Regulation of pluripotency and lineage decisions by histone methylation

• Applicant: Professor Dr. Adrian Francis Stewart
• Subject Area: Developmental Biology ; Cell Biology
• Term: from 2008 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 66393500

• Final Report Year: 2014

Final Report Abstract

The work in the funded period characterised epigenetic aspects of embryonic stem cell (ESC) pluripotency, self-renewal and exit. Earlier progress with ESCs identified three stages within the pluripotent window; namely Nanog positive ESCs (Nanog on), Nanog negative (Nanog off) and Epiblast stem cells (EpiSCs). Work in this project during the first funding period examined linkages between these ESC transitions and histone 3 trimethylation at lysines 4 (H3K4me3) and 27 (H3K27me3), which are also hallmarks of the opposing regulatory systems based on gene activation/maintenance by the trithorax- Group (trx-G) and silencing by the Polycomb-Group (PcG) respectively. Unexpectedly, we found that H3K27 trimethylation of lineage specific genes is increased during transition from Nanog on to Nanog off states. We extended these observations to find that H3K4me3 on ESC bivalent gene promoters is specifically regulated by the trx- G factor, Mll2. However Mll2 is not the major H3K4me3 enzyme but Setd1a is. Simultaneous mutation of the sister genes, Mll1 and 2, revealed a subset of promoters that require either protein thereby indicating that the H3k4 methylation system has implicit redundancy. Then we examined exit from ESC self renewal to find that regulation of gene expression exerted by aspects of the H3K4me3 mechanism exhibit epigenetic characteristics in the neuronal differentiation pathway. More work is needed to secure this observation, which could establish a paradigm that has been anticipated but not yet proven by example.

Publications

• (2010) Mll2 is required in oocytes for bulk histone 3 lysine 4 trimethylation and global transcriptional silencing. PLoS Biology, 17, 8(8)
  Andreu-Vieyra CV, Chen R, Agno J, Glaser S, Anastassiadis K, Stewart AF and Matzuk MM
  
• (2012) The transcriptional and epigenetic foundations of ground state pluripotency. Cell, 149, 590-604
  Marks H, Denissov S, Menafra R, Kalkan T, Jones K, Hofemeister H, Nichols J, Kranz A, Stewart AF, Smith A and Stunnenberg H
  
• (2013) The histone demethylase UTX regulates stem cell migration and hematopoiesis. Blood. 121, 2462-73
  Thieme S, Gyárfás T, Richter C, Ozhan G, Fu J, Alexopoulou D, Muders MH, Michalk I, Jakob C, Dahl A, Klink B, Bandola J, Bachmann M, Schröck E, Buchholz F, Stewart AF, Weidinger G, Anastassiadis K, Brenner S
  
• (2014) The H3K4 methyltransferase Setd1a is first required at the epiblast stage, whereas Setd1b becomes essential after gastrulation. Development, 141, 1022-35
  Bledau A, Schmidt K, Neumann K, Kranz A, Stewart AF and Anastassiadis K
  
• Mll2 is required for H3K4 trimethylation of bivalent promoters in ES cells whereas Mll1 is redundant. Development, 141, 526-37
  Denisov S, Hofemeister H, Marks H, Kranz A, Ciotta G, Singh S, Anastassiadis K, Stunnenberg HG and Stewart AF