Biology subjects

Bell, G. W.

Publications and source records attributed to Bell, G. W..

10 recordsLinked to original sources

bioRxiv2025

Atlas of Lysosomal Aging Reveals a Molecular Clock of Storage Disorder-Associated Metabolites

Lysosomal dysfunction is a well-recognized feature of aging, yet its systematic molecular investigation remains limited. Here, we employ a suite of tools for rapid lysosomal isolation to construct a multi-tissue atlas of the metabolite changes that murine lysosomes undergo during aging. Aged lysosomes in brain, heart, muscle and adipose accumulate glycerophosphodiesters and cystine, metabolites that are causally linked to juvenile lysosomal storage disorders like Batten disease. Levels of these metabolites increase linearly with age, preceding organismal decline. Caloric restriction, a lifespan-extending intervention, mitigates these changes in the heart but not the brain. Our findings link lysosomal storage disorders to aging-related dysfunction, uncover a metabolic lysosomal "aging clock," and open avenues for the mechanistic investigation of how lysosomal functions deteriorate during aging and in age-associated diseases. One-Sentence SummaryAging in mice is tracked by a lysosomal "clock", where glycerophosphodiesters and cystine - metabolites causally linked to juvenile lysosomal storage disorders - gradually accumulate in lysosomes of the brain, heart, skeletal muscle and adipose tissue.

cell biology↗

bioRxiv2025

Reprogramming Factors Activate a Non-Canonical Oxidative Resilience Pathway That Can Rejuvenate RPEs and Restore Vision

Oct4, Sox2, and Klf4 (OSK) Yamanaka factors induce pluripotency and reverse age-related epigenetic changes, yet the mechanisms by which they promote rejuvenation remain poorly explored. Oxidative stress contributes to CNS aging and retinal pigmented epithelium (RPE) degeneration in age-related macular degeneration. We find that OSK expression in RPE restores retinal structure and visual function in aged mice and promotes oxidative resilience through a non-canonical, Tet2-independent pathway. Integrative functional genomics identifies GSTA4, a detoxifying enzyme that clears the lipid peroxidation byproduct 4-HNE, as a necessary and sufficient OSK effector. Dynamic GSTA4 regulation by OSK recapitulates a stem cell derived stress resilience program. GSTA4 overexpression alone enhances mitochondrial resilience, rejuvenates the aged RPE transcriptome, and reverses visual decline. GSTA4 is consistently upregulated across diverse lifespan-extending interventions suggesting a broader pro-longevity role. These findings uncover a previously unrecognized protective axis driven by Yamanaka factors that circumvents reprogramming, providing therapeutic insights for age-related diseases. HIGHLIGHTSO_LIOSK-GSTA4 provides a dynamic, Tet2-independent stress-resilience axis. C_LIO_LIFunctional genomics pinpoints GSTA4 as a direct downstream effector activated by OSK. C_LIO_LIRPE aging involves progressive accumulation of 4-HNE that can be detoxified by GSTA4. C_LIO_LIEnhancing GSTA4 rejuvenates RPE cells, restores vision and is associated with lifespan-extending interventions. C_LI

genetics↗

bioRxiv2025

CD4+ T-cells sensitize quasi-mesenchymal breast tumors lacking CD73 to anti-CTLA4 immune checkpoint blockade therapy

Although immune checkpoint blockade therapy has generated dramatic responses in certain cancer types, breast tumors are largely unresponsive. Epithelial-mesenchymal plasticity leads to the assembly of an immunosuppressive tumor microenvironment and drives resistance of breast tumors to immunotherapies. Importantly, targeting CD73 completely sensitizes quasi-mesenchymal breast tumors to anti-CTLA4 immune checkpoint blockade therapy. However, the mechanism(s) of sensitization remained unknown. We demonstrate that targeting CD73 in quasi-mesenchymal breast tumors sensitizes them to anti-CTLA4 immune checkpoint blockade therapy in a CD4+ T-cell dependent manner. Moreover, epithelial-mesenchymal plasticity results in elevated expression of cancer cell-intrinsic CD73 in human triple negative breast cancers. Given the ability of quasi-mesenchymal cancer cells to metastasize and resist multiple therapies, these findings can instruct the formation of novel translational strategies for the treatment of human breast cancers. These findings also bring to the forefront the attractive possibility of utilizing the phenotypic plasticity of cancer cells along with CD73 and CD4+ T-cells as a predictive criterion for immunotherapy responsiveness. TeaserTargeting CD73 sensitizes breast cancer cells with mesenchymal traits to anti-CTLA4 therapy in a CD4+ T-cell dependent manner.

cancer biology↗

bioRxiv2024

CD47 predominates over CD24 as a macrophage immune checkpoint in cancer.

Macrophages hold tremendous promise as effectors of cancer immunotherapy, but the best strategies to provoke these cells to attack tumors remain unknown. Here, we evaluated the therapeutic potential of targeting two distinct macrophage immune checkpoints: CD47 and CD24. We found that antibodies targeting these antigens could elicit maximal levels of phagocytosis when combined together in vitro. However, to our surprise, via unbiased genome-wide CRISPR screens, we found that CD24 primarily acts as a target of opsonization rather than an immune checkpoint. In a series of in vitro and in vivo genetic validation studies, we found that CD24 was neither necessary nor sufficient to protect cancer cells from macrophage phagocytosis in most mouse and human tumor models. Instead, anti-CD24 antibodies exhibit robust Fc-dependent activity, and as a consequence, they cause significant on-target hematologic toxicity in mice. To overcome these challenges and leverage our findings for therapeutic purposes, we engineered a collection of 77 novel bispecific antibodies that bind to a tumor antigen with one arm and engage macrophages with the second arm. We discovered multiple novel bispecifics that maximally activate macrophage-mediated cytotoxicity and reduce binding to healthy blood cells, including bispecifics targeting macrophage immune checkpoint molecules in combination with EGFR, TROP2, and CD71. Overall, our findings indicate that CD47 predominates over CD24 as a macrophage immune checkpoint in cancer, and that the novel bispecifics we created may be optimal immunotherapies to direct myeloid cells to eradicate solid tumors.

cancer biology↗

bioRxiv2024

Multi-species genome-wide CRISPR screens identify GPX4 as a conserved suppressor of cold-induced cell death

Cells must adapt to environmental changes to maintain homeostasis. One of the most striking environmental adaptations is entry into hibernation during which core body temperature can decrease from 37C to as low at 4C. How mammalian cells, which evolved to optimally function within a narrow range of temperatures, adapt to this profound decrease in temperature remains poorly understood. In this study, we conducted the first genome-scale CRISPR-Cas9 screen in cells derived from Syrian hamster, a facultative hibernator, as well as human cells to investigate the genetic basis of cold tolerance in a hibernator and a non-hibernator in an unbiased manner. Both screens independently revealed glutathione peroxidase 4 (GPX4), a selenium-containing enzyme, and associated proteins as critical for cold tolerance. We utilized genetic and pharmacological approaches to demonstrate that GPX4 is active in the cold and its catalytic activity is required for cold tolerance. Furthermore, we show that the role of GPX4 as a suppressor of cold-induced cell death extends across hibernating species, including 13-lined ground squirrels and greater horseshoe bats, highlighting the evolutionary conservation of this mechanism of cold tolerance. This study identifies GPX4 as a central modulator of mammalian cold tolerance and advances our understanding of the evolved mechanisms by which cells mitigate cold-associated damage - one of the most common challenges faced by cells and organisms in nature.

cell biology↗

bioRxiv2024

Ether lipids influence cancer cell fate by modulating iron uptake

Cancer cell fate has been widely ascribed to mutational changes within proteincoding genes associated with tumor suppressors and oncogenes. In contrast, the mechanisms through which the biophysical properties of membrane lipids influence cancer cell survival, dedifferentiation and metastasis have received little scrutiny. Here, we report that cancer cells endowed with high metastatic ability and cancer stem celllike traits employ ether lipids to maintain low membrane tension and high membrane fluidity. Using genetic approaches and lipid reconstitution assays, we show that these ether lipid-regulated biophysical properties permit non-clathrin-mediated iron endocytosis via CD44, resulting in significant increases in intracellular redox-active iron and enhanced ferroptosis susceptibility. Using a combination of in vitro threedimensional microvascular network systems and in vivo animal models, we show that loss of ether lipids from plasma membranes also strongly attenuates extravasation, metastatic burden and cancer stemness. These findings illuminate a mechanism whereby ether lipids in carcinoma cells serve as key regulators of malignant progression while conferring a unique vulnerability that can be exploited for therapeutic intervention.

cancer biology↗

bioRxiv2023

Targeted therapies prime oncogene-driven lung cancers for macrophage-mediated destruction

Macrophage immune checkpoint inhibitors, such as anti-CD47 antibodies, show promise in clinical trials for solid and hematologic malignancies. However, the best strategies to use these therapies remain unknown and ongoing studies suggest they may be most effective when used in combination with other anticancer agents. Here, we developed a novel screening platform to identify drugs that render lung cancer cells more vulnerable to macrophage attack, and we identified therapeutic synergy exists between genotype-directed therapies and anti-CD47 antibodies. In validation studies, we found the combination of genotype-directed therapies and CD47 blockade elicited robust phagocytosis and eliminated persister cells in vitro and maximized anti-tumor responses in vivo. Importantly, these findings broadly applied to lung cancers with various RTK/MAPK pathway alterations--including EGFR mutations, ALK fusions, or KRASG12C mutations. We observed downregulation of {beta}2-microglobulin and CD73 as molecular mechanisms contributing to enhanced sensitivity to macrophage attack. Our findings demonstrate that dual inhibition of the RTK/MAPK pathway and the CD47/SIRPa axis is a promising immunotherapeutic strategy. Our study provides strong rationale for testing this therapeutic combination in patients with lung cancers bearing driver mutations. Brief summaryUnbiased drug screens identify targeted therapies as drugs that make lung cancers with driver mutations more vulnerable to macrophage attack.

cancer biology↗

bioRxiv2022

Deregulation of Y-linked protamine-like genes in sex chromosome-biased spermatid demise

Meiotic drive is a phenomenon wherein a genetic element achieves a higher rate of transmission than dictated by Mendelian segregation (1-3). One proposed mechanism for meiotic drivers to achieve biased transmission is by sabotaging essential processes of gametogenesis (e.g. spermatogenesis), leading to demise of gametes that contain their opponents (1). Studies in D. simulans have recently found that a set of meiotic driver genes contain a sequence homologous to protamines (4, 5), critical proteins that package sperm chromatin (6-8). However, the underlying mechanisms of drive and the relevance of protamine-like sequences in meiotic drive remain unknown. While studying the function of Modulo, the homolog of Nucleolin in Drosophila melanogaster (9, 10), we unexpectedly discovered Y-linked protamine genes function as a meiotic driver: we found that modulo mutants known sterility is caused by deregulation of the autosomal protamine-like gene (Mst77F) and its Y chromosome-linked homolog (Mst77Y). Modulo regulates these genes at the step of polyadenylation of the transcripts. We show that Mst77Y likely acts as a dominant-negative form of Mst77F, interfering with the process of histone-to-protamine transition, leading to nuclear decompaction. Overexpression of Mst77Y in a wild-type background is sufficient to cause nuclear decompaction and results in the biased demise of X chromosome-bearing sperm. We propose that dominant-negative protamine variants may be a common strategy found in male meiotic drive and may explain known rapid divergence of protamine genes. Significance statementProtamines are small, highly positively charged proteins that are required for packaging DNA to produce mature sperm with highly-condensed nuclei capable of fertilization. Even small changes in the dosage of protamines in humans is associated with infertility. Yet, despite their essential function, protamines are rapidly evolving. It has been speculated that protamines rapid divergence may be explained by their potential participation in genomic conflict. Our work implicates the involvement of Y chromosome-linked multicopy protamine-like genes in meiotic drive in Drosophila melanogaster. Our results suggest that dominant negative protamines can sabotage the process of nuclear compaction during spermiogenesis, revealing a potential cellular mechanism of sperm killing in meiotic drive.

genetics↗

bioRxiv2022

Drosophila Males Use 5'-to-3' Phased Biogenesis to Make Stellate-silencing piRNAs that Lack Homology to Maternally Deposited piRNA Guides

PIWI-interacting RNAs (piRNAs) direct PIWI proteins to silence complementary targets such as transposons. In animals with a maternally specified germline, e.g. Drosophila melanogaster, maternally deposited piRNAs initiate piRNA biogenesis in the progeny. Normal fertility in D. melanogaster males requires repression of tandemly repeated Stellate genes by piRNAs from Suppressor of Stellate [Su(Ste)]. Because the Su(Ste) loci are on the Y chromosome, Su(Ste) piRNAs are not deposited in oocytes. How the male germline produces Su(Ste) piRNAs in the absence of maternally deposited Su(Ste) piRNAs is unknown. Here, we show that Su(Ste) piRNAs are made in the early male germline via 5'-to-3' phased piRNA biogenesis triggered by maternally deposited 1360/Hoppel transposon piRNAs. Strikingly, deposition of Su(Ste) piRNAs from XXY mothers obviates the need for phased piRNA biogenesis in sons. Together, our study uncovers the developmentally programmed mechanism that allows fly mothers to protect their sons using a Y-linked piRNA locus.

developmental biology↗

bioRxiv2019

Development of Human Neuroblastomas in Mouse-Human Neural Crest Chimeras

Neuroblastoma (NB), derived from the neural crest (NC), is the most common pediatric extracranial solid tumor. Here we establish a platform that allows studying human NBs in mouse-human NC chimeras. Chimeric mice were produced by injecting human NC cells carrying NB relevant oncogenes in-utero into gastrulating mouse embryos. The mice developed tumors composed of a heterogenous cell population that closely resembled that seen in primary NBs of patients but were significantly different from homogenous tumors formed in xenotransplantation models. The human tumors emerged in immunocompetent hosts and were extensively infiltrated by mouse cytotoxic T cells reflecting a vigorous host anti-tumor immune response. However, the tumors blunted the immune response by inducing infiltration of regulatory T cells and expression of immune checkpoints similar to escape mechanisms seen in human cancer patients. Thus, this experimental platform allows studying human tumor initiation, progression, manifestation and tumor - immune-system interactions in an animal model system.

cancer biology↗