title: Neural induction promotes large-scale chromatin reorganisation of the Mash1 locus.
abstract: Determining how genes are epigenetically regulated to ensure their correct spatial and temporal expression during development is key to our understanding of cell lineage commitment. Here we examined epigenetic changes at an important proneural regulator gene Mash1 (Ascl1), as embryonic stem (ES) cells commit to the neural lineage. In ES cells where the Mash1 gene is transcriptionally repressed, the locus replicated late in S phase and was preferentially positioned at the nuclear periphery with other late-replicating genes (Neurod, Sprr2a). This peripheral location was coupled with low levels of histone H3K9 acetylation at the Mash1 promoter and enhanced H3K27 methylation but surprisingly location was not affected by removal of the Ezh2/Eed HMTase complex or several other chromatin-silencing candidates (G9a, SuV39h-1, Dnmt-1, Dnmt-3a and Dnmt-3b). Upon neural induction however, Mash1 transcription was upregulated (>100-fold), switched its time of replication from late to early in S phase and relocated towards the interior of the nucleus. This spatial repositioning was selective for neural commitment because Mash1 was peripheral in ES-derived mesoderm and other non-neural cell types. A bidirectional analysis of replication timing across a 2 Mb region flanking the Mash1 locus showed that chromatin changes were focused at Mash1. These results suggest that Mash1 is regulated by changes in chromatin structure and location and implicate the nuclear periphery as an important environment for maintaining the undifferentiated state of ES cells.
authors.affiliation: Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College London, Hammersmith Hospital, Du Cane Road, London, W12 0NN, UK. ruth.williams@csc.mrc.ac.uk
authors.forename: Ruth R E
authors.initials: RR
authors.lastname: Williams
authors.forename: Véronique
authors.initials: V
authors.lastname: Azuara
authors.forename: Pascale
authors.initials: P
authors.lastname: Perry
authors.forename: Stephan
authors.initials: S
authors.lastname: Sauer
authors.forename: Maria
authors.initials: M
authors.lastname: Dvorkina
authors.forename: Helle
authors.initials: H
authors.lastname: Jørgensen
authors.forename: Jeffery
authors.initials: J
authors.lastname: Roix
authors.forename: Philip
authors.initials: P
authors.lastname: McQueen
authors.forename: Tom
authors.initials: T
authors.lastname: Misteli
authors.forename: Matthias
authors.initials: M
authors.lastname: Merkenschlager
authors.forename: Amanda G
authors.initials: AG
authors.lastname: Fisher
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D019070:Cell Lineage; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism*; D004248:DNA (Cytosine-5-)-Methyltransferases / Q000378:metabolism; D000090205:DNA Methyltransferase 3A; D004627:Embryonic Induction / Q000502:physiology*; D053595:Embryonic Stem Cells / Q000166:cytology / Q000502:physiology; D044127:Epigenesis, Genetic; D018507:Gene Expression Regulation, Developmental; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D009690:Nucleic Acid Conformation; D011496:Protein Methyltransferases; D014158:Transcription, Genetic
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D002843:Chromatin; D004248:DNA (Cytosine-5-)-Methyltransferases; D000090205:DNA Methyltransferase 3A; D000076983:Histone Methyltransferases; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones; D011496:Protein Methyltransferases; C499317:Ascl1 protein, mouse; C000715535:Dnmt3a protein, mouse