参考文献

Skeletal dysplasias (SDs) are caused by abnormal chondrogenesis during cartilage growth plate differentiation. To study early stages of aberrant cartilage formation in vitro,we generated the first induced pluripotent stem cells (iPSCs) from fibroblasts of an SD patient with a lethal form of metatropic dysplasia,caused by a dominant mutation (I604M) in the calcium channel gene TRPV4. When micromasses were grown in chondrogenic differentiation conditions and compared with control iPSCs,mutant TRPV4-iPSCs showed significantly (Ptextless0.05) decreased expression by quantitative real-time polymerase chain reaction of COL2A1 (IIA and IIB forms),SOX9,Aggrecan,COL10A1,and RUNX2,all of which are cartilage growth plate markers. We found that stimulation with BMP2,but not TGF$\$1,up-regulated COL2A1 (IIA and IIB) and SOX9 gene expression,only in control iPSCs. COL2A1 (Collagen II) expression data were confirmed at the protein level by western blot and immunofluorescence microscopy. TRPV4-iPSCs showed only focal areas of Alcian blue stain for proteoglycans,while in control iPSCs the stain was seen throughout the micromass sample. Similar staining patterns were found in neonatal cartilage from control and patient samples. We also found that COL1A1 (Collagen I),a marker of osteogenic differentiation,was significantly (Ptextless0.05) up-regulated at the mRNA level in TRPV4-iPSCs when compared with the control,and confirmed at the protein level. Collagen I expression in the TRPV4 model also may correlate with abnormal staining patterns seen in patient tissues. This study demonstrates that an iPSC model can recapitulate normal chondrogenesis and that mutant TRPV4-iPSCs reflect molecular evidence of aberrant chondrogenic developmental processes,which could be used to design therapeutic approaches for disorders of cartilage. View Publication

The clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) systems have evolved as an adaptive surveillance and defense mechanism in bacteria and archaea that uses short RNAs to direct degradation of foreign genetic elements. Here,we present our protocol for utilizing the S. pyogenes type II bacterial CRISPR system to achieve sequence-specific genome alterations in human cells. In principle,any genomic sequence of the form N(19)NGG can be targeted with the generation of custom guide RNA (gRNA) which functions to direct the Cas9 protein to genomic targets and induce DNA cleavage. Here,we describe our methods for designing and generating gRNA expression constructs either singly or in a multiplexed manner,as well as optimized protocols for the delivery of Cas9-gRNA components into human cells. Genomic alterations at the target site are then introduced either through nonhomologous end joining (NHEJ) or through homologous recombination (HR) in the presence of an appropriate donor sequence. This RNA-guided editing tool offers greater ease of customization and synthesis in comparison to existing sequence-specific endonucleases and promises to become a highly versatile and multiplexable human genome engineering platform. View Publication

Efficient approaches for the precise genetic engineering of stem cells can enhance both basic and applied stem cell research. Adeno-associated virus (AAV) vectors have demonstrated high-efficiency gene delivery and gene targeting to numerous cell types,and AAV vectors developed specifically for gene delivery to stem cells have further increased gene targeting frequency compared to plasmid construct techniques. This chapter details the production and purification techniques necessary to generate adeno-associated viral vectors for use in high-efficiency gene targeting of adult or pluripotent stem cell applications. Culture conditions used to achieve high gene targeting frequencies in rat neural stem cells and human pluripotent stem cells are also described. View Publication

The ability of human embryonic stem cells and induced pluripotent stem cells to differentiate into all adult cell types greatly facilitates the study of human development,disease pathogenesis,and the generation of screening systems to identify novel therapeutic agents. Autologous cell therapies based on patient-derived induced pluripotent stem cells also hold great promise for the treatment and correction of many inherited and acquired diseases. The full potential of human pluripotent stem cells can be unleashed by genetically modifying a chosen locus with minimal impact on the remaining genome,which can be achieved by targeting genes by homologous recombination. This chapter will describe a protocol for gene modification of pluripotent stem cells by homologous recombination and several methods for the screening and identification of successfully modified clones. View Publication

Basal-like breast cancers (BLBC) are poorly differentiated and display aggressive clinical behavior. These tumors become resistant to cytotoxic agents,and tumor relapse has been attributed to the presence of cancer stem cells (CSC). One of the pathways involved in CSC regulation is the Wnt/$$-catenin signaling pathway. LRP6,a Wnt ligand receptor,is one of the critical elements of this pathway and could potentially be an excellent therapeutic target. Niclosamide has been shown to inhibit the Wnt/$$-catenin signaling pathway by causing degradation of LRP6. TRA-8,a monoclonal antibody specific to TRAIL death receptor 5,is cytotoxic to BLBC cell lines and their CSC-enriched populations. The goal of this study was to examine whether niclosamide is cytotoxic to BLBCs,specifically the CSC population,and if in combination with TRA-8 could produce increased cytotoxicity. Aldehyde dehydrogenase (ALDH) is a known marker of CSCs. By testing BLBC cells for ALDH expression by flow cytometry,we were able to isolate a nonadherent population of cells that have high ALDH expression. Niclosamide showed cytotoxicity against these nonadherent ALDH-expressing cells in addition to adherent cells from four BLBC cell lines: 2LMP,SUM159,HCC1187,and HCC1143. Niclosamide treatment produced reduced levels of LRP6 and $$-catenin,which is a downstream Wnt/$$-catenin signaling protein. The combination of TRA-8 and niclosamide produced additive cytotoxicity and a reduction in Wnt/$$-catenin activity. Niclosamide in combination with TRA-8 suppressed growth of 2LMP orthotopic tumor xenografts. These results suggest that niclosamide or congeners of this agent may be useful for the treatment of BLBC. View Publication

OBJECTIVE The KLF4 gene has been shown to be inactivated in cervical carcinogenesis as a tumor suppressor. However,the mechanism of KLF4 silencing in cervical carcinomas has not yet been identified. DNA methylation plays a key role in stable suppression of gene expression. METHODS The methylation status of the KLF4 promoter CpG islands was analyzed by bisulfite sequencing (BSQ) in tissues of normal cervix and cervical cancer. KLF4 gene expression was detected by RT-PCR,immunohistochemistry and western blot. KLF4 promoter methylation in cervical cancer cell line was determined by BSQ and methylation-specific polymerase chain reaction (MS-PCR). Cell proliferation ability was detected by cell growth curve and MTT assay. RESULTS The methylated allele was found in 41.90% of 24 cervical cancer tissues but only in 11.11% of 11 normal cervix tissues (Ptextless0.005). KLF4 mRNA levels were significantly reduced in cervical cancer tissues compared with normal cervix tissues (Ptextless0.01) and KLF4 mRNA expression showed a significant negative correlation with the promoter hypermethylation (r = -0.486,P = 0.003). Cervical cancer cell lines also showed a significant negative correlation between KLF4 expression and hypermethylation. After treatment with the demethylating agent 5-Azacytidine (5-Aza),the expression of KLF4 in the cervical cancer cell lines at both mRNA and protein levels was drastically increased,the cell proliferation ability was inhibited and the chemosensitivity for cisplatin was significantly increased. CONCLUSION KLF4 gene is inactivated by methylation-induced silencing mechanisms in a large subset of cervical carcinomas and KLF4 promoter hypermethylation inactivates the gene's function as a tumor suppressor in cervical carcinogenesis. View Publication

Bone morphogenetic proteins (BMPs) initiate differentiation in human embryonic stem cells (hESCs) but the exact mechanisms have not been fully elucidated. We demonstrate here that SLUG and MSX2,transcription factors involved in epithelial-mesenchymal transitions,essential features of gastrulation in development and tumor progression,are important mediators of BMP4-induced differentiation in hESCs. Phosphorylated Smad1/5/8 colocalized with the SLUG protein at the edges of hESC colonies where differentiation takes place. The upregulation of the BMP target SLUG was direct as shown by the binding of phosphorylated Smad1/5/8 to its promoter,which interrupted the formation of adhesion proteins,resulting in migration. Knockdown of SLUG by short hairpin RNA blocked these changes,confirming an important role for SLUG in BMP-mediated mesodermal differentiation. Furthermore,BMP4-induced MSX2 expression leads to mesoderm formation and then preferential differentiation toward the cardiovascular lineage. View Publication

Murine hybridomas producing neutralizing mAbs specific to the pandemic influenza virus A/California/07/2009 haemagglutinin (HA) were isolated. These antibodies recognized at least two different but overlapping new epitopes that were conserved in the HA of most Spanish pandemic isolates. However,one of these isolates (A/Extremadura/RR6530/2010) lacked reactivity with the mAbs and carried two unique mutations in the HA head (S88Y and K136N) that were required simultaneously to eliminate reactivity with the murine antibodies. This unusual requirement directly illustrates the phenomenon of enhanced antigenic change proposed previously for the accumulation of simultaneous amino acid substitutions at antigenic sites of the influenza A virus HA during virus evolution (Shih et al.,Proc Natl Acad Sci USA,104,6283-6288,2007). The changes found in the A/Extremadura/RR6530/2010 HA were not found in escape mutants selected in vitro with one of the mAbs,which contained instead nearby single amino acid changes in the HA head. Thus,either single or double point mutations may similarly alter epitopes of the new antigenic site identified in this work in the 2009 H1N1 pandemic virus HA. Moreover,this site is relevant for the human antibody response,as shown by competition of mAbs and human post-infection sera for virus binding. The results are discussed in the context of the HA antigenic structure and challenges posed for identification of sequence changes with possible antigenic impact during virus surveillance. View Publication

Skeletal muscle aging results in a gradual loss of skeletal muscle mass,skeletal muscle function and regenerative capacity,which can lead to sarcopenia and increased mortality. Although the mechanisms underlying sarcopenia remain unclear,the skeletal muscle stem cell,or satellite cell,is required for muscle regeneration. Therefore,identification of signaling pathways affecting satellite cell function during aging may provide insights into therapeutic targets for combating sarcopenia. Here,we show that a cell-autonomous loss in self-renewal occurs via alterations in fibroblast growth factor receptor-1,p38α and p38β mitogen-activated protein kinase signaling in satellite cells from aged mice. We further demonstrate that pharmacological manipulation of these pathways can ameliorate age-associated self-renewal defects. Thus,our data highlight an age-associated deregulation of a satellite cell homeostatic network and reveal potential therapeutic opportunities for the treatment of progressive muscle wasting. View Publication

The elderly often suffer from progressive muscle weakness and regenerative failure. We demonstrate that muscle regeneration is impaired with aging owing in part to a cell-autonomous functional decline in skeletal muscle stem cells (MuSCs). Two-thirds of MuSCs from aged mice are intrinsically defective relative to MuSCs from young mice,with reduced capacity to repair myofibers and repopulate the stem cell reservoir in vivo following transplantation. This deficiency is correlated with a higher incidence of cells that express senescence markers and is due to elevated activity of the p38α and p38β mitogen-activated kinase pathway. We show that these limitations cannot be overcome by transplantation into the microenvironment of young recipient muscles. In contrast,subjecting the MuSC population from aged mice to transient inhibition of p38α and p38β in conjunction with culture on soft hydrogel substrates rapidly expands the residual functional MuSC population from aged mice,rejuvenating its potential for regeneration and serial transplantation as well as strengthening of damaged muscles of aged mice. These findings reveal a synergy between biophysical and biochemical cues that provides a paradigm for a localized autologous muscle stem cell therapy for the elderly. View Publication