Biology subjects

Melani, M.

Publications and source records attributed to Melani, M..

5 recordsLinked to original sources

bioRxiv2026

DrosoTracker: a web application with a self-calibrating thermal model for husbandry scheduling and lifespan analysis in Drosophila melanogaster

Planning husbandry tasks and experiments with Drosophila melanogaster requires converting a target date into development times that depend on the rearing temperature. This calculation needs to be done for each cross, genotype, and temperature, and the risk of error grows quickly. Available laboratory management tools let users register stocks, crosses, and track them, but they do not create schedules based on a clear, adjustable thermal model. To fill that gap, we developed DrosoTracker, a self-contained web application that works offline and predicts Drosophila development with a thermal summation model recalibrated through regression on data from Powsner (1935) (T0 = 11.78 {degrees}C, DD = 116.38 {degrees}C{middle dot}days, R{superscript 2} = 0.997). The model offers an optional two-level calibration driven by user observations. A wild-type strain first adjusts the model to the laboratorys own conditions. Then each genotype is calibrated against that reference using a random-effects shrinkage estimator that accounts for measurement error and between-batch variability. The model creates schedules for husbandry tasks, evaluates adult cohort survival with the Kaplan-Meier estimator and the log-rank test, and calculates sample size for lifespan studies using Schoenfelds formula. The quantitative components were checked against independent references, including Rs survival package and manual calculations. Ongoing work is focused on validating the calibrated model using cohorts specifically bred for this purpose. DrosoTracker runs entirely in the browser, stores data locally, and is available in English and Spanish.

developmental biology↗

bioRxiv2024

Autophagy controls differentiation of Drosophila blood cells by regulating Notch levels in response to nutrient availability

Drosophila larval hematopoiesis takes place at the lymph gland, where blood cell progenitors differentiate into two possible cell types: plasmatocytes, analogous to mammalian macrophages, or crystal cells that share features with mammalian megakaryocytes; a third cell type, the lamellocytes, can develop only upon specific immune challenges. In this work, we investigate the role of autophagy in Drosophila hematopoiesis. We found that autophagy inhibition in blood cell progenitors results in augmented crystal cell differentiation due to accumulation of high levels of Notch protein. Notch activation during hematopoiesis depends on the endocytic pathway, which cross-talks with autophagy: While endocytosis and endosomal maturation are essential for Notch activation, autophagosomes are required for Notch lysosomal degradation. TOR signaling inhibits autophagosome biogenesis, which in turn prevents the formation of Notch-containing amphisomes, being the latter necessary for Notch lysosomal destruction. Reduction of Notch lysosomal degradation shifts the balance towards Notch activation at late endosomal membranes, thereby enhancing differentiation of crystal cells. Our work defines a novel mechanism of regulation of immune cell differentiation in response to the nutritional status of the organism: High nutrient availability induces TOR activation, thereby inhibiting autophagy, hindering lysosomal degradation of Notch, and promoting crystal cell differentiation.

developmental biology↗

bioRxiv2024

Regulation of angiogenesis by endocytic trafficking mediated by cytoplasmic dynein 1 light intermediate chain 1

Dynein cytoplasmic 1 light intermediate chain 1 (LIC1, DYNC1LI1) is a core subunit of the dynein motor complex. The LIC1 subunit also interacts with various cargo adaptors to regulate Rab-mediated endosomal recycling and lysosomal degradation. Defects in this gene are predicted to alter dynein motor function, Rab binding capabilities, and cytoplasmic cargo trafficking. Here, we have identified a dync1li1 zebrafish mutant, harboring a premature stop codon at the exon 12/13 splice acceptor site, that displays increased angiogenesis. In vitro, LIC1-deficient human endothelial cells display increases in cell surface levels of the pro-angiogenic receptor VEGFR2, SRC phosphorylation, and Rab11-mediated endosomal recycling. In vivo, endothelial-specific expression of constitutively active Rab11a leads to excessive angiogenesis, similar to the dync1li1 mutants. Increased angiogenesis is also evident in zebrafish harboring mutations in rilpl1/2, the adaptor proteins that promote Rab docking to Lic1 to mediate lysosomal targeting. These findings suggest that LIC1 and the Rab-adaptor proteins RILPL1 and 2 restrict angiogenesis by promoting degradation of VEGFR2-containing recycling endosomes. Disruption of LIC1- and RILPL1/2-mediated lysosomal targeting increases Rab11-mediated recycling endosome activity, promoting excessive SRC signaling and angiogenesis.

cell biology↗

bioRxiv2023

The exocyst complex controls multiple events in the pathway of regulated exocytosis.

Eukaryotic cells depend on exocytosis to direct intracellularly synthesized material towards the extracellular space or the plasma membrane, so exocytosis constitutes a basic function for cellular homeostasis and communication between cells. The secretory pathway includes biogenesis of secretory granules (SGs), their maturation and fusion with the plasma membrane (exocytosis), resulting in release of SG content to the extracellular space. The larval salivary gland of Drosophila melanogaster is an excellent model for studying exocytosis. This gland synthesizes mucins that are packaged in SGs that sprout from the trans-Golgi network and then undergo a maturation process that involves homotypic fusion, condensation and acidification. Finally, mature SGs are directed to the apical domain of the plasma membrane with which they fuse, releasing their content into the gland lumen. The exocyst is a hetero-octameric complex that participates in tethering of vesicles to the plasma membrane during constitutive exocytosis. By precise temperature-dependent gradual activation of the Gal4-UAS expression system, we have induced different levels of silencing of exocyst complex subunits, and identified three temporarily distinctive steps of the regulated exocytic pathway where the exocyst is critically required: SG biogenesis, SG maturation and SG exocytosis. Our results shed light on previously unidentified functions of the exocyst along the exocytic pathway. We propose that the exocyst acts as a general tethering factor in various steps of this cellular process. O_FIG O_LINKSMALLFIG WIDTH=124 HEIGHT=200 SRC="FIGDIR/small/555734v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@4057f5org.highwire.dtl.DTLVardef@4ed694org.highwire.dtl.DTLVardef@1e9a859org.highwire.dtl.DTLVardef@12b971f_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstract.C_FLOATNO Proposed model of the action of the exocyst in maintenance of normal Golgi complex structure, maturation and exocytosis of secretory granules in Drosophila larval salivary gland cells. 1-Before secretory granule (SG) biogenesis (<96 hours AEL), the exocyst (pink dots) localizes at the Golgi complex, where it is required to maintain the normal Golgi structure. The mucine Sgs3 (brown dots) moves through the secretory pathway from the endoplasmic reticulum (ER) to the Golgi complex, from where immature SGs containing the mucine sprout out. 2-After sprouting, SGs undergo maturation (96-116 hours AEL). During maturation, the exocyst localizes in between immature SGs, where it is required for homotypic fusion. The exocyst is also required for incorporation of maturation factors to the membrane of SGs. These maturation factors include Syt-1 (purple line), DC63 (orange line), Rab11 (green oval) and Rab1 (light blue oval). At this stage, the exocyst no longer localizes at the Golgi complex. 3-When maturation has been completed SGs fuse with the apical plasma membrane and exocytosis takes place. During exocytosis (116-120 hours AEL), the exocyst localizes at mature SGs, in contact with the apical plasma membrane, where it is required for tethering and subsequent fusion, prior to release of the SG content to the salivary gland lumen. C_FIG

cell biology↗

bioRxiv2020

The immunophilin Zonda controls regulated exocytosis in endocrine and exocrine tissues

Exocytosis is a fundamental process in physiology, communication between cells, organs and even organisms. Hormones, neuropeptides and antibodies, among other cargoes are packed in exocytic vesicles that need to reach and fuse with the plasma membrane to release their content to the extracellular milieu. Hundreds of proteins participate in this process and several others in its regulation. We report here a novel component of the exocytic machinery, the Drosophila transmembrane immunophilin Zonda (Zda), previously found to participate in autophagy. Zda is highly expressed in secretory tissues, and regulates exocytosis in at least three of them: the ring gland, insulin-producing cells and the salivary gland. Using the salivary gland as a model system, we found that Zda is required at final steps of the exocytic process for fusion of secretory granules to the plasma membrane. In a genetic screen we identified the small GTPase RalA as a crucial regulator of secretory granule exocytosis that operates upstream of Zda in the process.

cell biology↗