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1.  Trisomy Correction in Down Syndrome Induced Pluripotent Stem Cells 
Cell stem cell  2012;11(5):615-619.
Human trisomies can alter cellular phenotypes and produce congenital abnormalities such as Down syndrome (DS). Here we have generated induced pluripotent stem cells (iPSCs) from DS fibroblasts and introduced a TKNEO transgene into one copy of chromosome 21 by gene targeting. When selecting against TKNEO, spontaneous chromosome loss was the most common cause for survival, with a frequency of ∼10−4, while point mutations, epigenetic silencing, and TKNEO deletions occurred at lower frequencies in this unbiased comparison of inactivating mutations. Mitotic recombination events resulting in extended loss of heterozygosity were not observed in DS iPSCs. The derived, disomic cells proliferated faster and produced more endothelia in vivo than their otherwise isogenic trisomic counterparts, but in vitro hematopoietic differentiation was not consistently altered. Our study describes a targeted removal of a human trisomy, which could prove useful in both clinical and research applications.
PMCID: PMC3705773  PMID: 23084023
2.  Targeting SOX17 in human embryonic stem cells creates unique strategies for isolating and analyzing developing endoderm 
Cell stem cell  2011;8(3):335-346.
Investigating development of inaccessible human tissues like embryonic endoderm with embryonic stem cell (ESC) has been hindered by a lack of methods for marking and isolating endodermal cells, and tracing fates of their progeny toward differentiated lineages. Using homologous recombination in human ESC, we inserted an enhanced green fluorescent protein (eGFP) transgene into a locus encoding a postulated marker of human endoderm, SOX17, permitting purification of SOX17+ hESC progeny by fluorescence activated cell sorting (FACS). Microarray studies revealed a unique gene expression profile of human SOX17+ cells including endodermal marker enrichment, and unveiled specific cell surface protein combinations that permitted FACS-based isolation of primitive gut tube endodermal cells produced from unmodified human ESCs and from induced pluripotent stem cells (iPSC). FACS-isolated SOX17+ endodermal cells differentiated to progeny expressing markers of liver, pancreas, and intestinal epithelium, providing unprecedented evidence that human gastrointestinal lineages derive from SOX17+ cells. Thus, prospective isolation, lineage tracing, and developmental studies of hESCs described here have revealed fundamental aspects of human endodermal biology.
PMCID: PMC3063711  PMID: 21362573
3.  Deconstructing Pancreas Development to Reconstruct Human Islets from Pluripotent Stem Cells 
Cell stem cell  2010;6(4):300-308.
There is considerable excitement about harnessing the potential of human stem cells to replace pancreatic islets that are destroyed in type 1 diabetes mellitus. However, our current understanding of the mechanisms underlying pancreas and islet ontogeny has come largely from the powerful genetic, developmental, and embryological approaches available in nonhuman organisms. Successful islet reconstruction from human pluripotent cells will require greater attention to “deconstructing” human pancreas and islet developmental biology and consistent application of conditional genetics, lineage tracing, and cell purification to stem cell biology.
PMCID: PMC3148083  PMID: 20362535

Results 1-3 (3)