CRISPR activation screens identify the SWI/SNF ATPases as suppressors of ferroptosis.

Ferroptosis is an iron-dependent cell death mechanism characterized by the accumulation of toxic lipid peroxides and cell membrane rupture. GPX4 (glutathione peroxidase 4) prevents ferroptosis by reducing these lipid peroxides into lipid alcohols. Ferroptosis induction by GPX4 inhibition has emerged as a vulnerability of cancer cells, highlighting the need to identify ferroptosis regulators that may be exploited therapeutically. Through genome-wide CRISPR activation screens, we identify the SWI/SNF (switch/sucrose non-fermentable) ATPases BRM (SMARCA2) and BRG1 (SMARCA4) as ferroptosis suppressors. Mechanistically, they bind to and increase chromatin accessibility at NRF2 target loci, thus boosting NRF2 transcriptional output to counter lipid peroxidation and confer resistance to GPX4 inhibition. We further demonstrate that the BRM/BRG1 ferroptosis connection can be leveraged to enhance the paralog dependency of BRG1 mutant cancer cells on BRM. Our data reveal ferroptosis induction as a potential avenue for broadening the efficacy of BRM degraders/inhibitors and define a specific genetic context for exploiting GPX4 dependency.

Single-cell analysis of human adipose tissue identifies depot and disease specific cell types.

The complex relationship between metabolic disease risk and body fat distribution in humans involves cellular characteristics which are specific to body fat compartments. Here we show depot-specific differences in the stromal vascual fraction of visceral and subcutaneous adipose tissue by performing single-cell RNA sequencing of tissue specimen from obese individuals. We characterize multiple immune cells, endothelial cells, fibroblasts, adipose and hematopoietic stem cell progenitors. Subpopulations of adipose-resident immune cells are metabolically active and associated with metabolic disease status and those include a population of potential dysfunctional CD8+ T cells expressing metallothioneins. We identify multiple types of adipocyte progenitors that are common across depots, including a subtype enriched in individuals with type 2 diabetes. Depot-specific analysis reveals a class of adipocyte progenitors unique to visceral adipose tissue, which shares common features with beige preadipocytes. Our human single-cell transcriptome atlas across fat depots provides a resource to dissect functional genomics of metabolic disease.

UCP1 expression-associated gene signatures of human epicardial adipose tissue.

Multiple reports of uncoupling protein 1 (UCP1) expression have established its presence in human epicardial adipose tissue (eAT). Its functional relevance to eAT, however, remains largely unknown. In a recent study, we reported that adrenergic stimulation of eAT was associated with downregulation of secreted proteins involved in oxidative stress-related and immune-related pathways. Here, we explored the UCP1-associated features of human eAT using next-generation deep sequencing. Paired biopsies of eAT, mediastinal adipose tissue (mAT), and subcutaneous adipose tissue (sAT) obtained from cardiac surgery patients, with specific criteria of high and low expression of UCP1 in eAT, were subjected to RNA sequencing. Although eAT exhibited a depot-specific upregulation in the immune-related pathways relative to mAT and sAT, high UCP1 expression in eAT was specifically associated with differential gene expression that functionally corresponded with downregulation in the production of reactive oxygen species and immune responses, including T cell homeostasis. Our data indicate that UCP1 and adaptive immunity share a reciprocal relationship at the whole-transcriptome level, thereby supporting a plausible role for UCP1 in maintaining tissue homeostasis in human eAT.