title: Dynamic regulation of genes involved in mitochondrial DNA replication and transcription during mouse brown fat cell differentiation and recruitment.
abstract: BACKGROUND
  Brown adipocytes are specialised in dissipating energy through adaptive thermogenesis, whereas white adipocytes are specialised in energy storage. These essentially opposite functions are possible for two reasons relating to mitochondria, namely expression of uncoupling protein 1 (UCP1) and a remarkably higher mitochondrial abundance in brown adipocytes.
  
  
  RESULTS
  Here we report a comprehensive characterisation of gene expression linked to mitochondrial DNA replication, transcription and function during white and brown fat cell differentiation in vitro as well as in white and brown fat, brown adipose tissue fractions and in selected adipose tissues during cold exposure. We find a massive induction of the majority of such genes during brown adipocyte differentiation and recruitment, e.g. of the mitochondrial transcription factors A (Tfam) and B2 (Tfb2m), whereas only a subset of the same genes were induced during white adipose conversion. In addition, PR domain containing 16 (PRDM16) was found to be expressed at substantially higher levels in brown compared to white pre-adipocytes and adipocytes. We demonstrate that forced expression of Tfam but not Tfb2m in brown adipocyte precursor cells promotes mitochondrial DNA replication, and that silencing of PRDM16 expression during brown fat cell differentiation blunts mitochondrial biogenesis and expression of brown fat cell markers.
  
  
  CONCLUSIONS
  Using both in vitro and in vivo model systems of white and brown fat cell differentiation, we report a detailed characterisation of gene expression linked to mitochondrial biogenesis and function. We find significant differences in differentiating white and brown adipocytes, which might explain the notable increase in mitochondrial content observed during brown adipose conversion. In addition, our data support a key role of PRDM16 in triggering brown adipocyte differentiation, including mitochondrial biogenesis and expression of UCP1.
authors.affiliation: Department of Biomedical Sciences, The Panum Institute, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Maria
authors.initials: M
authors.lastname: Murholm
authors.forename: Karen
authors.initials: K
authors.lastname: Dixen
authors.forename: Klaus
authors.initials: K
authors.lastname: Qvortrup
authors.forename: Lillian H L
authors.initials: LH
authors.lastname: Hansen
authors.forename: Ez-Zoubir
authors.initials: EZ
authors.lastname: Amri
authors.forename: Lise
authors.initials: L
authors.lastname: Madsen
authors.forename: Giorgio
authors.initials: G
authors.lastname: Barbatelli
authors.forename: Bjørn
authors.initials: B
authors.lastname: Quistorff
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Hansen
mesh_terms: D052437:Adipocytes, Brown / Q000166:cytology* / Q000201:enzymology / Q000648:ultrastructure; D052438:Adipocytes, White / Q000166:cytology / Q000201:enzymology / Q000648:ultrastructure; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics*; D002465:Cell Movement / Q000235:genetics*; D002467:Cell Nucleus / Q000378:metabolism; D003080:Cold Temperature; D004247:DNA / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D018628:Gene Dosage; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D006609:High Mobility Group Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000235:genetics / Q000648:ultrastructure; D056971:Nuclear Receptor Co-Repressor 1 / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D056971:Nuclear Receptor Co-Repressor 1; C521133:Prdm16 protein, mouse; C081930:Tfam protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA