Biology subjects

Montell, D.

Publications and source records attributed to Montell, D..

11 recordsLinked to original sources

bioRxiv2026

A kinome inhibitor screen implicates adhesion and growth factor signaling in cellular recovery after caspase activation

Apoptosis is a common form of regulated cell death and requires cysteine-aspartic proteases called effector caspases. Caspase activation triggers positive feedback, leading to the idea that apoptosis is irreversible. However, we and others have demonstrated that cancer cells can survive effector caspase activation and become more aggressive and drug-resistant as a result. Despite the profound implications of apoptotic reversal, also known as anastasis, for both regenerative medicine and cancer therapy, the molecular pathways that enable cells to survive executioner caspase activation remain largely unmapped. To systematically dissect this phenomenon, we developed a quantitative screening platform that combines inducible caspase activation with kinome-wide pharmacological profiling. This approach uniquely allowed us to: (1) identify pharmacological modulators of post-caspase survival, (2) identify specific kinases regulating post-caspase survival, and (3) distinguish general toxicity from anastasis effects. This approach implicated regulators of cell adhesion and the cytoskeleton, consistent with the known rounding of apoptotic cells and respreading during recovery. Growth factor signaling also emerged from the analysis. In addition to its expected effects on unstressed cells, fetal bovine serum markedly increased anastasis. Some growth factor combinations were more effective than individual ones at recapitulating the serum effect. Similarly, pleiotropic kinase inhibitors were generally more effective than selective ones. Nevertheless, selective Rho kinase inhibition significantly enhanced anastasis whereas Akt inhibition impaired it, suggesting that these kinases serve as central nodes that integrate multiple upstream inputs. Beyond identifying specific kinase targets, our work provides a framework for anti-anastasis therapies that could prevent cancer cell recovery after chemotherapy.

cell biology↗

bioRxiv2025

Hyperactive Rac converts sublethal nibbling to lethal phagocytosis in vivo

The small GTPase Rac is an essential regulator of cell shape, migration, macropinocytosis and phagocytosis. We recently reported that expression of constitutively active RacG12V is sufficient to cause a few migratory cells called border cells to cannibalize nurse cells in the Drosophila ovary. Building on that insight, we engineered mammalian Rac-enhanced chimeric-antigen-receptor macrophages (RaceCAR-Ms) to avidly engulf and kill cancer cells. Here we investigate the cellular and molecular mechanisms by which border cells efficiently kill the much larger nurse cells. Surprisingly, wild type border cells normally nibble on nurse cells as they migrate between them, and RacG12V causes border cells to take larger, lethal bites. These larger bites trigger rapid germline shrinkage, nuclear damage, and caspase activation, which spreads through the nurse cell syncytium. Then, many somatic follicle cells join in to engulf the dying germline. Rac and the engulfment receptor Draper are critical for both sublethal nibbling and lethal phagocytosis. Using clonal analysis, we show small groups of follicle cells expressing RacG12V induced caspase activation in neighboring follicle cells while larger RacG12V clones were required to cause germline killing. Increasing Draper expression or JNK activity in border cells also caused germline death, in a Rac-independent manner, suggesting that border cells can be activated to kill through multiple mechanisms. The series of events elucidated here reveals how hyperactivated Rac expressed in a few cells can trigger destruction of a much larger mass of cells. Significance StatementRac is a key protein in the cellular eating process called phagocytosis. Rac hyperactivity enhances the consumption of tumor cells by chimeric antigen receptor-macrophages (CAR-M), a promising type of cellular immunotherapy. Elucidating the mechanisms by which hyperactive Rac enhances cell killing may lead to improvements in CAR-M. Key insights into the in vivo effects of Rac have come from studying Drosophila oogenesis. Here we report molecular and cellular mechanisms by which hyperactivated Rac stimulates migratory cells to engulf and kill much larger cells in the fly ovary, ultimately resulting in destruction of the entire tissue. These insights have implications for how hyperactivating Rac might improve antibody and CAR-M therapies for cancer and other diseases.

cell biology↗

bioRxiv2024

A genome-wide association study implicates the olfactory system in Drosophila melanogaster diapause-associated lifespan extension and fecundity

The effects of environmental stress on animal life are gaining importance. Diapause is a reversible dormancy program triggered by adverse environmental conditions. To characterize the genetic basis of this complex program, we leveraged the Drosophila Genome Reference Panel (DGRP) to conduct a Genome-Wide Association Study (GWAS). We assessed post-diapause and non-diapause fecundity across 193 DGRP lines. GWAS revealed 546 variants, encompassing single nucleotide polymorphisms, insertions, and deletions associated with post-diapause fecundity. We identified 291 candidate diapause-associated genes, 40 of which were previously associated with diapause. Gene network analysis indicated that the diapause-associated genes were primarily linked to neuronal and reproductive system development. Similarly, comparison with other fly GWAS revealed the greatest overlap with olfactory-behavior-associated and fecundity-and-lifespan-associated genes. An RNAi screen of selected candidates identified two neuronal genes, Dip-{gamma} and Scribbler, to be required during recovery for post-diapause fecundity. To complement the genetic analysis, we tested which neurons are required for successful diapause. Although amputation of the antenna had little effect on non-diapause lifespan, it reduced diapause lifespan and post-diapause fecundity. Furthermore, olfactory receptor neurons and temperature-sensing neurons were required for successful diapause recovery. Our results provide insights into the molecular, cellular, and genetic basis of Drosophila adult reproductive diapause.

genetics↗

bioRxiv2024

Altered circadian rhythm, sleep, and rhodopsin 7-dependent shade preference during diapause in Drosophila melanogaster

To survive adverse environments, many animals enter a dormant state such as hibernation, dauer, or diapause. Various Drosophila species undergo adult reproductive diapause in response to cool temperatures and/or short day-length. While it is known that flies are less active during diapause, an in-depth understanding of diapause effects on circadian rhythms and sleep is lacking. Here we show that, in diapause-inducing conditions, Drosophila melanogaster exhibit altered circadian activity profiles, including a severely reduced morning activity peak and an advanced evening activity peak. Consequently, the flies have a single activity peak at a time similar to when non-diapausing flies have a siesta. Temperatures [≤]15 {degrees}C, rather than short day-length, primarily drive the behavior. At cool temperatures, flies also rapidly enter a deep sleep state that lacks the sleep cycles of flies at higher temperatures and requires particularly high levels of stimulation for arousal. Furthermore, we show that at 18-25 {degrees}C, flies prefer to siesta in the shade, a preference that is virtually eliminated at 10 {degrees}C. Resting in the shade is driven by an aversion to blue light, sensed by rhodopsin 7 (Rh7) outside of the eyes. Flies at 10 {degrees}C show neuronal markers of elevated sleep pressure, including increased expression of Bruchpilot and elevated Ca2+ in the R5 ellipsoid body neurons. Therefore sleep pressure might overcome blue light aversion. Thus at temperatures known to cause reproductive arrest, preserve germline stem cells, and extend lifespan, Drosophila melanogaster are prone to deep sleep and exhibit dramatically altered - yet rhythmic - daily activity patterns. Significance statementClimate change is impacting many animals, including insects. In diverse organisms, adverse environments trigger dormancy programs such as hibernation and diapause. Fruit flies undergo diapause to survive winter. Here we develop new methods and show that the same cool temperatures that delay fruit fly reproduction and extend lifespan, also promote deep sleep. Cool flies rapidly fall asleep and are difficult to arouse. Once awake, they immediately fall back to sleep. Whereas in warm environments, midday blue light drives flies to siesta in the shade, in cool temperatures the need to sleep overwhelms light-aversion, reducing shade preference. Animals that adjust their behavior directly to temperature, rather than day length, may be more resilient to a changing climate.

neuroscience↗

bioRxiv2023

Rescue of proteotoxic stress and neurodegeneration by the Zn2+ transporter ZIP7

Proteotoxic stress drives numerous degenerative diseases. In response to misfolded proteins, cells adapt by activating the unfolded protein response (UPR), including endoplasmic reticulum-associated protein degradation (ERAD). However persistent stress triggers apoptosis. Enhancing ERAD is a promising therapeutic approach for protein misfolding diseases. From plants to humans, loss of the Zn2+ transporter ZIP7 causes ER stress, however the mechanism is unknown. Here we show that ZIP7 enhances ERAD and that cytosolic Zn2+ is limiting for deubiquitination of client proteins by the Rpn11 Zn2+ metalloproteinase as they enter the proteasome in Drosophila and human cells. ZIP7 overexpression rescues defective vision caused by misfolded rhodopsin in Drosophila. Thus ZIP7 overexpression may prevent diseases caused by proteotoxic stress, and existing ZIP inhibitors may be effective against proteasome-dependent cancers. One-Sentence SummaryZn2+ transport from the ER to the cytosol promotes deubiquitination and proteasomal degradation of misfolded proteins and prevents blindness in a fly neurodegeneration model.

cell biology↗

bioRxiv2021

Nuclear lamins promote protrusion dynamics and collective, confined migration in vivo

Cells migrate collectively through confined environments during development and cancer metastasis. The nucleus, a stiff organelle, impedes single cells from squeezing into narrow channels within artificial environments, but how nuclei affect collective cell migration into compact tissues in vivo is unknown. Here, we use border cells in the fly ovary to study nuclear dynamics in collective, confined in vivo migration. Border cells delaminate from the follicular epithelium and squeeze into tiny spaces between cells called nurse cells. The lead cell nucleus transiently deforms as it extends into the lead cell protrusion, which then widens. The nuclei of follower cells deform less. Depletion of the Drosophila B-type lamin, Lam, compromises nuclear integrity, hinders expansion of a leading protrusion, and impedes border cell movement. Cortical myosin II accumulates behind the nucleus and moves it into the protrusion in wildtype but not Lam-depleted cells. These data suggest that the nucleus stabilizes lead cell protrusions to help cells wedge open spaces between nurse cells. SummaryDuring Drosophila border cell migration, the B-type lamin Lam maintains nuclear envelope integrity, stabilizes the lead cell protrusion, and promotes cluster invasion between nurse cells. The nucleus may function as a wedge to prom collective, confined in vivo movement.

cell biology↗

bioRxiv2021

Independently paced calcium oscillations in progenitor and differentiated cells in an ex vivo epithelial organ

Cytosolic calcium is a highly dynamic, tightly regulated, and broadly conserved cellular signal. Calcium dynamics have been studied widely in cellular monocultures, yet in vivo most organs comprise heterogeneous populations of stem and differentiated cells. We examined calcium dynamics in each cell type of the adult Drosophila intestine, a self-renewing epithelial organ where multipotent stem cells give rise to mature absorptive enterocytes and secretory enteroendocrine cells. Here we perform live imaging of whole organs ex vivo, and we employ orthogonal expression of red and green calcium sensors to determine whether calcium oscillations between different cell types are coupled. We show that stem cell daughters adopt strikingly distinct patterns of calcium oscillations when they acquire their terminal fates: Enteroendocrine cells exhibit single-cell calcium oscillations, while enterocytes exhibit rhythmic, long-range calcium waves. These multicellular waves do not propagate through progenitor cells (stem cells and enteroblasts), whose oscillation frequency is approximately half that of enteroendocrine cells. Organ-scale inhibition of gap junctions eliminates calcium oscillations in all three cell types, even, intriguingly, in progenitor and enteroendocrine cells that are surrounded only by enterocytes. Our findings establish that cells adopt fate-specific modes of calcium dynamics as they terminally differentiate and reveal that the oscillatory dynamics of different cell types in a single, coherent epithelium are paced independently.

cell biology↗

bioRxiv2021

Collective border cell migration requires the zinc transporter Catsup to limit endoplasmic reticulum stress

Collective cell migration is critical for normal development, wound healing, and in tumor progression and metastasis. Border cells in the Drosophila ovary provide a genetically tractable model to identify molecular mechanisms that drive this important cell behavior. In an unbiased screen for defects in border cell migration in mosaic clones, we identified a mutation in the catsup gene. Catsup, the Drosophila ortholog of Zip7, is a large, multifunctional, transmembrane protein of the endoplasmic reticulum (ER), which has been reported to negatively regulate catecholamine biosynthesis, to regulate Notch signaling, to function as a zinc transporter, and to limit ER stress. Here we report that catsup knockdown caused ER stress in border cells and that ectopic induction of ER stress was sufficient to block migration. Notch and EGFR trafficking were also disrupted. Wild type Catsup rescued the migration defect but point mutations known to disrupt the zinc ion transport of Zip7 did not. We conclude that migrating cells are particularly susceptible to defects in zinc transport and ER homeostasis.

cell biology↗

bioRxiv2021

Unconventional Translation Initiation Factor EIF2A is required for Drosophila spermatogenesis

The eukaryotic initiation factor EIF2A is an unconventional translation factor required for initiation of protein synthesis from non-AUG codons from a variety of transcripts, including oncogenes and stress related genes in mammalian cells. Its function in multicellular organisms has not been reported. Here, we identify and characterize mutant alleles of the CG7414 gene, which encodes the Drosophila EIF2A ortholog. We identified that CG7414 undergoes sex-specific splicing that regulates its male-specific expression. We characterized a Mi{Mic} transposon insertion that disrupts the coding regions of all predicted isoforms and is a genetic null allele, and a PBac transposon insertion into an intron, which is a hypomorph. The Mi{Mic} allele is homozygous lethal, while the viable progeny from the hypomorphic PiggyBac allele are male sterile and female fertile. In dEIF2A mutant flies, sperm failed to individualize due to defects in F-actin cones and failure to form and maintain cystic bulges, ultimately leading to sterility. These results demonstrate that EIF2A is essential in a multicellular organism, both for normal development and spermatogenesis, and provide an entree into the elucidation of the role of EIF2A and unconventional translation in vivo.

developmental biology↗

bioRxiv2020

Tissue topography steers migrating Drosophila border cells

Moving cells can sense and respond to physical features of the microenvironment, however in vivo the significance of tissue topography is mostly unknown. Here we use the Drosophila border cells, an established model for in vivo cell migration, to study how chemical and physical information influence migration path selection. Live imaging, genetics, modeling, and simulations show that, although chemical cues were thought to be sufficient, microtopography is also important. Chemoattractants promote predominantly posterior movement, whereas tissue architecture presents orthogonal information, a path of least resistance concentrated near the center of the egg chamber. E-cadherin supplies a permissive haptotactic cue. Our results provide insight into how cells integrate and prioritize topographical, adhesive, and chemoattractant cues to choose one path amongst many.

developmental biology↗

bioRxiv2017

Src42A required for collective border cell migration in vivo

The tyrosine kinase Src is over-expressed in numerous human cancers and is associated with poor prognosis. While Src has been extensively studied, its contributions to collective cell migration in vivo remain incompletely understood. Here we show that Src42A, but not Src64, is required for the specification and migration of the border cells in the Drosophila ovary, a well-developed and genetically tractable in vivo cell migration model. We found active Src42A enriched at border cell/nurse cell interfaces, where E-cadherin is less abundant, and depleted from border cell/border cell and border cell/polar cell junctions where E-cadherin is more stable, whereas total Src42A protein co-localizes with E-cadherin. Over-expression of wild type Src42A mislocalized Src activity and prevented border cell migration. Constitutively active or kinase dead forms of Src42A also impeded border cells. These findings establish border cells as a model for investigating the mechanisms of action of Src in cooperative, collective, cell-on-cell migration in vivo.

cell biology↗