The PPARγ locus makes long-range chromatin interactions with selected tissue-specific gene loci during adipocyte differentiation in a protein kinase A dependent manner.
Differentiation signaling results in reprogramming of cellular gene expression that leads to morphological changes and functional specialization of a precursor cell. This global change in gene expression involves temporal regulation of differentiation-specific genes that are located throughout the genome, raising the idea that genome structure may also be re-organized during cell differentiation to facilitate regulated gene expression. Using in vitro adipocyte differentiation as a model, we explored whether gene organization within the nucleus is altered upon exposure of precursor cells to signaling molecules that induce adipogenesis. The peroxisome proliferator-activated receptor gamma (PPARγ) nuclear hormone receptor is a master determinant of adipogenesis and is required for adipose differentiation. We utilized the chromosome conformation capture (3C) assay to determine whether the position of the PPARγ locus relative to other adipogenic genes is changed during differentiation. We report that the PPARγ2 promoter is transiently positioned in proximity to the promoters of genes encoding adipokines and lipid droplet associated proteins at 6 hours post-differentiation, a time that precedes expression of any of these genes. In contrast, the PPARγ2 promoter was not in proximity to the EF1α promoter, which drives expression of a constitutively active, housekeeping gene that encodes a translation elongation factor, nor was the PPARγ2 promoter in proximity to the promoter driving the expression of the C/EBPα regulatory protein. The formation of the long-range, intergenic interactions involving the PPARγ2 promoter required the regulatory factor C/EBPβ, elevated cyclic AMP (cAMP) levels, and protein kinase A (PKA) signaling. We conclude that genome organization is dynamically remodeled in response to adipogenic signaling, and we speculate that these transient inter-genic interactions may be formed for the purposes of selecting some of the transcriptionally silent tissue-specific loci for subsequent transcriptional activation.
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
Scott E
SE
LeBlanc
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
Qiong
Q
Wu
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
A Rasim
AR
Barutcu
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America ; Laboratory of Aging Research, State Key Laboratory of Biotherapy, West China Hospital, West China Medical School, Sichuan University, Chengdu, China.
Hengyi
H
Xiao
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America ; Department of Advanced Medical Initiatives, JST-CREST, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Yasuyuki
Y
Ohkawa
Department of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America.
Anthony N
AN
Imbalzano
D041721:3T3-L1 Cells; D050156:Adipogenesis; D054392:Adipokines / Q000235:genetics; D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics; D002843:Chromatin / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D056426:Genetic Loci; D051379:Mice; D047495:PPAR gamma / Q000235:genetics*; D000070778:Perilipin-1; D010750:Phosphoproteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D015398:Signal Transduction
D054392:Adipokines; D022782:CCAAT-Enhancer-Binding Protein-beta; D002352:Carrier Proteins; D002843:Chromatin; D047495:PPAR gamma; D000070778:Perilipin-1; D010750:Phosphoproteins; D017868:Cyclic AMP-Dependent Protein Kinases