Project description:B3GNT7, an important glycosyltransferase highly expressed in intestinal epithelial cells, is involved in physiological processes in the intestine. This study presents novel findings on the potential role and mechanism of B3GNT7 in ulcerative colitis (UC). DSS-induced mouse model of colitis was established to investigate the expression of B3GNT7 in the colon using transcriptomics and immunohistochemistry. Bioinformatics analysis was conducted to explore the biological functions of B3GNT7. The correlation between the transcription levels of B3GNT7 in the colonic tissues of UC patients from the IBDMDB database was analyzed and the severity of colonic inflammation, along with potential mechanisms. The DSS-induced colitis mouse model was successfully established, and transcriptomic analysis revealed a significant downregulation of B3GNT7 expression in the colonic tissues compared to healthy mice. Functional enrichment analysis showed that the main biological function of B3GNT7 was to participate in the mucin O-glycosylation process. Protein interaction analysis indicates that the molecules showing strong interaction with B3GNT7 were members of the mucin MUC family, including MUC2, MUC3, and MUC6. In UC patients, the transcription levels of B3GNT7 were significantly decreased, particularly in patients with moderate to severe disease activity. The expression level of B3GNT7 was negatively correlated with the endoscopic severity of UC. Gene set enrichment analysis (GSEA) further revealed significant enrichment of B3GNT7 in the mucin O-glycosylation synthesis signaling pathway. The downregulation of B3GNT7 expression in the colonic tissues of UC may contribute to impaired mucin barrier function and the progression of colitis.
Project description:Hematopoietic stem and progenitor cells (HSPCs) sustain blood production through tightly regulated fate decisions. Disruption of this control underlies disorders such as myelodysplastic syndromes, myeloproliferative neoplasms, and inherited thrombocytopenias. While transcriptional and epigenetic regulation of HSPCs is well established, the contribution of glycosylation has remained largely unexplored. Here, we identify the glycosyltransferase B4GALT1 as a central regulator of hematopoiesis that integrates extrinsic niche cues with intrinsic transcriptional programs. B4GALT1 shapes the bone marrow microenvironment by generating complex glycan niches that support HSPC function. However, its deficiency produces oncogenic glycan signatures, disrupts HSPC niche integrity, and induces aberrant expression of Mucin 13 (MUC13). These changes expand stem and progenitor pools, enforce megakaryocyte lineage bias, and activate the Wnt–MUC13/β-catenin signaling axis, a pathway tightly linked to proliferation and malignant transformation. Consequently, B4GALT1 loss uncouples proliferation from self-renewal, altering key regulators of stem cell quiescence, lineage balance, and marrow homeostasis. Our findings define a previously unrecognized glycan-dependent regulatory axis that directs HSPC fate through coordinated transcriptional reprogramming, signaling modulation, and niche remodeling. This work establishes aberrant glycosylation as a driver of hematopoietic dysfunction and highlights B4GALT1 as a potential therapeutic target in stem cell–driven blood disorders.
Project description:Aberrant mucin type O-linked glycosylation is a common occurrence in cancer. This type of O-linked glycosylation can occur on many cell surface glycoproteins where only a small number of sites may be present. EGFR is one such glycoprotein. Upon EGF ligation, EGFR induces a signaling cascade but can also translocate to the nucleus where it can directly regulate gene transcription. Here we show that upon EGF binding, breast cancer cells carrying different O-linked glycans respond by transcribing differential gene expression signatures. This is not a result of changes in signal transduction but due to the differential nuclear translocation of EGFR in the two glyco-phenotypes. This appears to be regulated by the formation of a EGFR/galectin-3/MUC1 complex at the cell surface that is present in cells carrying short core1-based O-glycans characteristic of tumour cells but absent in core 2 O-glycan carrying cells representative of normal mammary epithelial cells.
Project description:Activation of the Wnt pathway is at the core of many human cancers. During canonical Wnt signaling, the Lrp6 and Frizzled receptors bind to the Wnt growth factor, which leads to the complex being endocytosed. Glycogen Synthase Kinase 3 (GSK3), Dishevelled (Dvl), and Axin are sequestered inside the intraluminal vesicles of late endosomes, known as multivesicular bodies (MVBs). Here we present experiments showing that Wnt causes the endocytosis of focal adhesion (FA) proteins and depletion of Integrin β 1 (ITGβ1) from the cell surface. FAs and integrins provide link the cytoskeleton to the extracellular matrix. Wnt-induced macropinocytosis of the plasma membrane caused ITGβ1 depletion and was accompanied by striking changes in the actin cytoskeleton. In situ protease protection assays in cultured cells showed that ITGβ1 was sequestered within membrane-bounded organelles that corresponded to Wnt-induced MVBs containing GSK3 and focal adhesion-associated proteins. An in vivo model using Xenopus embryos dorsalized by Wnt8 mRNA showed that ITGβ1 depletion decreased Wnt signaling. The cross-talk between Wnt signaling, membrane trafficking, and focal adhesions should be relevant to human cancer and cell biology.
Project description:The Xenopus laevis embryo has been subjected to almost saturating screens for molecules specifically expressed in dorsal Spemann organizer tissue. In this study, we performed high-throughput RNA sequencing of ectodermal explants, called animal caps, which normally give rise to epidermis. We analyzed dissociated animal cap cells that, through sustained activation of MAPK, differentiate into neural tissue. We also microinjected mRNAs for Cerberus, Chordin, FGF8, BMP4, Wnt8, and Xnr2, which induce neural or other germ layer differentiations. The searchable database provided here represents a valuable resource for the early vertebrate cell differentiation. These analyses resulted in the identification of a gene present in frog and fish, which we call Bighead. Surprisingly, at gastrula, it was expressed in the Spemann organizer and endoderm, rather than in ectoderm as we expected. Despite the plethora of genes already mined from Spemann organizer tissue, Bighead encodes a secreted protein that proved to be a potent inhibitor of Wnt signaling in a number of embryological and cultured cell signaling assays. Overexpression of Bighead resulted in large head structures very similar to those of the well-known Wnt antagonists Dkk1 and Frzb-1. Knockdown of Bighead with specific antisense morpholinos resulted in embryos with reduced head structures, due to increased Wnt signaling. Bighead protein bound specifically to the Wnt coreceptor lipoprotein receptor-related protein 6 (Lrp6), leading to its removal from the cell surface. Bighead joins two other Wnt antagonists, Dkk1 and Angptl4, which function as Lrp6 endocytosis regulators. These results suggest that endocytosis plays a crucial role in Wnt signaling.
Project description:The cell-intrinsic and extrinsic programs governing hematopoietic stem and progenitor cells (HSPCs) cell fate determination remain unresolved. Our data reveals that loss of B4GALT1 glycosyltransferase biosynthetic activity restricts HSPC N- and O-glycosylation and reprograms previously unrecognized N-glycan gradients in the bone marrow environment with high expression of complex N-glycans in HSPC-rich regions to accumulate aberrant, cancer-like N-glycan signatures. The loss of B4GALT1 increases the expression of aberrantly glycosylated intracellular oncogenic Mucin13, which is likely to disrupt the destruction complex and mediate Wnt/β-catenin hyperactivation. This enhances metabolic and cell cycle activity, expands the megakaryocyte-primed stem cell pool, and promotes emergence from a steady state, highlighting the essential role of B4GALT1 in modulating the BM glycosylation landscape and its significance in regulating the expansion and differentiation of HSPCs.