"To understand better how Tbx3 may contribute to improving iPS cell quality, we performed Solexa chromatin immunoprecipitation (ChIP)-sequencing to uncover the direct regulatory targets of Tbx3 in ESCs (Supplementary Table 6). Hierarchical clustering of Tbx3 with the previously mapped ESC factors18 showed that it shares a large number of common binding sites with the classic pluripotency-associated transcription factors Oct4, Sox2, Nanog and Smad1 (Supplementary Fig. 17). Tbx3 is also found to target ESC factors Oct4, Sox2, Sall4, Lefty1, Lefty2 and Zfp42, as well as reprogramming factors Klf2, Klf4, Klf5, N-myc (also known as Mycn) and c-myc (Myc) (Supplementary Fig. 18)."
"The initial ChIP-sequencing data suggests that Tbx3 may be important for the effective re-establishment of the ESC circuitry during the onset of reprogramming, and its subsequent maintenance. The presence of exogenous Tbx3 during the initiation of reprogramming may ensure proper titration of pluripotency-associated and reprogramming factors that are reactivated by OSK to the optimal level. We propose a model in which the re-establishment of pluripotency from a somatic state is achieved in an increasing probabilistic step-wise manner (Supplementary Fig. 19)."
Nature. 2010 Feb 7. [Epub ahead of print]
Tbx3 improves the germ-line competency of induced pluripotent stem cells.
Han J, Yuan P, Yang H, Zhang J, Soh BS, Li P, Lim SL, Cao S, Tay J, Orlov YL, Lufkin T, Ng HH, Tam WL, Lim B.
[1] Stem Cell and Developmental Biology, [2] State Key Laboratory for Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
Induced pluripotent stem (iPS) cells can be obtained by the introduction of defined factors into somatic cells. The combination of Oct4 (also known as Pou5f1), Sox2 and Klf4 (which we term OSK) constitutes the minimal requirement for generating iPS cells from mouse embryonic fibroblasts. These cells are thought to resemble embryonic stem cells (ESCs) on the basis of global gene expression analyses; however, few studies have tested the ability and efficiency of iPS cells to contribute to chimaerism, colonization of germ tissues, and most importantly, germ-line transmission and live birth from iPS cells produced by tetraploid complementation. Using genomic analyses of ESC genes that have roles in pluripotency and fusion-mediated somatic cell reprogramming, here we show that the transcription factor Tbx3 significantly improves the quality of iPS cells. iPS cells generated with OSK and Tbx3 (OSKT) are superior in both germ-cell contribution to the gonads and germ-line transmission frequency. However, global gene expression profiling could not distinguish between OSK and OSKT iPS cells. Genome-wide chromatin immunoprecipitation sequencing analysis of Tbx3-binding sites in ESCs suggests that Tbx3 regulates pluripotency-associated and reprogramming factors, in addition to sharing many common downstream regulatory targets with Oct4, Sox2, Nanog and Smad1. This study underscores the intrinsic qualitative differences between iPS cells generated by different methods, and highlights the need to rigorously characterize iPS cells beyond in vitro studies.
This is exciting! With OSKT (Oct4 Sox2 Klf4 Tbx3), the iPS cells are better in all aspects and the mice have better quality life - meaning improved germ-line transmission and higher percentage of live birth. orz, I was just discussing about the life quality this morning ...
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