Biology subjects

Shintani, Y.

Publications and source records attributed to Shintani, Y..

5 recordsLinked to original sources

bioRxiv2024

Spatial transcriptomics elucidates medulla niche supporting germinal center response in myasthenia gravis thymoma

Myasthenia gravis (MG) is known to be epidemiologically associated with abnormalities of the thymus, an organ that maintains central tolerance. However, due to the complexity of the thymus, specific characteristics related to the pathogenesis of MG remain elusive. In our study, we attempted to narrow down the features associated with MG using spatial transcriptome analysis of thymoma and thymic hyperplasia samples. We found that the majority of thymomas were constituted by the cortical region, whereas the medullary region was localized in comparatively restricted areas. Moreover, the medullary region contained polygenic enrichment, MG-specific germinal center structures, and a supporting immune microenvironment. Additionally, neuromuscular medullary thymic epithelial cells (nmTECs), previously identified as MG-specific autoantigen-producing cells, were situated at the cortico-medullary junction. The immune microenvironment in the medulla was characterized by a specific chemokine pattern and specific immune cells, such as CCR7+ migratory dendritic cells (migDCs) and effector regulatory T (Treg) cells. Furthermore, similar germinal center structures and immune microenvironments were observed in the medulla during thymic hyperplasia. This study indicates that the medulla and junction areas are related to the pathology of MG, suggesting that these areas should be the focus of future studies on MG pathogenesis and drug targeting.

immunology↗

bioRxiv2023

Atf3 controls transitioning in female mitochondrial cardiomyopathy as identified by single-cell transcriptomics

Oxidative phosphorylation defects results in mitochondrial diseases, with cardiac involvement markedly impacting prognosis. However, the mechanisms underlying the transition from compensation to dysfunction in response to metabolic deficiency remain unclear, impeding the development of effective treatments. Here, we employed single-nucleus RNA sequencing (snRNA-seq) on hearts from mitochondrial cardiomyopathy (MCM) mice with cardiac-specific Ndufs6 knockdown (FS6KD). Pseudotime trajectory analysis of cardiomyocytes from early stage of female FS6KD hearts revealed dynamic cellular state transitioning from compensation to severe compromise, coincided with transient upregulation of a critical transcription factor, activating transcription factor 3 (Atf3). Genetic ablation or adeno-associated virus-mediated Atf3 knockdown in FS6KD mice effectively delayed cardiomyopathy progression in a female-specific manner. Notably, human MCM snRNA-seq revealed a similar transition, including the dynamic expression of ATF3. In conclusion, our findings highlight a fate-determining role of Atf3 in female MCM progression, providing a promising therapeutic candidate for the currently intractable disease.

cell biology↗

bioRxiv2021

Myasthenia gravis-specific aberrant neuromuscular gene expression by medullary thymic epithelial cells in thymoma

Myasthenia gravis (MG) is a neurological disease caused by autoantibodies against neuromuscular-associated proteins. While MG is frequently developed in thymoma patients, the etiologic factors for MG are not well understood. Here, by constructing a comprehensive atlas of thymoma using bulk and single-cell RNA-seq, we identified ectopic expression of neuromuscular molecules in MG-associated thymoma (MG-thymoma). These molecules were originated from a distinct subpopulation of medullary thymic epithelial cells (mTECs), which we named neuromuscular mTECs (nmTECs). MG-thymoma also exhibited microenvironments dedicated to autoantibody production, including ectopic germinal center formation, T follicular helper cell accumulation, and type 2 conventional dendritic cell migration. Cell-cell interaction analysis also predicted the interaction between nmTECs and T/B cells via CXCL12-CXCR4. The enrichment of nmTECs presenting neuromuscular molecules within MG-thymoma was further confirmed by immunohistochemically and by cellular composition estimation from MG-thymoma transcriptome. Altogether, this study suggests that nmTECs play a significant role in MG pathogenesis via ectopic expression of neuromuscular molecules.

immunology↗

bioRxiv2020

AMPK regulates cell shape of cardiomyocytes by modulating turnover of microtubules through CLIP-170

AMP-activated protein kinase (AMPK) is a multifunctional kinase that regulates microtubule (MT) dynamic instability through CLIP-170 phosphorylation; however, its physiological relevance in vivo remains to be elucidated. In this study, we identified an active form of AMPK localized at the intercalated discs in the heart, a specific cell-cell junction present between cardiomyocytes. A contractile inhibitor, MYK-461, prevented the localization of AMPK at the intercalated discs, and the effect was reversed by the removal of MYK-461, suggesting that the localization of AMPK is regulated by mechanical stress. Time-lapse imaging analysis revealed that the inhibition of CLIP-170 Ser-311 phosphorylation by AMPK leads to the accumulation of MTs at the intercalated discs. Interestingly, MYK-461 increased the individual cell area of cardiomyocytes in CLIP-170 phosphorylation-dependent manner. Moreover, heart-specific CLIP-170 S311A transgenic mice demonstrated elongation of cardiomyocytes along with accumulated MTs, leading to progressive decline in cardiac contraction. In conclusion, these findings suggest that AMPK regulates the cell shape and aspect ratio of cardiomyocytes by modulating the turnover of MTs through homeostatic phosphorylation of CLIP-170 at the intercalated discs.

cell biology↗

bioRxiv2019

Sox17 expression in endocardium precursor cells regulates heart development in mice

The endocardium is the endothelial component of the vertebrate heart and plays a key role in heart development. Cardiac progenitor cells (CPCs) that express the homeobox gene Nkx2-5 give rise to the endocardium. Where, when, and how the endocardium segregates during embryogenesis have remained largely unknown, however. We now show that Nkx2-5+ CPCs that express the Sry-type HMG box gene Sox17 specifically differentiate into the endocardium in mouse embryos. Approximately 20% to 30% of Nkx2-5+CPCs transiently express Sox17 from embryonic day (E) 7.5 to E8.5.Although Sox17 is not essential or sufficient for endocardium fate, it can bias the fate of CPCs toward the endocardium. On the other hand, Sox17 expression in the endocardium is required for heart development. Deletion of Sox17 specifically in the mesoderm markedly impaired endocardium development with regard to cell proliferation and behavior. The proliferation of cardiomyocytes, ventricular trabeculation, and myocardium thickening were also impaired in a non-cell-autonomous manner in the Sox17 mutant, resulting in anomalous morphology of the heart, likely as a consequence of down-regulation of NOTCH signaling. Changes in gene expression profile in both the endocardium and myocardium preceded the reduction in NOTCH-related gene expression in the mutant embryos, suggesting that Sox17 expression in the endocardium regulates an unknown signal required for nurturing of the myocardium. Our results thus provide insight into differentiation of the endocardium and its role in heart development. SignificanceThe endocardium is vital for vertebrate heart development; however, the molecular mechanisms regulating fate determination and differentiation remain largely unknown. Here, we show that a part of the earliest cardiac progenitor cells (CPCs) transiently and exclusively express Sry-type HMG box gene Sox17 in the mouse embryo. Sox17-expressing CPCs specifically differentiate to the endocardium. Sox17 biases the fate of CPCs toward the endocardium, and regulates proliferation and cellular behavior cell autonomously. Conversely, Sox17 in the endocardium regulates the myocardium non-cell autonomously. Notably, Sox17 is required for the ventricular trabeculation via the NOTCH signal that is not directly induced but maintained by Sox17. This study, thus, sheds light on endocardium development.

developmental biology↗