Visualization of Endogenous Type I TGF-β Receptor Baboon in the Drosophila Brain

Abstract

the transforming growth factor β (tGf-β) signaling pathway is evolutionarily conserved and widely used in the animal kingdom to regulate diverse developmental processes. prior studies have shown that Baboon (Babo), a Drosophila type i tGf-β receptor, plays essential roles in brain development and neural circuit formation. However, the expression pattern for Babo in the developing brain has not been previously reported. We generated a knock-in fly with a human influenza hemagglutinin (HA) tag at the C-terminus of Babo and assessed its localization. Babo::HA was primarily expressed in brain structures enriched with neurites, including the mushroom body lobe and neuropils of the optic lobe, where Babo has been shown to instruct neuronal morphogenesis. Since the babo 3' untranslated region contains a predicted microRNA-34 (miR-34) target sequence, we further tested whether Babo::HA expression was affected by modulating the level of miR-34. We found that Babo was upregulated by mir-34 deletion and downregulated by miR-34 overexpression, confirming that it is indeed a miR-34 target gene. Taken together, our results demonstrate that the babo HA fly permits accurate visualization of endogenous Babo expression during brain development and the construction of functional neural circuits.The transforming growth factor β (TGF-β) signaling pathway is evolutionarily conserved and widely utilized in animals as a regulator of diverse and complex processes, such as cell growth, differentiation and morphogenesis during development 1,2 . In Drosophila, two major groups of ligands, Activins and Bone morphogenetic proteins, stimulate distinct TGF-β signaling pathways that involve different sets of downstream effectors (reviewed by Upadhyay et al. 1 ). Activin signals bind to Baboon (Babo), a type I TGF-β receptor that transduces TGF-β signaling by binding to type II TGF-β receptors, Punt and Wishful thinking (Wit), to regulate several essential processes in brain development and neural circuit formation 1,3-5 . For instance, Activin-β and an Activin-like protein Dawdle were shown to signal through Babo to regulate neuroblast proliferation in the larval brain, with loss of babo function resulting in fewer cells within the central brain and optic lobe 4 . Besides controlling neuroblast proliferation, Babo also transduces the signals of Activin-β and Activin-like protein Myoglianin to control neuronal morphogenesis during neural circuit formation, including in mushroom body (MB) neurons of the central brain and in medulla projection (Tm) neurons of the optic lobe 3,5,6 . When babo is mutated, MB neurons display both axon growth and pruning defects 3,7 , while Tm neurons exhibit multiple dendritic patterning phenotypes 5 . Taken together, these studies demonstrate the crucial role of Babo in brain development and in neural circuit formation.Despite the fact that Babo is known to act as an important regulator, the Babo pattern expression in the brain has not been previously reported. In this study, we overcame a lack of reliable Babo antib...

Insect metamorphosis is regulated differently between sexes by members of a microRNA cluster

“…Previous studies have demonstrated miR-277 play various functional roles in flies, including circadian rhythm (Anna et al 2023), life span (Esslinger et al 2013), neurodegeneration and neuromuscular control (Tan et al 2012; Deshpante et al 2024; Cerro-Herreros et al 2016), homeostasis (Jones et al 2013; Li et al 2020), fatty acid metabolism (Zipper et al 2022), and amino acid metabolism (Esslinger et al 2013; Stark et al 2003). On the other hand, miR-34 has also been shown to play other roles in flies such as in autophagy, brain development, life span, survivorship, and regulation of ecdysone (Liu et al 2012, Lai et al 2016, Kennerdell et al 2018, McNeill et al 2020; Kennerdell et al 2018, McNeill et al 2020, Srinivasan et al 2022; Lai et al 2020; Xiong et al 2016). Together with the correlated expression data (AstC-R1, Kr-h1, miR-277 and miR-34), in vivo mutants construction, hormone measurement and transcriptomic analyses, this study strongly demonstrated that miR-277 and miR-34 can play cooperative biological roles in sesquiterpenoid hormones in the fly sexes during metamorphosis.…”