Julija Mazej

The GGGGCC (G4C2) repeat expansion mutation in C9ORF72 gene is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS). Transcription of the repeat and formation of nuclear RNA foci, which sequester specific RNA-binding proteins is one of the possible pathological mechanisms. Here, we show that (G4C2)n repeat RNA predominantly associates with essential paraspeckle proteins SFPQ, NONO, RBM14, FUS and hnRNPH and co-localizes with known paraspeckle-associated RNA hLinc-p21. As formation of paraspeckles in motor neurons has been associated with early phases of ALS, we investigated the extent of similarity between paraspeckles and (G4C2)n RNA foci. Overexpression of (G4C2)72 RNA results in their increased number and co-localization with SFPQ-stained nuclear bodies. These paraspeckle-like (G4C2)72 RNA foci form independently of the known paraspeckle scaffold, the long non-coding RNA NEAT1. Moreover, the knockdown of SFPQ protein in C9ORF72 expansion mutation positive fibroblasts significantly reduces the number of (G4C2)n RNA foci. In conclusion, (G4C2)n RNA foci have characteristics of paraspeckles, which suggests that both RNA foci and paraspeckles play role in FTD and ALS and implies approaches for regulation of their formation.

Abstract Type 1 innate lymphoid cells (ILC1) are tissue‐resident lymphocytes that provide early protection against bacterial and viral infections. Discrete transcriptional states of ILC1 have been identified in homeostatic and pathological contexts. However, whether these states delineate ILC1 with different functional properties is not completely understood. Here, we show that liver ILC1 are heterogeneous for the expression of distinct effector molecules and surface receptors, including granzyme A (GzmA) and CD160, in mice. ILC1 expressing high levels of GzmA are enriched in the liver of adult mice, and represent the main hepatic ILC1 population at birth. However, the heterogeneity of GzmA and CD160 expression in hepatic ILC1 begins perinatally and increases with age. GzmA + ILC1 differ from NK cells for the limited homeostatic requirements of JAK/STAT signals and the transcription factor Nfil3 . Moreover, by employing Rorc(γt) ‐fate map (fm) reporter mice, we established that ILC3‐ILC1 plasticity contributes to delineate the heterogeneity of liver ILC1, with RORγt‐fm + cells skewed toward a GzmA – CD160 + phenotype. Finally, we showed that ILC1 defined by the expression of GzmA and CD160 are characterized by graded cytotoxic potential and ability to produce IFN‐γ. In conclusion, our findings help deconvoluting ILC1 heterogeneity and provide evidence for functional diversification of liver ILC1.

Natural killer (NK) cells and type 1 innate lymphoid cells (ILC1) require signal transducer and activator of transcription 4 (STAT4) to elicit rapid effector responses and protect against pathogens. By combining genetic and transcriptomic approaches, we uncovered divergent roles for STAT4 in regulating effector differentiation of these functionally related cell types. Stat4 deletion in Ncr1 -expressing cells led to impaired NK cell terminal differentiation as well as to an unexpected increased generation of cytotoxic ILC1 during intestinal inflammation. Mechanistically, Stat4 -deficient ILC1 exhibited upregulation of gene modules regulated by STAT5 in vivo and an aberrant effector differentiation upon in vitro stimulation with IL-2, used as a prototypical STAT5 activator. Moreover, STAT4 expression in NCR + innate lymphocytes restrained gut inflammation in the dextran sulfate sodium-induced colitis model limiting pathogenic production of IL-13 from adaptive CD4 + T cells in the large intestine. Collectively, our data shed light on shared and distinctive mechanisms of STAT4-regulated transcriptional control in NK cells and ILC1 required for intestinal inflammatory responses.

NK cells are critical for immunosurveillance, yet become dysfunctional when chronically stimulated by virally infected or cancerous cells. This phenomenon is similar to T cell exhaustion but less characterized, limiting therapeutic interventions. As shown for T cells, NK cells often display an increased expression of immune checkpoint proteins (ICP) following chronic stimulation, and ICP blockade therapies are currently being explored for several cancer types, with remarkable patient benefits. Nevertheless, the nature of ICP expression in NK cells is still poorly documented. In this study, we aimed to identify the conditions that lead to and the phenotype of immune checkpoint LAG3-expressing NK cells. Using various experimental models, we found that LAG3 is expressed by murine NK cells upon activation in different contexts, including in response to cancer and acute viral infections. LAG3 marks a subset of immature, proliferating, and activated cells, which, despite activation, have a reduced capacity to respond to a broad range of stimuli. Further characterization also revealed that LAG3+ NK cells exhibit a transcriptional signature similar to that of exhausted CD8+ T cells. Taken together, our results support the use of LAG3 as a marker of dysfunctional NK cells across diverse chronic and acute inflammatory conditions.