Netrin-1、Slit2在夹脊电针结合神经松动术调节兔坐骨神经损伤后Rho GTPases失衡的作用

目的 观察夹脊电针结合神经松动术疗法对兔坐骨神经损伤后神经传导速度及Netrin-1、Slit2、Rho GTPases表达的影响。方法 将216只新西兰家兔随机分为正常对照组、病毒空载组、夹脊电针结合神经松动术组、Netrin-1组、Slit2组、Netrin-1+Slit2腺病毒结合组,按术后1、2、4周三个时间点分为3个亚组,每个亚组12只。钳夹法造兔左侧坐骨神经SunderlandⅢ度损伤模型。正常对照组无干预;各病毒组在模型制备时完成目的基因转染病毒注射;夹脊电针结合神经松动术组术后3 d即进行夹脊电针及神经松动术治疗。肌电图测量兔坐骨神经传导速度,取损伤坐骨神经和L4-6脊髓,荧光实时定量聚合酶链反应检测Netrin-1 mRNA、Slit2mRNA表达,Western blotting检测Rac1、Cdc42、RhoA蛋白表达。结果 术后1、2、4周,夹脊电针结合神经松动术组、Netrin-1+Slit2腺病毒结合组坐骨神经神经传导速度高于Netrin-1组和Slit2组(P <0.05);电针结合神经松动术组、 Netrin-1+Slit2腺病毒结合组Netrin-1和Slit2mRNA表达高于正常对照组、病毒空载组(P <0.05);电针结合神经松动术组和Netrin-1+Slit2腺病毒结合组Rac1、Cdc42蛋白表达高于Netrin-1组、Slit2组和病毒空载组(P <0.05),而RhoA蛋白表达低于Netrin-1组、Slit2组和病毒空载组(P <0.05)。结论 夹脊电针结合神经松动术促进轴突再生可能是通过调节Netrin-1、Slit2的表达,恢复Rho GTPases酶系统失衡状态,重组细胞骨架,促进周围神经损伤后的再生。

Subcellular localization of Rho GTPases: implications for axon regeneration

Damage to neurons in the central nervous system often leads to a permanent loss of function due to several factors,including reduced capacity of axons to regenerate and an environment that inhibits axon regeneration because of disruption of myelin and the formation of a growth-refractory glial scar around the injury（Yoon and Tuszynski,2012）.

A RHOse by any other name:a comparative analysis of animal and plant Rho GTPases

Rho GTPases are molecular switches that act as key regulators of a many cellular processes, including cell movement, morphogenesis, host defense, cell division and gene expression. Rho GTPases are found in all eukaryotic kingdoms. Plants lack clear homologs to conventional Rho GTPases found in yeast and animals; instead, they have over time developed a unique subfamily, ROPs, also known as RAC. The origin of ROP-like proteins appears to precede the appearance of land plants. This review aims to discuss the evolution of ROP/RAC and to compare plant ROP and animal Rho GTPases, focusing on similarities and differences in regulation of the GTPases and their downstream effectors.

The impact of Rho GTPases on the cell uptake of single-walled carbon nanohorns

Rho GTPases play an important role on the regulation of cytoskeleton, which can affect the cell morphogenesis, cell migration, endocytosis and vesicle transport by controlling the growth and maintenance of microfilaments and microtubules. It has been known that regulation of cell cytoskeleton is inseparable from the cell uptake of nano-medicine or nano-drug delivery systems. However, only few studies have focused on the impacts of Rho GTPases on cell uptake of nano-medicine or nano-drug delivery systems. This study selected single-walled carbon nanohoms （SWCNHs）, which have emerged as promising drug delivery systems, to explore the impacts of Rho GTPases on cell uptake of nano-drug delivery systems. SWCNHs were oxidized with concentrated nitric acid and prepared into nano dispersion by ultrasonic dispersion. Confocal laser scanning microscope （CLSM） and transmission electron microscopy （TEM） were used to observe the cell uptake and intracellular distribution of nanoparticles after incubated A549 cells with the dispersion mentioned above. Mechanism of cell uptake was assessed using various inhibitors. The results showed that the cell uptake of oxSWCNHs was significantly reduced when RhoA was inhibited. The oxSWCNHs were internalized through clathrin-mediated endocytosis and mainly positioned in lysosomes ofA549 cells.

N~ε-fatty acylation of Rho GTPases by a MARTX toxin effector

With the support by the National Natural Science Foundation of China,a study by Prof.Zhu Yongqun’s(朱永群)research group from the Life Sciences Institute,Zhejiang University revealed that a conserved effector protein of bacterial MARTX toxins catalyzes N~ε-fatty acylation on the lysine residues in the C-

Clinical significance of upregulated Rho GTPase activating protein 12 causing resistance to tyrosine kinase inhibitors in hepatocellular carcinoma

BACKGROUND Hepatocellular carcinoma(HCC)is a major health challenge with high incidence and poor survival rates in China.Systemic therapies,particularly tyrosine kinase inhibitors(TKIs),are the first-line treatment for advanced HCC,but resistance is common.The Rho GTPase family member Rho GTPase activating protein 12(ARHGAP12),which regulates cell adhesion and invasion,is a potential therapeutic target for overcoming TKI resistance in HCC.However,no studies on the expression of ARHGAP12 in HCC and its role in resistance to TKIs have been reported.AIM To unveil the expression of ARHGAP12 in HCC,its role in TKI resistance and its potential associated pathways.METHODS This study used single-cell RNA sequencing(scRNA-seq)to evaluate ARHGAP12 mRNA levels and explored its mechanisms through enrichment analysis.CellChat was used to investigate focal adhesion(FA)pathway regulation.We integrated bulk RNA data(RNA-seq and microarray),immunohistochemistry and proteomics to analyze ARHGAP12 mRNA and protein levels,correlating with clinical outcomes.We assessed ARHGAP12 expression in TKI-resistant HCC,integrated conventional HCC to explore its mechanism,identified intersecting FA pathway genes with scRNA-seq data and evaluated its response to TKI and immunotherapy.RESULTS ARHGAP12 mRNA was found to be highly expressed in malignant hepatocytes and to regulate FA.In malignant hepatocytes in high-score FA groups,MDK-[integrin alpha 6(ITGA6)+integrinβ-1(ITGB1)]showed specificity in ligand-receptor interactions.ARHGAP12 mRNA and protein were upregulated in bulk RNA,immunohistochemistry and proteomics,and higher expression was associated with a worse prognosis.ARHGAP12 was also found to be a TKI resistance gene that regulated the FA pathway.ITGB1 was identified as a crossover gene in the FA pathway in both scRNA-seq and bulk RNA.High expression of ARHGAP12 was associated with adverse reactions to sorafenib,cabozantinib and regorafenib,but not to immunotherapy.CONCLUSION ARHGAP12 expression is elevated in HCC and TKI-resistant HCC,and its regulatory role in FA may underlie the TKI-resistant phenotype.

mRNA expression of Rho GTPase-related signaling molecules during rat hippocampal development

BACKGROUND： Rho GTPase family members have been shown to participate in neurite growth by regulating the neuronal cytoskeleton. However, there are very few reports of developmental roles of signaling molecules related to Rho GTPases. OBJECTIVE： To investigate messenger ribonucleic acid mRNA expression of signaling molecules associated with Rho GTPases, including Rho-A, Rac-1, collapsin response mediator protein 1 （CRMP-1）, and tubulin 133 （Tub/33） during rat hippocampus development. DESIGN, TIME AND SETTING- A non-randomized, controlled, animal experiment, based on different developmental stages of the rat hippocampus, was performed at the Guangdong Key Laboratory of Tissue Construction and Detection, Institute of Clinical Anatomy, Southern Medical University between December 2005 and July 2007. MATERIALS： Trizol reagent was purchased from Invitrogen, USA. RNA PCR kit （AMV） Ver 3.0 and 150 bp DNA Ladder Marker were purchased from TaKaRa, Japan. Unless otherwise specified, all other reagents were purchased from Sigma-Aldrich, USA. METHODS： Twenty-five Sprague Dawley rats were assigned to five groups （n = 5） according to developmental stages： embryonic （embryonic 15 days）, neonatal （postnatal 5 days）, juvenile （postnatal 1 month）, adult （postnatal 3 months）, and senile （postnatal 18 months）. MAIN OUTCOME MEASURES： Detection of mRNA expression of Rho-A, Rac-1, CRMP-1, and Tub β3 during various hippocampal developmental stages by reverse-transcription polymerase chain reaction. RESULTS： Hippocampal mRNA expression of Rho-A, as well as Rac-1, reached peak levels at embryonic, juvenile, and senile stages, and was relatively less during neonatal and adult stages. mRNA expression of Rac-1 was greater than Rho-A during each hippocampal developmental stage. CRMP-1 mRNA expression levels were as follows： embryonic 〉 neonatal 〉 juvenile 〉 adult 〈 senile, while Tubβ3 mRNA expression was embryonic 〉 neonatal 〉 juvenile 〉 adult = senile. CONCLUSION： Rho-A and Rac-1 shared similar expression profiles, which demonstrated similar variations during the entire rat hippocampus developmental process. However, Rac-1 mRNA expression remained greater than Rho-A. Both CRMP-1 and Tubβ3 mRNA expression profiles gradually declined during hippocampal development from embryonic to adult stages. Tubβ3 mRNA expression arrested during the adult stage, and CRMP-1 mRNA expression increased during the senile stage.

The role of Rho GTPase family in cochlear hair cells and hearing

Rho GTPases are essential regulators of the actin cytoskeleton.They are involved in various physiological and biochemical processes such as the regulation of cytoskeleton dynamics,development,proliferation,survival,and regeneration.During the development of cochlear hair cells,Rho GTPases are activated by various extracellular signals through membrane receptors to further stimulate multiple downstream effectors.Specifically,RhoA,Cdc42,and Rac1,members of the classical subfamily of the Rho GTPase family,regulate the development and maintenance of cilia by inducing the polymerization of actin monomers and stabilizing actin filaments.In addition,they also regulate the normal morphology orientation of ciliary bundles in auditory hair cells,which is an important element of cell polarity regulation.Moreover,the actin-related pathways mediated by RhoA,Cdc42,and Rac1 also play a role in the motility of outer hair cells,indicating that the function of Rho GTPases is crucial in the highly polar auditory sensory system.In this review,we focus on the expression of RhoA,Cdc42,and Rac1 in cochlear hair cells and how these small molecules participate in ciliary bundle morphogenesis and cochlear hair cell movement.We also discuss the progress of current research investigating the use of these small molecules as drug targets for deafness treatment.

血管新生过程中的Rho GTPase

缺血性心脑血管疾病是影响我国居民健康的头号杀手,血管新生参与组织缺血缺氧损伤后的修复过程,为缺血性心脑血管疾病的治疗提供有效方法。Rho GTPase家族在调节内皮细胞骨架形态、迁移和成管中起着核心作用。目前已发现Cdc42、Rac1及RhoA参与血管新生过程,其中Cdc42诱导内皮细胞丝状伪足的形成并指引内皮细胞迁移方向,促进受损血管内皮屏障的恢复;Rac1控制片状伪足的形成;RhoA调节黏着斑形成及内皮细胞迁移过程中前缘和后端基质黏附的动态重塑,三者协作参与缺血损伤后的血管新生过程。尽管Rho GTPase在血管新生中的作用尚未完全明了,但它从基础研究到临床应用的前景仍然值得探索,这对于防治缺血性心脑血管疾病有重要意义。

胰腺癌组织中miR-939-5p、ARHGAP4基因表达变化及意义

目的探讨胰腺癌组织中微小RNA-939-5p(miR-939-5p)与Rho GTPase激活蛋白4(ARHGAP4)的表达变化及临床意义。方法用荧光定量PCR技术检测98例胰腺癌组织及癌旁正常组织中miR-939-5p、ARHGAP4 mRNA的相对表达量,并分析二者表达与胰腺癌患者临床病理特征的关系,用Pearson线性相关法分析miR-939-5p、ARHGAP4 mRNA的关系。结果与癌旁正常组织比较,胰腺癌组织中miR-939-5p相对表达量高,ARHGAP4 mRNA相对表达量低(P均<0.001)。胰腺癌组织中miR-939-5p、ARHGAP4 mRNA表达与肿瘤TNM分期、组织分化程度、淋巴结转移有关(P均<0.05),与患者年龄、性别及肿瘤直径无关(P均>0.05)。胰腺癌组织中miR-939-5p表达与ARHGAP4 mRNA表达呈负相关(r=-0.574,P<0.05)。结论胰腺癌组织中miR-939-5p呈高表达,ARHGAP4 mRNA呈低表达,二者可能协同参与肿瘤的发生发展。

Rac1及Cdc42在肾上腺髓质肽(AM)缓解嘌呤霉素氨基核苷(PAN)所诱导足细胞损伤中作用机制的初步探讨

目的观察肾上腺髓质肽(adrenomedullin,AM)对嘌呤霉素氨基核苷(puromycin aminonucleoside,PAN)所诱导受损足细胞的作用以及Rac1/Cdc42表达变化,初步探讨其可能机制。方法将小鼠肾足细胞株分为对照组、PAN处理组(100μg/mL)、PAN联合AM处理组(10-7mol/L)及PAN联合AM和蛋白激酶A(PKA)抑制剂H89(10-6mol/L)处理组。经一次性腹腔注射PAN(150 mg/kg)建立大鼠足细胞损伤模型,每天经尾静脉注射AM蛋白(66μg/kg)进行干预。SDS-PAGE法检测尿蛋白水平,电镜观察足细胞足突宽度变化,双重免疫荧光染色及/或Western blot观察足细胞特异性骨架蛋白(synaptopodin、nephrin)、Rac1及Cdc42的蛋白表达水平,实时定量PCR(qRT-PCR)检测synaptopodin、nephrin的mRNA表达,谷胱甘肽巯基转移酶-拉下实验(GST-pull down assay)法检测Rac1及Cdc42活性变化。结果PAN在体内、外均显著降低synaptopodin、nephrin的蛋白或/及mRNA表达水平,且显著升高desmin表达;大鼠PAN肾病模型的尿蛋白水平显著升高,足突宽度显著增加;PAN显著降低Rac1、Cdc42总蛋白及活性水平。上述由PAN所介导的效应被AM显著抑制;H89显著阻断AM的体外作用。结论AM主要通过PKA通路促进受损足细胞的修复,该保护机制与AM调控Rac1/Cdc42表达密切相关。

ROPs:植物细胞内多种信号通路的分子开关

植物RHO相关蛋白GTPases(RHO-related GTPases of plants,ROPs)是广泛存在于植物中的一类信号转导G蛋白(又称GTP结合蛋白),其通过结合GDP或GTP在非活性和活性状态间进行切换,进而在细胞极性控制、形态发育、激素水平调控、逆境反应等诸多植物生命活动的信号转导过程中扮演重要的分子开关角色。本文对ROP蛋白的结构域及基于蛋白质结构分类进行了介绍,并对拟南芥、玉米、水稻和大麦中的ROP家族蛋白质进行了系统进化分析。分析结果表明,这些植物中的ROP蛋白根据蛋白质结构域组成可分为Ⅰ类(typeⅠ)和Ⅱ类(typeⅡ)两种类型,而根据蛋白质序列的保守性可将其在植物中的ROP蛋白划分为4个进化枝。本综述不但对ROP蛋白作为分子开关在细胞内调控各种信号通路的机制进行了叙述,还对ROP在花粉管、根毛及植物表皮铺盖细胞极性发育,以及其他抗逆反应中的具体作用和机制及研究进展进行了阐述。本文还对ROP蛋白在ABA、IAA、BR等植物激素信号传导过程中的调控作用及研究进展进行了阐述。本文对植物ROP蛋白研究过程中尚未解决的问题,例如不同的ROP蛋白在同一个信号通路中的作用为何如此不同,以及ROP是如何协调不同的信号通路以共同调控一个植物发育或者生理过程等问题进行了总结,并在此基础上对未来的研究方向进行了展望。

Inhibition of growth and metastasis of triple-negative breast cancer targeted by Traditional Chinese Medicine Tubeimu in orthotopic mice models

Objective： Triple-negative breast cancer（TNBC） is highly invasive and metastatic, which is in urgent need of transformative therapeutics. Tubeimu（TBM）, the rhizome of Bolbostemma paniculatum（Maxim.） Franquet, is one of the Chinese medicinal herbs used for breast diseases since the ancient times. The present study evaluated the efficacy, especially the anti-metastatic effects of the dichloromethane extract of Tubeimu（ETBM） on TNBC orthotopic mouse models and cell lines.Methods： We applied real-time imaging on florescent orthotopic TNBC mice model and tested cell migration and invasion abilities with MDA-MB-231 cell line. Digital gene expression sequencing was performed and Kyoto Encyclopedia of Genes and Genomes（KEGG） analysis applied to explore the pathways influenced by ETBM.Moreover, quantitative real-time polymerase chain reactions（q RT-PCR） and Western blot were delivered to confirm the gene expression changes.Results： ETBM exhibited noticeable control on tumor metastasis and growth of TNBC tumors with no obvious toxicity. In compliance with this, it also showed inhibition of cell migration and invasion in vitro. Its impact on the changed biological behavior in TNBC may be a result of decreased expression of integrin β1（ITGβ1）, integrin β8（ITGβ8） and Rho GTPase activating protein 5（ARHGAP5）, which disabled the focal adhesion pathway and caused change in cell morphology.Conclusions： This study reveals that ETBM has anti-metastatic effects on MDA-MB-231-GFP tumor and may lead to a new therapeutic agent for the integrative treatment of highly invasive TNBC.

Rnd2介导的生命活动及其作用机制

Rnd2是Rho GTPase超家族下的Rnd亚家族中非典型成员之一,且Rnd2主要以活性鸟苷三磷酸结合态存在。研究表明,Rnd2通过调节细胞骨架,可在影响细胞的运动与突起的生长在神经元发育以及妊娠的维持等过程中发挥着重要作用。主要概述了Rnd亚家族成员Rnd2通过与上下游信号分子相互作用调节其相关生理学活性,并影响下游信号的通路的转导,进而调控细胞骨架的重塑等过程影响的一系列生理活动及其相关作用机制。

ARHGAP10基因在肺腺癌中的表达及其机制

目的:基于生物信息学技术探讨Rho GTPase活化蛋白10(ARHGAP10)在肺腺癌发生发展中的潜在分子机制,为后续深入研究提供生物信息学证据。方法:通过利用TCGA数据库,获取肺腺癌患者RNA高通量序列及相关患者的临床资料,其中包括514例肺腺癌患者的癌组织以及59例相关的癌旁组织;GSE115002肺腺癌基因芯片数据从GEO下载,芯片包含52例肺腺癌患者的癌组织和匹配的癌旁正常组织。通过R语言技术比较ARHGAP10在TCGA和GSE115002中肺腺癌组织和癌旁正常组织之间表达差异,并进一步分析ARHGAP10表达与肺癌患者临床预后的相关性;挖掘两个数据库中ARHGAP10重叠基因,对重叠基因进行GO和KEGG富集分析,采用STRING数据库获取ARHGAP10的相关基因互作蛋白网络,TIMER数据库分析ARHGAP10与免疫浸润的相关性。结果:与癌旁正常组织相比较,肺腺癌组织中ARHGAP10呈现低表达状态(P<0.01)。与ARHGAP10低表达组相比较,ARHGAP10高表达患者拥有更长的总生存期和无进展生存期(P<0.05)。TCGA和GSE115002肺腺癌数据库中ARHGAP10的共同相关基因共133个,与MAPK、PI3K-AKT等信号通路以及细胞外基质受体结合、肌动蛋白细胞骨架、肿瘤信号通路等生物学进程相关。本研究发现PRELP、LIMS2、PPAP2B、MRPL42、SRP9、TSNAX等蛋白在ARHGAP10相互作用网络中发挥重要作用,ARHGAP10与DC细胞、中性粒细胞浸润正相关,与PD-L1表达呈正相关。结论:ARHGAP10在肺腺癌中起抑癌作用,与肺腺癌的生存预后正相关,可作为肺腺癌患者潜在的临床预后标志物。

胃癌组织中ARHGAP4、FBLN5的表达及与病人预后的关系

目的探讨扣针蛋白5(FBLN5)、Rho GTPase激活蛋白4(ARHGAP4)在胃癌组织中的表达及与病人预后的关系。方法2013年12月~2018年12月我院收治的胃癌病人100例,收集距肿瘤边缘>1 cm处的胃癌组织以及距肿瘤边缘>5 cm的癌旁组织。分析FBLN5与ARHGAP4表达情况与胃癌临床病理学指标的关系,以及其对生存状况的影响,对病人的临床资料进行单因素和多因素Cox回归分析。采用免疫组织化学染色法检测FBLN5和ARHGAP4的表达情况。利用Kaplan-Meier法分析不同ARHGAP4、FBLN5表达水平与病人生存时间的关系。结果胃癌组织ARHGAP4阳性表达率低于癌旁组织,FBLN5的阳性表达率高于癌旁组织(P<0.05);ARHGAP4表达与肿瘤部位、Lauren分型、淋巴结转移、TNM分期、分化程度、CEA、CA19-9、CA125、免疫评分有关(P<0.05);FBLN5表达与Lauren分型、淋巴结转移、TNM分期、分化程度、CE、CA19-9、CA125、免疫评分有关(P<0.05);FBLN5高表达组病人3年累积生存率低于低表达组(P=0.044);ARHGAP4高表达病人3年累积生存率高于低表达病人(P=0.021);Cox分析结果显示,ARHGAP4高表达为影响生存的保护因素(P<0.05)。结论FBLN5高表达组病人预后较低表达病人差,ARHGAP4低表达病人预后较高表达病人好。FBLN5高表达为影响生存的危险因素,二者与胃癌病人病情发展和预后密切相关。

Rho-GTP酶类及相关调控因子在足细胞中作用的研究进展

足细胞又称肾小球脏层上皮细胞,是构成肾小球滤过膜功能的重要屏障。以肌动蛋白为基础的细胞骨架在维持足细胞的正常功能中起着重要作用。本文综述了近年来发现的Rho-GTP酶类(Rho-GTPases)及相关调控因子在足细胞肌动蛋白骨架调控中的研究进展。在足细胞中,以RhoA、Rac1和Cdc42为代表的Rho-GTPases在调控肌动蛋白细胞骨架中起着核心作用。

Djrho2 is involved in regeneration of visual nerves in Dugesia japonica

The freshwater planarian is a powerful animal model for studying regeneration and stem cell activity in vivo. During regeneration, stem cells （neoblasts in planarian） migrated to the wounding edge to re-build missing parts of the body. However, proteins involved in regulating cell migration during planarian regeneration have not been studied extensively. Here we report two small GTPase genes （Djrho2 and Djrho3） of Dugesiajaponica （strain Pek-1）. In situ hybridization results indicated that Djrho2 was expressed throughout the body with the exception of thc pharynx region while Djrho3 was specifically expressed along the gastro-vascular system. Djrho2 was largely expressed in neoblasts since its expression was sensitive to X-ray irradiation. In Djrho2-RNAi planarians, smaller anterior blastemas were observed in tail fragments during regeneration. Consistently, defective regeneration of visual nerve was detected by immunostairming with VC-1 antibody. These results suggested that Djrho2 is required for proper anterior regeneration in planairan. In contrast, no abnormality was observed after RNAi of Djrho3. We compared protein compositions of control and Djrho2-RNAi planarians using an optimized proteomic approach. Twenty-two up-regulated and 26 de-regulated protein spots were observed in the two-dimensional elec- trophoresis gels, and 17 proteins were successfully identified by Mass Spectrometry （MS） analysis. Among them, 6 actin-binding or cytoskeleton-related proteins were found de-expressed in Djrho2-RNAi animals, suggesting that abnormal cytoskeleton assembling and cell migration were likely reasons of defected regeneration.

Plant Rho GTPase signaling promotes autophagy

The roles of Rho family guanosine triphosphatases(GTPases)of plants(ROPs)in modulating plant growth and development have been well characterized.However,little is known about the roles of ROP signaling pathways in regulating plant autophagy and autophagosome formation.In this study,we identify a unique ROP signaling mechanism,which mediates developmental to autophagic transition under stress conditions in the model plant Arabidopsis.Loss-of-function mutants of ROP8 showed stress-induced hypersensitive phenotypes and compromised autophagic flux.Similar to other ROPs in the ROP/RAC family,ROP8 exhibits both plasma membrane and cytosolic punctate localization patterns.Upon autophagic induction,active ROP8 puncta colocalize with autophagosomal markers and are degraded inside the vacuole.In human cells,RalB,an RAS subfamily GTPase,engages its effector Exo84 for autophagosome assembly.However,a RalB counterpart is missing in the plant lineage.Intriguingly,we discovered that plant ROP8 promotes autophagy via its downstream effector Sec5.Live-cell super-resolution imaging showed that ROP8 and Sec5 reside on phagophores for autophagosome formation.Taken together,our findings highlight a previously unappreciated role of an ROP8-Sec5 signaling axis in autophagy promotion,providing new insights into how plants utilize versatile ROP signaling networks to coordinate developmental and autophagic responses depending on environmental changes.

Cdc42 deletion yielded enamel defects by disrupting mitochondria and producing reactive oxygen species in dental epithelium

Developmental defects of enamel are common due to genetic and environmental factors before and after birth.Cdc42,a Rho family small GTPase,regulates prenatal tooth development in mice.However,its role in postnatal tooth development,especially enamel formation,remains elusive.Here,we investigated Cdc42 functions in mouse enamel development and tooth repair after birth.Cdc42 showed highly dynamic temporospatial patterns in the developing incisors,with robust expression in ameloblast and odontoblast layers.Strikingly,epithelium-specific Cdc42 deletion resulted in enamel defects in incisors.Ameloblast differentiation was inhibited,and hypomineralization of enamel was observed upon epithelial Cdc42 deletion.Proteomic analysis showed that abnormal mitochondrial components,phosphotransferase activity,and ion channel regulator activity occurred in the Cdc42 mutant dental epithelium.Reactive oxygen species accumulation was detected in the mutant mice,suggesting that abnormal oxidative stress occurred after Cdc42 depletion.Moreover,Cdc42 mutant mice showed delayed tooth repair and generated less calcified enamel.Mitochondrial dysfunction and abnormal oxygen consumption were evidenced by reduced Apool and Timm8a1 expression,increased Atp5j2 levels,and reactive oxygen species overproduction in the mutant repair epithelium.Epithelium-specific Cdc42 deletion attenuated ERK1/2 signaling in the labial cervical loop.Aberrant Sox2 expression in the mutant labial cervical loop after clipping might lead to delayed tooth repair.These findings suggested that mitochondrial dysfunction,up-regulated oxidative stress,and abnormal ion channel activity may be among multiple factors responsible for the observed enamel defects in Cdc42 mutant incisors.Overall,Cdc42 exerts multidimensional and pivotal roles in enamel development and is particularly required for ameloblast differentiation and enamel matrix formation.