The Drosophila wg gene was identified in an RNAi-based screen to identify muscle-secreted proteins that, when inhibited, cause an obese phenotype. The flies exhibit increased abdominal fat body mass, enlarged lipid droplets in fat body cells, and an increase in total triglyceride amounts. Consistent with the results from wg knockdown experiments, wg overexpression in muscle decreases fat accumulation. A second gene in the Wnt signaling pathway, arm, was assessed in the same assays, with comparable results.
See the FlyBase report for the Wnt-TCF Signaling Pathway Core Components (FBgg0000890).
UAS constructs of the human genes Hsap\WNT1 (an ortholog of wg) and Hsap\CTNNB1 (an ortholog of arm) have been introduced into flies, but have not been characterized.
The fly ortholog of MED13 (Dmel\skd), which is not a secreted protein, also exhibits obesity-related phenotypes when knocked down in muscle; see the human disease model 'obesity, susceptibility to (postulated), MED13-related' (FBhh0000506). Genetic experiments have been performed to assess epistatic relationships between wg and skd for the obesity-related phenotypes. These data support the conclusion that muscle-secreted wg protein acts as a downstream effector of skd function in muscle to suppress fat deposition in the fat body.
[updated Apr. 2020 by FlyBase; FBrf0222196]
Obesity is an abnormal accumulation of body fat, usually 20% or more over an individual's ideal body weight. Obesity is associated with increased risk of illness, disability, and death. (http://medical-dictionary.thefreedictionary.com/obesity).
The development of obesity is recognized as having both genetic and environmental components (https://www.sciencelearn.org.nz/resources/203-obesity-genetic-or-environmental).
The canonical Wnt signaling pathway is initiated by the binding of a Wnt ligand to a frizzled family receptor on the cell surface. Activation of the pathway leads to the inhibition of cytoplasmic β-catenin (arm) degradation and its subsequent accumulation in the nucleus, where it regulates the transcription of target genes (FBgg0000890).
Moderate- to high-scoring ortholog of human CTNNB1 and JUP (1 Drosophila to 2 human). Dmel\arm shares 63-67% identity and 76-77% similarity with the human genes.
High-scoring ortholog of human WNT1 (1 Drosophila to 1 human, best and reverse best hits); multiple orthologs and paralogs in both species. Dmel\wg shares 44% identity and 55% similarity with the human gene.