Developmental biology has long benefited from studies of classic model organisms. Recently, human pluripotent stem cells (hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, have emerged as a new model system that offers unique advantages for developmental studies. Here, we discuss how studies of hPSCs can complement classic approaches using model organisms, and how hPSCs can be used to recapitulate aspects of human embryonic development 'in a dish'. We also summarize some of the recently developed genetic tools that greatly facilitate the interrogation of gene function during hPSC differentiation. With the development of high-throughput screening technologies, hPSCs have the potential to revolutionize gene discovery in mammalian development.
"Reprogramming technology using several pluripotency-specific transcription factors, such as combination of OCT4, SOX2, KLF4, and c-MYC  or combination of OCT4, SOX2, NANOG, and LIN28 , converts somatic cells of the body into stem cells, called iPS cells, which have similar pluripotency to ES cells but possess even more potential in terms of drug screening and discovery, disease modelling, and clinical therapy because of their disease-specific or patient-specific state [10–12]. Recent remarkable progress in stem cell research has brought great optimism and offered the possibility to use them for developmental biology studies, disease modelling, cell replacement therapy, and tissue engineering in regenerative medicine [5, 10–13]. As stem cell research progressing, vast application potential of it in modern and future medicine can be easily deduced. "
[Show abstract][Hide abstract] ABSTRACT: Stem cells possess huge importance in developmental biology, disease modelling, cell replacement therapy, and tissue engineering in regenerative medicine because they have the remarkable potential for self-renewal and to differentiate into almost all the cell types in the human body. Elucidation of molecular mechanisms regulating stem cell potency and differentiation is essential and critical for extensive application. Heterogeneous nuclear ribonucleoproteins (hnRNPs) are modular proteins consisting of RNA-binding motifs and auxiliary domains characterized by extensive and divergent functions in nucleic acid metabolism. Multiple roles of hnRNPs in transcriptional and posttranscriptional regulation enable them to be effective gene expression regulators. More recent findings show that hnRNP proteins are crucial factors implicated in maintenance of stem cell self-renewal and pluripotency and cell differentiation. The hnRNPs interact with certain sequences in target gene promoter regions to initiate transcription. In addition, they recognize 3'UTR or 5'UTR of specific gene mRNA forming mRNP complex to regulate mRNA stability and translation. Both of these regulatory pathways lead to modulation of gene expression that is associated with stem cell proliferation, cell cycle control, pluripotency, and committed differentiation.
[Show abstract][Hide abstract] ABSTRACT: Activin/Nodal and Wnt signaling are known to play important roles in the regional specification of endoderm. Here we have investigated the effect of the length of stimulation with Activin A plus Wnt3a on the development of hepatic and pancreatic progenitors from the definitive endoderm (DE) cells derived from human pluripotent stem cells (hPSC). We show that DE-cells derived from hPSC with three days high Activin A and Wnt3a treatment were able to differentiate further into both tested endodermal lineages. When prolonging the DE-induction protocol from three to five or seven days, almost pure DE-marker positive cell populations were obtained. However, these cells had an impaired pancreatic differentiation capacity, while they still developed into hepatocyte-like cells. Further propagation of the DE-cells in the presence of Wnt3a and Activin A led to the complete loss of differentiation capacity into hepatic or pancreatic lineages. When Wnt3a was removed after 24h from the initiation of the differentiation, the cells were able to differentiate into PDX1+/NKX6.1+ pancreatic progenitors even with longer DE induction time while efficiency of hepatic differentiation was lower. Our results suggest that both the length and the timing of Wnt3a treatment during DE induction is crucial for the final differentiation outcome. Although it is possible to derive apparently pure DE cells with prolonged Activin A/Wnt-stimulation, their progenitor capacity is restricted to a limited time window.
Experimental Cell Research 08/2013; 319(17). DOI:10.1016/j.yexcr.2013.07.007 · 3.25 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: As directors of two NIH institutes supporting neuroscience research, we explore the gap between 25 years of stunning progress in fundamental neuroscience and the persistent needs of those with brain disorders. We conclude that closing this gap will require a more detailed comprehension of brain function, a rethinking of how we approach translational science, a focus on human neurobiology, and a continuing commitment to build a diverse, innovative neuroscience workforce. In contrast to many other areas of medicine, we lack basic knowledge about our organ of interest. The next phase of progress on brain disorders will require a significantly deeper understanding of fundamental neurobiology.
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