Wnt-induced lipid droplet formation could be conveniently visualized using BODIPY, which accumulated in lipid droplets ( Figure 1A) and ( Scott et al., 2015), and quantified by automated microscopy ( Figure 1B, and all subsequent figures). We thus conclude that TFAP2 may function as a ‘master’ regulator of lipid droplet biogenesis. Our data show that the pro-lipid droplet signal induced by Wnt3a is mediated by members of the TFAP2 family of transcription factors. In this paper, we report that the biogenesis of lipid droplets induced by Wnt signaling does not depend on the canonical TCF/LEF transcription factors. This analysis revealed that the Wnt ligand can potently stimulate lipid droplet accumulation in multiple cell types ( Scott et al., 2015). Recently, we used genome-wide, high-content siRNA screens to identify genes that affect cellular lipids. Despite the recognized importance of this organelle in health and disease, little is known of the signaling systems or proximal transcriptional regulators that control lipid droplet biogenesis, function and turnover in cells. While a major function of lipid droplets is clearly as the storehouse of triglycerides and sterol esters, the diversity and variation of this organelle likely reflect the number of reported alternate functions of lipid droplets such as regulation of inflammation, general metabolism, and host-pathogen interplay ( Barisch and Soldati, 2017 Melo and Weller, 2016 Konige et al., 2014). Intriguingly, the number and nature of these organelles vary greatly, both over time within a cell, and between cell types ( Thiam and Beller, 2017). Lipid droplets are the primary storage organelle for neutral lipids in the cell ( Meyers et al., 2017). While the functional details of this control are still under investigation, coordinated transcriptional control of specific organelles is an emerging theme in cell biology. In recent years, several transcriptional ‘master regulators’ of organellar biogenesis have been reported for mitochondria ( Jornayvaz and Shulman, 2010), autophagosomes ( Kang et al., 2012 Chauhan et al., 2013) and lysosomes ( Sardiello et al., 2009). This is effected through a collection of sensing and signaling pathways that integrate information about the local environment and induce the requisite changes in various cellular programs that control organelle abundance and function, through multiple routes, including the modulation of transcription. Cellular adaptation to a changing local environment is imperative for survival and proliferation.
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