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Chronic granulomatous disease (CGD) is an inherited immunodeficiency,caused by the inability of neutrophils to produce functional NADPH oxidase required for fighting microbial infections. The X-linked form of CGD (X-CGD),which is due to mutations in the CYBB (gp91phox) gene,a component of NADPH oxidase,accounts for about two-thirds of CGD cases. We derived induced pluripotent stem cells (iPSCs) from X-CGD patient keratinocytes using a Flp recombinase excisable lentiviral reprogramming vector. For restoring gp91phox function,we applied two strategies: transposon-mediated bacterial artificial chromosome (BAC) transgenesis and gene targeting using vectors with a fixed 5' homology arm (HA) of 8 kb and 3'HA varying in size from 30 to 80 kb. High efficiency of homologous recombination (up to 22%) was observed with increased size of the 3'HA. Both,BAC transgenesis and gene targeting resulted in functional restoration of the gp91phox measured by an oxidase activity assay in X-CGD iPSCs differentiated into the myeloid lineage. In conclusion,we delivered an important milestone towards the use of genetically corrected autologous cells for the treatment of X-CGD and monogenic diseases in general. View Publication

Significant efforts have been invested into the differentiation of stem cells into functional hepatocyte-like cells that can be used for cell therapy,disease modeling and drug screening. Most of these efforts have been concentrated on the use of growth factors to recapitulate developmental signals under in vitro conditions. Using small molecules instead of growth factors would provide an attractive alternative since small molecules are cell-permeable and cheaper than growth factors. We have developed a protocol for the differentiation of human embryonic stem cells into hepatocyte-like cells using a predominantly small molecule-based approach (SM-Hep). This 3 step differentiation strategy involves the use of optimized concentrations of LY294002 and bromo-indirubin-3'-oxime (BIO) for the generation of definitive endoderm; sodium butyrate and dimethyl sulfoxide (DMSO) for the generation of hepatoblasts and SB431542 for differentiation into hepatocyte-like cells. Activin A is the only growth factor required in this protocol. Our results showed that SM-Hep were morphologically and functionally similar or better compared to the hepatocytes derived from the growth-factor induced differentiation (GF-Hep) in terms of expression of hepatic markers,urea and albumin production and cytochrome P450 (CYP1A2 and CYP3A4) activities. Cell viability assays following treatment with paradigm hepatotoxicants Acetaminophen,Chlorpromazine,Diclofenac,Digoxin,Quinidine and Troglitazone showed that their sensitivity to these drugs was similar to human primary hepatocytes (PHHs). Using SM-Hep would result in 67% and 81% cost reduction compared to GF-Hep and PHHs respectively. Therefore,SM-Hep can serve as a robust and cost effective replacement for PHHs for drug screening and development. View Publication

Human pluripotent stem cells (hPSC) are self-renewing cells having the potential of differentiation into the three lineages of somatic cells and thus can be medically used in diverse cellular therapies. One of the requirements for achieving these clinical applications is development of completely defined xeno-free systems for large-scale cell expansion and differentiation. Previously,we demonstrated that microcarriers (MCs) coated with mouse laminin-111 (LN111) and positively charged poly-l-lysine (PLL) critically enable the formation and evolution of cells/MC aggregates with high cell yields obtained under agitated conditions. In this article,we further improved the MC system into a defined xeno-free MC one in which the MCs are coated with recombinant human laminin-521 (LN521) alone without additional positive charge. The high binding affinity of the LN521 to cell integrins enables efficient initial HES-3 cell attachment (87%) and spreading (85%),which leads to generation of cells/MC aggregates (400 $\$ in size) and high cell yields (2.4-3.5×10(6) cells/mL) within 7 days in agitated plate and scalable spinner cultures. The universality of the system was demonstrated by propagation of an induced pluripotent cells line in this defined MC system. Long-term pluripotent (textgreater90% expression Tra-1-60) cell expansion and maintenance of normal karyotype was demonstrated after 10 cell passages. Moreover,tri-lineage differentiation as well as directed differentiation into cardiomyocytes was achieved. The new LN521-based MC system offers a defined,xeno-free,GMP-compatible,and scalable bioprocessing platform for the production of hPSC with the quantity and quality compliant for clinical applications. Use of LN521 on MCs enabled a 34% savings in matrix and media costs over monolayer cultures to produce 10(8) cells. View Publication

Deciphering the multitude of epigenomic and genomic factors that influence the mutation rate is an area of great interest in modern biology. Recently,chromatin has been shown to play a part in this process. To elucidate this relationship further,we integrated our own ultra-deep sequenced human nucleosomal DNA data set with a host of published human genomic and cancer genomic data sets. Our results revealed,that differences in nucleosome occupancy are associated with changes in base-specific mutation rates. Increasing nucleosome occupancy is associated with an increasing transition to transversion ratio and an increased germline mutation rate within the human genome. Additionally,cancer single nucleotide variants and microindels are enriched within nucleosomes and both the coding and non-coding cancer mutation rate increases with increasing nucleosome occupancy. There is an enrichment of cancer indels at the theoretical start (74 bp) and end (115 bp) of linker DNA between two nucleosomes. We then hypothesized that increasing nucleosome occupancy decreases access to DNA by DNA repair machinery and could account for the increasing mutation rate. Such a relationship should not exist in DNA repair knockouts,and we thus repeated our analysis in DNA repair machinery knockouts to test our hypothesis. Indeed,our results revealed no correlation between increasing nucleosome occupancy and increasing mutation rate in DNA repair knockouts. Our findings emphasize the linkage of the genome and epigenome through the nucleosome whose properties can affect genome evolution and genetic aberrations such as cancer. View Publication

The fundamental repeating unit of eukaryotic chromatin is the nucleosome. Besides being involved in packaging DNA,nucleosome organization plays an important role in transcriptional regulation and cellular identity. Currently,there is much debate about the major determinants of the nucleosome architecture of a genome and its significance with little being known about its role in stem cells. To address these questions,we performed ultra-deep sequencing of nucleosomal DNA in two human embryonic stem cell lines and integrated our data with numerous epigenomic maps. Our analyses have revealed that the genome is a determinant of nucleosome organization with transcriptionally inactive regions characterized by a ground state" of nucleosome profiles driven by underlying DNA sequences. DNA sequence preferences are associated with heterogeneous chromatin organization around transcription start sites. Transcription� View Publication

INTRODUCTION Numerous pathogenic mutations responsible for mitochondrial diseases have been identified in mitochondrial DNA (mtDNA)-encoded tRNA genes. In most cases,however,the detailed molecular pathomechanisms and cellular pathophysiology of these mtDNA mutations -how such genetic defects determine the variation and the severity of clinical symptoms in affected individuals- remain unclear. To investigate the molecular pathomechanisms and to realize in vitro recapitulation of mitochondrial diseases,intracellular mutant mtDNA proportions must always be considered. RESULTS We found a disease-causative mutation,m.5541CtextgreaterT heteroplasmy in MT-TW gene,in a patient exhibiting mitochondrial myopathy,encephalopathy,lactic acidosis,and stroke-like episodes (MELAS) with multiple organ involvement. We identified the intrinsic molecular pathomechanisms of m.5541CtextgreaterT. This mutation firstly disturbed the translation machinery of mitochondrial tRNA(Trp) and induced mitochondrial respiratory dysfunction,followed by severely injured mitochondrial homeostasis. We also demonstrated cell-type-specific disease phenotypes using patient-derived induced pluripotent stem cells (iPSCs) carrying ˜100 % mutant m.5541CtextgreaterT. Significant loss of terminally differentiated iPSC-derived neurons,but not their stem/progenitor cells,was detected most likely due to serious mitochondrial dysfunction triggered by m.5541CtextgreaterT; in contrast,m.5541CtextgreaterT did not apparently affect skeletal muscle development. CONCLUSIONS Our iPSC-based disease models would be widely available for understanding the definite" genotype-phenotype relationship of affected tissues and organs in various mitochondrial diseases caused by heteroplasmic mtDNA mutations� View Publication

Astrocytes are instrumental to major brain functions,including metabolic support,extracellular ion regulation,the shaping of excitatory signaling events and maintenance of synaptic glutamate homeostasis. Astrocyte dysfunction contributes to numerous developmental,psychiatric and neurodegenerative disorders. The generation of adult human fibroblast-derived induced pluripotent stem cells (iPSCs) has provided novel opportunities to study mechanisms of astrocyte dysfunction in human-derived cells. To overcome the difficulties of cell type heterogeneity during the differentiation process from iPSCs to astroglial cells (iPS astrocytes),we generated homogenous populations of iPS astrocytes using zinc-finger nuclease (ZFN) technology. Enhanced green fluorescent protein (eGFP) driven by the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter was inserted into the safe harbor adeno-associated virus integration site 1 (AAVS1) locus in disease and control-derived iPSCs. Astrocyte populations were enriched using Fluorescence Activated Cell Sorting (FACS) and after enrichment more than 99% of iPS astrocytes expressed mature astrocyte markers including GFAP,S100$\$,NFIA and ALDH1L1. In addition,mature pure GFP-iPS astrocytes exhibited a well-described functional astrocytic activity in vitro characterized by neuron-dependent regulation of glutamate transporters to regulate extracellular glutamate concentrations. Engraftment of GFP-iPS astrocytes into rat spinal cord grey matter confirmed in vivo cell survival and continued astrocytic maturation. In conclusion,the generation of GFAP::GFP-iPS astrocytes provides a powerful in vitro and in vivo tool for studying astrocyte biology and astrocyte-driven disease pathogenesis and therapy. View Publication

To realize the potential of human embryonic stem cells (hESCs) in regenerative medicine and drug discovery applications,large numbers of cells that accurately recapitulate cell and tissue function must be robustly produced. Previous studies have suggested that genetic instability and epigenetic changes occur as a consequence of enzymatic passaging. However,the potential impacts of such passaging methods on the metabolism of hESCs have not been described. Using stable isotope tracing and mass spectrometry-based metabolomics,we have explored how different passaging reagents impact hESC metabolism. Enzymatic passaging caused significant decreases in glucose utilization throughout central carbon metabolism along with attenuated de novo lipogenesis. In addition,we developed and validated a method for rapidly quantifying glycan abundance and isotopic labeling in hydrolyzed biomass. Enzymatic passaging reagents significantly altered levels of glycans immediately after digestion but surprisingly glucose contribution to glycans was not affected. These results demonstrate that there is an immediate effect on hESC metabolism after enzymatic passaging in both central carbon metabolism and biosynthesis. HESCs subjected to enzymatic passaging are routinely placed in a state requiring re-synthesis of biomass components,subtly influencing their metabolic needs in a manner that may impact cell performance in regenerative medicine applications. View Publication

Pluripotent stem cells,including embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs),have the potential to treat type 1 diabetes through cell replacement therapy. However,the protocols used to generate insulin-expressing cells in vitro frequently result in cells which have an immature phenotype and are functionally restricted. MicroRNAs (miRNAs) are now known to be important in cell fate specification,and a unique miRNA signature characterises pancreatic development at the definitive endoderm stage. Several studies have described differences in miRNA expression between ESCs and iPSCs. Here we have used microarray analysis both to identify miRNAs up- or down-regulated upon endoderm formation,and also miRNAs differentially expressed between ESCs and iPSCs. Several miRNAs fulfilling both these criteria were identified,suggesting that differences in the expression of these miRNAs may affect the ability of pluripotent stem cells to differentiate into definitive endoderm. The expression of these miRNAs was validated by qRT-PCR,and the relationship between one of these miRNAs,miR-151a-5p,and its predicted target gene,SOX17,was investigated by luciferase assay,and suggested an interaction between miR-151a-5p and this key transcription factor. In conclusion,these findings demonstrate a unique miRNA expression pattern for definitive endoderm derived from both embryonic and induced pluripotent stem cells. View Publication

GTF2IRD1 is one of the three members of the GTF2I gene family,clustered on chromosome 7 within a 1.8 Mb region that is prone to duplications and deletions in humans. Hemizygous deletions cause Williams-Beuren syndrome (WBS) and duplications cause WBS duplication syndrome. These copy number variations disturb a variety of developmental systems and neurological functions. Human mapping data and analyses of knockout mice show that GTF2IRD1 and GTF2I underpin the craniofacial abnormalities,mental retardation,visuospatial deficits and hypersociability of WBS. However,the cellular role of the GTF2IRD1 protein is poorly understood due to its very low abundance and a paucity of reagents. Here,for the first time,we show that endogenous GTF2IRD1 has a punctate pattern in the nuclei of cultured human cell lines and neurons. To probe the functional relationships of GTF2IRD1 in an unbiased manner,yeast two-hybrid libraries were screened,isolating 38 novel interaction partners,which were validated in mammalian cell lines. These relationships illustrate GTF2IRD1 function,as the isolated partners are mostly involved in chromatin modification and transcriptional regulation,whilst others indicate an unexpected role in connection with the primary cilium. Mapping of the sites of protein interaction also indicates key features regarding the evolution of the GTF2IRD1 protein. These data provide a visual and molecular basis for GTF2IRD1 nuclear function that will lead to an understanding of its role in brain,behaviour and human disease. View Publication