Biology subjects

Shimell, M.

Publications and source records attributed to Shimell, M..

4 recordsLinked to original sources

bioRxiv2025

Linking Expression and Function of Drosophila Type-I TGF-b Receptor Baboon Isoforms: Multiple Roles of BaboA Isoform in Shaping of the Adult Central Nervous System

Evolutionarily conserved transforming growth factor {beta} (TGF-{beta}) signaling is used in both vertebrates and invertebrates to regulate a variety of developmental and cellular processes. The baboon (babo) gene encoding a Drosophila type-I TGF-{beta} receptor produces three isoforms via alternative splicing: BaboA, BaboB, and BaboC. In this study, we generated three fly lines, each carrying an isoform-specific GFP tag, and another line with a GFP conjugated at the C-terminus common to all isoforms. Using these lines, we assessed (1) whether the tagged proteins function properly in rescue assays and (2) how the isoform expression is regulated in various tissues including the central nervous system (CNS). A Gal4 knock-in line in the babo locus was also characterized for reporter expression, mutant phenotypes, and isoform-specific knockdown phenotypes. We found that the C-terminal tag does not interrupt the subcellular targeting and functions of the tagged isoforms, but the internal isoform tags do so in a cell- and isoform-specific fashion. Nevertheless, our results demonstrated that these tags faithfully reflect endogenous expression of individual isoforms. Certain cell types express single or multiple isoforms at different levels, suggesting that alternative splicing could determine the isoform types and their levels depending on cell (or tissue) type. The larval CNS displays distinct patterns of two isoforms, BaboA and BaboC. BaboC is mostly expressed in neural cells originating during embryogenesis, while BaboA is broadly expressed in neural cells produced from both embryonic and postembryonic stages. Assays of both isoform-specific mutants and cell-specific knockdown of individual isoforms revealed broad roles played by BaboA in postembryonic neurogenesis and differentiation of precursor neurons, remodeling processes of persisting larval neurons, and metamorphic CNS reorganization, which are essential for establishing of the adult CNS. Taken together, this study demonstrates that the GFP-tagged lines permit visualization of endogenous expression of individual isoforms, which further provides clues about cell- and stage-specific functions played by each isoform.

developmental biology↗

bioRxiv2023

Ptth regulates lifespan through innate immunity pathway in Drosophila

The prothoracicotropic hormone (PTTH) is a well-known neuropeptide that regulates insect metamorphosis (the juvenile-to-adult transition) by inducing the biosynthesis of steroid hormones. However, the role of PTTH in adult physiology and longevity is largely unexplored. Here, we show that Ptth loss-of-function mutants are long-lived and exhibit increased resistance to oxidative stress in Drosophila. Intriguingly, we find that loss of Ptth blunt age-dependent upregulation of NF-{kappa}B signaling specifically in fly hepatocytes (oenocytes). We further show that oenocyte-specific overexpression of Relish/NF-{kappa}B blocks the lifespan extension of Ptth mutants, suggesting that PTTH regulates lifespan through oenocyte-specific NF-{kappa}B signaling. Surprisingly, adult-specific knockdown of Ptth did not prolong lifespan, indicating that PTTH controls longevity through developmental programs. Indeed, knockdown of PTTH receptor Torso in prothoracic gland (PG) during fly development prolongs lifespan. To uncover the developmental processes underlying PTTH-regulated lifespan, we perform a developmental transcriptomic analysis and identify an unexpected activation of NF-{kappa}B signaling in developing oenocytes during fly metamorphosis, which is blocked in Ptth mutants. Importantly, knockdown of Relish/NF-{kappa}B specifically in oenocytes during early pupal stages significantly prolongs the lifespan of adult flies. Thus, our findings uncover an unexpected role of PTTH in controlling adult lifespan through temporal and spatial activation of NF-{kappa}B signaling in developing hepatocytes and highlight the vital role of developmental NF-{kappa}B signaling in shaping adult physiology. Significance StatementDespite the strong link between animal development and adult lifespan, we know little about how developmental programs impact adult longevity, and when and where such programs are activated during development. Here, we demonstrate that loss of insect hormone PTTH prolongs lifespan and healthspan by repressing chronic inflammation in Drosophila. Intriguingly, we demonstrate that PTTH regulates adult lifespan through temporal and spatial activation of NF-{kappa}B signaling in developing hepatocytes during insect metamorphosis. These findings provide novel insights into the developmental programs that impact adult longevity.

physiology↗

bioRxiv2021

The NDNF-like factor Nord is a Hedgehog-induced extracellular BMP modulator that regulates Drosophila wing patterning and growth

Hedgehog (Hh) and bone morphogenetic proteins (BMPs) pattern the developing Drosophila wing by functioning as short- and long-range morphogens, respectively. Here, we show that a previously unknown Hh-dependent mechanism fine-tunes the activity of BMPs. Through genome-wide expression profiling of the Drosophila wing imaginal discs, we identify nord as a novel target gene of the Hh signaling pathway. Nord is related to the vertebrate Neuron Derived Neurotrophic Factor (NDNF) involved in Congenital Hypogonadotropic Hypogonadism and several types of cancer. Loss- and gain-of-function analyses implicate Nord in the regulation of wing growth and proper crossvein patterning. At the molecular level, we present biochemical evidence that Nord is a secreted BMP-binding protein and localizes to the extracellular matrix. Nord binds to Decapentaplegic (Dpp) or the heterodimer Dpp-Glass bottom boat (Gbb) to modulate their release and activity. Furthermore, we demonstrate that Nord is a dosage-depend biphasic BMP modulator, where low levels of Nord promote and high levels inhibit BMP signaling. Taken together, we propose that Hh-induced Nord expression fine tunes both the range and strength of BMP signaling in the developing Drosophila wing. One sentence summaryThe NDNF-like factor Nord is a Hedgehog-induced and extracellular-localized biphasic BMP modulator that regulates Drosophila wing patterning and growth

developmental biology↗

bioRxiv2020

A novel juxtamembrane basolateral targeting motif regulates TGF-β receptor signaling in Drosophila

In polarized epithelial cells, receptor-ligand interactions can be restricted by different spatial distributions of the two interacting components, giving rise to an underappreciated layer of regulatory complexity. We explored whether such regulation occurs in the Drosophila wing disc, an epithelial tissue that requires the TGF-{beta} family member Dpp for growth and patterning. Dpp protein has been observed in a gradient within the columnar cells of the disc, but also uniformly in the disc lumen, leading to the question of how graded signaling is achieved in the face of two distinctly localized pools. We find the Dpp type II receptor Punt, but not the type I receptor Tkv, is enriched at the basolateral membrane, and depleted at the junctions and apical surface. Wit, a second type II receptor, shows a markedly different behavior, with the protein detected on all membrane regions but enriched at the apical side. Mutational studies identified the BLT, a short juxtamembrane sequence required for basolateral targeting of Punt in both wing discs and mammalian MDCK cells, and that dominantly confers basolateral localization on an otherwise apical receptor. Rescue of punt mutants with transgenes altered in the targeting motif showed that flies expressing apicalized Punt due to the lack of a functional BLT displayed developmental defects, female sterility and significant lethality. We also show that apicalized Punt does not produce an ectopic signal, indicating that the apical pool of Dpp is not a significant signaling source even when presented with Punt. Finally, we present evidence that the BLT acts through polarized sorting machinery that differs between types of epithelia. This suggests a code whereby each epithelial cell type may differentially traffic common receptors to enable distinctive responses to spatially localized pools of extracellular ligands.

cell biology↗