RNA-seq of age-associated transcriptome changes in brown adipose tissue
ABSTRACT: Brown adipose tissue (BAT) plays a central role in energy homeostasis through non-shivering thermogenesis. Besides, recent human studies using 18FDG-PET/CT imaging demonstrated that BAT acts as a significant metabolic-sink for glucose. Notably, these functions in BAT decrease with age: however what regulates this process remains poorly understood. To this end, we employed RNA-seq to identify the transcriptional changes in BAT of young and old mice.
Project description:To study the gene expression profiles of brown (BAT) and white (WAT) adipose tissues in wild type and LR11-deficeint mice. The four RNA sources, WT scWAT, Lr11 -/- scWAT, WT BAT and Lr11 -/- BAT, were prepared from subcutaneous WAT and BAT from wild-type mice and Lr11 -/- mice, respectively (n=3 each).
Project description:Prdm16 is a transcription factor that drives a complete program of brown adipocyte differentiation, but the mechanism by which Prdm16 activates gene transcription remains unknown. Utilizing ChIP-seq teqhnique, we found that Prdm16 binds to chromatin at/near many brown fat-selective genes in BAT. Interestingly, Prdm16-deficiency dramatically reduced the binding of Med1 to Prdm16-target sites. Indeed, Prdm16 binds and recruits Med1 to BAT-enriched genes and the loss of Prdm16 caused a fundamental change in chromatin architecture at key BAT-selective genes and also reduced transcirptional activity. Moreover, Prdm16, through its interaction with Med1, defines and regulates the activity of super-enhancers that drive the expression of cell identity genes. Together, these data demonstrate that Prdm16 drives gene transcription by recruiting Med1 to control chromatin architecture and super-enhancers. Brown adipose tissues were collected from Prdm16 knockout and wiletype 9-month-old mice and ChIP-seq was performed for Prdm16, PolII, Med1, and H3K27ac.
Project description:Adaptive thermogenesis of brown adipose tissue (BAT) is critical for thermoregulation and contributes to total energy expenditure. However, whether BAT has non-thermogenic functions is largely unknown. Here, we describe that mice with a BAT-specific Liver kinase b1 deletion (Lkb1BKO mice) exhibited impaired mitochondrial respiration and thermogenesis in BAT, but reduced adiposity and liver triglyceride accumulation under high-fat-diet feeding at room temperature. Importantly, these metabolic benefits were also present in Lkb1BKO mice at thermoneutrality, where BAT thermogenesis was not required. Mechanistically, decreased mRNA levels of mtDNA-encoded electron transport chain (ETC) subunits and ETC proteome imbalance led to impaired mitochondrial respiration in BAT of Lkb1BKO mice. Furthermore, reducing mtDNA gene expression directly in BAT by removing mitochondrial transcription factor A (Tfam) in BAT also showed ETC proteome imbalance and the tradeoff between BAT thermogenesis and systemic metabolism at both room temperature and thermoneutrality. Collectively, our data demonstrates that ETC proteome imbalance in BAT regulates systemic metabolism independently of BAT thermogenic capacity.
Project description:Brown adipose tissue (BAT) dissipates chemical energy in the form of heat, as a defense against hypothermia and obesity. Current evidence indicates that brown adipocytes arise from Myf5+-dermotomal precursors through the action of a PRDM16-C/EBP-_ transcriptional complex; however, the underlying mechanisms that determine lineage specification and maintenance of brown adipose cells remain poorly understood. Here we study the role of euchromatic histone-lysine N-methyltransferase 1 (EHMT1), a brown fat-enriched lysine methyltransferase, as an essential enzymatic component of the PRDM16 transcriptional complex and controls brown adipose cell fate. To identify targets and function of EHMT1, we performed genome-wide gene expression profiling of BAT from control mouce (Ehmt1flox/flox), Ehmt1Myf5 KO mouse (Myf5-Cre+/-; Ehmt1flox/flox) and Ehmt1adipo KO mouse (Adipo-Cre+/-; Ehmt1flox/flox). Loss of EHMT1 in Myf5+ lineage causes a near total loss of brown fat characteristics and induces muscle-selective gene program in vivo. In addition, adipose-specific deletion of EHMT1 by Adipo-Cre leads to a marked reduction of the thermogenic and fat oxidation genes.
Project description:Ambient temperature affects energy intake and expenditure to maintain homeostasis in a continuously fluctuating environment. Here, mice with an adipose-specific defect in fatty acid oxidation (Cpt2A-/-) were subjected to varying temperature to determine the role of adipose bioenergetics to environmental adaptation. Cpt2A-/- brown adipose tissue (BAT) failed to induce thermogenic genes such as Ucp1 and Pgc1α in response to adrenergic stimulation, which is exacerbated by increasing temperature. Thermoneutrality induced a mitochondrial DNA stress in Cpt2A-/- BAT that resulted in a loss of classical interscapular BAT, but did not affect body weight gain or glucose tolerance in response to a high-fat diet. In this dataset, we include the expression data obtained from dissected mouse interscapular brown adipose tissue from mice acclimatized to thermoneutrality (30C) with and without beta3adrenergic stimulation with and without the deletion of carnitine palmitoyltransferase 2 (i.e., adipose unable to beta-oxidize long chain fatty acids in mitochondria). WildType and Cpt2A KnockOut mice were treated either with or without beta3adrenergic stimulation, thus four classes. Three biologic replicates were compared per class, thus twelve mice.
Project description:Brown adipose tissue (BAT) protects against obesity by promoting energy expenditure via uncoupled respiration. To uncover BAT-specific long non-coding RNAs (lncRNAs), we used RNA-seq to reconstruct de novo transcriptomes of mouse brown, inguinal white, and epididymal white fat and identified ~1500 lncRNAs, including 127 BAT-restricted loci induced during differentiation and often targeted by key regulators PPARγ, C/EBPα and C/EBPβ. One of them, lnc-BATE1, is required for establishment and maintenance of BAT identity and thermogenic capacity. lnc-BATE1 inhibition impairs concurrent activation of brown fat and repression of white fat genes, and is partially rescued by exogenous lnc-BATE1 with mutated siRNA-targeting sites, demonstrating a function in trans. We show that lnc-BATE1 binds heterogeneous nuclear ribonucleoprotein U and that both are required for brown adipogenesis. Our work provides an annotated catalog for the study of fat depot-selective lncRNAs, available online, and establishes lnc-BATE1 as a novel regulator of BAT development and physiology. Total RNA profiles of BAT, iWAT and eWAT samples were sequenced on the Illumina HiSeq2000 platform
Project description:Brown adipose tissue (BAT) evolved in mammals as a natural defence system against hypothermia and obesity. While existence of BAT in adult humans has been recently appreciated, its cellular origin and molecular identity remain elusive due in large to high cellular heterogeneity within adipose tissues. Here we isolated clonal adipocytes from adult human BAT as well as WAT (control) and critically analyzed their transcriptome to identify bona fide BAT markers and its new functions.
Project description:Experiments were designed to compare white adipose tissue (WAT) or brown adipose tissue (BAT) -in male and female mice- between Bscl2 knock-out mice and their wild-type control mice. RNA was pooled to obtain 2x 8µg per tissue source and subjected to dye-swap hybridization.
Project description:This experiment was carried out to determine whether social genetic effects (also called indirect genetic effects) contribute to variation in gene expression. That is to say, are differences in gene expression attributable to genetic differences in cage mates? The block factor refers to the order of mouse sacrificing within each cage.