Project Summary/Abstract
Obesity and its metabolic sequelae are rapidly increasing in the United States and worldwide, leading to high
morbidity and mortality in type 2 diabetes, cardiovascular disease, and certain cancer. Under the current
pandemic, obesity has been recognized as a key risk factor for severe COVID-19. Central to these pathologies
is adipose tissue. There are functionally distinct types of adipose tissue. White adipose tissue is the primary
site of the triglyceride storehouse. In contrast, thermogenic fat, which consists of classical brown adipose
tissue (BAT) and inducible beige/brite adipocytes, concentrates on thermogenic energy expenditure. It has
been recently reported that people with BAT have a significantly lower prevalence of cardiometabolic diseases,
highlighting the metabolic benefits and therapeutic potential of BAT in humans. To make the therapeutics
possible, improved knowledge of the regulation of thermogenic adipocytes is urgently needed. The
thermogenic function of brown and beige adipocytes are coordinately regulated by specific transcriptional and
epigenetic regulators. While transcription of the thermogenic gene uncoupling protein 1 (Ucp1) in response to
beta-adrenergic stimulation has been broadly studied, little is known about how histone positioning and
chromatin folding influences the expression of Ucp1 and other thermogenic genes. Using an unbiased
CRISPR-based screen, we identified the histone variant H2A.Z and the LIM domaining-containing zinc-finger
protein Crip2 as trans-acting factors recruited to the Ucp1 promoter/enhancer region by beta3-adrenergic
receptor stimulation. Importantly, deletion of H2A.Z or Crip2 in mature brown adipocytes not only impeded
Ucp1 transcription, but also reduced the expression of multiple thermogenic genes and led to impaired cellular
thermogenesis. This proposal will determine the signaling events mediating the activation of Crip2 and H2A.Z
deposition and the impact of Crip2 or H2A.Z deficiency in the cellular thermogenesis and bioenergetic profiles
of thermogenic adipocytes murine and human origins. Since histone variants play an important role in
determining chromatin remodeling, we will examine how Crip2-H2A.Z interaction influences chromatin
architecture, thereby regulating thermogenic transcription and cellular respiration. To establish the
physiological significance of Crip2 and H2A.Z in metabolic regulation, we will generate brown fat-specific Crip2
or H2A.Z knockout mice and thoroughly characterize their metabolic phenotypes. Completing the proposed
studies will increase fundamental knowledge on the role of chromatin remodeling in the regulation of
thermogenic program and pave ways to establish new therapeutic approaches for combating metabolic
diseases.