Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Cell Biology, EPIBLAST STEM-CELLS, GROUND-STATE, PLURIPOTENT STATE, IMPRINTED GENES, SOMATIC-CELLS, GERM-CELL, MOUSE, METHYLATION, EXPRESSION, 5-HYDROXYMETHYLCYTOSINE, chromatin remodelling, epigenetics, gene activation kinetics, genomics, germline, induced pluripotent stem cells, reprogramming roadmap, transgenic reporters, Animals, Cellular Reprogramming, DNA Demethylation, DNA-Binding Proteins, Epigenomics, Female, Genomics, Induced Pluripotent Stem Cells, Male, Mice, Mice, Inbred C57BL, Mice, Transgenic, Octamer Transcription Factor-3, Pregnancy, Proto-Oncogene Proteins, Transcriptome, C14/16/077#53765170, 11E7920N|11E7922N#54543759, 0601 Biochemistry and Cell Biology, 1116 Medical Physiology, 31 Biological sciences

Abstract:

Reprogramming somatic cells into induced pluripotent stem cells (iPSCs) involves the reactivation of endogenous pluripotency genes and global DNA demethylation, but temporal resolution of these events using existing markers is limited. Here, we generate murine transgenic lines harboring reporters for the 5-methylcytosine dioxygenase Tet1 and for Oct4. By monitoring dual reporter fluorescence during pluripotency entry, we identify a sequential order of Tet1 and Oct4 activation by proximal and distal regulatory elements. Full Tet1 activation marks an intermediate stage that accompanies predominantly repression of somatic genes, preceding full Oct4 activation, and distinguishes two waves of global DNA demethylation that target distinct genomic features but are uncoupled from transcriptional changes. Tet1 knockout shows that TET1 contributes to both waves of demethylation and activates germline regulatory genes in reprogramming intermediates but is dispensable for Oct4 reactivation. Our dual reporter system for time-resolving pluripotency entry thus refines the molecular roadmap of iPSC maturation.