title: Single-cell transcriptomics and functional target validation of brown adipocytes show their complex roles in metabolic homeostasis.
abstract: Brown adipocytes (BAs) are specialized for adaptive thermogenesis and, upon sympathetic stimulation, activate mitochondrial uncoupling protein (UCP)-1 and oxidize fatty acids to generate heat. The capacity for brown adipose tissue (BAT) to protect against obesity and metabolic disease is recognized, yet information about which signals activate BA, besides β3-adrenergic receptor stimulation, is limited. Using single-cell transcriptomics, we confirmed the presence of mRNAs encoding traditional BAT markers (i.e., UCP1, expressed in 100% of BAs Adrb3, expressed in <50% of BAs) in mouse and have shown single-cell variability (>1000-fold) in their expression at both the mRNA and protein levels. We further identified mRNAs encoding novel markers, orphan GPCRs, and many receptors that bind the classic neurotransmitters, neuropeptides, chemokines, cytokines, and hormones. The transcriptome variability between BAs suggests a much larger range of responsiveness of BAT than previously recognized and that not all BAs function identically. We examined the in vivo functional expression of 12 selected receptors by microinjecting agonists into live mouse BAT and analyzing the metabolic response. In this manner, we expanded the number of known receptors on BAs at least 25-fold, while showing that the expression of classic BA markers is more complex and variable than previously thought.
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Jennifer M
authors: JM
authors: Spaethling
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Manuel
authors: M
authors: Sanchez-Alavez
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: JaeHee
authors: J
authors: Lee
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Feng C
authors: FC
authors: Xia
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Hannah
authors: H
authors: Dueck
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Wenshan
authors: W
authors: Wang
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Stephen A
authors: SA
authors: Fisher
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Jai-Yoon
authors: JY
authors: Sul
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Patrick
authors: P
authors: Seale
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Junhyong
authors: J
authors: Kim
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA.
authors: Tamas
authors: T
authors: Bartfai
authors: *Department of Pharmacology, Department of Genomics and Computational Biology, and Department of Cell and Developmental Biology, Perelman School of Medicine, and Department of Biology, School of Arts and Sciences, University of Pennsylvania, Philadelphia, Pennsylvania, USA; and Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA eberwine@upenn.edu.
authors: James
authors: J
authors: Eberwine
mesh_terms: D052437:Adipocytes, Brown / Q000166:cytology*; D002001:Adipose Tissue, Brown / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D006706:Homeostasis / Q000502:physiology*; D007473:Ion Channels / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000378:metabolism*; D009765:Obesity / Q000378:metabolism; D022722:Thermogenesis / Q000502:physiology; D059467:Transcriptome
chemical_list: D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins
keywords: GPCR; brown fat; drug targets; in vivo validation; thermogenesis