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ABSTRACT: As is the case for embryo-derived stem cells, application of reprogrammed human induced pluripotent stem cells is limited by our understanding of lineage specification. Here we demonstrate the ability to generate progenitors and mature cells of the haematopoietic fate directly from human dermal fibroblasts without establishing pluripotency. Ectopic expression of OCT4 (also called POU5F1)-activated haematopoietic transcription factors, together with specific cytokine treatment, allowed generation of cells expressing the pan-leukocyte marker CD45. These unique fibroblast-derived cells gave rise to granulocytic, monocytic, megakaryocytic and erythroid lineages, and demonstrated in vivo engraftment capacity. We note that adult haematopoietic programs are activated, consistent with bypassing the pluripotent state to generate blood fate: this is distinct from haematopoiesis involving pluripotent stem cells, where embryonic programs are activated. These findings demonstrate restoration of multipotency from human fibroblasts, and suggest an alternative approach to cellular reprogramming for autologous cell-replacement therapies that avoids complications associated with the use of human pluripotent stem cells.
Nature 11/2010; 468(7323):521-6. · 36.28 Impact Factor
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ABSTRACT: Pluripotent stem cells (PSCs) have been derived from the embryos of mice and humans, representing the two major sources of PSCs. These cells are universally defined by their developmental properties, specifically their self-renewal capacity and differentiation potential which are regulated in mice and humans by complex transcriptional networks orchestrated by conserved transcription factors. However, significant differences exist in the transcriptional networks and signaling pathways that control mouse and human PSC self-renewal and lineage development. To distinguish between universally applicable and species-specific features, we collated and compared the molecular and cellular descriptions of mouse and human PSCs. Here we compare and contrast the response to signals dictated by the transcriptome and epigenome of mouse and human PSCs that will hopefully act as a critical resource to the field. These analyses underscore the importance of accounting for species differences when designing strategies to capitalize on the clinical potential of human PSCs.
Stem Cells 03/2010; 28(3):419-30. · 7.78 Impact Factor
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Tamra E Werbowetski-Ogilvie,
Marc Bossé,
Morag Stewart, Angelique Schnerch,
Veronica Ramos-Mejia,
Anne Rouleau,
Tracy Wynder,
Mary-Jo Smith,
Steve Dingwall,
Tim Carter,
Christopher Williams,
Charles Harris,
Joanna Dolling,
Christopher Wynder,
Doug Boreham,
Mickie Bhatia
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ABSTRACT: Cultured human embryonic stem (hES) cells can acquire genetic and epigenetic changes that make them vulnerable to transformation. As hES cells with cancer-cell characteristics share properties with normal hES cells, such as self-renewal, teratoma formation and the expression of pluripotency markers, they may be misconstrued as superior hES cells with enhanced 'stemness'. We characterize two variant hES cell lines (v-hESC-1 and v-hESC-2) that express pluripotency markers at high levels and do not harbor chromosomal abnormalities by standard cytogenetic measures. We show that the two lines possess some features of neoplastic progression, including a high proliferative capacity, growth-factor independence, a 9- to 20-fold increase in frequency of tumor-initiating cells, niche independence and aberrant lineage specification, although they are not malignant. Array comparative genomic hybridization reveals an amplification at 20q11.1-11.2 in v-hESC-1 and a deletion at 5q34a-5q34b;5q3 and a mosaic gain of chromosome 12 in v-hESC-2. These results emphasize the need for functional characterization to distinguish partially transformed and normal hES cells.
Nature Biotechnology 02/2009; 27(1):91-7. · 29.50 Impact Factor
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ABSTRACT: The histone demethylase lysine demethylase 5b (KDM5b) specifically demethylates lysine 4 of histone H3 (meH3K4), thereby repressing gene transcription. KDM5b regulates cell cycle control genes in cancer and is expressed in the early epiblast. This suggests that KDM5b plays a developmental role by maintaining uncommitted progenitors. Here we show that transient overexpression of KDM5b in embryonic stem cells decreases the expression of at least three different modulators of cell fate decisions, Egr1, p27(KIP1), and BMI1, by demethylation of their promoters. Constitutively increased KDM5b expression results in an increased mitotic rate and a decreased global 3meH3K4 but no change in cell identity. Results of two separate differentiation assays, neural differentiation and embryoid body EB (EB) formation, showed that KDM5b reduced the terminally differentiated cells and increased proliferating progenitors. These were achieved by two mechanisms, blocking of the upregulation of cell lineage markers and maintenance of cyclins, that allowed cells to escape differentiation and remain uncommitted. Additionally, EBs maintain high levels of Oct4 and Nanog and can be dissociated to reestablish highly proliferative cultures. The persistence of uncommitted progenitors may be due to the direct regulation of the Tcf/Lef family member mTcf3/hTcf7L1, an upstream regulator of Nanog expression. These findings demonstrate a role for KDM5b in the choice between proliferation and differentiation during development.
Molecular and cellular biology 07/2008; 28(17):5312-27. · 6.06 Impact Factor
