Dynamic regulation of genes involved in mitochondrial DNA replication and transcription during mouse brown fat cell differentiation and recruitment.
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.
Murholm
Maria
M
Department of Biomedical Sciences, The Panum Institute, University of Copenhagen, Copenhagen, Denmark.
Dixen
Karen
K
Qvortrup
Klaus
K
Hansen
Lillian H L
LH
Amri
Ez-Zoubir
EZ
Madsen
Lise
L
Barbatelli
Giorgio
G
Quistorff
Bjørn
B
Hansen
Jacob B
JB
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
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