Control of ground-state pluripotency by allelic regulation of Nanog

Nature. 2012 Feb 12;483(7390):470-3. doi: 10.1038/nature10807.

Abstract

Pluripotency is established through genome-wide reprogramming during mammalian pre-implantation development, resulting in the formation of the naive epiblast. Reprogramming involves both the resetting of epigenetic marks and the activation of pluripotent-cell-specific genes such as Nanog and Oct4 (also known as Pou5f1). The tight regulation of these genes is crucial for reprogramming, but the mechanisms that regulate their expression in vivo have not been uncovered. Here we show that Nanog--but not Oct4--is monoallelically expressed in early pre-implantation embryos. Nanog then undergoes a progressive switch to biallelic expression during the transition towards ground-state pluripotency in the naive epiblast of the late blastocyst. Embryonic stem (ES) cells grown in leukaemia inhibitory factor (LIF) and serum express Nanog mainly monoallelically and show asynchronous replication of the Nanog locus, a feature of monoallelically expressed genes, but ES cells activate both alleles when cultured under 2i conditions, which mimic the pluripotent ground state in vitro. Live-cell imaging with reporter ES cells confirmed the allelic expression of Nanog and revealed allelic switching. The allelic expression of Nanog is regulated through the fibroblast growth factor-extracellular signal-regulated kinase signalling pathway, and it is accompanied by chromatin changes at the proximal promoter but occurs independently of DNA methylation. Nanog-heterozygous blastocysts have fewer inner-cell-mass derivatives and delayed primitive endoderm formation, indicating a role for the biallelic expression of Nanog in the timely maturation of the inner cell mass into a fully reprogrammed pluripotent epiblast. We suggest that the tight regulation of Nanog dose at the chromosome level is necessary for the acquisition of ground-state pluripotency during development. Our data highlight an unexpected role for allelic expression in controlling the dose of pluripotency factors in vivo, adding an extra level to the regulation of reprogramming.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alleles*
  • Animals
  • Blastocyst / cytology
  • Blastocyst / metabolism*
  • Blastocyst Inner Cell Mass / cytology
  • Blastocyst Inner Cell Mass / metabolism
  • Cell Cycle Proteins / metabolism
  • Cellular Reprogramming / genetics*
  • Chromosomal Proteins, Non-Histone / metabolism
  • DNA Replication
  • Embryonic Stem Cells / drug effects
  • Embryonic Stem Cells / metabolism
  • Female
  • Gene Expression Regulation, Developmental*
  • Genomic Imprinting
  • Germ Layers / cytology
  • Germ Layers / metabolism
  • Homeodomain Proteins / genetics*
  • Homeodomain Proteins / metabolism*
  • In Situ Hybridization, Fluorescence
  • Leukemia Inhibitory Factor / pharmacology
  • Male
  • Mediator Complex / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred CBA
  • Nanog Homeobox Protein
  • Octamer Transcription Factor-3
  • Pluripotent Stem Cells / cytology
  • Pluripotent Stem Cells / metabolism*
  • Time Factors

Substances

  • Cell Cycle Proteins
  • Chromosomal Proteins, Non-Histone
  • Homeodomain Proteins
  • Leukemia Inhibitory Factor
  • Mediator Complex
  • Nanog Homeobox Protein
  • Nanog protein, mouse
  • Octamer Transcription Factor-3
  • Pou5f1 protein, mouse
  • cohesins