title: A role for cohesin in T-cell-receptor rearrangement and thymocyte differentiation.
abstract: Cohesin enables post-replicative DNA repair and chromosome segregation by holding sister chromatids together from the time of DNA replication in S phase until mitosis. There is growing evidence that cohesin also forms long-range chromosomal cis-interactions and may regulate gene expression in association with CTCF, mediator or tissue-specific transcription factors. Human cohesinopathies such as Cornelia de Lange syndrome are thought to result from impaired non-canonical cohesin functions, but a clear distinction between the cell-division-related and cell-division-independent functions of cohesion--as exemplified in Drosophila--has not been demonstrated in vertebrate systems. To address this, here we deleted the cohesin locus Rad21 in mouse thymocytes at a time in development when these cells stop cycling and rearrange their T-cell receptor (TCR) α locus (Tcra). Rad21-deficient thymocytes had a normal lifespan and retained the ability to differentiate, albeit with reduced efficiency. Loss of Rad21 led to defective chromatin architecture at the Tcra locus, where cohesion-binding sites flank the TEA promoter and the Eα enhancer, and demarcate Tcra from interspersed Tcrd elements and neighbouring housekeeping genes. Cohesin was required for long-range promoter-enhancer interactions, Tcra transcription, H3K4me3 histone modifications that recruit the recombination machinery and Tcra rearrangement. Provision of pre-rearranged TCR transgenes largely rescued thymocyte differentiation, demonstrating that among thousands of potential target genes across the genome, defective Tcra rearrangement was limiting for the differentiation of cohesin-deficient thymocytes. These findings firmly establish a cell-division-independent role for cohesin in Tcra locus rearrangement and provide a comprehensive account of the mechanisms by which cohesin enables cellular differentiation in a well-characterized mammalian system.
authors.affiliation: Lymphocyte Development Group, MRC Clinical Sciences Centre, Imperial College London, Du Cane Road, London W12 0NN, UK.
authors.forename: Vlad C
authors.initials: VC
authors.lastname: Seitan
authors.forename: Bingtao
authors.initials: B
authors.lastname: Hao
authors.forename: Kikuë
authors.initials: K
authors.lastname: Tachibana-Konwalski
authors.forename: Thais
authors.initials: T
authors.lastname: Lavagnolli
authors.forename: Hegias
authors.initials: H
authors.lastname: Mira-Bontenbal
authors.forename: Karen E
authors.initials: KE
authors.lastname: Brown
authors.forename: Grace
authors.initials: G
authors.lastname: Teng
authors.forename: Tom
authors.initials: T
authors.lastname: Carroll
authors.forename: Anna
authors.initials: A
authors.lastname: Terry
authors.forename: Katie
authors.initials: K
authors.lastname: Horan
authors.forename: Hendrik
authors.initials: H
authors.lastname: Marks
authors.forename: David J
authors.initials: DJ
authors.lastname: Adams
authors.forename: David G
authors.initials: DG
authors.lastname: Schatz
authors.forename: Luis
authors.initials: L
authors.lastname: Aragon
authors.forename: Amanda G
authors.initials: AG
authors.lastname: Fisher
authors.forename: Michael S
authors.initials: MS
authors.lastname: Krangel
authors.forename: Kim
authors.initials: K
authors.lastname: Nasmyth
authors.forename: Matthias
authors.initials: M
authors.lastname: Merkenschlager
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002868:Chromosomal Proteins, Non-Histone / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D015329:Gene Rearrangement, T-Lymphocyte / Q000235:genetics; D016654:Genes, RAG-1 / Q000235:genetics; D051379:Mice; D009687:Nuclear Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics* / Q000378:metabolism*; D045522:Recombinases / Q000378:metabolism; D013950:Thymus Gland / Q000166:cytology* / Q000378:metabolism; D014158:Transcription, Genetic; D000097722:Cohesins
chemical_list: D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D016693:Receptors, Antigen, T-Cell, alpha-beta; D045522:Recombinases; D000097722:Cohesins; C465862:Rad21 protein, mouse