Biology subjects

Garelis, N. E.

Publications and source records attributed to Garelis, N. E..

5 recordsLinked to original sources

bioRxiv2025

Genome-wide screen in Mycobacterium tuberculosis infected macrophages reveals innate regulation of antibacterial mediators by IRF2

Controlling Mycobacterium tuberculosis (Mtb) infection requires a precisely balanced host inflammatory response. Too little inflammation leads to uncontrolled bacterial growth but exacerbated inflammation, activated by mediators such as TNF and type I IFN, inhibits effective antibacterial responses. How these immunopathological states are established is unknown. Deeper understanding of the pathways elicited upon initial Mtb infection of the host macrophage may reveal vital regulatory mechanisms that govern the subsequent inflammatory environment and ultimate resolution of infection. To elucidate these early regulators of inflammation, we performed a genome-wide CRISPR knockout screen in macrophages to identify genes that influence the induction of TNF and iNOS upon infection with Mtb. The resulting dataset is a valuable resource that includes genes representing a wide range of unexpected regulatory mechanisms that control cytokine responses to Mtb and also cell-intrinsic resistance to infection by the bacterial pathogen Listeria monocytogenes. We show that type I IFN signaling enhances TNF production early after infection, and IRF2 acts to inhibit induction of the antibacterial state of macrophages. Our data support a model in which early production of type I IFN in response to bacterial infection serves to increase innate antibacterial resistance during the earliest stages of infection.

immunology↗

bioRxiv2025

An unusual genetic switch controls Mycobacterium avium pathogenesis, antibiotic resistance and colony morphology

Mycobacterium avium subspecies hominissuis (Mah) is an emerging environmental pathogen highly adapted to a wide range of niches, from treated water systems to mammalian tissues. On solid media, Mah forms two distinct colony morphologies, smooth transparent (SmT) and smooth opaque (SmO). These colony morphologies are representative of broader differential phenotypic states in which SmT cells are virulent and have high resistance to antibiotics while SmO cells are avirulent, antibiotic-sensitive and grow faster than SmT cells in culture. Importantly, Mah interconverts between these two morphotypes but the mechanism of SmT-SmO switching is unknown. Here we show that SmT-SmO switching is governed by a reversible transposition event that regulates expression of a periplasmic lipoprotein, Erp (extracellular repetitive protein). We found that transposition of IS1245, an endogenous insertion sequence, into the erp gene correlated with the SmT-SmO transition, and its precise removal coincided with the switch back to SmT. Genetic analyses showed that erp is required for maintenance of the SmT state and sufficient to drive the switch from SmO to SmT. We also identified a mutation in a periplasmic protease, MarP, that locks Mah in the SmO state and blocks erp-mediated switching to SmT. Our results indicate that Erp and MarP function in a signal transduction pathway that regulates a broad transcriptional response to periplasmic stress. Moreover, identification of components that control Mah colony morphology switching has revealed a potential new strategy for combating the inherent antibiotic resistance of Mycobacterium avium infections.

microbiology↗

bioRxiv2024

UFMylation suppresses Type I IFN signaling during M. tuberculosis infection of human macrophages

Type I Interferons (IFN-I) promote host defense against a wide range of viral infections, but inhibit control of several bacterial pathogens, including Mycobacterium tuberculosis (Mtb). Given the significance of IFN-I signaling in determining Mtb infection outcomes, we sought to uncover new molecular mechanisms that regulate IFN-I during mycobacterial infection, specifically focusing on how IFN-I signaling is regulated at the earliest stages of mycobacterial infection as modeled by macrophage infection. To comprehensively identify these host genes, we performed a reporter-based, genome- wide CRISPR-interference screen in human macrophages infected with Mycobacterium marinum, a close relative of Mtb. Our screen detected 2035 significantly enriched genes (p<0.05), which included many known regulators of IFN-I, but also many unexpected genes as potentially novel regulators of IFN-I signaling. One of these unexpected genes was UFL1, an E3-like ligase that catalyzes conjugation of the ubiquitin-like protein, UFM1, in a process termed UFMylation. UFL1-deficiency during Mtb macrophage infection resulted in increased expression of IFN-{beta}, interferon-stimulated genes, and other pro-inflammatory genes, such as TNF and IL-6, at both the transcript and protein level. Depletion of other UFMylation components phenocopied UFL1-deficiency, suggesting that UFMylation activity is required for IFN-I repression. Full transcriptional profiling revealed a broad increase in the inflammatory response of UFL1-deficient cells during Mtb infection, including both protective inflammatory cytokines and potentially detrimental interferon-stimulated genes. Our results suggest a role for UFMylation in suppressing IFN-I signaling and inflammatory responses during the earliest stages of Mtb infection. IMPORTANCEMycobacterium tuberculosis was estimated to have caused over 1 million deaths in 2025 - the most deaths globally by a single bacterial pathogen. Past studies in mice and humans have shown that some host immune responses, such as IFN-I signaling, can enhance susceptibility to M. tuberculosis. We report the results of our genome-wide CRISPR-interference screen to determine regulators of IFN-I signaling during the earliest stages of mycobacterial infection. This screen identified new regulators of IFN-I signaling, including the UFMylation pathway, which appears to play an unexpected role in suppressing both IFN-I signaling and a broader inflammatory response. These findings may be relevant for the development of therapeutics and prophylactics for tuberculosis that impact IFN-I signaling - a known determinant of tuberculosis susceptibility.

microbiology↗

bioRxiv2022

Cas9+ conditionally immortalized neutrophil progenitors as a tool for genome wide CRISPR screening for neutrophil differentiation and function

Neutrophils are short-lived cells of the innate immune system that play numerous roles in defense against infection, regulation of immune responses, tissue damage and repair, autoimmunity, and other non-communicable diseases. Understanding neutrophil function at a mechanistic level has been hampered by the difficulty of working with primary neutrophils, which die rapidly upon isolation, and the relative paucity of neutrophil cell lines. Murine neutrophil progenitors that are immortalized with estrogen-regulated expression of Hoxb8 differentiate into neutrophils upon withdrawal of estrogen and facilitate the quantitative production of neutrophils in vitro. Here we report the creation of a Cas9+ER-Hoxb8 neutrophil progenitor cell line that enables both forward and reverse genetic analysis of neutrophils for the first time. By editing progenitors via transduction with sgRNAs, and then withdrawing estrogen, Cas9 edited neutrophils are produced with high efficiency. Importantly, neutrophil differentiation of edited progenitors occurs both in vitro in cell culture and when transferred into murine recipients. To demonstrate the utility of Cas9+ER-Hoxb8 progenitors for forward genetics, we performed a pooled CRISPR screen to identify factors required for survival during neutrophil differentiation. This screen identified hundreds of genes both negatively and positively selected under differentiation conditions. One of the top hits from this screen was Cebpe, a transcription factor known to be required for neutrophil differentiation from pre-neutrophils to immature neutrophils. Using the progenitor cell line, we also confirmed that Cepbe is required for neutrophil differentiation in vivo, validating the utility of this cell line both for screening and for studying in vivo phenotypes. The genome-wide screen also identified all components of the WASH complex as being required for neutrophil differentiation, a finding that extends the known role of WASH in hematopoietic stem cell differentiation to later stages of neutrophil development. Taken together, we demonstrate that Cas9+ER-Hoxb8 immortalized neutrophils can be used to study neutrophil function both in vitro and in vivo. This new resource will enable the analysis of the role of neutrophils in numerous disease states using genetics for the first time.

immunology↗

bioRxiv2019

Global proteomic profiling of primary macrophages during M. tuberculosis infection identifies TAX1BP1 as a mediator of autophagy targeting

Macrophages are highly plastic cells that adopt diverse functional capabilities and play critical roles in immunity, cancer, and tissue homeostasis, but how these different cell fates and activities are triggered in response to their environmental cues is not well understood. We used new proteomic tools to identify protein post-translational modifications (PTMs) that control antibacterial responses of macrophages. Here, we report an unbiased and global analysis of the changes in host protein abundance, phosphorylation, and ubiquitylation, during the first 24-hours of Mycobacterium tuberculosis (Mtb) infection of primary macrophages. We discovered 1379 proteins with changes in their phosphorylation state and 591 proteins with changes in their ubiquitylation in response to Mtb infection. We identified pathways regulated by phosphorylation and ubiquitylation that werent reflected by changes in protein abundance, indicating that the activity of these pathways was regulated. These include pathways known to be regulated by ubiquitylation and phosphorylation (e.g. autophagy) as well as pathways that were not known to be regulated during Mtb infection (e.g. nucleocytoplasmic transport and mRNA metabolism). We identified an enrichment in phosphorylation of autophagy receptors (TAX1BP1, p62, optineurin, BNIP3L), several of which were not previously implicated in the host response to Mtb infection. We found that p62 deficiency blocks ubiquitylation and TAX1BP1 deficiency enhances ubiquitylation, suggesting p62 ubiquitylation acts as an amplification loop by promoting downstream adaptor recruitment and serves as a platform for recruitment of ubiquitin. Our results show that TAX1BP1 mediates clearance of ubiquitylated Mtb and targets the bacteria to LC3-positive phagophores. Taken together, our proteomic profiling is likely a valuable resource for initiating mechanistic studies of macrophage biology.

microbiology↗