世界生命科學(xué)前沿動態(tài)周報（六十一）

（10.10-10.16/2011）
美寶國際集團:陶國新 

　　主要內(nèi)容：快速高效的將體細胞重組為干細胞；微小RNA-101是有效的細胞自噬抑制劑；用分子感受器原位定量顯示細胞脂質(zhì)；運動能夠防治偏頭痛；在傷后肺部修復(fù)中環(huán)支氣管平滑肌細胞構(gòu)建氣管上皮干細胞微環(huán)境；在胰腺β細胞中PDGF信號控制年齡依賴性增殖。

　　焦點動態(tài)：在傷后肺部修復(fù)中環(huán)支氣管平滑肌細胞構(gòu)建氣管上皮干細胞微環(huán)境

1.快速高效的將體細胞重組為干細胞

【動態(tài)】
通過表達四種轉(zhuǎn)錄因子Oct4, Sox2, Klf4, 和 c-Myc，體細胞能夠重組成誘導(dǎo)多能干細胞（iPSCs）。中美英三國科學(xué)家的聯(lián)合研究發(fā)現(xiàn)了可以將重組效率提高100倍的的方法。他們發(fā)現(xiàn)通過表達維甲酸受體（RARs）或通過維甲酸激動劑增強維甲酸信號能夠極大的促進細胞重組，但是用RAR-α陰性形式抑制維甲酸信號會完全阻斷細胞重組。與上述四種轉(zhuǎn)錄因子同時表達RAR-γ和Lrh-1(肝受體同源物-1)能夠大大加速細胞重組，通過這種方法老鼠胚胎成纖維細胞重組成基態(tài)的誘導(dǎo)多能干細胞僅僅需要4天。該發(fā)現(xiàn)說明RARs介導(dǎo)的信號在重組中有關(guān)鍵作用以及RAR-γ和Lrh-1之間的協(xié)同作用指導(dǎo)細胞向基態(tài)多能性方向重組。

【點評】
該發(fā)現(xiàn)大大提高了體細胞重組為干細胞的效率和速度，使干細胞的獲得變得容易，對于深入研究干細胞的生命規(guī)律會有很大幫助。       

【參考論文】
Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1100893108
Rapid and efficient reprogramming of somatic cells to induced pluripotent stem cells by retinoic acid receptor gamma and liver receptor homolog.
Wang et al.
Somatic cells can be reprogrammed to induced pluripotent stem cells (iPSCs) by expressing four transcription factors: Oct4, Sox2, Klf4, and c-Myc. Here we report that enhancing RA signaling by expressing RA receptors (RARs) or by RA agonists profoundly promoted reprogramming, but inhibiting it using a RAR-α dominant-negative form completely blocked it. Coexpressing Rarg (RAR-γ) and Lrh-1 (liver receptor homologue 1; Nr5a2) with the four factors greatly accelerated reprogramming so that reprogramming of mouse embryonic fibroblast cells to ground-state iPSCs requires only 4 d induction of these six factors. The six-factor combination readily reprogrammed primary human neonatal and adult fibroblast cells to exogenous factor-independent iPSCs, which resembled ground-state mouse ES cells in growth properties, gene expression, and signaling dependency. Our findings demonstrate that signaling through RARs has critical roles in molecular reprogramming and that the synergistic interaction between Rarg and Lrh1 directs reprogramming toward ground-state pluripotency. The human iPSCs described here should facilitate functional analysis of the human genome.

2. 微小RNA-101是有效的細胞自噬抑制劑

【動態(tài)】
自噬是一種進化上保守的細胞自消化機制，把蛋白和細胞器送到溶酶體來降解。在包括癌癥在內(nèi)的許多人體疾病中牽涉到這一過程存在的缺陷。為了進一步闡明自噬的調(diào)節(jié)機制，丹麥科學(xué)家對在乳腺癌細胞中調(diào)節(jié)自噬流的微小RNA（miRNA）進行了功能篩選，鑒定出腫瘤抑制性miRNA, miR-101,是依托伯苷和雷帕霉素誘導(dǎo)的基礎(chǔ)自噬的有效抑制劑。通過轉(zhuǎn)錄組分析，他們確定了三個miR-101的新靶點，STMN1, RAB5A 和 ATG4D，通過siRNA靜默這些基因，能夠模擬過多表達miR-101產(chǎn)生的表型，顯示了這些基因在自噬調(diào)節(jié)中的重要性。特別是，過表達STMN1能夠部分拯救細胞于miR-101介導(dǎo)的自噬抑制，揭示了該靶點的重要功能。最后，他們的研究還顯示miR-101介導(dǎo)的自噬抑制能夠使乳腺癌細胞對4-羥基他莫西芬（4-OHT）引起的細胞死亡更敏感?？偠灾?，這些研究結(jié)果在兩個非常重要的快速發(fā)展的研究領(lǐng)域間建立了新的聯(lián)系，提出了miR-101作為關(guān)鍵的自噬調(diào)節(jié)子的新作用。

【點評】
miR-101對細胞尤其是乳腺癌細胞自噬的調(diào)節(jié)的研究，對于解決癌細胞對部分抗癌藥物的抗藥性開啟了一條新路。

【參考論文】
The EMBO Journal, 2011; DOI: 10.1038/emboj.2011.331
microRNA-101 is a potent inhibitor of autophagy
Lisa B Frankel, Jiayu Wen, Michael Lees, et al.
Autophagy is an evolutionarily conserved mechanism of cellular self-digestion in which proteins and organelles are degraded through delivery to lysosomes. Defects in this process are implicated in numerous human diseases including cancer. To further elucidate regulatory mechanisms of autophagy, we performed a functional screen in search of microRNAs (miRNAs), which regulate the autophagic flux in breast cancer cells. In this study, we identified the tumour suppressive miRNA, miR-101, as a potent inhibitor of basal, etoposide- and rapamycin-induced autophagy. Through transcriptome profiling, we identified three novel miR-101 targets, STMN1, RAB5A and ATG4D. siRNA-mediated depletion of these genes phenocopied the effect of miR-101 overexpression, demonstrating their importance in autophagy regulation. Importantly, overexpression of STMN1 could partially rescue cells from miR-101-mediated inhibition of autophagy, indicating a functional importance for this target. Finally, we show that miR-101-mediated inhibition of autophagy can sensitize breast cancer cells to 4-hydroxytamoxifen (4-OHT)-mediated cell death. Collectively, these data establish a novel link between two highly important and rapidly growing research fields and present a new role for miR-101 as a key regulator of autophagy.

3.  用分子感受器原位定量顯示細胞脂質(zhì)

【動態(tài)】
膜脂是動態(tài)的分子，在細胞信號傳導(dǎo)和調(diào)節(jié)中起重要作用，但目前還缺少在活細胞中定量追蹤膜脂分子的原位顯像技術(shù)。美國科學(xué)家最近報道了一種新的化學(xué)方法用環(huán)境敏感性熒光團標記的工程蛋白作為感受器定量顯像膜脂分子。這種感受器能夠在哺乳動物細胞中進行強力和敏感的顯影。在免疫細胞中的應(yīng)用揭示了觸發(fā)吞噬作用必須的PtdIns(4,5)P2（一種關(guān)鍵的信號脂分子）濃度閾值。這一策略普遍適用于細胞脂類分子的原位定量。

【點評】
原位定量顯示特定分子的技術(shù)使得我們能夠深入了解一些重要的生物分子的數(shù)量和濃度水平與特定生物事件的關(guān)系，從而能更準確地把握事件的發(fā)生過程和機理。

【參考論文】
Nature Chemistry, 2011; DOI: 10.1038/nchem.1163
In situ quantitative imaging of cellular lipids using molecular sensors
Youngdae Yoon, Park J. Lee, Svetlana Kurilova, Wonhwa Cho.
Membrane lipids are dynamic molecules that play important roles in cell signalling and regulation, but an in situ imaging method for quantitatively tracking lipids in living cells is lacking at present. Here, we report a new chemical method of quantitative lipid imaging using sensors engineered by labelling proteins with an environmentally sensitive fluorophore. A prototype sensor for phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2)—a key signalling lipid in diverse cellular processes—was generated by covalently attaching a single 2-dimethylamino-6-acyl-naphthalene group to the N-terminal α-helix of the engineered epsin1 ENTH domain, a protein that selectively binds PtdIns(4,5)P2. The sensor allows robust and sensitive in situ quantitative imaging in mammalian cells, providing new insight into the spatiotemporal dynamics and fluctuation of this key signalling lipid. Application of the sensor to immune cells reveals the presence of a local threshold PtdIns(4,5)P2 concentration required for triggering phagocytosis. This sensor strategy is generally applicable to in situ quantification of other cellular lipids.

4.  運動能夠防治偏頭痛

【動態(tài)】
瑞典科學(xué)家最近報道了運動防治偏頭痛的第一個確鑿的科學(xué)證據(jù)。在一項涉及91例成年偏頭痛患者的隨機對照臨床試驗中，1/3人在理療師監(jiān)督下每周運動3次，每次40分鐘；另外1/3做放松活動；最后1/3服用藥物Topiramate（妥泰）。研究持續(xù)3個月，其間對患者的偏頭痛狀態(tài)、生活質(zhì)量、身體活動水平和氧氣攝入量都進行評估。主要的效果參數(shù)是相對于基線水平，治療最后一個月偏頭痛發(fā)作頻率的平均減少量。結(jié)果顯示三組偏頭痛次數(shù)都減少了，有意思的是，三組間預(yù)防和減少偏頭痛的效果沒有差異，意味著運動和放松、服藥對于防治偏頭痛有相同作用，可以作為不能或不愿服藥時的選擇。

【點評】
該研究提供了比較充分的科學(xué)依據(jù)證明對于偏頭痛，運動的確能夠起到和藥物一樣的防治效果。

【參考論文】
Cephalalgia, 2011; DOI: 10.1177/0333102411419681
Exercise as migraine prophylaxis: A randomized study using relaxation and topiramate as controls
E. Varkey, A. Cider, J. Carlsson, M. Linde.

Aim: Scientific evidence regarding exercise in migraine prophylaxis is required. Therefore this study aimed to evaluate the effects of exercise in migraine prevention.
Methods: In a randomized, controlled trial of adults with migraine, exercising for 40 minutes three times a week was compared to relaxation according to a recorded programme or daily topiramate use, which was slowly increased to the individual’s highest tolerable dose (maximum 200 mg/day). The treatment period lasted for 3 months, and migraine status, quality of life, level of physical activity, and oxygen uptake were evaluated. The primary efficacy variable was the mean reduction of the frequency of migraine attacks during the final month of treatment compared with the baseline.
Results: Ninety-one patients were randomized and included in the intention-to-treat analysis. The primary efficacy variable showed a mean reduction of 0.93 (95% confidence interval (CI) 0.31–1.54) attacks in the exercise group, 0.83 (95% CI 0.22–1.45) attacks in the relaxation group, and 0.97 (95% CI 0.36–1.58) attacks in the topiramate group. No significant difference was observed between the groups (p = 0.95).
Conclusion: Exercise may be an option for the prophylactic treatment of migraine in patients who do not benefit from or do not want to take daily medication.

5.  在傷后肺部修復(fù)中環(huán)支氣管平滑肌細胞構(gòu)建氣管上皮干細胞微環(huán)境

【動態(tài)】
美國比利時和德國的科學(xué)家的一項合作研究最近確定了觸發(fā)肺部受傷后的修復(fù)的細胞和信號分子。老鼠肺部組織受傷誘導(dǎo)氣管周圍平滑肌細胞分泌纖維母細胞生長因子10（FGF10），后者誘導(dǎo)氣管的幸存上皮細胞回歸干細胞狀態(tài)并增殖、修復(fù)和重整肺部組織，該修復(fù)過程很像肺部形成時的原始發(fā)育過程。

【點評】
該研究結(jié)果說明機體具有傷后自我修復(fù)的能力并且是通過將體細胞激活到干細胞狀態(tài)再進行類似器官發(fā)育的過程修復(fù)受損組織。

【參考論文】
Journal of Clinical Investigation, 2011; DOI: 10.1172/JCI58097
Parabronchial smooth muscle constitutes an airway epithelial stem cell niche in the mouse lung after injury
Thomas Volckaert, Erik Dill, Alice Campbell, et al.
During lung development, parabronchial SMC (PSMC) progenitors in the distal mesenchyme secrete fibroblast growth factor 10 (Fgf10), which acts on distal epithelial progenitors to promote their proliferation. β-catenin signaling within PSMC progenitors is essential for their maintenance, proliferation, and expression of Fgf10. Here, we report that this Wnt/Fgf10 embryonic signaling cascade is reactivated in mature PSMCs after naphthalene-induced injury to airway epithelium. Furthermore, we found that this paracrine Fgf10 action was essential for activating surviving variant Clara cells (the cells in the airway epithelium from which replacement epithelial cells originate) located at the bronchoalveolar duct junctions and adjacent to neuroendocrine bodies. After naphthalene injury, PSMCs secreted Fgf10 to activate Notch signaling and induce Snai1 expression in surviving variant Clara cells, which subsequently underwent a transient epithelial to mesenchymal transition to initiate the repair process. Epithelial Snai1 expression was important for regeneration after injury. We have therefore identified PSMCs as a stem cell niche for the variant Clara cells in the lung and established that paracrine Fgf10 signaling from the niche is critical for epithelial repair after naphthalene injury. These findings also have implications for understanding the misregulation of lung repair in asthma and cancer.

6.  在胰腺β細胞中PDGF信號控制年齡依賴性增殖

【動態(tài)】
美國科學(xué)家最近確定了一個導(dǎo)致人隨年齡增長生產(chǎn)胰島素的細胞的增殖自然減少的關(guān)鍵信號途徑。在老鼠和人體內(nèi)胰腺β細胞的旺盛增殖隨年齡增加而減弱，血小板源生長因子受體（Pdgfr）信號控制胰島的年齡依賴性β細胞增殖。隨著變老，β細胞Pdgfr水平和β細胞增強子Ezh2以及β細胞增殖同時減少。

【點評】
該研究發(fā)現(xiàn)為增強胰島β細胞增殖提供了新的研究方向。

【參考論文】
Nature, 2011; DOI: 10.1038/nature10502
PDGF signalling controls age-dependent proliferation in pancreatic β-cells
Hainan Chen, Xueying Gu, Yinghua Liu, et al.  
Determining the signalling pathways that direct tissue expansion is a principal goal of regenerative biology. Vigorous pancreatic β-cell replication in juvenile mice and humans declines with age, and elucidating the basis for this decay may reveal strategies for inducing β-cell expansion, a long-sought goal for diabetes therapy. Here we show that platelet-derived growth factor receptor (Pdgfr) signalling controls age-dependent β-cell proliferation in mouse and human pancreatic islets. With age, declining β-cell Pdgfr levels were accompanied by reductions in β-cell enhancer of zeste homologue 2 (Ezh2) levels and β-cell replication. Conditional inactivation of the Pdgfra gene in β-cells accelerated these changes, preventing mouse neonatal β-cell expansion and adult β-cell regeneration. Targeted human PDGFR-α activation in mouse β-cells stimulated Erk1/2 phosphorylation, leading to Ezh2-dependent expansion of adult β-cells. Adult human islets lack PDGF signalling competence, but exposure of juvenile human islets to PDGF-AA stimulated β-cell proliferation. The discovery of a conserved pathway controlling age-dependent β-cell proliferation indicates new strategies for β-cell expansion