The unfolded protein response of the endoplasmic reticulum protects Caenorhabditis elegans against DNA damage caused by stalled replication forks

All animals must maintain genome and proteome integrity, especially when experiencing endogenous or exogenous stress. To cope, organisms have evolved sophisticated and conserved response systems: unfolded protein responses (UPRs) ensure proteostasis, while DNA damage responses (DDRs) maintain genome integrity. Emerging evidence suggests that UPRs and DDRs crosstalk, but this remains poorly understood. Here, we demonstrate that depletion of the DNA primases pri-1 or pri-2, which synthesize RNA primers at replication forks and whose inactivation causes DNA damage, activates the UPR of the endoplasmic reticulum (UPR-ER) in Caenorhabditis elegans, with especially strong activation in the germline. We observed activation of both the inositol-requiring-enzyme 1 (ire-1) and the protein kinase RNA-like endoplasmic reticulum kinase (pek-1) branches of the (UPR-ER). Interestingly, activation of the (UPR-ER) output gene heat shock protein 4 (hsp-4) was partially independent of its canonical activators, ire-1 and X-box binding protein (xbp-1), and instead required the third branch of the (UPR-ER), activating transcription factor 6 (atf-6), suggesting functional redundancy. We further found that primase depletion specifically induces the (UPR-ER), but not the distinct cytosolic or mitochondrial UPRs, suggesting that primase inactivation causes compartment-specific rather than global stress. Functionally, loss of ire-1 or pek-1 sensitizes animals to replication stress caused by hydroxyurea. Finally, transcriptome analysis of pri-1 embryos revealed several deregulated processes that could cause (UPR-ER) activation, including protein glycosylation, calcium signaling, and fatty acid desaturation. Together, our data show that the (UPR-ER), but not other UPRs, responds to replication fork stress and that the (UPR-ER) is required to alleviate this stress.

Claudin-11 in health and disease: implications for myelin disorders, hearing, and fertility

Claudin-11 plays a critical role in multiple physiological processes, including myelination, auditory function, and spermatogenesis. Recently, stop-loss mutations in CLDN11 have been identified as a novel cause of hypomyelinating leukodystrophy (HLD22). Understanding the multifaceted roles of claudin-11 and the potential pathogenic mechanisms in HLD22 is crucial for devising targeted therapeutic strategies. This review outlines the biological roles of claudin-11 and the implications of claudin-11 loss in the context of the Cldn11 null mouse model. Additionally, HLD22 and proposed pathogenic mechanisms, such as endoplasmic reticulum stress, will be discussed.

Activation of the cGAS-STING innate immune response in cells with deficient mitochondrial topoisomerase TOP1MT

The recognition that cytosolic mitochondrial DNA (mtDNA) activates cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) innate immune signaling has unlocked novel disease mechanisms. Here, an uncharacterized variant predicted to affect TOP1MT function, P193L, was discovered in a family with multiple early onset autoimmune diseases, including Systemic Lupus Erythematosus (SLE). Although there was no previous genetic association between TOP1MT and autoimmune disease, the role of TOP1MT as a regulator of mtDNA led us to investigate whether TOP1MT could mediate the release of mtDNA to the cytosol, where it could then activate the cGAS-STING innate immune pathway known to be activated in SLE and other autoimmune diseases. Through analysis of cells with reduced TOP1MT expression, we show that loss of TOP1MT results in release of mtDNA to the cytosol, which activates the cGAS-STING pathway. We also characterized the P193L variant for its ability to rescue several TOP1MT functions when expressed in TOP1MT knockout cells. We show that the P193L variant is not fully functional, as its re-expression at high levels was unable to rescue mitochondrial respiration deficits, and only showed partial rescue for other functions, including repletion of mtDNA replication following depletion, nucleoid size, steady state mtDNA transcripts levels and mitochondrial morphology. Additionally, expression of P193L at endogenous levels was unable to rescue mtDNA release-mediated cGAS-STING signaling. Overall, we report a link between TOP1MT and mtDNA release leading to cGAS-STING activation. Moreover, we show that the P193L variant has partial loss of function that may contribute to autoimmune disease susceptibility via cGAS-STING mediated activation of the innate immune system.

T-cell activation-induced marker assays in health and disease

Activation-induced marker (AIM) assays have proven to be an accessible and rapid means of antigen-specific T-cell detection. The method typically involves short-term incubation of whole blood or peripheral blood mononuclear cells with antigens of interest, where autologous antigen-presenting cells process and present peptides in complex with major histocompatibility complex (MHC) molecules. Recognition of peptide-MHC complexes by T-cell receptors then induces upregulation of activation markers on the T cells that can be detected by flow cytometry. In this review, we highlight the most widely used activation markers for assays in the literature while identifying nuances and potential downfalls associated with the technique. We provide a summary of how AIM assays have been used in both discovery science and clinical studies, including studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunity. This review primarily focuses on AIM assays using human blood or peripheral blood mononuclear cell samples, with some considerations noted for tissue-derived T cells and nonhuman samples. AIM assays are a powerful tool that enables detailed analysis of antigen-specific T-cell frequency, phenotype and function without needing to know the precise antigenic peptides and their MHC restriction elements, enabling a wider analysis of immunity generated following infection and/or vaccination.

Generation of tandem alternative splice acceptor sites and CLTC haploinsufficiency: A cause of CLTC-related disorder

Tandem splice acceptors (NAGN_n AG) are a common mechanism of alternative splicing, but variants that are likely to generate or to disrupt tandem splice sites have rarely been reported as disease causing. We identify a pathogenic intron 23 CLTC variant (NM_004859.4:c.[3766-13_3766-5del];[=]) in a propositus with intellectual disability and behavioral problems. By RNAseq analysis of peripheral blood mRNA, this variant generates transcripts using cryptic proximal splice acceptors (NM_004859.4: r.3765_3766insTTCACAGAAAGGAACTAG, and NM_004859.4:r.3765_3766insAAAGGAACTAG). Given that the propositus expresses 38% the level of CLTC transcripts as unaffected controls, these variant transcripts, which encode premature termination codons, likely undergo nonsense mediated mRNA decay (NMD). This is the first functional evidence for CLTC haploinsufficiency as a cause of CLTC-related disorder and the first evidence that the generation of tandem alternative splice sites causes CLTC-related disorder. We suggest that variants creating tandem alternative splice sites are an underreported disease mechanism and that transcriptome-level analysis should be routinely pursued to define the pathogenicity of such variants.

Canadian infants presenting with Brief Resolved Unexplained Events (BRUEs) and validation of clinical prediction rules for risk stratification: a protocol for a multicentre, retrospective cohort study

INTRODUCTION

Brief Resolved Unexplained Events (BRUEs) are a common presentation among infants. While most of these events are benign and self-limited, guidelines published by the American Academy of Pediatrics inaccurately identify many patients as higher-risk of a serious underlying aetiology (positive predictive value 5%). Recently, new clinical prediction rules have been derived to more accurately stratify patients. This data were however geographically limited to the USA, with no large studies to date assessing the BRUE population in a different healthcare setting. The study's aim is to describe the clinical management and outcomes of infants presenting to Canadian hospitals with BRUEs and to externally validate the BRUE clinical prediction rules in identified cases.

METHODS AND ANALYSIS

This is a multicentre retrospective study, conducted within the Canadian Paediatric Inpatient Research Network (PIRN). Infants (<1 year) presenting with a BRUE at one of 11 Canadian paediatric centres between 1 January 2017 and 31 December 2021 will be included. Eligible patients will be identified using diagnostic codes.The primary outcome will be the presence of a serious underlying illness. Secondary outcomes will include BRUE recurrence and length of hospital stay. We will describe the rates of hospital admissions and whether hospitalisation was associated with an earlier diagnosis or treatment. Variation across Canadian hospitals will be assessed using intraclass correlation coefficient. To validate the newly developed clinical prediction rule, measures of goodness of fit will be evaluated. For this validation, a sample size of 1182 is required to provide a power of 80% to detect patients with a serious underlying illness with a significance level of 5%.

ETHICS AND DISSEMINATION

Ethics approval has been granted by the UBC Children's and Women's Research Board (H21-02357). The results of this study will be disseminated as peer-reviewed manuscripts and presentations at national and international conferences.

Calcium-dependent transcriptional changes in human pancreatic islet cells reveal functional diversity in islet cell subtypes

AIMS/HYPOTHESIS

Pancreatic islets depend on cytosolic calcium (Ca²⁺) to trigger the secretion of glucoregulatory hormones and trigger transcriptional regulation of genes important for islet response to stimuli. To date, there has not been an attempt to profile Ca²⁺-regulated gene expression in all islet cell types. Our aim was to construct a large single-cell transcriptomic dataset from human islets exposed to conditions that would acutely induce or inhibit intracellular Ca²⁺ signalling, while preserving biological heterogeneity.

METHODS

We exposed intact human islets from three donors to the following conditions: (1) 2.8 mmol/l glucose; (2) 16 mmol/l glucose and 40 mmol/l KCl to maximally stimulate Ca²⁺ signalling; and (3) 16 mmol/l glucose, 40 mmol/l KCl and 5 mmol/l EGTA (Ca²⁺ chelator) to inhibit Ca²⁺ signalling, for 1 h. We sequenced 68,650 cells from all islet cell types, and further subsetted the cells to form an endocrine cell-specific dataset of 59,373 cells expressing INS, GCG, SST or PPY. We compared transcriptomes across conditions to determine the differentially expressed Ca²⁺-regulated genes in each endocrine cell type, and in each endocrine cell subcluster of alpha and beta cells.

RESULTS

Based on the number of Ca²⁺-regulated genes, we found that each alpha and beta cell cluster had a different magnitude of Ca²⁺ response. We also showed that polyhormonal clusters expressing both INS and GCG, or both INS and SST, are defined by Ca²⁺-regulated genes specific to each cluster. Finally, we identified the gene PCDH7 from the beta cell clusters that had the highest number of Ca²⁺-regulated genes, and showed that cells expressing cell surface PCDH7 protein have enhanced glucose-stimulated insulin secretory function.

CONCLUSIONS/INTERPRETATION

Here we use our large-scale, multi-condition, single-cell dataset to show that human islets have cell-type-specific Ca²⁺-regulated gene expression profiles, some of them specific to subpopulations. In our dataset, we identify PCDH7 as a novel marker of beta cells having an increased number of Ca²⁺-regulated genes and enhanced insulin secretory function.

DATA AVAILABILITY

A searchable and user-friendly format of the data in this study, specifically designed for rapid mining of single-cell RNA sequencing data, is available at https://lynnlab.shinyapps.io/Human_Islet_Atlas/ . The raw data files are available at NCBI Gene Expression Omnibus (GSE196715).

Islet prohormone processing in health and disease

Biosynthesis of peptide hormones by pancreatic islet endocrine cells is a tightly orchestrated process that is critical for metabolic homeostasis. Like neuroendocrine peptides, insulin and other islet hormones are first synthesized as larger precursor molecules that are processed to their mature secreted products through a series of proteolytic cleavages, mediated by the prohormone convertases Pc1/3 and Pc2, and carboxypeptidase E. Additional posttranslational modifications including C-terminal amidation of the β-cell peptide islet amyloid polypeptide (IAPP) by peptidyl-glycine α-amidating monooxygenase (Pam) may also occur. Genome-wide association studies (GWAS) have showed genetic linkage of these processing enzymes to obesity, β-cell dysfunction, and type 2 diabetes (T2D), pointing to their important roles in metabolism and blood glucose regulation. In both type 1 diabetes (T1D) and T2D, and in the face of metabolic or inflammatory stresses, islet prohormone processing may become impaired; indeed elevated proinsulin:insulin (PI:I) ratios are a hallmark of the β-cell dysfunction in T2D. Recent studies suggest that genetic or acquired defects in proIAPP processing may lead to the production and secretion of incompletely processed forms of proIAPP that could contribute to T2D pathogenesis, and additionally that impaired processing of both PI and proIAPP may be characteristic of β-cell dysfunction in T1D. In islet α-cells, the prohormone proglucagon is normally processed to bioactive glucagon by Pc2 but may express Pc1/3 under certain conditions leading to production of GLP-1(7-36_NH2 ). A better understanding of how β-cell processing of PI and proIAPP, as well as α-cell processing of proglucagon, are impacted by genetic susceptibility and in the face of diabetogenic stresses, may lead to new therapeutic approaches for improving islet function in diabetes.

What are effective strategies for implementing trauma-informed care in youth inpatient psychiatric and residential treatment settings? A realist systematic review

BACKGROUND

Many young people who receive psychiatric care in inpatient or residential settings in North America have experienced various forms of emotional trauma. Moreover, these settings can exacerbate trauma sequelae. Common practices, such as seclusion and restraint, put young people at risk of retraumatization, development of comorbid psychopathology, injury, and even death. In response, psychiatric and residential facilities have embraced trauma-informed care (TIC), an organizational change strategy which aligns service delivery with treatment principles and discrete interventions designed to reduce rates of retraumatization through responsive and non-coercive staff-client interactions. After more than two decades, a number of TIC frameworks and approaches have shown favorable results. Largely unexamined, however, are the features that lead to successful implementation of TIC, especially in child and adolescent inpatient psychiatric and residential settings.

METHODS

Using methods proposed by Pawson et al. (J Health Serv Res Policy 10:21-34, 2005), we conducted a modified five-stage realist systematic review of peer-reviewed TIC literature. We rigorously searched ten electronic databases for peer reviewed publications appearing between 2000 and 2015 linking terms "trauma-informed" and "child*" or "youth," plus "inpatient" or "residential" plus "psych*" or "mental." After screening 693 unique abstracts, we selected 13 articles which described TIC interventions in youth psychiatric or residential settings. We designed a theoretically-based evaluative framework using the active implementation cycles of the National Implementation Research Network (NIRN) to discern which foci were associated with effective TIC implementation. Excluded were statewide mental health initiatives and TIC implementations in outpatient mental health, child welfare, and education settings. Interventions examined included: Attachment, Self-Regulation, and Competency Framework; Six Core Strategies; Collaborative Problem Solving; Sanctuary Model; Risking Connection; and the Fairy Tale Model.

RESULTS

Five factors were instrumental in implementing trauma informed care across a spectrum of initiatives: senior leadership commitment, sufficient staff support, amplifying the voices of patients and families, aligning policy and programming with trauma informed principles, and using data to help motivate change.

CONCLUSIONS

Reduction or elimination of coercive measures may be achieved by explicitly targeting specific coercive measures or by implementing broader therapeutic models. Additional research is needed to evaluate the efficacy of both approaches.