title: The B-MYB transcriptional network guides cell cycle progression and fate decisions to sustain self-renewal and the identity of pluripotent stem cells.
abstract: Embryonic stem cells (ESCs) are pluripotent and have unlimited self-renewal capacity. Although pluripotency and differentiation have been examined extensively, the mechanisms responsible for self-renewal are poorly understood and are believed to involve an unusual cell cycle, epigenetic regulators and pluripotency-promoting transcription factors. Here we show that B-MYB, a cell cycle regulated phosphoprotein and transcription factor critical to the formation of inner cell mass, is central to the transcriptional and co-regulatory networks that sustain normal cell cycle progression and self-renewal properties of ESCs. Phenotypically, B-MYB is robustly expressed in ESCs and induced pluripotent stem cells (iPSCs), and it is present predominantly in a hypo-phosphorylated state. Knockdown of B-MYB results in functional cell cycle abnormalities that involve S, G2 and M phases, and reduced expression of critical cell cycle regulators like ccnb1 and plk1. By conducting gene expression profiling on control and B-MYB deficient cells, ChIP-chip experiments, and integrative computational analyses, we unraveled a highly complex B-MYB-mediated transcriptional network that guides ESC self-renewal. The network encompasses critical regulators of all cell cycle phases and epigenetic regulators, pluripotency transcription factors, and differentiation determinants. B-MYB along with E2F1 and c-MYC preferentially co-regulate cell cycle target genes. B-MYB also co-targets genes regulated by OCT4, SOX2 and NANOG that are significantly associated with stem cell differentiation, embryonic development, and epigenetic control. Moreover, loss of B-MYB leads to a breakdown of the transcriptional hierarchy present in ESCs. These results coupled with functional studies demonstrate that B-MYB not only controls and accelerates cell cycle progression in ESCs it contributes to fate decisions and maintenance of pluripotent stem cell identity.
authors.affiliation: Bioinformatics Unit, National Institute on Aging, National Institutes of Health, Baltimore, Maryland, United States of America.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhan
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Riordon
authors.forename: Bin
authors.initials: B
authors.lastname: Yan
authors.forename: Yelena S
authors.initials: YS
authors.lastname: Tarasova
authors.forename: Sarah
authors.initials: S
authors.lastname: Bruweleit
authors.forename: Kirill V
authors.initials: KV
authors.lastname: Tarasov
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Li
authors.forename: Robert P
authors.initials: RP
authors.lastname: Wersto
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Boheler
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000235:genetics / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D051379:Mice; D008962:Models, Theoretical; D020411:Oligonucleotide Array Sequence Analysis; D039904:Pluripotent Stem Cells / Q000166:cytology* / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C499306:Mybl2 protein, mouse; D015534:Trans-Activators