University of Pennsylvania ScholarlyCommons Publicly Accessible Penn Dissertations 2015 Controlling Thermogenesis: Understanding the Role of PRDM16 in the Development and Function of Brown Fat Matthew James Harms University of Pennsylvania, [email protected] Follow this and additional works at: https://repository.upenn.edu/edissertations Part of the Biology Commons, Developmental Biology Commons, and the Molecular Biology Commons Recommended Citation Harms, Matthew James, "Controlling Thermogenesis: Understanding the Role of PRDM16 in the Development and Function of Brown Fat" (2015). Publicly Accessible Penn Dissertations. 1059. https://repository.upenn.edu/edissertations/1059 This paper is posted at ScholarlyCommons. https://repository.upenn.edu/edissertations/1059 For more information, please contact [email protected]. Controlling Thermogenesis: Understanding the Role of PRDM16 in the Development and Function of Brown Fat Abstract The alarming rise in the incidence of obesity found throughout the world has precipitated a need to look for novel methods to increase energy expenditure to counter weight gain. Recently it was discovered that adult humans possess a substantial mass of brown adipose tissue (BAT), a tissue that consumes stored lipid to produce heat. Although the primary physiologic role for BAT is to protect mammals from the cold, it is currently thought that enhancing BAT mass or activating BAT in humans is a novel way to decrease adiposity. However, before BAT can be effectively utilized for therapeutic purposes a better understanding of the transcriptional regulation underlying BAT function is required. Here, we investigated the role of the transcription factor PRDM16 in BAT. We found that PRDM16 is not required for BAT development, however it is required to maintain BAT identity in adult mice. The loss of PRDM16 in adult mice led to a loss of BAT functionality and an inability to produce heat. We found that PRDM16s ability to drive a thermogenic program is due to its recruitment of Med1/the Mediator Complex to BAT-selective genes. Without PRDM16 in BAT a loss of higher order chromatin structure and a corresponding loss of transcription takes place at genes required for BAT identity and function. Degree Type Dissertation Degree Name Doctor of Philosophy (PhD) Graduate Group Cell & Molecular Biology First Advisor Patrick Seale Keywords brown fat, Prdm16, thermogenesis, Ucp1 Subject Categories Biology | Developmental Biology | Molecular Biology This dissertation is available at ScholarlyCommons: https://repository.upenn.edu/edissertations/1059 CONTROLLING THERMOGENESIS: UNDERSTANDING THE ROLE OF PRDM16 IN THE DEVELOPMENT AND FUNCTION OF BROWN FAT Matthew J. Harms A DISSERTATION in Cell and Molecular Biology Presented to the Faculties of the University of Pennsylvania in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy 2015 Supervisor of Dissertation: ____ ____________________ Patrick Seale, Ph.D. Assistant Professor of Cell and Developmental Biology Graduate Group Chairperson: ____ ____________________ Daniel S. Kessler, Ph.D. Associate Professor of Cell and Developmental Biology Dissertation Committee: Paul J. Gadue, Ph.D., Assistant Professor of Pathology and Laboratory Medicine Mitchell A. Lazar, MD, Ph.D., Sylvan H. Eisman Professor of Medicine and Genetics Michael L. Atchison, Ph.D., Professor of Biochemistry Kenneth S. Zaret, Ph.D., Joseph Leidy Professor of Cell and Developmental Biology CONTROLLING THERMOGENESIS: UNDERSTANDING THE ROLE OF PRDM16 IN THE DEVELOPMENT AND FUNCTION OF BROWN FAT COPYRIGHT 2015 Matthew James Harms This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License To view a copy of this license, visit http://creativecommons.org/licenses/by-ny-sa/2.0/ ABSTRACT CONTROLLING THERMOGENESIS: UNDERSTANDING THE ROLE OF PRDM16 IN THE DEVELOPMENT AND FUNCTION OF BROWN FAT Matthew J. Harms Patrick Seale, P.hD. The alarming rise in the incidence of obesity found throughout the world has precipitated a need to look for novel methods to increase energy expenditure to counter weight gain. Recently it was discovered that adult humans possess a substantial mass of brown adipose tissue (BAT), a tissue that consumes stored lipid to produce heat. Although the primary physiologic role for BAT is to protect mammals from the cold, it is currently thought that enhancing BAT mass or activating BAT in humans is a novel way to decrease adiposity. However, before BAT can be effectively utilized for therapeutic purposes a better understanding of the transcriptional regulation underlying BAT function is required. Here, we investigated the role of the transcription factor PRDM16 in BAT. We found that PRDM16 is not required for BAT development, however it is required to maintain BAT identity in adult mice. The loss of PRDM16 in adult mice led to a loss of BAT functionality and an inability to produce heat. We found that PRDM16s ability to drive a thermogenic program is due to its recruitment of Med1/the Mediator Complex to BAT-selective genes. Without PRDM16 in BAT a loss of higher order chromatin structure and a corresponding loss of transcription takes place at genes required for BAT identity and function. iii TABLE OF CONTENTS ABSTRACT .............................................................................................................................. III LIST OF FIGURES .................................................................................................................. VI CHAPTER 1: BROWN AND BEIGE FAT: DEVELOPMENT, FUNCTION AND THERAPEUTIC POTENTIAL ................................................................................................ 1 The Development of Brown/Beige Adipocytes ............................................................................... 7 Developmental regulation of brown and beige adipocytes by Prdm16 ................................... 12 Role of brown/beige fat in regulating weight and metabolism .................................................. 14 Sympathetic nerve control of brown/beige fat ............................................................................. 17 Novel BAT/beige fat recruiters/activators ..................................................................................... 24 Outlook and challenges .................................................................................................................... 28 CHAPTER 2: PRDM16 IS REQUIRED FOR THE MAINTENANCE OF BROWN ADIPOCYTE IDENTITY AND FUNCTION IN ADULT MICE .................................... 30 Abstract ............................................................................................................................................... 31 Introduction ......................................................................................................................................... 32 Results ................................................................................................................................................. 34 • Prdm16 is dispensable for embryonic BAT development ............................................ 34 • Prdm16 recruits Ehmt1 to repress the expression of white fat-selective genes ...... 36 • Prdm16 maintains iBAT identity during aging ................................................................ 39 • Prdm16 is required for induction of the brown fat gene program in isolated precursors ............................................................................................................................. 43 iv • Reduced BAT function in Myf5-ΔPrdm16 mice ............................................................... 46 • Prdm3 compensates for the loss of Prdm16 to preserve brown fat fate in young mice ........................................................................................................................................ 50 Materials and Methods ...................................................................................................................... 58 CHAPTER 3: PRDM16 BINDS MED1 AND CONTROLS CHROMATIN ARCHITECTURE TO DETERMINE A BROWN FAT TRANSCRIPTIONAL PROGRAM ................................................................................................................................ 64 Abstract ............................................................................................................................................... 65 Introduction ......................................................................................................................................... 66 Results and Discussion .................................................................................................................... 67 • PRDM16 binding is enriched at BAT-selective genes ................................................... 67 • PRDM16 recruits MED1 to BAT-selective genes ............................................................ 70 • PRDM16 controls higher order chromatin structure .................................................... 76 • Prdm16 controls BAT-selective super-enhancers ......................................................... 77 Materials and Methods ...................................................................................................................... 81 DISCUSSION AND FUTURE DIRECTIONS .................................................................. 86 REFERENCES ........................................................................................................................