SARM1 loss protects retinal ganglion cells in a mouse model of Autosomal Dominant Optic Atrophy

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Abstract

Autosomal Dominant Optic Atrophy (ADOA), the most prevalent hereditary optic neuropathy, leads to retinal ganglion cell (RGC) degeneration and vision loss. ADOA is primarily caused by mutations in the OPA1 gene, which encodes a conserved GTPase important for mitochondrial inner membrane dynamics. To date, the disease mechanism remains unclear, and no therapies are available. We generated a mouse model carrying the pathogenic Opa1R290Q/+ allele that recapitulated key features of human ADOA, including mitochondrial defects, age-related RGC loss, optic nerve degeneration, and reduced RGC functions. We identified SARM1, a neurodegeneration switch, as a key driver of RGC degeneration in these mice. Sarm1 knockout nearly completely suppressed all the degeneration phenotypes without reversing mitochondrial fragmentation. Additionally, we showed that a portion of SARM1 localized within the mitochondrial intermembrane space (IMS). These findings indicated that SARM1 was activated downstream of mitochondrial dysfunction in ADOA, highlighting it as a promising therapeutic target.

Authors

Chen Ding, Papa S. Ndiaye, Sydney R. Campbell, Michelle Y. Fry, Jincheng Gong, Sophia R. Wienbar, Whitney Gibbs, Philippe Morquette, Luke H. Chao, Michael Tri H. Do, Thomas Schwarz

The tumor suppressor HNRNPK induces p53-dependent nucleolar stress to drive ribosomopathies

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Abstract

The nucleolus is a membraneless organelle and an excellent stress sensor. Any changes in its architecture or composition lead to nucleolar stress, resulting in cell cycle arrest and interruption of ribosomal activity, critical factors in aging and cancer. In this study, we identified and described the pivotal role of the RNA-binding protein (RBP) HNRNPK in ribosome and nucleolar dynamics. We developed an in vitro model of endogenous HNRNPK overexpression and an in vivo mouse model of ubiquitous HNRNPK overexpression. These models showed disruptions in translation and caused alterations in the nucleolar structure, resulting in p53-dependent nucleolar stress, cell cycle arrest, senescence, and bone marrow failure phenotype, similar to what is observed in patients with ribosomopathies. Together, our findings identify HNRNPK as a master regulator of ribosome biogenesis (RiBi) and nucleolar homeostasis through p53, providing a new perspective on the orchestration of nucleolar integrity, ribosome function and cellular senescence.

Authors

Pedro Aguilar-Garrido, María Velasco-Estévez, Miguel Ángel Navarro-Aguadero, Alvaro Otero-Sobrino, Marta Ibañez-Navarro, Miguel Ángel Marugal, María Hernández-Sánchez, Prerna Malaney, Ashley Rodriguez, Oscar Benitez, Xiaorui Zhang, Marisa J.L. Aitken, Alejandra Ortiz-Ruiz, Diego Megias, Manuel Pérez-Martínez, Gadea Mata, Jesús Gomez, Miguel Lafarga, Orlando Dominguez, Osvaldo Graña-Castro, Eduardo Caleiras, Pilar Ximenez-Embun, Marta Isasa, Paloma J. de Andrés, Sandra Rodriguez-Perales, Raul Torres-Ruiz, Enrique Revilla, Rosa María García-Martín, Daniel Azorín, Josune Zubicaray, Julian Sevilla, Oleksandra Sirozh, Vanesa Lafarga, Joaquín Martinez-Lopez, Sean M. Post, Miguel Gallardo

Thrombospondin-1 inhibits alternative complement pathway activation in antineutrophil cytoplasmic antibody-associated vasculitis

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Abstract

Complement activation is a relevant driver in the pathomechanisms of vasculitis. The involved proteins in the interaction between endothelia, complement and platelets in these conditions are only partially understood. Thrombospondin-1 (TSP-1), found in platelet α-granules and released from activated endothelial cells, interacts with factor H (FH) and von Willebrand factor (vWF). However, direct regulatory interaction with the complement cascade has not yet been described. We could show that TSP-1 is a potent, FH-independent inhibitor of the alternative complement pathway. TSP-1 binds to complement proteins, inhibits cleavage of C3 and C5 and the formation of the membrane attack complex. Complement-regulatory function is validated in blood samples from patients with primary complement defects. Physiological relevance of TSP-1 is demonstrated in ANCA-associated vasculitis (AAV) patients by significantly enhanced TSP-1 staining in glomerular lesions and increased complement activity and NETosis following TSP-1 deficiency in an in vitro and in vivo model of AAV. The newly described complement-inhibiting function of TSP-1 represents an important mechanism in the interaction of endothelia and complement. In particular, the interplay between released TSP-1 and the complement system locally, especially on surfaces, influences the balance between complement activation and inhibition and may be relevant in various vascular diseases.

Authors

Swagata Konwar, Sophie Schroda, Manuel Rogg, Jessika Kleindienst, Eva L. Decker, Martin Pohl, Barbara Zieger, Jens Peter Panse, Hong Wang, Robert Grosse, Christoph Schell, Sabine Vidal, Xiaobo Liu, Christian Gorzelanny, Todor Tschongov, Karsten Häffner

NK cell activation and CD4 T cell α4β7 expression are associated with susceptibility to HIV-1

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Abstract

We leveraged specimens from the RV217 prospective study that enrolled participants at high risk of HIV-1 acquisition to investigate how NK, conventional T cells, and unconventional T cells influence HIV-1 acquisition. We observed low levels of α4β7 expression on memory CD4 T cells and iNKT cells, two cell types highly susceptible to HIV-1 infection, in highly exposed seronegative (HESN) compared to highly exposed seroconverter (HESC) participants. NK cells from HESN had higher levels of α4β7 compared to HESC, presented a quiescent phenotype, and had a higher capacity to respond to opsonized target cells. We also measured translocated microbial products in plasma and found differences in phylum distribution between HESN and HESC that were associated with the immune phenotypes impacting the risk of HIV-1 acquisition. Finally, a logistic regression model combining features of NK cells activation, α4β7 expression on memory CD4 T cells, and Tbet expression by iNKT cells achieved the highest accuracy in identifying HESN and HESC participants. This immune signature comprised of increased α4β7 on cells susceptible to HIV infection combined with higher NK cells activation and lower gut homing potential could impact the efficacy of HIV-1 prevention strategies such as vaccines.

Authors

Kawthar Machmach, Kombo F. N'guessan, Rohit Farmer, Sucheta Godbole, Dohoon Kim, Lauren McCormick, Noemia S. Lima, Amy R. Henry, Farida Laboune, Isabella Swafford, Sydney K. Mika, Bonnie M. Slike, Jeffrey R. Currier, Leigh Anne Eller, Julie A. Ake, Sandhya Vasan, Merlin L. Robb, Shelly J. Krebs, Daniel C. Douek, Dominic Paquin-Proulx

PPIL2 is a target of the JAK2/STAT5 pathway and promotes myeloproliferation via p53-mediated degradation

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Abstract

The activated JAK2/STAT pathway is characteristic of myeloproliferative neoplasms (MPNs). Pleckstrin-2 (PLEK2) signalosome is downstream of the JAK2/STAT5 pathway and plays an important role in MPN development. The detailed molecular composition of this signalosome is unclear. Here, we revealed peptidylprolyl isomerase-like 2 (PPIL2) as a critical component of the complex in regulating human and murine erythropoiesis. PPIL2 was a direct target of STAT5 and was upregulated in MPN patients and a Jak2V617F MPN mouse model. Mechanistically, PPIL2 interacted with and catalyzed p53 polyubiquitination and proteasome-mediated degradation to promote cell growth. Ppil2 deficiency, or inhibition by cyclosporin A, led to a marked upregulation of p53 in vivo and ameliorated myeloproliferative phenotypes in Jak2V617F mice. Cyclosporin A also markedly reduced JAK2 mutated erythroid and myeloid proliferation in an induced pluripotent stem cell-derived human bone marrow organoid model. Our findings revealed PPIL2 as a critical component of the PLEK2 signalosome in driving MPN pathogenesis through negatively regulating p53, thus providing a target and an opportunity for drug repurposing by using cyclosporin A to treat MPNs.

Authors

Pan Wang, Xu Han, Kehan Ren, Ermin Li, Honghao Bi, Inci Aydemir, Madina Sukhanova, Yijie Liu, Jing Yang, Peng Ji

GluN2B suppression restores phenylalanine-induced neuroplasticity and cognition impairments in a mouse model of phenylketonuria

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Abstract

Phenylketonuria (PKU), an inborn error of phenylalanine (Phe) metabolism, is a common cause of intellectual disability. However, the mechanisms by which elevated phenylalanine (Phe) levels cause cognitive impairment remain unclear. Here, we show that submillimolar Phe perturbs synaptic plasticity through the hyperactivation of GluN2B-containing NMDARs. PahEnu2 PKU model mice exhibited submillimolar and supramillimolar concentrations of Phe in the cerebrospinal fluid (CSF) and serum, respectively. L-Phe produced concentration-dependent bidirectional effects on NMDA-induced currents, without affecting synaptic NMDARs in hippocampal CA1 neurons. L-Phe-induced hyperactivation of extrasynaptic GluN2B resulted in activity-dependent downregulation of AMPARs during burst or sustained synaptic activity. Administration of L-Phe in mice decreased neural activity and impaired memory, which were blocked by pretreatment with GluN2B inhibitors. Furthermore, pharmacological and virus-mediated suppression of GluN2B reversed the impaired learning in PahEnu2 mice. Collectively, these results suggest that the concentration of Phe in the CSF of patients with PKU perturbs extrasynaptic NMDARs and synaptic plasticity, and that suppression of GluN2B may have the potential to improve cognitive function in patients with PKU.

Authors

Woo Seok Song, Young Sook Kim, Young-Soo Bae, Sang Ho Yoon, Jae Min Lim, Myoung-Hwan Kim

Tebentafusp elicits on-target cutaneous immune responses driven by cytotoxic T-cells in uveal melanoma patients

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Abstract

Background: Tebentafusp is the first T-cell receptor-based bispecific protein approved for clinical use in HLA-A*02:01+ adult patients with unresectable/metastatic uveal melanoma. It redirects T-cells toward gp100-expressing target cells, frequently inducing skin-related early adverse events. Methods: This study investigated immunological and cellular responses using single-cell and spatial analysis of skin biopsies from patients with metastatic uveal melanoma treated with tebentafusp. Results: 81.8% of patients developed acute cutaneous adverse events, which correlated with improved survival. Multimodal analysis revealed a brisk infiltration of CD4+ and CD8+ T-cells, while melanocyte numbers declined. Single-cell RNA-sequencing revealed T-cell activation, proliferation, and IFN-γ/cytotoxic gene upregulation. CD8+ T-cells co-localized with melanocytes and upregulated LAG3, suggesting potential for combination therapies with tebentafusp. Melanocytes upregulated antigen presentation and apoptotic pathways, while pigmentation gene expression decreased. However, gp100 remained stably expressed. Conclusion: Sequential skin biopsies enable in vivo pharmacodynamic modeling of tebentafusp, offering insights into immune activation, toxicity, and treatment response. Examining the on-target effects of bispecifics in tissues amenable to longitudinal sampling enhances our understanding of toxicity and therapeutic escape mechanisms, guiding strategies for treatment optimization.

Authors

Ramon Staeger, Aizhan Tastanova, Adhideb Ghosh, Nicola Winkelbeiner, Prachi Shukla, Isabel Kolm, Patrick Turko, Adel Benlahrech, Jane Harper, Anna Broomfield, Antonio Camera, Marianna Ambrosio, Veronika Haunerdinger, Phil F. Cheng, Egle Ramelyte, James P. Pham, Stefanie Kreutmair, Burkhard Becher, Mitchell P. Levesque, Reinhard Dummer, Barbara Meier-Schiesser

Widespread distribution of transcriptionally active, clonally expanded, HIV-1 proviruses despite suppressive antiretroviral therapy

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Abstract

The rapid viral rebound observed following treatment interruption, despite prolonged time on antiretroviral therapy with plasma HIV-RNA levels <40 copies/mL, suggests persistent HIV-1 reservoir(s) outside of the blood. Studies of HIV-1 proviruses in autopsy tissue samples have hinted at their persistence. However, their distribution across different anatomical compartments and their transcriptional activity within tissues remains unclear. The present study has examined molecular DNA and RNA reservoirs of HIV-1 in autopsy samples from 13 individuals with HIV-1 infection. Of the 13, 5 had detectable levels of HIV-1 RNA in plasma while 8 did not. Cell associated HIV-RNA was detected in 12 out of 13 donors and in 27 of the 30 different tissues examined. HIV-specific DNA and RNA were widely distributed and predominantly associated with clonal expansions. No significant differences were noted between the groups and no tissues were preferentially affected. These data imply that a substantial seeding of tissues with cells harboring transcriptionally active proviral DNA can be seen in the setting of HIV-1 infection despite ART and highlight one of the challenges in achieving an HIV-1 cure.

Authors

Hiromi Imamichi, Ven Natarajan, Francesca Scrimieri, Mindy Smith, Yunden Badralmaa, Marjorie Bosche, Jack M. Hensien, Thomas Buerkert, Weizhong Chang, Brad T. Sherman, Kanal Singh, H. Clifford Lane

OCA-B promotes pathogenic maturation of stem-like CD4⁺ T cells and autoimmune demyelination

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Abstract

Stem-like T cells selectively contribute to autoimmunity, but the activities that promote their pathogenicity are incompletely understood. Here, we identify the transcription coregulator OCA-B as a driver of the pathogenic maturation of stem-like CD4+ T cell to promote autoimmune demyelination. Using two human multiple sclerosis (MS) datasets, we show that POU2AF1, the gene encoding OCA-B, is elevated in CD4+ T cells from MS patients. We show that T cell-intrinsic OCA-B loss protects mice from experimental autoimmune encephalomyelitis (EAE) while preserving responses to viral CNS infection. In EAE models driven by antigen reencounter, OCA-B deletion nearly eliminates CNS infiltration, proinflammatory cytokine production and clinical disease. OCA-B-expressing CD4+ T cells of mice primed with autoantigen express an encephalitogenic gene program and preferentially confer disease. In a relapsing-remitting EAE model, OCA-B loss protects mice specifically at relapse. During remission, OCA-B promotes the expression of Tcf7, Slamf6, and Sell in proliferating CNS T cell populations. At relapse timepoints, OCA-B loss results in both the accumulation of an immunomodulatory CD4+ T cell population expressing Ccr9 and Bach2, and loss of pro-inflammatory gene expression from Th17 cells. These results identify OCA-B as a driver of pathogenic CD4+ T cells.

Authors

Erik P. Hughes, Amber R. Syage, Elnaz Mirzaei Mehrabad, Thomas E. Lane, Benjamin T. Spike, Dean Tantin

DNA demethylating agents suppress preclinical models of synovial sarcoma

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Abstract

Synovial sarcoma is an aggressive soft tissue cancer driven by the chimeric SS18::SSX fusion oncoprotein, which disrupts chromatin remodeling by combining two antagonistic transcriptional regulators. SS18 participates in BAF complexes that open chromatin, while the SSX genes are cancer-testis antigens that interface with chromatin decorated with monoubiquitinated histone H2A placed by Polycomb repressive complexes (PRCs) activity. Because KDM2B brings PRC to unmethylated CpG islands, it is plausible that methylation directly determines the distribution of SS18::SSX to target loci. Given that synovial sarcoma is also characterized by a peculiarly low DNA hypomethylation profile, we hypothesized that further disturbance of DNA methylation would have a negative impact on synovial sarcoma growth. DNMT1 disruption by CRISPR/Cas9 targeting or pharmacologic inhibition with cytidine analogs 5-aza-2ʹ-deoxycytidine (decitabine) and 5-azacytidine led to decreased genome-wide methylation, redistribution of SS18::SSX, and altered gene expression profiles, most prominently including upregulation of tumor suppressor genes, immune-related genes, and mesenchymal differentiation-related genes. These drugs suppressed growth of synovial sarcoma cell lines and drove cytoreduction in mouse genetic models. DNMT1 inhibitors, already approved for treating myelodysplastic syndromes, warrant further clinical investigation for synovial sarcoma as repurposed, targeted treatments exploiting a vulnerability in the intrinsic biology of this cancer.

Authors

Nobuhiko Hasegawa, Nezha S. Benabdallah, Kyllie Smith-Fry, Li Li, Sarah McCollum, Jinxiu Li, Caelen A. Jones, Lena Wagner, Vineet Dalal, Viola Golde, Anastasija Pejkovska, Lara Carroll, Malay Haldar, Seth M. Pollack, Scott W. Lowe, Torsten O. Nielsen, Ana Banito, Kevin B. Jones