细胞生命进程中microRNA调控的意义

细胞生命进程经历从生到死多个阶段,涉及基因表达程序在整体机制控制下的一系列协调性改变.遗传信息网络在整体机制中控制基因组表达程序,地位至关重要,是细胞分裂时发生的可遗传性而不涉及DNA链自身序列改变的稳定性分子变化,包括microRNA及其非蛋白编码RNA、DNA甲基化（常发生于CpG岛）及组蛋白尾修饰（影响染色质结构）.microRNA是一种由22个左右核苷酸组成的非蛋白编码微小RNA.Bartel等[1,2]于1993年首次从线虫中发现,至2009年已经识别的人类microRNA达900多种.据生物信息学评估,人类基因组有30%～60%受microRNA调控.

人类干细胞启动子区CG含量与组蛋白修饰的相关性

组蛋白修饰与基因的转录表达关系密切,是表观遗传学的主要内容之一。启动子是调控基因表达的重要元件之一。按照Cp G含量的不同,可以将启动子分为高Cp G含量(HCG)和低Cp G含量(LCG)两类。通过比较人类H1细胞系中16种组蛋白修饰在HCG启动子及LCG启动子上的分布,发现大部分组蛋白修饰在整个启动子区域都是HCG启动子的修饰水平较高,个别组蛋白修饰在启动子的部分区域上是LCG启动子的修饰水平较高;计算了两类启动子中不同组蛋白修饰之间的相关系数,分别得到了HCG启动子和LCG启动子中特有及共有的组蛋白修饰簇;选取了10个与干细胞自我更新相关的关键转录因子基因,对这10个基因的启动子进行了HCG和LCG分类,并得到了每个启动子上组蛋白修饰的分布特异性。这些结果为研究CG含量对于不同组蛋白修饰的影响,以及组蛋白修饰与CG含量共同调控干细胞自我更新的机制,提供了一些理论依据。

Comparative Analysis of Five Different Homologous Feeder Cell Lines in the Ability to Support Rhesus Embryonic Stem Cells

In our previous study, five homologous feeder cell lines, Monkey ear skin fibroblasts （MESFs）, clonally derived fibroblasts from the MESFs （CMESFs）, monkey oviductal fibroblasts （MOFs）, monkey follicular granulosa fibroblast-like （MFGs） cells, monkey follicular granulosa epithelium-like （MFGEs） cells, were developed for the maintenance of rhesus embryonic stem cells （rESCs）. We found that MESFs, CMESFs, MOFs and MFGs, but not MFGEs, support the growth of rhesus embryonic stem cells. Moreover, we detected some genes that are upregulated in supportive feeder cell lines by semi-quantitative PCR. In the present study, we applied the GeneChip Rhesus Macaque Genome Array of Affymetrix Corporation to study the expression profiles of these five feeder cell lines, in purpose to find out which cytokines and signaling pathways were important in maintaining the rESCs, mRNAs of eight genes, including GREM2, bFGF, KITLG, DKK3, GREM1, AREG, SERPINF1 and LTBP1, were found to be upregulated in supportive feeder cell lines, but not in MFGE. The results indicate that many signaling pathways may play redundant roles in supporting the undifferentiated growth and maintenance of pluripotency in rESCs.

Inhibition of lung cancer stem cells self-renewal and tumorigenicity by lentivirus-delivered Bmi1 shRNA

Objective： The aim of the study was to observe the effect of Bmil reduction on the self-renewal and tumorigenicity ability of lung cancer stem cells （LCSCs） in human lung adenocarcinoma. Methods： Human lung adenocarcinoma cells A549 were consecutively passaged in NOD/SCID mice treated with Paclitaxel weekly. The proportions of LCSCs in A549 cells and the cells from the third passage （A549-3rd） were compared. The expression of Bmil in LCSCs was silenced by intratumoral injection with lentivirus-delivered Broil small hairpin RNA （shRNA）. RT-PCR and Western blot were used to test the mRNA and protein expressions of Broil in LCSCs. The protein level of p16INK4A was analyzed by Western blotting. The self- renewal and tumorigenicity ability of LCSCs were evaluated by counting the sphere formation rate in serum-free medium and the tumor formation rate in NOD/SCID mice. Results： In vivo passaging ofA549 cells under chemotherapy pressure enriched for LCSCs. The expression of Broil in LCSCs increased. Down-regulation of Bmil by RNA interference resulted in reduced self-renewal and tumorigenicity ability of LCSCs and paralleled the increased expression of p16INK4A, a Bmil target. Conclu- sion： Broil regulates self-renewal and tumorigenicity of LCSCs by silencing some target genes, including p16INK4A.

Regulation of hematopoietic stem cells in the niche

Hematopoiesis provides a suitable model for understanding adult stem cells and their niche. Hematopoietic stem cells(HSCs) continuously produce blood cells through orchestrated proliferation, self-renewal, and differentiation in the bone marrow(BM). Within the BM exists a highly organized microenvironment termed "niche" where stem cells reside and are maintained. HSC niche is the first evidence that a microenvironment contributes to protecting stem cell integrity and functionality in mammals. Although multiple models exist, recent progress has principally elucidated the cellular complexity of the HSC niche that maintains and regulates HSCs in BM. Here we introduce the development and summarize the achievements of HSC niche studies.

Telomerase as a “stemness” enzyme

Pluripotent or multipotent stem cells are involved in development and tissue homeostasis;they have the ability to self-renew and differentiate into various types of functional cells.To maintain these properties,stem cells must undergo sustained or unlimited proliferation that requires the stabilization of telomeres,which are essential for chromosome end protection.Telomerase,an RNA-dependent DNA polymerase,synthesizes telomeric DNA.Through the lengthening of telomeres the lifespans of cells are extended,or indefinite proliferation is conferred;this is intimately associated with stem cell phenotype.This review highlights our current understanding of telomerase as a"stemness"enzyme and discusses the underlying implications.