Pref-1 in brown adipose tissue: specific involvement in brown adipocyte differentiation and regulatory role of C/EBPδ.
Pref-1 (pre-adipocyte factor-1) is known to play a central role in regulating white adipocyte differentiation, but the role of Pref-1 in BAT (brown adipose tissue) has not been analysed. In the present study we found that Pref-1 expression is high in fetal BAT and declines progressively after birth. However, Pref-1-null mice showed unaltered fetal development of BAT, but exhibited signs of over-activation of BAT thermogenesis in the post-natal period. In C/EBP (CCAAT/enhancer-binding protein) α-null mice, a rodent model of impaired fetal BAT differentiation, Pref-1 was dramatically overexpressed, in association with reduced expression of the Ucp1 (uncoupling protein 1) gene, a BAT-specific marker of thermogenic differentiation. In brown adipocyte cell culture models, Pref-1 was mostly expressed in pre-adipocytes and declined with brown adipocyte differentiation. The transcription factor C/EBPδ activated the Pref-1 gene transcription in brown adipocytes, through binding to the proximal promoter region. Accordingly, siRNA (small interfering RNA)-induced C/EBPδ knockdown led to reduced Pref-1 gene expression. This effect is consistent with the observed overexpression of C/EBPδ in C/EBPα-null BAT and high expression of C/EBPδ in brown pre-adipocytes. Dexamethasone treatment of brown pre-adipocytes suppressed Pref-1 down-regulation occurring throughout the brown adipocyte differentiation process, increased the expression of C/EBPδ and strongly impaired expression of the thermogenic markers UCP1 and PGC-1α [PPARγ (peroxisome-proliferator-activated receptor γ) co-activator-α]. However, it did not alter normal fat accumulation or expression of non-BAT-specific genes. Collectively, these results specifically implicate Pref-1 in controlling the thermogenic gene expression program in BAT, and identify C/EBPδ as a novel transcriptional regulator of Pref-1 gene expression that may be related to the specific role of glucocorticoids in BAT differentiation.
Departament de Bioquímica i Biologia Molecular, Institut de Biomedicina de la Universitat de Barcelona (IBUB) and CIBER Fisiopatologia de la Obesidad y Nutrición (CIBEROBN), 08028 Barcelona, Spain.
Jordi
J
Armengol
Josep A
JA
Villena
Elayne
E
Hondares
María C
MC
Carmona
Hei Sook
HS
Sul
Roser
R
Iglesias
Marta
M
Giralt
Francesc
F
Villarroya
D002001:Adipose Tissue, Brown / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D051743:CCAAT-Enhancer-Binding Protein-delta / Q000235:genetics / Q000502:physiology*; D002135:Calcium-Binding Proteins; D002454:Cell Differentiation / Q000502:physiology*; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D017931:DNA Primers; D005786:Gene Expression Regulation; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D060888:Real-Time Polymerase Chain Reaction
D002135:Calcium-Binding Proteins; D017931:DNA Primers; C512925:Dlk1 protein, mouse; D036341:Intercellular Signaling Peptides and Proteins; D051743:CCAAT-Enhancer-Binding Protein-delta