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Item does not contain fulltext, Embryonic stem (ES) cells are pluripotent and characterized by open chromatin and high transcription levels, achieved through auto-regulatory and feed-forward transcription factor loops. ES-cell identity is maintained by a core of factors including Oct4 (also known as Pou5f1), Sox2, Klf4, c-Myc (OSKM) and Nanog, and forced expression of the OSKM factors can reprogram somatic cells into induced pluripotent stem cells (iPSCs) resembling ES cells. These gene-specific factors for RNA-polymerase-II-mediated transcription recruit transcriptional cofactors and chromatin regulators that control access to and activity of the basal transcription machinery on gene promoters. How the basal transcription machinery is involved in setting and maintaining the pluripotent state is unclear. Here we show that knockdown of the transcription factor IID (TFIID) complex affects the pluripotent circuitry in mouse ES cells and inhibits reprogramming of fibroblasts. TFIID subunits and the OSKM factors form a feed-forward loop to induce and maintain a stable transcription state. Notably, transient expression of TFIID subunits greatly enhanced reprogramming. These results show that TFIID is critical for transcription-factor-mediated reprogramming. We anticipate that, by creating plasticity in gene expression programs, transcription complexes such as TFIID assist reprogramming into different cellular states.

Contains fulltext : 50526.pdf (publisher's version ) (Closed access)

Contains fulltext : 51018.pdf (publisher's version ) (Closed access), In this paper we focus on the behavior of radio frequency (RF)-sputtered calcium phosphate (CaP) thin films in a rat bone marrow (RBM) cell model. Two issues are addressed. Firstly, we benchmarked the in vitro cell behavior of these CaP coatings by comparing their proliferation, differentiation and mineralization behavior and the structure of the formed interface to similar coatings of alumina and titania. We found that the CaP coatings showed reduced proliferation, enhanced early differentiation and enhanced activity of mature osteoblasts compared to the alumina coatings. Enhanced production of mineralized extracellular matrix (ECM) was seen for both CaP and titania. Two types of CaP precipitates could be observed, one directly bonded CaP layer at the coating interface and one of globular accretions associated with the ECM. The directly bonded layer was not observed on the alumina coatings. Further, no thin film effects were found. Secondly, the effect of pre-immersion of the CaP coatings in SBF2 was explored. We found that the early formation of a directly bonded CaP layer is obstructed by the absence of CaP nuclei. After approximately 8 days, cell activity induces the nucleation of CaP crystals on both the surface and the ECM, and growth is enhanced. By initially providing these coatings with CaP crystals, growth of the directly bonded CaP layer is immediate. Hence, the formation of the interfacial CaP layer and the matrix-associated CaP accretions can effectively be decoupled.