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Glycosylation is critical to megakaryocyte (MK) and thrombopoiesis in the context of gene mutations that affect sialylation and galactosylation. Here, we identify the conserved B4galt1 gene as a critical regulator of thrombopoiesis in MKs. β4GalT1 deficiency increases the number of fully differentiated MKs. However, the resulting lack of glycosylation enhances β1 integrin signaling leading to dysplastic MKs with severely impaired demarcation system formation and thrombopoiesis. Platelets lacking β4GalT1 adhere avidly to β1 integrin ligands laminin, fibronectin, and collagen, while other platelet functions are normal. Impaired thrombopoiesis leads to increased plasma thrombopoietin (TPO) levels and perturbed hematopoietic stem cells (HSCs). Remarkably, β1 integrin deletion, specifically in MKs, restores thrombopoiesis. TPO and CXCL12 regulate β4GalT1 in the MK lineage. Thus, our findings establish a non-redundant role for β4GalT1 in the regulation of β1 integrin function and signaling during thrombopoiesis. Defective thrombopoiesis and lack of β4GalT1 further affect HSC homeostasis. Mutations affecting sialylation and galactosylation affect megakaryocyte function and thrombopoiesis. Here the authors show that the enzyme β4GalT1 regulates thrombopoiesis and hematopoietic stem cell homeostasis by controlling beta-1 integrin function.

Platelets are blood components that survive in circulation for 7 to 10 days in humans. Thus, platelet production by bone marrow (BM) megakaryocytes (MKs), and their removal from the blood circulation is precisely orchestrated to maintain an average platelet count. Abnormalities in both processes can result in thrombocytopenia (low platelet count) or thrombocytosis (high platelet count), often associated with the risk of bleeding or overt thrombus formation, respectively. Platelet glycans, particularly sialic acids, are indicators of platelet count. Loss of platelet sialic acids leads to platelet clearance. A State‐of‐the‐Art lecture titled “Platelet and Megakaryocyte Glycobiology” was presented at the ISTH virtual congress 2021 to discuss (i) the loss of O‐glycan sialic acid on BM MKs, revealing the Thomsen‐Friedenreich (TF) antigen as a new concept of thrombocytopenia; herein, impaired thrombopoiesis is attributed to activation of immune cells with a plasmacytoid dendritic cell signature; and (ii) upregulation of antibodies against the TF antigen in pediatric patients with immune thrombocytopenia (ITP), positing that glycan alterations such as MK asialylation can lead to immune cell responses. Here, we discuss our findings alongside new data presented at the 2020 and 2021 ISTH congresses on the role of sialic acids and glycans in regulating platelet count. Desialylation is a prominent feature in thrombocytopenia, notably in ITP presentation. We compare similarities between ITP mediated with shear‐stress and with storage‐related asialylation. We also discuss genes involved in sialic acid synthesis leading to thrombocytopenia. Increased awareness in gene‐regulating MK and platelet glycans is a giant leap to understanding the underpinning mechanisms of ITP and other forms of thrombocytopenia.

M strain, the most prevalent multidrug-resistant strain of Mycobacterium tuberculosis (Mtb) in Argentina, has mounted mechanisms to evade innate immune response. The role of human bronchial epithelium in Mtb infection remains unknown as well as its crosstalk with neutrophils (PMN). In this work, we evaluate whether M and H37Rv strains invade and replicate within bronchial epithelial cell line Calu-6 and how conditioned media (CM) derived from infected cells alter PMN responses. We demonstrated that M infects and survives within Calu-6 without promoting death. CM from M-infected Calu-6 (M-CM) did not attract PMN in correlation with its low IL-8 content compared to H37Rv-CM. Also, PMN activation and ROS production in response to irradiated H37Rv were impaired after treatment with M-CM due to the lack of TNF-α. Interestingly, M-CM increased H37Rv replication in PMN which would allow the spreading of mycobacteria upon PMN death and sustain IL-8 release. Thus, our results indicate that even at low invasion/replication rate within Calu-6, M induces the secretion of factors altering the crosstalk between these nonphagocytic cells and PMN, representing an evasion mechanism developed by M strain to persist in the host. These data provide new insights on the role of bronchial epithelium upon M infection.

M strain, the most prevalent multidrug-resistant strain of Mycobacterium tuberculosis (Mtb) in Argentina, has mounted mechanisms to evade innate immune response. The role of human bronchial epithelium in Mtb infection remains unknown as well as its crosstalk with neutrophils (PMN). In this work, we evaluate whether M and H37Rv strains invade and replicate within bronchial epithelial cell line Calu-6 and how conditioned media (CM) derived from infected cells alter PMN responses. We demonstrated that M infects and survives within Calu-6 without promoting death. CM from M-infected Calu-6 (M-CM) did not attract PMN in correlation with its low IL-8 content compared to H37Rv- CM. Also, PMN activation and ROS production in response to irradiated H37Rv were impaired after treatment with M- CM due to the lack of TNF-[alpha]. Interestingly, M-CM increased H37Rv replication in PMN which would allow the spreading of mycobacteria upon PMN death and sustain IL-8 release. Thus, our results indicate that even at low invasion/replication rate within Calu-6, M induces the secretion of factors altering the crosstalk between these nonphagocytic cells and PMN, representing an evasion mechanism developed by M strain to persist in the host. These data provide new insights on the role of bronchial epithelium upon M infection.

Definitive hematopoietic stem and progenitor cells (HSPCs) development relies on intrinsic and extrinsic programs to meet homeostatic and stress-related demands. The comprehensive mechanisms governing HSPCs fate remain poorly understood. Our study identifies B4GALT1, a glycosyltransferase essential for N-glycosylation, as a key modulator of HSPC lineage decisions. We demonstrate that B4GALT1 deficiency disrupts glycosylation patterns within the bone marrow (BM) niche, resulting in oncogenic glycan signatures and altered expression of Mucin13 in HSPCs. Loss of B4GALT1 expands HSPC pools and promotes megakaryocyte priming in HSPCs through transcriptional and chromatin modifications, enhancing the Wnt-Mucin13 axis. Mucin13, an oncogene characterized by aberrant glycosylation, underscores the critical role of B4GALT1 in sustaining BM glycosylation and mechanosensing, thereby regulating HSPC fate through functional, transcriptional, and chromatin dynamics. These observations provide insights into the impact of glycan structures on HSPC function, lineage reprogramming, and malignant transformation.Competing Interest StatementThe authors have declared no competing interest.

Viral hemorrhagic fevers (VHFs) caused by arenaviruses are acute diseases characterized by fever, headache, general malaise, impaired cellular immunity, eventual neurologic involvement, and hemostatic alterations that may ultimately lead to shock and death. The causes of the bleeding are still poorly understood. However, it is generally accepted that these causes are associated to some degree with impaired hemostasis, endothelial cell dysfunction and low platelet counts or function. In this article, we present the current knowledge about the hematological alterations present in VHF induced by arenaviruses, including new aspects on the underlying pathogenic mechanisms.

The analysis of contemporary protest movements of the Nahuas and Totonaques of Puebla's Nororiental Sierra (Mexico) leads us to formulate the hypothesis that the religious and the political are closely intertwined. The strongest link concerns the Theology of Liberation, which has contributed to a revalorisation of Indigenous identities since the 1960s legitimated social struggles. A much deeper link with religion appears when we analyse Amerindian cosmology, which is periodically actualized in large community rituals. L'analyse des mouvements de protestation contemporains chez les Nahuas et Totonaques de la Sierra Nororiental de Puebla (Mexique) nous amène à formuler l'hypothèse que le religieux et le politique y sont étroitement reliés. Le lien le plus évident concerne la Théologie de la Libération, qui a contribué à une revalorisation des identités autochtones depuis les années 1960 et à la légitimation des luttes sociales. Un lien beaucoup plus profond avec le religieux apparaît lorsque nous analysons la cosmologie amérindienne, périodiquement réactualisée dans de grands rituels communautaires.

Los cuatro autores de este texto hemos intercambiado mucho durante una estancia de Pierre Beaucage en la Sierra Nororiental de Puebla en septiembre-octubre 2016. Hemos recorrido sitios de proyectos hidroeléctricos, hemos asistido a varios encuentros y hemos dialogado con los principales actores populares que participan en la lucha contra la construcción de represas y de líneas de alta tensión. El texto que sigue resume nuestras observaciones y nuestras reflexiones; su redacción ha sido la ocasión de intercambios constantes entre los autores.En las páginas que siguen haremos la crónica de un proceso social actual: la lucha por los ríos que se libra en la Sierra Nororiental de Puebla entre los pueblos nahuas (maseualmej) y totonacos (totonakú), por una parte, y las empresas hidroeléctricas y el Estado mexicano por otra. Primero, relataremos brevemente dos eventos cargados de significado que el azar hizo coincidir el día 29 de septiembre 2016: la Fiesta de San Miguel y un encuentro de alto nivel en la Ciudad de México.