Transcriptomic Profile of Genes Encoding Proteins Involved in Pathogenesis of Sjögren's Syndrome Related Xerostomia-Molecular and Clinical Trial

Tmed10 deficiency results in impaired exocrine pancreatic differentiation in zebrafish larvae

Transmembrane p24 trafficking protein 10 (TMED10) is a conserved vesicle trafficking protein. It is dysregulated in Alzheimer disease and plays a pivotal role in the pathogenesis of Alzheimer disease. In addition to the brain, TMED10 is highly expressed in the exocrine pancreas; however, its biological functions and underlying mechanisms remain largely unknown. We studied reduced Tmed10 in zebrafish embryos by morpholino oligonucleotide knockdown and CRISPR-Cas9 mutagenesis. Tmed10-deficient embryos showed extensive loss of acinar mass and impaired acinar differentiation. TMED10 has been reported to have an inhibitory effect on γ-secretase. As one of the substrates of γ-secretase, membrane-bound β-catenin was significantly reduced in Tmed10-deficient embryos. Increased γ-secretase activity in wild-type embryos resulted in a phenotype similar to that of tmed10 mutants. And the mutant phenotype could be rescued by treatment with the γ-secretase inhibitor, N-[N-(3, 5-difluorophenacetyl)-l-alanyl]-s-phenylglycinet-butyl ester (DAPT). In addition, the reduced membrane-bound β-catenin was accompanied with up-regulated β-catenin target genes in Tmed10-deficient embryos. Overexpression of β-catenin signaling inhibitor Dickkopf-1 (DKK-1) could rescue the exocrine pancreas defects. Taken together, our study reveals that Tmed10 regulates exocrine pancreatic differentiation through γ-secretase. Reduced membrane-bound β-catenin, accompanied with hyperactivation of β-catenin signaling, is an important cause of exocrine pancreas defects in Tmed10-deficient embryos. Our study reaffirms the importance of appropriate β-catenin signaling in exocrine pancreas development. These findings may provide a theoretical basis for the development of treatment strategies for TMED10-related diseases.

Id4 modulates salivary gland homeostasis and its expression is downregulated in IgG4-related disease via miR-486-5p

Salivary glands are physiologically orchestrated by the coordinated balance between cell differentiation, proliferation, apoptosis, and interactions between epithelial, mesenchymal endothelial, and neuronal cells, and they are frequent sites of manifestations of Sjögren's syndrome (SS) or IgG4-related disease (IgG4-RD). However, little is known about salivary gland homeostasis and its involvement in those diseases. Inhibitor of DNA binding/differentiation 4 (Id4) is an Id protein involved in the transcriptional control of many biological events, including differentiation. Studies of Id4-deficient mice revealed that Id4-deficient submandibular glands were smaller and exhibited accelerated differentiation, compared with those from wild-type littermates. In addition, dry mouth symptoms and Th17 expansion in splenocytes were also observed in the absence of Id4. Furthermore, Id4 levels in the salivary glands of patients with IgG4-RD, but not SS, were significantly decreased compared with those of healthy controls. miRNA-mRNA integrated analysis demonstrated that miR-486-5p was upregulated in IgG4-RD patients and that it might regulate Id4 in the lesion sites. Together, these results provide evidence for the inhibitory role of Id4 in salivary differentiation, and a critical association between Id4 downregulation and IgG4-RD.

Sjogren's Syndrome: Recent Updates

Primary Sjögren's syndrome (SS) is a chronic systemic autoimmune disorder affecting primarily perimenopausal women [...].

Cellular and molecular diversity in Sjogren's syndrome salivary glands: Towards a better definition of disease subsets

Primary Sjögren's syndrome (pSS) is a highly heterogeneous disease in terms of clinical presentation ranging from a mild disease localised to the salivary and lacrimal glands, to multiorgan complications of various degrees of severity, finishing with the evolution, in around 5% of pSS patients, to B cell lymphomas most commonly arising in the inflamed salivary glands. Currently, there are poor positive or negative predictors of disease evolution able to guide patient management and treatment at early stages of the diseases. Recent understanding of the pathogenic mechanisms driving immunopathology in pSS, particularly through histological and transcriptomic analysis of minor and parotid salivary gland (SG) biopsies, has highlighted a high degree of cellular and molecular heterogeneity of the inflammatory lesions but also allowed the identification of clusters of patients with similar underlying SG immunopathology. In particular, patients presenting with high degrees of B/T cell infiltration and the formation of ectopic lymphoid structures (ELS) in the SG have been associated, albeit with conflicting results, with higher degree of disease severity and enhanced risk of lymphoma evolution, suggesting that a dysregulated adaptive immune response plays a key role in driving disease manifestations in pSS. Recent data from randomised clinical trials with novel biological therapies in pSS have also highlighted the potential role of SG immunopathology and molecular pathology in stratifying patients for trial inclusion as well as assessing proof of mechanisms in longitudinal SG biopsies before and after treatment. Although significant progress has been made in the understanding of disease pathogenesis and heterogeneity through cellular and molecular SG pathology, further work is needed to validate their clinical utility in routine clinical settings and in randomised clinical trials.