控基因沉默、转录及mRNA的稳定性。图4A列举了3个差异lncRNA与其靶mRNA的antisense作用,antisense作用具有高度的保守性和稳定性[6],其中lncRNA Ppp1ca被报道通过MAPK通路参与肿瘤的发生[7],其与Rad9A的互作关系未被研究,lncRNA 1010001N08Rik、AC154652.2未曾有报道。差异lncRNA antisense作用的靶mRNA的KEGG、GO富集分析如图4所示,KEGG信号通路分析中按富集基因数量排序,前5位分别是metabolic pathways(511个基因)、癌症通路(pathway in cancer) (204个基因)、MAPK信号通路(MAPK signaling pathway)(167个基因)、次生代谢物的生物合成 (biosynthesis of secondary metabolites)(158个基因)、 PI3K ⁃Akt signaling pathway(157个基因)(图4B)。 GO功能注释分析中按基因数目排序,BP中前5位是cellular process(4 050个基因)、single ⁃ organism process(3 712个基因)、biological regulation(3 208个基因)、metabolic process(2 184个基因)、response to stimulus(1 904个基因);CC中前5位分别是cell (4 249个基因)、cell part(4 224个基因)、organelle (3 310个基因)、membrane(2 520个基因)、organelle part(2 128个基因);MF中前5位分别是binding (4 499个基因)、catalytic activity(1 943个基因)、 transporter activity(460个基因)、分子功能调节 (molecular function regulator)(437个基因)、核酸结合转录因子活性(nucleic acid binding transcription factor activity)(377个基因)(图4C)。

  • 图4 差异lncRNA与其靶mRNA的antisense作用及靶mRNA的KEGG和GO富集分析

  • Fig.4 The antisense between differentially expressed lncRNA and its target mRNA,the KEGG and GO enrichment analysis of the target mRNA

  • 2.3.2 cis作用

  • cis作用指同一染色体上lncRNA的功能与其邻近的蛋白编码基因相关,位于这些基因上游或下游10kb的lncRNA可能在转录或转录后水平对基因的表达进行调控。图5A列举了3个差异lncRNA与其靶mRNA的cis作用。cis调控主要依赖顺式作用元件进行,顺式作用元件是指存在于基因旁侧序列中能影响基因表达的序列,包括启动子、增强子、调控序列和可诱导元件等,它们参与核内基因表达的调控,顺式作用元件通常转录为非编码RNA,如lncRNA。图5A中lncRNA Ppp1ca、1010001N08Rik、 AC154652.2通过cis分别和Rad9A、Gata6、Slc37a1有互作关系,而图4A是通过antisense作用有互作关系,这是因为lncRNA和mRNA链较长,antisense作用的位置和区域与cis作用的位置区域有所不同。差异lncRNA cis作用的靶mRNA的KEGG、GO富集分析如图5所示,KEGG信号通路富集分析中按照基因数量排序,前5位分别是metabolic pathways (847个基因)、pathways in cancer(284个基因)、 biosynthesis of secondary metabolites(254个基因)、胞吞(endocytosis)(229个基因)、PI3K ⁃ Akt signaling pathway(219个基因)(图5B)。GO功能注释分析中按基因数目排序,BP中前5位是cellular process (6 308个基因)、single⁃organism process(5 438个基因)、biological regulation(4 618个基因)、metabolic process(3 780个基因)、response to stimulus(2 718个基因);CC中前5位分别是cell(6 745个基因)、cell part(6 430个基因)、organelle(5 119个基因)、 membrane(3 610个基因)、organelle part(3 459个基因);MF中前5位分别是binding(6 813个基因)、 catalytic activity(3 102个基因)、molecular function regulator(601个基因)、transporter activity(555个基因)、nucleic acid binding transcription factor activity (515个基因)(图5C)。

  • 2.3.3 trans作用

  • trans作用指lncRNA的功能与编码基因的位置没有关系,而与其共表达的蛋白编码基因相关,可以通过样本间lncRNA与蛋白编码基因的表达量相关性分析或共表达分析方法来预测其靶mRNA, lncRNA在其转录或转录后水平对基因的表达进行调控。图6A列举了3个差异lncRNA与其靶mRNA的trans作用,两者可以位于不同的染色体上,内源性竞争RNA(ceRNA)就属于此类[8],lncRNA Ppp1ca可以竞争性地结合miR⁃125b从而阻止其诱导的tau磷酸化[9]。差异lncRNA trans作用的靶mRNA的KEGG、GO富集分析如图6所示,KEGG信号通路富集分析中按基因数量排序,前5位分别是metabolic pathways(675个基因)、pathways in cancer(241个基因)、biosynthesis of secondary metabolites(183个基因)、MAPK signaling pathway(180个基因)、PI3K⁃Akt signaling pathway(179个基因)(图6B)。GO功能注释分析中按基因数目排序,BP中前5位是cellular process(4 692个基因)、single ⁃ organism process (4 239个基因)、biological regulation(3 550个基因)、metabolic process(2 473个基因)、response to stimulus(2 138个基因);CC中前5位分别是cell (4 487个基因)、cell part(4 437个基因)、organelle (3 100个基因)、membrane(3 071个基因)、细胞膜部分(membrane part)(2 641个基因);MF中前5位分别是binding(5 144个基因)、catalytic activity(2 200个基因)、分子传感器活性(molecular transducer activity) (578个基因)、transporter activity(543个基因)、信号转导活性(signal transducer activity)(540个基因) (图6C)。

  • 图5 差异性lncRNA与其靶mRNA的cis作用,差异性lncRNA cis作用的靶mRNA的KEGG和GO富集分析

  • Fig.5 The cis between differentially expressed lncRNA and its target mRNA,the KEGG and GO enrichment analysis of differentially expressed lncRNA cis target mRNA

  • 图6 差异性lncRNA与其靶mRNA的trans作用,差异性lncRNA trans作用的靶mRNA的KEGG和GO富集分析

  • Fig.6 The trans between differentially expressed lncRNA and its target mRNA,the KEGG and GO enrichment analysis of differentially expressed lncRNA trans target mRNA

  • 2.4 差异表达lncRNA FTX和Neat1的进一步分析

  • 选取在NP和IP中高差异表达且可能与孕期胰岛发育、细胞增殖相关的lncRNA FTX和Neat1进一步分析,qRT⁃PCR示正常小鼠、IUGR小鼠怀孕后FTX的表达量分别较未孕时下降(P< 0.001),而Neat1的表达量分别较未孕时升高(P< 0.01,图7)。FTX、Neat1在怀孕后的正常小鼠和IUGR小鼠之间表达水平有显著差异(P< 0.05,图7)。

  • 为明确lncRNA的表达是否受糖浓度调节,本研究测定了min6细胞在不同糖浓度刺激下FTX和Neat1的表达情况。FTX在低糖浓度(5.5、11.1、 16.7mmol/L)、高糖浓度(33.3mmol/L)下表达水平较正常糖浓度上调(P< 0.001,图8A),而Neat1的表达相反(P< 0.01,图8B)。

  • 进一步查找FTX和Neat1与其靶mRNA的互作关系,图9A示FTX与其靶mRNA均为trans作用,图9B示Neat1与Frmd8(mRNA)为cis作用,余为trans作用。

  • 图7 lncRNA FTX(A)、Neat1(B)在正常小鼠、IUGR小鼠的未孕和孕期的表达

  • Fig.7 Expression of lncRNA FTX(A)and Neat1(B)in pre⁃pregnancy and pregnancy of normal mice and IUGR mice

  • 图8 不同糖浓度下min6细胞中lncRNA FTX(A)、Neat1(B)的表达

  • Fig.8 Expression of lncRNA FTX(A)and Neat1(B)in min6cells under different glucose concentrations

  • 图9 lncRNA FTX(A)与靶mRNA的trans作用,lncRNA Neat1(B)与靶mRNA的cis作用(左)、trans作用(右)

  • Fig.9 Trans⁃action of lncRNA FTX (A), cis (left) and trans (right) action of lncRNA Neat1(B)

  • 3 讨论

  • 妊娠是一个逐渐发生生理性胰岛素抵抗的过程,正常情况下胰岛β细胞通过代偿性增殖来维持孕期的糖代谢平衡,而IUGR个体在胚胎期和新生儿早期胰岛发育和功能出现损害,成年后是否能应对妊娠这一代谢压力测试不得而知,目前关于IUGR孕期的IUGR小鼠研究未见报道。本研究首次对IUGR孕鼠胰岛转录组进行高通量测序分析,为深入探究其发病机制提供理论基础。

  • 越来越多的报道显示lncRNA影响胰岛细胞的发育和功能、糖尿病的发生发展和IUGR的发病过程。研究发现,lncRNA paupar通过调控pax6促进了胰岛α细胞的发育和功能[10];lncRNA hottip通过调节p38⁃MAPK通路改善糖尿病视网膜病变[11];本课题组前期研究表明,lncRNA TUG1参与了IUGR致2型糖尿病胰岛功能损伤的过程[1]。此外, lncRNA在小鼠妊娠期不同阶段动态表达,其中lncRNA Gm16308(lnc03)促进小鼠妊娠期胰岛β细胞增殖[12],而lncRNA表达谱的改变可诱发妊娠期糖尿病[13],Zhang等[14] 证明了lncRNA MALAT1在妊娠期糖尿病孕妇组血清中的表达水平高于正常孕妇组。

  • 本课题组前期实验结果显示:小鼠孕期存在胰岛增殖,但IUGR雌鼠孕期较正常小鼠孕期胰岛β细胞增殖能力减弱,胰岛大小及数量增加较少,出现糖耐量异常,为进一步探讨其发病原因,本研究对IUGR孕鼠胰岛进行全转录组测序及分析,结果提示,差异lncRNA的靶mRNA、差异mRNA的GO分析中BP集中于细胞及组织过程、生物调节、代谢及应激过程,CC集中在细胞及器官、胞膜等过程,MF集中于整合、催化活性、转运活性、分子功能调节等,这些基因均可对IUGR妊娠期胰岛功能产生影响,如能量代谢、β细胞周期调节及胰岛素胞吐过程等变化。 KEGG富集分析显示差异lncRNA的靶mRNA、差异mRNA主要集中在代谢通路、癌症通路、次生代谢产物的生物合成、PI3K⁃AKT通路及MAPK通路。这表明IUGR孕鼠和正常孕鼠在合成代谢、分解代谢以及癌症的发生发展方面存在差异。

  • PI3K/AKT、MAPK通路在维持胰岛β细胞增殖和存活方面起着关键作用。文献报道,催乳素受体和PI3K(AKT、mTOR、p70S6K)通路、MAPK(MEK、 ERK1/2)通路参与大鼠妊娠期胰岛质量的增加和葡萄糖敏感性的增强[15]。妊娠期胎盘生长因子可能刺激胰岛内皮细胞释放生长因子,激活β细胞中的PI3K/AKT信号以增加其增殖[16]。表皮生长因子通过PI3K/AKT和MAPK通路激活存活蛋白survivin,抑制β细胞凋亡[17]。这些过程和通路异常可能导致IUGR小鼠孕期发生胰岛功能障碍。

  • 本研究发现lncRNA Neat1、FTX在小鼠怀孕后表达量改变,并可能分别通过MAPK途径、PI3K/AKT途径影响小鼠孕期胰岛细胞增殖及功能,提示lncRNA的表达在妊娠期这个特殊的时间段受到严格的调控。既往研究发现Neat1可以通过调节细胞的增殖及凋亡,导致疾病的发生,如肿瘤、白血病及糖尿病肾病[18]。研究证实,lncRNA Neat1在宫内发育迟缓模型的绒毛滋养细胞中表达上调[19],提示Neat1与特发性IUGR胎儿的胎盘功能障碍有关,而Neat1在IUGR孕鼠胰岛发育、胰岛结构及功能维持中的作用及机制尚未见报道。lncRNA FTX参与多种疾病的发生、发展,如lncRNA FTX通过调节miR⁃192⁃5p/EIF5A2轴促进直肠癌的进展[20],通过海绵化miRNA⁃22调节pten/PI3K/AKT信号通路而减少新生小鼠心肌细胞肥大[21],但FTX在胰岛中尚未被研究。本研究在IUGR孕鼠和正常孕鼠胰岛中检测lncRNA Neat1和FTX的表达水平,差异有统计学意义。不同糖浓度刺激min6细胞后,发现二者的表达受糖浓度影响,lncRNA这一特点可能在IUGR孕鼠发生糖耐量异常过程中发挥作用。测序结果还发现lncRNA FTX与其靶mRNA均为trans作用,lncRNA Neat1与Frmd8(mRNA)为cis作用,余为trans作用,结合lncRNA和mRNA的互作分析 (图4A、5A、6A)可见,同一种lncRNA可以通过不同的互作方式调控不同mRNA的表达,而同一种lncRNA和同一种mRNA之间可以存在不同的互作方式,这是因为不同的作用方式在lncRNA和mRNA核苷酸链上所在的位置和区域不同。

  • 文献表明,lncRNA可能通过充当miRNA海绵并调节mRNA转录后沉默而起到基因调节剂的作用[3],本课题组正在实验验证测序结果中的互作关系,若干扰或过表达lncRNA后,其靶mRNA的表达量随之发生相应的变化,接下来再深入探讨其中是否涉及lncRNA⁃miRNA⁃mRNA这一“海绵”作用。

  • 本研究通过对IUGR孕鼠胰岛RNA进行高通量测序,筛选出了IUGR孕鼠和正常孕鼠差异表达的lncRNA及mRNA,并对差异lncRNA的靶mRNA进行GO、KEGG分析,为研究IUGR小鼠妊娠期发生胰岛功能障碍提供了理论基础。在此基础上,进一步深入探究差异表达的lncRNA对IUGR小鼠妊娠期胰岛功能的具体调控作用及其机制,以期早期防控糖尿病,降低糖尿病的发病率。

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  • 参考文献

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