Project description:Transcriptomic analysis of brown fat from fat-specific Afadin depleted mice either at thermoneutrality or after 6 houts of cold exposure (5 degree celsius)
Project description:Brown adipose tissue (BAT) generates heat via uncoupled respiration, providing mammals with an evolutionary defense against environmental cold. Although the molecular pathways by which cold activates brown adipocytes are well understood, little is known about how BAT maintains its thermogenic capacity during adaptation to environmental warmth. Here, we identify the transcriptional repressor BCL6 as the switch for maintaining brown adipocyte cellular identity under warm conditions. Mice lacking BCL6 in their brown adipocytes display normal thermogenic responses when housed in a cool environment, but fail to maintain thermogenic fitness when housed under warm conditions. In a temperature-dependent manner, BCL6 suppresses apoptosis, fatty acid storage, and coupled respiration to maintain thermogenic competence in brown adipocytes. Enhancer analysis revealed that BCL6 reinforces brown-specific while opposing white-specific enhancers to maintain cellular identity. Thus, unlike other regulators, BCL6 is dispensable for differentiation and activation of brown adipocytes, but specifically required for their maintenance in warmth.
Project description:To investigate the specific role of PGC-1 coactivators in brown fat cells, we generated immortal preadipocyte lines from the brown adipose tissue of mice lacking PGC-1alpha. We could then efficiently knockdown PGC-1beta expression by shRNA expression. Loss of PGC-1alpha did not alter brown fat differentiation but severly reduced the induction of thermogenic genes. In order to assess the specific requirement for PGC-1α in the global transcriptional response to cAMP, we used Affymetrix arrays to compare the sets of genes induced in response to a 4 hr dbcAMP treatment in differentiated wt and KO cells. This analysis revealed that 88 genes were induced more than 3-fold in the wt cells; of these, 54 (61% of total) were similarly increased in both wt and KO. However, 28 genes (32% of total) were decreased by at least 50% in the KO cells compared to wt cells. These data were confirmed by quantitative PCR for a subset of genes. These data indicate that PGC-1α is required for proper expression of approximately one third of the genes induced in response to cAMP in brown fat cells, but this set of sensitive genes is enriched in those involved in adaptative thermogenesis. Keywords: thermogenic gene program
Project description:The physiological adaptation to cold environmental temperatures involves the remodeling of energy-storing white adipose tissue (WAT) into an energy-burning thermogenic phenotype, characterized by the emergence of multi-locular beige adipocytes. To date, the full array of cold-responsive cells within WAT that mediate thermogenic remodeling remain undefined. Here, we demonstrate that distinct perivascular PDGFRb+ adipocyte precursor cell (APC) subpopulations are differentially sensitive to cold temperatures in vivo. One day of cold exposure elicits striking transcriptional changes in DPP4+ PDGFRb+ APCs, whereas committed DPP4- PDGFRb+ preadipocytes appear comparatively much less responsive. This adaptation includes beta-adrenergic receptor mediated induction in the expression of the pro-thermogenic cytokine, IL-33. DPP4+ PDGFRb+ cells represent the sole source of IL-33 within inguinal WAT of adult mice. Doxycycline-inducible deletion of Il33 in PDGFRb+ cells at the onset of cold exposure significantly compromises the thermogenic remodeling of WAT without directly impacting the differentiation capacity of APCs per se. Together, these studies reveal the presence of a cold-responsive progenitor cell subpopulation in adult WAT and highlight their ability to regulate tissue plasticity through the production of immunological factors.
Project description:Brown adipose tissue (BAT) is a thermogenic organ that requires Uncoupling Protein 1 (UCP1) to dissipate chemical energy as heat, to defend core body temperature against hypothermia, and counteract obesity and metabolic diseases1. However, the transcriptional mechanism ensuring BAT thermogenic capacity for survival prior to environmental cold is unknown. Here we show histone deacetylase 3 (HDAC3) is a required transcriptional regulator of BAT enhancers to ensure thermogenic aptitude and survival. Mice with genetic ablation of HDAC3 become severely hypothermic and fail to survive acute cold exposure. UCP1 is nearly absent in BAT lacking HDAC3 and there is marked down-regulation of mitochondrial oxidative phosphorylation (OXPHOS) genes. Remarkably, although HDAC3 canonically functions as a transcriptional corepressor2, HDAC3 functions as a coactivator of the estrogen-related receptor _ (ERR_) in BAT, and loss of HDAC3 leads to robust global down-regulation of ERR±-driven enhancers. HDAC3 coactivation of ERR_ is mediated through deacetylation of PGC-1_ and is required for basal transcription of Ucp1, OXPHOS, and Pgc-1_. Thus, HDAC3 uniquely primes Ucp1 and thermogenic gene transcription to ensure immediate BAT-driven thermogenesis upon acute exposure to dangerously cold temperatures.
Project description:The physiological adaptation to cold environmental temperatures involves the remodeling of energy-storing white adipose tissue (WAT) into an energy-burning thermogenic phenotype, characterized by the emergence of multi-locular beige adipocytes. To date, the full array of cold-responsive cells within WAT that mediate thermogenic remodeling remain undefined. Here, we demonstrate that distinct perivascular PDGFRb+ adipocyte precursor cell (APC) subpopulations are differentially sensitive to cold temperatures in vivo. One day of cold exposure elicits striking transcriptional changes in DPP4+ PDGFRb+ APCs, whereas committed DPP4- PDGFRb+ preadipocytes appear comparatively much less responsive. This adaptation includes beta-adrenergic receptor mediated induction in the expression of the pro-thermogenic cytokine, IL-33. DPP4+ PDGFRb+ cells represent the sole source of IL-33 within inguinal WAT of adult mice. Doxycycline-inducible deletion of Il33 in PDGFRb+ cells at the onset of cold exposure significantly compromises the thermogenic remodeling of WAT without directly impacting the differentiation capacity of APCs per se. Together, these studies reveal the presence of a cold-responsive progenitor cell subpopulation in adult WAT and highlight their ability to regulate tissue plasticity through the production of immunological factors.
Project description:Brown adipose tissue (BAT) is a thermogenic organ that requires Uncoupling Protein 1 (UCP1) to dissipate chemical energy as heat, to defend core body temperature against hypothermia, and counteract obesity and metabolic diseases1. However, the transcriptional mechanism ensuring BAT thermogenic capacity for survival prior to environmental cold is unknown. Here we show histone deacetylase 3 (HDAC3) is a required transcriptional regulator of BAT enhancers to ensure thermogenic aptitude and survival. Mice with genetic ablation of HDAC3 become severely hypothermic and fail to survive acute cold exposure. UCP1 is nearly absent in BAT lacking HDAC3 and there is marked down-regulation of mitochondrial oxidative phosphorylation (OXPHOS) genes. Remarkably, although HDAC3 canonically functions as a transcriptional corepressor2, HDAC3 functions as a coactivator of the estrogen-related receptor _ (ERR_) in BAT, and loss of HDAC3 leads to robust global down-regulation of ERR±-driven enhancers. HDAC3 coactivation of ERR_ is mediated through deacetylation of PGC-1_ and is required for basal transcription of Ucp1, OXPHOS, and Pgc-1_. Thus, HDAC3 uniquely primes Ucp1 and thermogenic gene transcription to ensure immediate BAT-driven thermogenesis upon acute exposure to dangerously cold temperatures.
Project description:The physiological adaptation to cold environmental temperatures involves the remodeling of energy-storing white adipose tissue (WAT) into an energy-burning thermogenic phenotype, characterized by the emergence of multi-locular beige adipocytes. To date, the full array of cold-responsive cells within WAT that mediate thermogenic remodeling remain undefined. Here, we demonstrate that distinct perivascular PDGFRb+ adipocyte precursor cell (APC) subpopulations are differentially sensitive to cold temperatures in vivo. One day of cold exposure elicits striking transcriptional changes in DPP4+ PDGFRb+ APCs, whereas committed DPP4- PDGFRb+ preadipocytes appear comparatively much less responsive. This adaptation includes beta-adrenergic receptor mediated induction in the expression of the pro-thermogenic cytokine, IL-33. DPP4+ PDGFRb+ cells represent the sole source of IL-33 within inguinal WAT of adult mice. Doxycycline-inducible deletion of Il33 in PDGFRb+ cells at the onset of cold exposure significantly compromises the thermogenic remodeling of WAT without directly impacting the differentiation capacity of APCs per se. Together, these studies reveal the presence of a cold-responsive progenitor cell subpopulation in adult WAT and highlight their ability to regulate tissue plasticity through the production of immunological factors.