ABSTRACT
The transmembrane protein ß-amyloid precursor protein (APP) is central to the pathophysiology of Alzheimer's disease (AD). The ß-amyloid hypothesis posits that aberrant processing of APP forms neurotoxic ß-amyloid aggregates, which lead to the cognitive impairments observed in AD. Although numerous additional factors contribute to AD, there is a need to better understand the synaptic function of APP. We have found that Drosophila APP-like (APPL) has both shared and non-shared roles at the synapse with Kismet (Kis), a chromatin helicase binding domain (CHD) protein. Kis is the homolog of CHD7 and CHD8, both of which are implicated in neurodevelopmental disorders including CHARGE Syndrome and autism spectrum disorders, respectively. Loss of function mutations in kis and animals expressing human APP and BACE in their central nervous system show reductions in the glutamate receptor subunit, GluRIIC, the GTPase Rab11, and the bone morphogenetic protein (BMP), pMad, at the Drosophila larval neuromuscular junction (NMJ). Similarly, processes like endocytosis, larval locomotion, and neurotransmission are deficient in these animals. Our pharmacological and epistasis experiments indicate that there is a functional relationship between Kis and APPL, but Kis does not regulate appl expression at the larval NMJ. Instead, Kis likely influences the synaptic localization of APPL, possibly by promoting rab11 transcription. These data identify a potential mechanistic connection between chromatin remodeling proteins and aberrant synaptic function in AD.
Subject(s)
Amyloid beta-Protein Precursor , Drosophila Proteins , Neuromuscular Junction , rab GTP-Binding Proteins , Animals , Neuromuscular Junction/metabolism , Drosophila Proteins/metabolism , Drosophila Proteins/genetics , rab GTP-Binding Proteins/metabolism , rab GTP-Binding Proteins/genetics , Amyloid beta-Protein Precursor/metabolism , Amyloid beta-Protein Precursor/genetics , Drosophila melanogaster/metabolism , Drosophila melanogaster/genetics , Synaptic Transmission , Synapses/metabolism , Receptors, Glutamate/metabolism , Receptors, Glutamate/genetics , DNA-Binding Proteins/metabolism , DNA-Binding Proteins/genetics , Humans , DNA Helicases/metabolism , DNA Helicases/genetics , Membrane Proteins , Nerve Tissue Proteins , Homeodomain Proteins , Receptors, Ionotropic GlutamateABSTRACT
HLA-B*27 was one of the first HLA alleles associated with an autoimmune disease, i.e., axial spondyloarthritis (axSpA) and acute anterior uveitis (B27AAU), which cause joint and eye inflammation, respectively. Gastrointestinal inflammation has been suggested as a trigger of axSpA. We recently identified a bacterial peptide (YeiH) that can be presented by HLA-B*27 to expanded public T cell receptors (TCRs) in the joint in axSpA and the eye in B27AAU. While YeiH is present in enteric microbiota and pathogens, additional evidence that pathogenic T cells in HLA-B*27-associated autoimmunity may have had a prior antigenic encounter within the gastrointestinal tract remains lacking. Here, we analyze ocular, synovial, and blood T cells in B27AAU and axSpA, showing that YeiH-specific CD8 T cells express a mucosal gene set and surface proteins consistent with intestinal differentiation, including CD161, integrin α4ß7, and CCR6. In addition, we find an expansion of YeiH-specific CD8 T cells in the blood of axSpA and B27AAU over healthy controls, whereas influenza-specific CD8 T cells were equivalent across groups. Lastly, we demonstrate the dispensability of TRBV9 for antigen recognition. Collectively, our data suggest that, in HLA-B27-associated autoimmunity, early antigen exposure and differentiation of pathogenic CD8 T cells may occur in enteric organs.
ABSTRACT
The tissue-specific drivers of neurosarcoidosis remain poorly defined. To identify cerebrospinal fluid (CSF) specific, antigen-driven T and B cell responses, we performed single-cell RNA sequencing of CSF and blood cells from neurosarcoid participants coupled to T and B cell receptor sequencing. In contrast to pulmonary sarcoidosis, which is driven by CD4 T cells, we found CD8 T cell clonal expansion enriched in the neurosarcoid CSF. These CSF-enriched CD8 T cells were composed of two subsets with differential expression of EBI2, CXCR3, and CXCR4. Lastly, our data suggest that IFNγ signaling may distinguish neurosarcoidosis from other neurological disorders.
Subject(s)
Central Nervous System Diseases , Sarcoidosis , CD4-Positive T-Lymphocytes/metabolism , CD8-Positive T-Lymphocytes/metabolism , Central Nervous System Diseases/cerebrospinal fluid , Humans , Sarcoidosis/cerebrospinal fluidABSTRACT
Objective: To identify molecular features that distinguish individuals with shared clinical features of granulomatous uveitis. Design: Cross-sectional, observational study. Participants: Four eyes from patients with active granulomatous uveitis. Methods: We performed single-cell RNA-sequencing with antigen-receptor sequence analysis to obtain an unbiased gene expression survey of ocular immune cells and identify clonally expanded lymphocytes. Main Outcomes Measures: For each inflamed eye, we measured the proportion of distinct immune cell types, the amount of B or T cell clonal expansion, and the transcriptional profile of T and B cells. Results: Each individual had robust clonal expansion arising from a single T or B cell lineage, suggesting distinct, antigen-driven pathogenic processes in each patient. This variability in clonal expansion was mirrored by individual variability in CD4 T cell populations, whereas ocular CD8 T cells and B cells were more transcriptionally similar between patients. Finally, ocular B cells displayed evidence of class-switching and plasmablast differentiation within the ocular microenvironment, providing additional support for antigen-driven immune responses in granulomatous uveitis. Conclusions: Collectively, our study identified both conserved and individualized features of granulomatous uveitis, illuminating parallel pathophysiologic mechanisms, and suggesting that future personalized therapeutic approaches may be warranted.