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Down syndrome (DS), the genetic condition caused by trisomy 21, is characterized by variable cognitive impairment, immune dysregulation, dysmorphogenesis and increased prevalence of diverse co-occurring conditions. The mechanisms by which trisomy 21 causes these effects remain largely unknown. We demonstrate that triplication of the interferon receptor ( IFNR ) gene cluster on chromosome 21 is necessary for multiple phenotypes in a mouse model of DS. Whole-blood transcriptome analysis demonstrated that IFNR overexpression associates with chronic interferon hyperactivity and inflammation in people with DS. To define the contribution of this locus to DS phenotypes, we used genome editing to correct its copy number in a mouse model of DS, which normalized antiviral responses, prevented heart malformations, ameliorated developmental delays, improved cognition and attenuated craniofacial anomalies. Triplication of the Ifnr locus modulates hallmarks of DS in mice, suggesting that trisomy 21 elicits an interferonopathy potentially amenable to therapeutic intervention. A mouse model of Down syndrome (DS) highlights the importance of triplication of the IFNR gene cluster for a variety of DS-associated traits. Copy number correction resulted in amelioration of multiple phenotypes associated with the condition.

Trisomy 21 (T21) causes Down syndrome (DS), affecting immune and neurological function by ill-defined mechanisms. Here we report a large metabolomics study of plasma and cerebrospinal fluid, showing in independent cohorts that people with DS produce elevated levels of kynurenine and quinolinic acid, two tryptophan catabolites with potent immunosuppressive and neurotoxic properties, respectively. Immune cells of people with DS overexpress IDO1 , the rate-limiting enzyme in the kynurenine pathway (KP) and a known interferon (IFN)-stimulated gene. Furthermore, the levels of IFN-inducible cytokines positively correlate with KP dysregulation. Using metabolic tracing assays, we show that overexpression of IFN receptors encoded on chromosome 21 contribute to enhanced IFN stimulation, thereby causing IDO1 overexpression and kynurenine overproduction in cells with T21. Finally, a mouse model of DS carrying triplication of IFN receptors exhibits KP dysregulation. Together, our results reveal a mechanism by which T21 could drive immunosuppression and neurotoxicity in DS. Down syndrome (DS) is caused by trisomy 21 (T21), but the underlying etiology of the related immune and neurological dysfunction is unclear. Here, the authors show that T21 activates the kynurenine pathway via increased interferon receptor copy number, which could contribute to DS pathophysiology.

Individuals with Down syndrome, the genetic condition caused by trisomy 21, exhibit strong inter-individual variability in terms of developmental phenotypes and diagnosis of co-occurring conditions. The mechanisms underlying this variable developmental and clinical presentation await elucidation. We report an investigation of human chromosome 21 gene overexpression in hundreds of research participants with Down syndrome, which led to the identification of two major subsets of co-expressed genes. Using clustering analyses, we identified three main molecular subtypes of trisomy 21, based on differential overexpression patterns of chromosome 21 genes. We subsequently performed multiomics comparative analyses among subtypes using whole blood transcriptomes, plasma proteomes and metabolomes, and immune cell profiles. These efforts revealed strong heterogeneity in dysregulation of key pathophysiological processes across the three subtypes, underscored by differential multiomics signatures related to inflammation, immunity, cell growth and proliferation, and metabolism. We also observed distinct patterns of immune cell changes across subtypes. These findings provide insights into the molecular heterogeneity of trisomy 21 and lay the foundation for the development of personalized medicine approaches for the clinical management of Down syndrome. Here, the authors reveal variability in chromosome 21 gene overexpression among individuals with Down syndrome, identifying three distinct molecular subtypes. Each subtype exhibits unique biosignatures and immune profiles, offering new insights into the complex biology of Down syndrome.

The most common genetic cause of intellectual and developmental disability is trisomy of human chromosome 21 (trisomy 21) or Down syndrome. Relative to the general population, individuals with Down syndrome heterogeneously experience atypical morphogenesis, a distinct neurocognitive profile, and a unique spectrum of diverse medical conditions that impact every major organ system. How trisomy 21 results in the highly variable manifestations of Down syndrome remains largely unknown and an active area of heavy investigation with therapeutic implications. For example, common inflammatory and metabolic signatures have begun to emerge across various co-occurring conditions in Down syndrome with assorted impacts on diverse yet intertwined organ systems that could directly or indirectly impact brain health. Here, we review current progress, resources, knowledge gaps, and bottlenecks for precision medicine approaches to promote brain health across the lifespan among individuals with Down syndrome within the larger context of research efforts geared towards our other distinct yet intertwined organ systems. Within this framework, we advocate for interdisciplinary pursuit of systems-level biomarkers to facilitate holistic intervention strategies that precisely benefit individuals with trisomy 21 each experiencing Down syndrome in their own unique way. To this end, we quantitatively assess clinical studies that are actively recruiting participants with Down syndrome and provide historical context through summary figures sourced to user-friendly tables that have been curated from federal websites to empower efficient exploration of research opportunities for interdisciplinary collaborations.

The emergence of SARS-CoV-2, which causes COVID-19, has led to over 400 million reported cases worldwide. COVID-19 disease ranges from asymptomatic infection to severe disease and may be impacted by individual immune differences. We used multiparameter flow cytometry to compare CD4+ and CD8+ T cell responses in severe (ICU admitted) and non-severe (admitted to observational unit) hospitalized COVID-19 patients. We found that patients with severe COVID- 19 had greater frequencies of CD4+ T cells expressing CD62L compared to non-severe patients and greater frequencies of perforin+ CD8+ T cells compared to recovered patients. Furthermore, greater frequencies of CD62L+ CD4+ and CD8+ T cells were seen in severely ill diabetic patients compared to non-severe and non-diabetic patients, and increased CD62L+ CD4+ T cells were also seen in severely ill patients with hypertension. This is the first report to show that CD62L+ T cells and perforin+ T cells are associated with severe COVID-19 illness and are significantly increased in patients with high-risk pre-existing conditions including older age and diabetes. These data provide a potential biological marker for severe COVID-19.

Individuals with Down syndrome (DS), the genetic condition caused by trisomy 21 (T21), display clear signs of immune dysregulation, including high rates of autoimmunity and severe complications from infections. Although it is well established that T21 causes increased interferon responses and JAK/STAT signaling, elevated autoantibodies, global immune remodeling, and hypercytokinemia, the interplay between these processes, the clinical manifestations of DS, and potential therapeutic interventions remain ill defined. We report a comprehensive analysis of immune dysregulation at the clinical, cellular, and molecular level in hundreds of individuals with DS, including autoantibody profiling, cytokine analysis, and deep immune mapping. We also report the interim analysis of a Phase II clinical trial investigating the safety and efficacy of the JAK inhibitor tofacitinib through multiple clinical and molecular endpoints. We demonstrate multi-organ autoimmunity of pediatric onset concurrent with unexpected autoantibody-phenotype associations in DS. Importantly, constitutive immune remodeling and hypercytokinemia occur from an early age prior to autoimmune diagnoses or autoantibody production. Analysis of the first 10 participants to complete 16 weeks of tofacitinib treatment shows a good safety profile and no serious adverse events. Treatment reduced skin pathology in alopecia areata, psoriasis, and atopic dermatitis, while decreasing interferon scores, cytokine scores, and levels of pathogenic autoantibodies without overt immune suppression. JAK inhibition is a valid strategy to treat autoimmune conditions in DS. Additional research is needed to define the effects of JAK inhibition on the broader developmental and clinical hallmarks of DS. NIAMS, Global Down Syndrome Foundation. NCT04246372.

Trisomy 21 (T21) causes Down syndrome (DS), a condition characterized by high prevalence of autoimmune disorders. However, the molecular and cellular mechanisms driving this phenotype remain unclear. Building upon our previous finding that T cells from people with DS show increased expression of interferon (IFN)-stimulated genes, we have completed a comprehensive characterization of the peripheral T cell compartment in adults with DS with and without autoimmune conditions. CD8+ T cells from adults with DS are depleted of naïve subsets and enriched for differentiated subsets, express higher levels of markers of activation and senescence (e.g., IFN-γ, Granzyme B, PD-1, KLRG1), and overproduce cytokines tied to autoimmunity (e.g., TNF-α). Conventional CD4+ T cells display increased differentiation, polarization toward the Th1 and Th1/17 states, and overproduction of the autoimmunity-related cytokines IL-17A and IL-22. Plasma cytokine analysis confirms elevation of multiple autoimmunity-related cytokines (e.g., TNF-α, IL17A–D, IL-22) in people with DS, independent of diagnosis of autoimmunity. Although Tregs are more abundant in DS, functional assays show that CD8+ and CD4+ effector T cells with T21 are resistant to Treg-mediated suppression, regardless of Treg karyotype. Transcriptome analysis ofwhite blood cells and T cells reveals strong signatures of T cell differentiation and activation that correlate positively with IFN hyperactivity. Finally, mass cytometry analysis of 8 IFN-inducible phosphoepitopes demonstrates that T cell subsets with T21 show elevated levels of basal IFN signaling and hypersensitivity to IFN-α stimulation. Therefore, these results point to T cell dysregulation associated with IFN hyperactivity as a contributor to autoimmunity in DS.

The most common genetic cause of intellectual and developmental disability is trisomy of human chromosome 21 (trisomy 21) or Down syndrome. Relative to the general population, individuals with Down syndrome heterogeneously experience atypical morphogenesis, a distinct neurocognitive profile, and a unique spectrum of diverse medical conditions that impact every major organ system. How trisomy 21 results in the highly variable manifestations of Down syndrome remains largely unknown and an active area of heavy investigation with therapeutic implications. For example, common inflammatory and metabolic signatures have begun to emerge across various co-occurring conditions in Down syndrome with assorted impacts on diverse yet intertwined organ systems that could directly or indirectly impact brain health. Here, we review current progress, resources, knowledge gaps, and bottlenecks for precision medicine approaches to promote brain health across the lifespan among individuals with Down syndrome within the larger context of research efforts geared towards our other distinct yet intertwined organ systems. Within this framework, we advocate for interdisciplinary pursuit of systems-level biomarkers to facilitate holistic intervention strategies that precisely benefit individuals with trisomy 21 each experiencing Down syndrome in their own unique way. To this end, we quantitatively assess clinical studies that are actively recruiting participants with Down syndrome and provide historical context through summary figures sourced to user-friendly tables that have been curated from federal websites to empower efficient exploration of research opportunities for interdisciplinary collaborations.

Trisomy 21 (T21) gives rise to Down syndrome (DS), the most commonly occurring chromosomal abnormality in humans. T21 affects nearly every organ and tissue system in the body, predisposing individuals with DS to congenital heart defects, autoimmunity, and Alzheimer's disease, among other co-occurring conditions. Here, using multi-omic analysis of plasma from more than 400 people, we report broad metabolic changes in the population with DS typified by increased bile acid levels and protein signatures of liver dysfunction. In a mouse model of DS, we demonstrate conservation of perturbed bile acid metabolism accompanied by liver pathology. Bulk RNA-sequencing revealed widespread impacts of the Dp16 model on hepatic metabolism and inflammation, while single-cell transcriptomics highlighted cell types associated with these observations. Modulation of dietary fat profoundly impacted gene expression, bile acids, and liver pathology. Overall, these data represent evidence for altered hepatic metabolism in DS that could be modulated by diet.