TCRαβ+CD8αα+ intraepithelial lymphocytes (CD8αα+ αβ IELs) are a specialized subset of T cells in the gut epithelium that develop from thymic agonist selected IEL precursors (IELps). The molecular mechanisms underlying the selection and differentiation of this T cell type in the thymus are largely unknown. Here, we found that Bcl6 deficiency in αβ T cells resulted in the near absence of CD8αα+ αβ IELs. BCL6 was expressed by approximately 50% of CD8αα+ αβ IELs and by the majority of thymic PD1+ IELps after agonist selection. Bcl6 deficiency blocked early IELp generation in the thymus, and its expression in IELps was induced by thymic TCR signaling in an ERK-dependent manner. As a result of Bcl6 deficiency, the precursors of IELps among CD4+CD8+ double-positive thymocytes exhibited increased apoptosis during agonist selection and impaired IELp differentiation and maturation. Together, our results elucidate BCL6 as a crucial transcription factor during the thymic development of CD8αα+ αβ IELs.

Atopic dermatitis (AD) is a chronic inflammatory skin disease that often precedes the development of food allergy, asthma, and allergic rhinitis. The prevailing paradigm holds that a reduced frequency and function of natural killer (NK) cell contributes to AD pathogenesis, yet the underlying mechanisms and contributions of NK cells to allergic comorbidities remain ill-defined. Here, analysis of circulating NK cells in a longitudinal early life cohort of children with AD revealed a progressive accumulation of NK cells with low expression of the activating receptor NKG2D, which was linked to more severe AD and sensitivity to allergens. This was most notable in children co-sensitized to food and aeroallergens, a risk factor for development of asthma. Individual-level longitudinal analysis in a subset of children revealed coincident reduction of NKG2D on NK cells with acquired or persistent sensitization, and this was associated with impaired skin barrier function assessed by transepidermal water loss. Low expression of NKG2D on NK cells was paradoxically associated with depressed cytolytic function but exaggerated release of the proinflammatory cytokine tumor necrosis factor-α. These observations provide important insights into a potential mechanism underlying the development of allergic comorbidity in early life in children with AD, which involves altered NK cell functional responses, and define an endotype of severe AD.

Inherited deficiency of the RNA lariat-debranching enzyme 1 (DBR1) is a rare etiology of brainstem viral encephalitis. The cellular basis of disease and the range of viral predisposition are unclear. We report inherited DBR1 deficiency in a 14-year-old boy who suffered from isolated SARS-CoV-2 brainstem encephalitis. The patient is homozygous for a previously reported hypomorphic and pathogenic DBR1 variant (I120T). Consistently, DBR1 I120T/I120T fibroblasts from affected individuals from this and another unrelated kindred have similarly low levels of DBR1 protein and high levels of RNA lariats. DBR1 I120T/I120T human pluripotent stem cell (hPSC)-derived hindbrain neurons are highly susceptible to SARS-CoV-2 infection. Exogenous WT DBR1 expression in DBR1 I120T/I120T fibroblasts and hindbrain neurons rescued the RNA lariat accumulation phenotype. Moreover, expression of exogenous RNA lariats, mimicking DBR1 deficiency, increased the susceptibility of WT hindbrain neurons to SARS-CoV-2 infection. Inborn errors of DBR1 impair hindbrain neuron-intrinsic antiviral immunity, predisposing to viral infections of the brainstem, including that by SARS-CoV-2.

ABSTRACT Foreign language classroom anxiety (FLCA) is ‘a distinct complex set of self-perceptions, beliefs, feelings and behaviours related to classroom language learning arising from the uniqueness of the language learning process’ (Horwitz, Horwitz and Cope 1986: 128) [Foreign language classroom anxiety. The Modern Language Journal 70, no. 2: 125–32] which potentially has a negative impact on achievement and engagement in language learning. The purpose of the investigation reported here was to examine how two online modalities – Zoom video conferencing and the virtual world, Second Life – affected FLCA among Chinese language beginners performing tasks using the different modes. Through statistical and thematical analyses of survey data along with open-ended questions from 55 participants, it was found that the relationship between FLCA levels experienced by learners on these modalities was influenced by various factors such as gender differences, task-related language skills, and self-perceived language proficiency. The study also suggests that FLCA is dependent on the learners’ immediate learning experience, particularly in relation to their level of engagement and task awareness. Despite the small sample size, the study sheds light on the advantages and limitations of each modality in terms of its effect on students’ FLCA and performance in task-based language teaching.

Autoantibody-mediated glomerulonephritis (AGN) arises from dysregulated renal inflammation, with urgent need for improved treatments. IL-17 is implicated in AGN and drives pathology in a kidney-intrinsic manner via renal tubular epithelial cells (RTECs). Nonetheless, downstream signaling mechanisms provoking kidney pathology are poorly understood. A noncanonical RNA binding protein (RBP), Arid5a, was upregulated in human and mouse AGN. Arid5a-/- mice were refractory to AGN, with attenuated myeloid infiltration and impaired expression of IL-17-dependent cytokines and transcription factors (C/EBPβ, C/EBPδ). Transcriptome-wide RIP-Seq revealed that Arid5a inducibly interacts with conventional IL-17 target mRNAs, including CEBPB and CEBPD. Unexpectedly, many Arid5a RNA targets corresponded to translational regulation and RNA processing pathways, including rRNAs. Indeed, global protein synthesis was repressed in Arid5a-deficient cells, and C/EBPs were controlled at the level of protein rather than RNA accumulation. IL-17 prompted Arid5a nuclear export and association with 18S rRNA, a 40S ribosome constituent. Accordingly, IL-17-dependent renal autoimmunity is driven by Arid5a at the level of ribosome interactions and translation.

Dermal fibroblasts deposit type I collagen, the dominant extracellular matrix molecule found in skin, during early postnatal development. Coincident with this biosynthetic program, fibroblasts proteolytically remodel pericellular collagen fibrils by mobilizing the membrane-anchored matrix metalloproteinase, Mmp14. Unexpectedly, dermal fibroblasts in Mmp14-/- mice commit to a large-scale apoptotic program that leaves skin tissues replete with dying cells. A requirement for Mmp14 in dermal fibroblast survival is recapitulated in vitro when cells are embedded within, but not cultured atop, three-dimensional hydrogels of crosslinked type I collagen. In the absence of Mmp14-dependent pericellular proteolysis, dermal fibroblasts fail to trigger β1 integrin activation and instead actuate a TGF-β1/phospho-JNK stress response that leads to apoptotic cell death in vitro as well as in vivo. Taken together, these studies identify Mmp14 as a requisite cell survival factor that maintains dermal fibroblast viability in postnatal dermal tissues.

L-type CaV1.2 current (ICa,L) links electrical excitation to contraction in cardiac myocytes. ICa,L is tightly regulated to control cardiac output. Rad is a Ras-related, monomeric protein that binds to L-type calcium channel β subunits (CaVβ) to promote inhibition of ICa,L. In addition to CaVβ interaction conferred by the Rad core motif, the highly conserved Rad C-terminus can direct membrane association in vitro and inhibition of ICa,L in immortalized cell lines. In this work, we test the hypothesis that in cardiomyocytes the polybasic C-terminus of Rad confers t-tubular localization, and that membrane targeting is required for Rad-dependent ICa,L regulation. We introduced a 3xFlag epitope to the N-terminus of the endogenous mouse Rrad gene to facilitate analysis of subcellular localization. Full-length 3xFlag-Rad (Flag-Rad) mice were compared with a second transgenic mouse model, in which the extended polybasic C-termini of 3xFlag-Rad was truncated at alanine 277 (Flag-RadΔCT). Ventricular cardiomyocytes were isolated for anti-Flag-Rad immunocytochemistry and ex vivo electrophysiology. Full-length Flag-Rad showed a repeating t-tubular pattern whereas Flag-RadΔCT failed to display membrane association. ICa,L in Flag-RadΔCT cardiomyocytes showed a hyperpolarized activation midpoint and an increase in maximal conductance. Additionally, current decay was faster in Flag-RadΔCT cells. Myocardial ICa,L in a Rad C-terminal deletion model phenocopies ICa,L modulated in response to β-AR stimulation. Mechanistically, the polybasic Rad C-terminus confers CaV1.2 regulation via membrane association. Interfering with Rad membrane association constitutes a specific target for boosting heart function as a treatment for heart failure with reduced ejection fraction.

Adaptive immune cell function is regulated by a highly diverse receptor recombined from variable germline-encoded segments that can recognize an almost unlimited array of epitopes. While this diversity enables the recognition of any pathogen, it also poses a risk of self-recognition, leading to autoimmunity. Many layers of regulation are present during both the generation and activation of B cells to prevent this phenomenon, although they are evidently imperfect. In recent years, our ability to analyze immune repertoires at scale has drastically increased, both through advances in sequencing and single-cell analyses. Here, we review the current knowledge on B cell repertoire analyses, focusing on their implication for autoimmunity. These studies demonstrate that a failure of tolerance occurs at multiple independent checkpoints in different autoimmune contexts, particularly during B cell maturation, plasmablast differentiation, and within germinal centers. These failures are marked by distinct repertoire features that may be used to identify disease- or patient-specific therapeutic approaches.