Modeling Hematological Diseases and Cancer With Patient-Specific Induced Pluripotent Stem Cells

The advent of induced pluripotent stem cells (iPSCs) together with recent advances in genome editing, microphysiological systems, tissue engineering and xenograft models present new opportunities for the investigation of hematological diseases and cancer in a patient-specific context. Here we review the progress in the field and discuss the advantages, limitations, and challenges of iPSC-based malignancy modeling. We will also discuss the use of iPSCs and its derivatives as cellular sources for drug target identification, drug development and evaluation of pharmacological responses

Genomic imprinting defect in Zfp57 mutant iPS cell lines

AbstractZFP57 maintains genomic imprinting in mouse embryos and ES cells. To test its roles during iPS reprogramming, we derived iPS clones by utilizing retroviral infection to express reprogramming factors in mouse MEF cells. After analyzing four imprinted regions, we found that parentally derived DNA methylation imprint was largely maintained in the iPS clones with Zfp57 but missing in those without maternal or zygotic Zfp57. Intriguingly, DNA methylation imprint was lost at the Peg1 and Peg3 but retained at the Snrpn and Dlk1-Dio3 imprinted regions in the iPS clones without zygotic Zfp57. This finding will be pursued in future studies

Regulation of Embryonic and Induced Pluripotency by Aurora Kinase-p53 Signaling

SummaryMany signals must be integrated to maintain self-renewal and pluripotency in embryonic stem cells (ESCs) and to enable induced pluripotent stem cell (iPSC) reprogramming. However, the exact molecular regulatory mechanisms remain elusive. To unravel the essential internal and external signals required for sustaining the ESC state, we conducted a short hairpin (sh) RNA screen of 104 ESC-associated phosphoregulators. Depletion of one such molecule, aurora kinase A (Aurka), resulted in compromised self-renewal and consequent differentiation. By integrating global gene expression and computational analyses, we discovered that loss of Aurka leads to upregulated p53 activity that triggers ESC differentiation. Specifically, Aurka regulates pluripotency through phosphorylation-mediated inhibition of p53-directed ectodermal and mesodermal gene expression. Phosphorylation of p53 not only impairs p53-induced ESC differentiation but also p53-mediated suppression of iPSC reprogramming. Our studies demonstrate an essential role for Aurka-p53 signaling in the regulation of self-renewal, differentiation, and somatic cell reprogramming

A human MIXL1 green fluorescent protein reporter embryonic stem cell line engineered using TALEN-based genome editing

We have generated a MIXL1-eGFP reporter human embryonic stem cell (hESC) line using TALEN-based genome engineering. This line accurately traces endogenous MIXL1 expression via an eGFP reporter to mesendodermal precursor cells. The utility of the MIXL1-eGFP reporter hESC line lies in the prospective isolation, lineage tracing, and developmental and mechanistic studies of MIXL1+ cell populations

A Marfan syndrome human induced pluripotent stem cell line with a heterozygous FBN1 c.4082G>A mutation, ISMMSi002-B, for disease modeling

Fibroblasts of a 28-year-old female with Marfan syndrome (MFS) due to a heterozygous FBN1 c.4082G>A mutation were reprogrammed using the Sendai virus delivery method. The established human induced pluripotent stem cell (hiPSC) line named ISMMSi002-B expresses pluripotency markers, has a normal karyotype, carries the specific FBN1 mutation and is able to differentiate into three germ layers in vitro. ISMMSi002-B has utility in studying MFS pathogenesis, including skeletal abnormalities, cardiomyopathy, and vascular smooth muscle cell dysfunction associated with aortic aneurysm. Furthermore, it can serve as a platform for drug discovery

Divisional History and Hematopoietic Stem Cell Function during Homeostasis

We investigated the homeostatic behavior of hematopoietic stem and progenitor cells (HSPCs) temporally defined according to their divisional histories using an HSPC-specific GFP label-retaining system. We show that homeostatic hematopoietic stem cells (HSCs) lose repopulating potential after limited cell divisions. Once HSCs exit dormancy and accrue divisions, they also progressively lose the ability to return to G0 and functional activities associated with quiescent HSCs. In addition, dormant HSPCs phenotypically defined as multipotent progenitor cells display robust stem cell activity upon transplantation, suggesting that temporal quiescence is a greater indicator of function than cell-surface phenotype. Our studies suggest that once homeostatic HSCs leave dormancy, they are slated for extinction. They self-renew phenotypically, but they lose self-renewal activity. As such, they question self-renewal as a characteristic of homeostatic, nonperturbed HSCs in contrast to self-renewal demonstrated under stress conditions