Derivation and Characterization of a UCP1 Reporter Human ES Cell Line

Interest in human brown fat as a novel therapeutic target to tackle the growing obesity and diabetes epidemic has increased dramatically in recent years. While much insight into brown fat biology has been gained from murine cell lines and models, few resources are available to study human brown fat in-vitro. In this study, we detail the derivation and characterization of a novel human ES UCP1 reporter cell line that marks UCP1 positive adipocytes in-vitro. We targeted a mCherry reporter to the UCP1 stop codon via CRISPR-Cas9 and demonstrated that when differentiated to brown adipocytes, reporter cells express UCP1, display high mitochondrial content and multi-locular lipid morphology, and exhibit functional properties such as lipolysis in the presence of isoproterenol and forskolin. Isolation and purification of mCherry positive cells demonstrated elevated expression of brown fat marker genes and a high similarity to isolated human brown fat versus white fat via RNA-seq. This reporter cell line thus presents new opportunities to study human brown fat biology by enabling future work to understand early human brown fat development, performing disease modeling, and enabling drug screening applications. RNA-seq was performed on isolated mCherry positive and negative cells in duplicate.