Growth retardation and early death of beta-1,4-galactosyltransferase knockout mice with augmented proliferation and abnormal differentiation of epithelial cells

Glucose-dependent glycosphingolipid biosynthesis fuels CD8+ T cell function and tumor control

Glucose is essential for T cell proliferation and function, yet its specific metabolic roles in vivo remain poorly defined. Here, we identify glycosphingolipid (GSL) biosynthesis as a key pathway fueled by glucose that enables CD8+ T cell expansion and cytotoxic function in vivo. Using 13C-based stable isotope tracing, we demonstrate that CD8+ effector T cells use glucose to synthesize uridine diphosphate-glucose (UDP-Glc), a precursor for glycogen, glycan, and GSL biosynthesis. Inhibiting GSL production by targeting the enzymes UGP2 or UGCG impairs CD8+ T cell expansion and cytolytic activity without affecting glucose-dependent energy production. Mechanistically, we show that glucose-dependent GSL biosynthesis is required for plasma membrane lipid raft integrity and aggregation following TCR stimulation. Moreover, UGCG-deficient CD8+ T cells display reduced granzyme expression and tumor control in vivo. Together, our data establish GSL biosynthesis as a critical metabolic fate of glucose-independent of energy production-required for CD8+ T cell responses in vivo.

Beta-1,4-galactosyltransferase-3 deficiency suppresses the growth of immunogenic tumors in mice

Background

Beta-1,4-galactosyltransferase-3 (B4GALT3) belongs to the family of beta-1,4-galactosyltransferases (B4GALTs) and is responsible for the transfer of UDP-galactose to terminal N-acetylglucosamine. B4GALT3 is differentially expressed in tumors and adjacent normal tissues, and is correlated with clinical prognosis in several cancers, including neuroblastoma, cervical cancer, and bladder cancer. However, the exact role of B4GALT3 in the tumor immune microenvironment (TIME) remains unclear. Here, we aimed to elucidate the function of B4GALT3 in the TIME.

Methods

To study the functions of B4GALT3 in cancer immunity, either weakly or strongly immunogenic tumor cells were subcutaneously transplanted into wild-type (WT) and B4galt3 knockout (KO) mice. Bone marrow transplantation and CD8+ T cell depletion experiments were conducted to elucidate the role of immune cells in suppressing tumor growth in B4galt3 KO mice. The cell types and gene expression in the tumor region and infiltrating CD8+ T cells were analyzed using flow cytometry and RNA sequencing. N-glycosylated proteins from WT and B4galt3 KO mice were compared using the liquid chromatography tandem mass spectrometry (LC-MS/MS)-based glycoproteomic approach.

Results

B4galt3 KO mice exhibited suppressed growth of strongly immunogenic tumors with a notable increase in CD8+ T cell infiltration within tumors. Notably, B4galt3 deficiency led to changes in N-glycan modification of several proteins, including integrin alpha L (ITGAL), involved in T cell activity and proliferation. In vitro experiments suggested that B4galt3 KO CD8+ T cells were more susceptible to activation and displayed increased downstream phosphorylation of FAK linked to ITGAL.

Conclusion

Our study demonstrates that B4galt3 deficiency can potentially boost anti-tumor immune responses, largely through enhancing the influx of CD8+ T cells. B4GALT3 might be suppressing cancer immunity by synthesizing the glycan structure of molecules on the CD8+ T cell surface, as evidenced by the changes in the glycan structure of ITGAL in immune cells. Importantly, B4galt3 KO mice showed no adverse effects on growth, development, or reproduction, underscoring the potential of B4GALT3 as a promising and safe therapeutic target for cancer treatment.

Aggrecan and Hyaluronan: The Infamous Cartilage Polyelectrolytes - Then and Now

Cartilages are unique in the family of connective tissues in that they contain a high concentration of the glycosaminoglycans, chondroitin sulfate and keratan sulfate attached to the core protein of the proteoglycan, aggrecan. Multiple aggrecan molecules are organized in the extracellular matrix via a domain-specific molecular interaction with hyaluronan and a link protein, and these high molecular weight aggregates are immobilized within the collagen and glycoprotein network. The high negative charge density of glycosaminoglycans provides hydrophilicity, high osmotic swelling pressure and conformational flexibility, which together function to absorb fluctuations in biomechanical stresses on cartilage during movement of an articular joint. We have summarized information on the history and current knowledge obtained by biochemical and genetic approaches, on cell-mediated regulation of aggrecan metabolism and its role in skeletal development, growth as well as during the development of joint disease. In addition, we describe the pathways for hyaluronan metabolism, with particular focus on the role as a "metabolic rheostat" during chondrocyte responses in cartilage remodeling in growth and disease.Future advances in effective therapeutic targeting of cartilage loss during osteoarthritic diseases of the joint as an organ as well as in cartilage tissue engineering would benefit from 'big data' approaches and bioinformatics, to uncover novel feed-forward and feed-back mechanisms for regulating transcription and translation of genes and their integration into cell-specific pathways.

Blocking DCIR mitigates colitis and prevents colorectal tumors by enhancing the GM-CSF-STAT5 pathway

Dendritic cell immunoreceptor (DCIR; Clec4a2), a member of the C-type lectin receptor family, plays important roles in homeostasis of the immune and bone systems. However, the intestinal role of this molecule is unclear. Here, we show that dextran sodium sulfate (DSS)-induced colitis and azoxymethane-DSS-induced intestinal tumors are reduced in Clec4a2^-/- mice independently of intestinal microbiota. STAT5 phosphorylation and expression of Csf2 and tight junction genes are enhanced, while Il17a and Cxcl2 are suppressed in the Clec4a2^-/- mouse colon, which exhibits reduced infiltration of neutrophils and myeloid-derived suppressor cells. Granulocyte-macrophage colony-stimulating factor (GM-CSF) administration ameliorates DSS colitis associated with reduced Il17a and enhanced tight junction gene expression, whereas anti-GM-CSF exacerbates symptoms. Furthermore, anti-NA2, a ligand for DCIR, ameliorates colitis and prevents colorectal tumors. These observations indicate that blocking DCIR signaling ameliorates colitis and suppresses colonic tumors, suggesting DCIR as a possible target for the treatment of these diseases.

The B-Cell-Specific Ablation of B4GALT1 Reduces Cancer Formation and Reverses the Changes in Serum IgG Glycans during the Induction of Mouse Hepatocellular Carcinoma

Simple Summary

As serum IgG glycosylation is associated with various cancers, our goal is to explore whether serum IgG galactosylation and its associated glycans could be used as tumor markers associated with hepatocellular carcinoma (HCC). At the same time, we explore the effect of the B-cell-specific ablation of B4GALT1 on HCC and finally analyze whether the low incidence of female cancer was related to the findings from the above perspective. The results demonstrate that the tumor marker of serum IgG glycosylation is galactosylation and its associated glycans and that the B-cell-specific ablation of B4GALT1 reduces HCC formation by reducing serum IgG galactosylation levels and by modulating the associated glycans, meaning that the lower incidence of cancer in women may be related to minor changes in the B-cell B4GALT1 and unchanged serum IgG galactosylation levels. This study aims to provide a theoretical basis for the early diagnosis and prevention of HCC and to determine why it has such a high incidence in males.

Abstract

Serum immunoglobulin G (IgG) glycosylation, especially galactosylation, has been found to be related to a variety of tumors, including hepatocellular carcinoma (HCC). However, whether IgG glycan changes occur in the early stages of HCC formation remains unclear. We found that the galactosylation level increased and that the related individual glycans showed regular changes over the course of HCC induction. Then, the effect of the B-cell-specific ablation of β1,4galactosyltransferase 1 (CKO B4GALT1) and B4GALT1 defects on the IgG glycans that were modified during the model induction process and HCC formation is investigated in this study. CKO B4GALT1 reduces serum IgG galactosylation levels and reduces cancer formation. Furthermore, insignificant changes in the B-cell B4GALT1 and unchanged serum IgG galactosylation levels were found during cancer induction in female mice, which might contribute to the lower cancer incidence in female mice than in male mice. The gender differences observed during glycan and B4GALT1 modification also add more evidence that the B4GALT1 in B cells and in serum IgG galactosylation may play an important role in HCC. Therefore, the findings of the present research can be used to determine the methods for the early detection of HCC as well as for prevention.

Genetic and functional evidence links a missense variant in B4GALT1 to lower LDL and fibrinogen

[Figure: see text].

Increased B4GALT1 expression is associated with platelet surface galactosylation and thrombopoietin plasma levels in MPNs

Aberrant megakaryopoiesis is a hallmark of the myeloproliferative neoplasms (MPNs), a group of clonal hematological malignancies originating from hematopoietic stem cells, leading to an increase in mature blood cells in the peripheral blood. Sialylated derivatives of the glycan structure β4-N-acetyllactosamine (Galβ1,4GlcNAc or type-2 LacNAc, hereafter referred to as LacNAc) regulate platelet life span, hepatic thrombopoietin (TPO) production, and thrombopoiesis. We found increased TPO plasma levels in MPNs with high allele burden of the mutated clones. Remarkably, platelets isolated from MPNs had a significant increase in LacNAc expression that correlated with the high allele burden regardless of the underlying identified mutation. Megakaryocytes derived in vitro from these patients showed an increased expression of the B4GALT1 gene encoding β-1,4-galactosyltransferase 1 (β4GalT1). Consistently, megakaryocytes from MPN showed increased LacNAc expression relative to healthy controls, which was counteracted by the treatment with a Janus kinase 1/2 inhibitor. Altered expression of B4GALT1 in mutant megakaryocytes can lead to the production of platelets with aberrant galactosylation, which in turn promote hepatic TPO synthesis regardless of platelet mass. Our findings provide a new paradigm for understanding aberrant megakaryopoiesis in MPNs and identify β4GalT1 as a potential actionable target for therapy.

Bombyx mori β1,4-N-acetylgalactosaminyltransferase possesses relaxed donor substrate specificity in N-glycan synthesis

N-Glycosylation is one of the most important post-translational protein modifications in eukaryotic cells. Although more than 200 N-glycogenes contributing to N-glycan biosynthesis have been identified and characterized, the information on insect N-glycosylation is still limited. Here, focusing on insect N-glycosylation, we characterized Bombyx mori N-acetylgalactosaminyltransferase (BmGalNAcT) participating in complex N-glycan biosynthesis in mammals. BmGalNAcT localized at the Golgi and was ubiquitously expressed in every organ and in the developmental stage of the middle silk gland of fifth instar larvae. Analysis of recombinant BmGalNAcT expressed in Sf9 cells showed that BmGalNAcT transferred GalNAc to non-reducing terminals of GlcNAcβ1,2-R with β1,4-linkage. In addition, BmGalNAcT mediated transfer of galactose and N-acetylglucosamine residues but not transfer of either glucose or glucuronic acid from the UDP-sugar donor substrate to the N-glycan. Despite this tri-functional sugar transfer activity, however, most of the endogenous glycoproteins of insect cells were present without GalNAc, Gal, or GlcNAc residues at the non-reducing terminal of β1,2-GlcNAc residue(s). Moreover, overexpression of BmGalNAcT in insect cells had no effect on N-acetylgalactosaminylation, galactosylation, or N-acetylglucosaminylation of the major N-glycan during biosynthesis. These results suggested that B. mori has a novel multifunctional glycosyltransferase, but the N-glycosylation is highly and strictly regulated by the endogenous N-glycosylation machineries.

Identification of novel single-nucleotide polymorphism at exon1 and 2 region of B4GALT1 gene and its association with milk production traits in crossbred cattle of Kerala, India

Beta 1,4-galactosyltransferase-I gene (B4GALT1) is an important candidate gene for milk performance traits, encodes catalytic part of lactose synthesis. Main objectives of present study is identification of single-nucleotide polymorphism in exon 1 and 2 region of B4GALT1 and to find significant association of genetic variants with milk performance traits in crossbred cattle of Kerala. The study was conducted on two hundred crossbred cattle maintained at various farms of Kerala Veterinary and Animal Sciences University, India. Genomic DNA was isolated and polymorphism of gene were detected by Single Strand Confirmation Polymorphism. Genotype and allelic frequency were estimated. Chi-square analysis revealed that screened population is under Hardy Weinberg equilibrium. Nucleotide sequence analysis revealed a novel non-synonymous single-nucleotide variation (T94A) in exon 1 and a non-synonymous mutation of T97C in exon 2 of B4GALT1 gene in the screened cattle population. Association analysis of genetic variants was done with milk production traits and major non-genetic factors using fixed models. Different genetic variants of B4GALT1 was significantly associated with 305 days milk yield, lactose, protein percent. Study indicates existence of genetic variability in B4GALT1 gene on crossbred cattle of Kerala and suggests a scope of considering genetic variants of B4GALT1in selection strategies.

Expression of β-1,4-galactosyltransferases during Aging in Caenorhabditis elegans

BACKGROUND

Altered plasma activity of β-1,4-galac-tosyl-transferases (B4GALTs) is a novel candidate biomarker of human aging. B4GALT1 is assumed to be largely responsible for this activity increase, but how it modulates the aging process is unclear at present.

OBJECTIVES

To determine how expression of B4GALT1 and other B4GALT enzymes changes during aging of an experimentally tractable model organism, Caenorhabditis elegans.

METHODS

Targeted analysis of mRNA levels of all 3 C. elegans B4GALT family members was performed by qPCR in wild-type and in long-lived daf-2 (insulin/IGF1-like receptor)-deficient or germline-deficient animals.

RESULTS

bre-4 (B4GALT1/2/3/4) is the only B4GALT whose expression increases during aging in wild-type worms. In addition, bre-4 levels also rise during aging in long-lived daf-2-deficient worms, but not in animals that are long-lived due to the lack of germline stem cells. On the other hand, expression of sqv-3 (B4GALT7) and of W02B12.11 (B4GALT5/6) appears decreased or constant, respectively, in all backgrounds during aging.

CONCLUSIONS

The age-dependent bre-4 mRNA increase in C. elegans parallels the age-dependent B4GALT activity increase in humans and is consistent with C. elegans being a suitable experimental organism to define potentially conserved roles of B4GALT1 during aging.

Various biological functions of carbohydrate chains learned from glycosyltransferase-deficient mice

Carbohydrate chains are attached to various proteins and lipids and modify their functions. The complex structures of carbohydrate chains, which have various biological functions, are involved not only in regulating protein conformation, transport, and stability but also in cell-cell and cell-matrix interactions. These functional carbohydrate structures are designated as "glyco-codes." Carbohydrate chains are constructed through complex reactions of glycosyltransferases, glycosidases, nucleotide sugars, and protein and lipid substrates in a cell. To elucidate the functions of carbohydrate chains, I and my colleagues generated and characterized knockout (KO) mice of galactosyltransferase family genes. In this review, I introduce our studies about galactosyltransferase family genes together with related studies performed by other researchers, which I presented in my award lecture for the Ando-Tajima Prize of the Japanese Association for Laboratory Animal Science (JALAS) in 2019.

Selectins-The Two Dr. Jekyll and Mr. Hyde Faces of Adhesion Molecules-A Review

Selectins belong to a group of adhesion molecules that fulfill an essential role in immune and inflammatory responses and tissue healing. Selectins are glycoproteins that decode the information carried by glycan structures, and non-covalent interactions of selectins with these glycan structures mediate biological processes. The sialylated and fucosylated tetrasaccharide sLe^x is an essential glycan recognized by selectins. Several glycosyltransferases are responsible for the biosynthesis of the sLe^x tetrasaccharide. Selectins are involved in a sequence of interactions of circulated leukocytes with endothelial cells in the blood called the adhesion cascade. Recently, it has become evident that cancer cells utilize a similar adhesion cascade to promote metastases. However, like Dr. Jekyll and Mr. Hyde’s two faces, selectins also contribute to tissue destruction during some infections and inflammatory diseases. The most prominent function of selectins is associated with the initial stage of the leukocyte adhesion cascade, in which selectin binding enables tethering and rolling. The first adhesive event occurs through specific non-covalent interactions between selectins and their ligands, with glycans functioning as an interface between leukocytes or cancer cells and the endothelium. Targeting these interactions remains a principal strategy aimed at developing new therapies for the treatment of immune and inflammatory disorders and cancer. In this review, we will survey the significant contributions to and the current status of the understanding of the structure of selectins and the role of selectins in various biological processes. The potential of selectins and their ligands as therapeutic targets in chronic and acute inflammatory diseases and cancer will also be discussed. We will emphasize the structural characteristic of selectins and the catalytic mechanisms of glycosyltransferases involved in the biosynthesis of glycan recognition determinants. Furthermore, recent achievements in the synthesis of selectin inhibitors will be reviewed with a focus on the various strategies used for the development of glycosyltransferase inhibitors, including substrate analog inhibitors and transition state analog inhibitors, which are based on knowledge of the catalytic mechanism.

Sperm-egg interaction and fertilization: past, present, and future

Fifty years have passed since the findings of capacitation and acrosome reaction. These discoveries and the extensive effort of researchers led to the success of in vitro fertilization, which has become a top choice for patients at infertility clinics today. The effort to understand the mechanism of fertilization is ongoing, but the small number of eggs and similarly small quantity of spermatozoa continue to hinder biochemical experiments. The emergence of transgenic animals and gene disruption techniques has had a significant effect on fertilization research. Factors considered important in the early years were shown not to be essential and were replaced by newly found proteins. However, there is much about sperm-egg interaction which remains to be learned before we can outline the mechanism of fertilization. In fact, our understanding of sperm-egg interaction is entering a new stage. Progress in transgenic spermatozoa helped us to observe the behavior of spermatozoa in vivo and/or at the moment of sperm-egg fusion. These advancements are discussed together with the paradigm-shifting research in related fields to help us picture the direction which fertilization research may take in the future.

Phenotype and response to growth hormone therapy in siblings with B4GALT7 deficiency

B4GALT7 encodes beta-1,4-galactosyltransferase which links glycosaminoglycans to proteoglycans in connective tissues. Rare, biallelic variants in B4GALT7 have been associated with spondylodysplastic Ehlers-Danlos and Larsen of Reunion Island syndromes. Thirty patients with B4GALT7-related disorders have been reported to date with phenotypic variability. Using whole exome sequencing, we identified male and female siblings with biallelic, pathogenic B4GALT7 variants and phenotypic features of spondylodysplastic Ehlers-Danlos syndrome as well as previously unreported skeletal characteristics. We also provide detailed radiological characterization and describe the siblings' responses to growth hormone treatment. Our report extends the phenotypic spectrum of B4GALT7-associated spondylodysplastic Ehlers-Danlos syndrome and reports results of growth hormone treatment for patients with this rare disorder.

Roles for Golgi Glycans in Oogenesis and Spermatogenesis

Glycosylation of proteins by N- and O-glycans or glycosaminoglycans (GAGs) mostly begins in the endoplasmic reticulum and is further orchestrated in the Golgi compartment via the action of >100 glycosyltransferases that reside in this complex organelle. The synthesis of glycolipids occurs in the Golgi, also by resident glycosyltransferases. A defect in the glycosylation machinery may impair the functions of glycoproteins and other glycosylated molecules, and lead to a congenital disorder of glycosylation (CDG). Spermatogenesis in the male and oogenesis in the female are tightly regulated differentiation events leading to the production of functional gametes. Insights into roles for glycans in gamete production have been obtained from mutant mice following deletion or inactivation of genes that encode a glycosylation activity. In this review, we will summarize the effects of altering the synthesis of N-glycans, O-glycans, proteoglycans, glycophosphatidylinositol (GPI) anchored proteins, and glycolipids during gametogenesis in the mouse. Glycosylation genes whose deletion causes embryonic lethality have been investigated following conditional deletion using various Cre recombinase transgenes with a cell-type specific promoter. The potential effects of mutations in corresponding glycosylation genes of humans will be discussed in relation to consequences to fertility and potential for use in contraception.

Galactosyl carbohydrate residues on hematopoietic stem/progenitor cells are essential for homing and engraftment to the bone marrow

The role of carbohydrate chains in leukocyte migration to inflamed sites during inflammation and trafficking to the lymph nodes under physiological conditions has been extensively characterized. Here, we report that carbohydrate chains also mediate the homing and engraftment of hematopoietic stem/progenitor cells (HSPCs) to the bone marrow (BM). In particular, we found that transplanted BM cells deficient in β-1,4-galactosyltransferase-1 (β4GalT-1) could not support survival in mice exposed to a lethal dose of irradiation. BM cells obtained from mice deficient in β4GalT-1 showed normal colony-forming activity and hematopoietic stem cell numbers. However, colony-forming cells were markedly rare in the BM of recipient mice 24 h after transplantation of β4GalT-1-deficient BM cells, suggesting that β4GalT-1 deficiency severely impairs homing. Similarly, BM cells with a point mutation in the UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase gene, encoding a key enzyme in sialic acid biosynthesis, showed mildly impaired homing and engraftment abilities. These results imply that the galactosyl, but not sialyl residues in glycoproteins, are essential for the homing and engraftment of HSPCs to the BM. These findings suggest the possibility of modifying carbohydrate structures on the surface of HSPCs to improve their homing and engraftment to the BM in clinical application.

SSeCKS promoted lipopolysaccharide-sensitized astrocytes migration via increasing β-1,4-galactosyltransferase-I activity

Astrocytes migration is essential in the formation of the glial scar during the injury response process of the central nervous system (CNS) especially during inflammation. Integrin β1 is part of the extracellular matrix receptors in the CNS and it has been reported that integrin β-deficient astrocytes randomly migrate into wounds. Previous studies have found that β-1,4 Galactosyltransferase-I (β-1,4-GalT-I) enhanced the β-1,4-galactosylation of integrin β1. Src-suppressed C kinase substrate (SSeCKS) is an inflammatory response protein which functionally interacts with β-1,4 Galactosyltransferase-I (β-1,4-GalT-I). In this study we aim to investigate the role of SSeCKS and β-1,4-GalT-I in the migration of astrocytes during lipopolysaccharide (LPS)-induced inflammation. Coimmunoprecipitation and immunofluorescence assays have demonstrated that SSeCKS and β-1,4-GalT-I were significantly enhanced in LPS-treated astrocytes and their interactions may occur in the Trans-Golgi Network. Lectin blot showed that the knockdown of β-1,4-GalT-I could inhibit the β-1,4-galactosylation of glycoproteins including integrin β1 with and without LPS, and that SSeCKS knockdown inhibits the β-1,4-galactosylation of glycoproteins including integrin β1 only in LPS-induced astrocytes. Additionally, wound healing assays indicated that β-1,4-GalT-I knockdown could inhibit astrocytes migration with and without LPS but SSeCKS inhibited cell migration only when LPS was present. Therefore our findings suggest that SSeCKS affects astrocytes migration by regulating the β-1,4-galactosylation of glycoproteins including integrin β1, via β-1,4-GalT-I expression in LPS-sensitized astrocytes.

The role of DNA methylation in human trophoblast differentiation

The placenta is a vital fetal exchange organ connecting mother and baby. Specialised placental epithelial cells, called trophoblasts, are essential for adequate placental function. Trophoblasts transform the maternal vasculature to allow efficient blood flow to the placenta and facilitate adequate nutrient uptake. Placental development is in part regulated by epigenetic mechanisms. However, our understanding of how DNA methylation contributes to human trophoblast differentiation is limited. To better understand how genome-wide methylation differences affect trophoblast differentiation, reduced representation bisulfite sequencing (RRBS) was conducted on four matched sets of trophoblasts; side-population trophoblasts (a candidate human trophoblast stem cell population), cytotrophoblasts (an intermediate progenitor population), and extravillous trophoblasts (EVT, a terminally differentiated population) each isolated from the same first trimester placenta. Each trophoblast population had a distinct methylome. In line with their close differentiation relationship, the methylation profile of side-population trophoblasts was most similar to cytotrophoblasts, whilst EVT had the most distinct methylome. In comparison to mature trophoblast populations, side-population trophoblasts exhibited differential methylation of genes and miRNAs involved in cell cycle regulation, differentiation, and regulation of pluripotency. A combined methylomic and transcriptomic approach was taken to better understand cytotrophoblast differentiation to EVT. This revealed methylation of 41 genes involved in epithelial to mesenchymal transition and metastatic cancer pathways, which likely contributes to the acquisition of an invasive EVT phenotype. However, the methylation status of a gene did not always predict gene expression. Therefore, while CpG methylation plays a role in trophoblast differentiation, it is likely not the only regulatory mechanism involved in this process.

CRISPR/Cas9-Multiplexed Editing of Chinese Hamster Ovary B4Gal-T1, 2, 3, and 4 Tailors N-Glycan Profiles of Therapeutics and Secreted Host Cell Proteins

In production of recombinant proteins for biopharmaceuticals, N-glycosylation is often important for protein efficacy and patient safety. IgG with agalactosylated (G0)-N-glycans can improve the activation of the lectin-binding complement system and be advantageous in the therapy of lupus and virus diseases. In this study, the authors aimed to engineer CHO-S cells for the production of proteins with G0-N-glycans by targeting B4Gal-T isoform genes with CRISPR/Cas9. Indel mutations in genes encoding B4Gal-T1, -T2, and -T3 with and without a disrupted B4Gal-T4 sequence resulted in only ≈1% galactosylated N-glycans on total secreted proteins of 3-4 clones per genotype. The authors revealed that B4Gal-T4 is not active in N-glycan galactosylation in CHO-S cells. In the triple-KO clones, transiently expressed erythropoietin (EPO) and rituximab harbored only ≈6% and ≈3% galactosylated N-glycans, respectively. However, simultaneous disruption of B4Gal-T1 and -T3 may decrease cell growth. Altogether, the authors present the advantage of analyzing total secreted protein N-glycans after disrupting galactosyltransferases, followed by expressing recombinant proteins in selected clones with desired N-glycan profiles at a later stage. Furthermore, the authors provide a cell platform that prevalently glycosylates proteins with G0-N-glycans to further study the impact of agalactosylation on different in vitro and in vivo functions of recombinant proteins.

Engineered Glycocalyx Regulates Stem Cell Proliferation in Murine Crypt Organoids

At the base of the intestinal crypt, long-lived Lgr5⁺ stem cells are intercalated by Paneth cells that provide essential niche signals for stem cell maintenance. This unique epithelial anatomy makes the intestinal crypt one of the most accessible models for the study of adult stem cell biology. The glycosylation patterns of this compartment are poorly characterized, and the impact of glycans on stem cell differentiation remains largely unexplored. We find that Paneth cells, but not Lgr5⁺ stem cells, express abundant terminal N-acetyllactosamine (LacNAc). Employing an enzymatic method to edit glycans in cultured crypt organoids, we assess the functional role of LacNAc in the intestinal crypt. We discover that blocking access to LacNAc on Paneth cells leads to hyperproliferation of the neighboring Lgr5⁺ stem cells, which is accompanied by the downregulation of genes that are known as negative regulators of proliferation.

Regulation of Notch Function by O-Glycosylation

The Notch receptor initiates a unique intercellular signaling pathway that is evolutionarily conserved across all metazoans and contributes to the development and maintenance of numerous tissues. Consequently, many diseases result from aberrant Notch signaling. Emerging roles for Notch in disease are being uncovered as studies reveal new information regarding various components of this signaling pathway. Notch activity is regulated at several levels, but O-linked glycosylation of Epidermal Growth Factor (EGF) repeats in the Notch extracellular domain has emerged as a major regulator that, depending on context, can increase or decrease Notch activity. Three types of O-linked glycosylation occur at consensus sequences found within the EGF repeats of Notch: O-fucosylation, O-glucosylation, and O-GlcNAcylation. Recent studies have investigated the site occupancy of these types of glycosylation and also defined specific roles for these glycans on Notch structure and function. Nevertheless, there are many functional aspects to each type of O-glycosylation that remain unclear. Here, we will discuss molecular mechanisms of how O-glycosylation regulates Notch signaling and describe disorders associated with defects in Notch O-glycosylation.

β1,4-galactosyltransferase 1 is a novel receptor for IgA in human mesangial cells

IgA nephropathy is characterized by mesangial deposition of IgA, mesangial cell proliferation, and extracellular matrix production. Mesangial cells bind IgA, but the identity of all potential receptors involved remains incomplete. The transferrin receptor (CD71) acts as a mesangial cell IgA receptor and its expression is upregulated in many forms of glomerulonephritis, including IgA nephropathy. CD71 is not expressed in healthy glomeruli and blocking CD71 does not completely abrogate mesangial cell IgA binding. Previously we showed that mesangial cells express a receptor that binds the Fc portion of IgA and now report that this receptor is an isoform of β-1,4-galactosyltransferase. A human mesangial cell cDNA library was screened for IgA binding proteins and β-1,4-galactosyltransferase identified. Cell surface expression of the long isoform of β-1,4-galactosyltransferase was shown by flow cytometry and confocal microscopy and confirmed by immunoblotting. Glomerular β-1,4-galactosyltransferase expression was increased in IgA nephropathy. IgA binding and IgA-induced mesangial cell phosphorylation of spleen tyrosine kinase and IL-6 synthesis were inhibited by a panel of β-1,4-galactosyltransferase-specific antibodies, suggesting IgA binds to the catalytic domain of β-1,4-galactosyltransferase. Thus, β-1,4-galactosyltransferase is a constitutively expressed mesangial cell IgA receptor with an important role in both mesangial IgA clearance and the initial response to IgA deposition.

6-OHDA-Lesioned Adult Zebrafish as a Useful Parkinson's Disease Model for Dopaminergic Neuroregeneration

Conventional mammalian models of neurodegeneration are often limited by futile axonogenesis with minimal functional recuperation of severed neurons. The emergence of zebrafish, a non-mammalian model with excellent neuroregenerative properties, may address these limitations. This study aimed to establish an adult zebrafish-based, neurotoxin-induced Parkinson's disease (PD) model and subsequently validate the regenerative capability of dopaminergic neurons (DpN). The DpN of adult male zebrafish (Danio rerio) were lesioned by microinjecting 6-hydroxydopamine (6-OHDA) neurotoxin (6.25, 12.5, 18.75, 25, 37.5, 50 and 100 mg/kg) into the ventral diencephalon (Dn). This was facilitated by an optimised protocol that utilised 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanineperchlorate (DiI) dye to precisely identify the injection site. Immunostaining was utilised to identify the number of tyrosine hydroxylase immunoreactive (TH-ir) DpN in brain regions of interest (i.e. olfactory bulb, telencephalon, preoptic area, posterior tuberculum and hypothalamus). Open tank video recordings were performed for locomotor studies. The Dn was accessed by setting the injection angle of the microinjection capillary to 60° and injection depth to 1200 μm (from the exposed brain surface). 6-OHDA (25 mg/kg) successfully ablated >85% of the Dn DpN (preoptic area, posterior tuberculum and hypothalamus) whilst maintaining a 100% survival. Locomotor analysis of 5-min recordings revealed that 6-OHDA-lesioned adult zebrafish were significantly (p < 0.0001) reduced in speed (cm/s) and distance travelled (cm). Lesioned zebrafish showed full recovery of Dn DpN 30 days post-lesion. This study had successfully developed a stable 6-OHDA-induced PD zebrafish model using a straightforward and reproducible approach. Thus, this developed teleost model poses exceptional potentials to study DpN regeneration.

Isolation of a methylated mannose-binding protein from terrestrial worm Enchytraeus japonensis

To elucidate a biological role of the methylated mannose residues found in N-glycans of terrestrial worm Enchytraeus japonensis, we first synthesized 3-O-methyl mannose- and 4-O-methyl mannose-derivatives and immobilized them to Sepharose 4B beads in order to isolate the sugar-binding protein. When whole protein extracts from the worms was applied to a series of the columns immobilized with the modified and unmodified mannose-derivatives, respectively, a protein with a molecular weight of 25,000 was isolated by 4-O-methyl mannose-immobilized column chromatography, and termed as a methylated mannose-binding protein (mMBP). mMBP bound weakly to a mannose-immobilized column and moderately to a 3-O-methyl mannose-immobilized column. The N-terminal amino acid sequences of mMBP and its endoprotease-digested peptides were determined. Using the degenerate first primers synthesized based on the primary sequence, a genomic DNA fragment was isolated. Then, the second primers were synthesized based on the genomic DNA fragment, and with use of them two cDNA fragments were obtained by the 3'- and 5'-RACE methods. Finally, the third primers were synthesized based on the sequences of the two cDNA fragments and one genomic DNA fragment, and with use of them a full-length cDNA of mMBP was isolated and shown to comprise a putative 633 bp open reading frame encoding 210 amino acid residues. BLAST analysis revealed that mMBP has identities by 26 ~ 55% to several proteins including the regeneration-upregulated protein 3 from the same species. Whether mMBP is involved in the regeneration of the worm is under investigation.

New insights into the role of Jmjd3 and Utx in axial skeletal formation in mice

Jmjd3 and Utx are demethylases specific for lysine 27 of histone H3. Previous reports indicate that Jmjd3 is essential for differentiation of various cell types, such as macrophages and epidermal cells in mice, whereas Utx is involved in cancer and developmental diseases in humans and mice, as well as Hox regulation in zebrafish and nematodes. Here, we report that Jmjd3, but not Utx, is involved in axial skeletal formation in mice. A Jmjd3 mutant embryo (Jmjd3^Δ18/Δ18), but not a catalytically inactive Utx truncation mutant (Utx^-/y), showed anterior homeotic transformation. Quantitative RT-PCR and microarray analyses showed reduced Hox expression in both Jmjd3^Δ18/Δ18 embryos and tailbuds, whereas levels of Hox activators, such as Wnt signaling factors and retinoic acid synthases, did not decrease, which suggests that Jmjd3 plays a regulatory role in Hox expression during axial patterning. Chromatin immunoprecipitation analyses of embryo tailbud tissue showed trimethylated lysine 27 on histone H3 to be at higher levels at the Hox loci in Jmjd3^Δ18/Δ18 mutants compared with wild-type tailbuds. In contrast, trimethylated lysine 4 on histone H3 levels were found to be equivalent in wild-type and Jmjd3^Δ18/Δ18 tailbuds. Demethylase-inactive Jmjd3 mutant embryos showed the same phenotype as Jmjd3^Δ18/Δ18 mice. These results suggest that the demethylase activity of Jmjd3, but not that of Utx, affects mouse axial patterning in concert with alterations in Hox gene expression.-Naruse, C., Shibata, S., Tamura, M., Kawaguchi, T., Abe, K., Sugihara, K., Kato, T., Nishiuchi, T., Wakana, S., Ikawa, M., Asano, M. New insights into the role of Jmjd3 and Utx in axial skeletal formation in mice.

Biological roles of glycans

Simple and complex carbohydrates (glycans) have long been known to play major metabolic, structural and physical roles in biological systems. Targeted microbial binding to host glycans has also been studied for decades. But such biological roles can only explain some of the remarkable complexity and organismal diversity of glycans in nature. Reviewing the subject about two decades ago, one could find very few clear-cut instances of glycan-recognition-specific biological roles of glycans that were of intrinsic value to the organism expressing them. In striking contrast there is now a profusion of examples, such that this updated review cannot be comprehensive. Instead, a historical overview is presented, broad principles outlined and a few examples cited, representing diverse types of roles, mediated by various glycan classes, in different evolutionary lineages. What remains unchanged is the fact that while all theories regarding biological roles of glycans are supported by compelling evidence, exceptions to each can be found. In retrospect, this is not surprising. Complex and diverse glycans appear to be ubiquitous to all cells in nature, and essential to all life forms. Thus, >3 billion years of evolution consistently generated organisms that use these molecules for many key biological roles, even while sometimes coopting them for minor functions. In this respect, glycans are no different from other major macromolecular building blocks of life (nucleic acids, proteins and lipids), simply more rapidly evolving and complex. It is time for the diverse functional roles of glycans to be fully incorporated into the mainstream of biological sciences.

RNA-Sequencing for profiling goat milk transcriptome in colostrum and mature milk

BACKGROUND

In this work we aimed at sequencing and assembling the goat milk transcriptome corresponding at colostrum and 120 days of lactation. To reconstruct transcripts we used both the genome as reference, and a de novo assembly approach. Additionally, we aimed at identifying the differentially expressed genes (DEGs) between the two lactation stages and at analyzing the expression of genes involved in oligosaccharides metabolism.

RESULTS

A total of 44,635 different transcripts, organized in 33,757 tentative genes, were obtained using the goat genome as reference. A significant sequence similarity match was found for 40,353 transcripts (90%) against the NCBI NT and for 35,701 (80%) against the NR databases. 68% and 69% of the de novo assembled transcripts, in colostrum and 120 days of lactation samples respectively, have a significant match with the merged transcriptome obtained using Cufflinks/Cuffmerge. CSN2, PAEP, CSN1S2, CSN3, LALBA, TPT1, FTH1, M-SAA3, SPP1, GLYCAM1, EEF1A1, CTSD, FASN, RPS29, CSN1S1, KRT19 and CHEK1 were found between the top fifteen highly expressed genes. 418 loci were differentially expressed between lactation stages, among which 207 and 122 were significantly up- and down-regulated in colostrum, respectively. Functional annotation and pathway enrichment analysis showed that in goat colostrum somatic cells predominate biological processes involved in glycolysis, carbohydrate metabolism, defense response, cytokine activity, regulation of cell proliferation and cell death, vasculature development, while in mature milk, biological process associated with positive regulation of lymphocyte activation and anatomical structure morphogenesis are enriched. The analysis of 144 different oligosaccharide metabolism-related genes showed that most of these (64%) were more expressed in colostrum than in mature milk, with eight expressed at very high levels (SLCA3, GMSD, NME2, SLC2A1, B4GALT1, B3GNT2, NANS, HEXB).

CONCLUSIONS

To our knowledge, this is the first study comparing goat transcriptome of two lactation stages: colostrum and 120 days. Our findings suggest putative differences of expression between stages and can be envisioned as a base for further research in the topic. Moreover because a higher expression of genes involved in immune defense response, carbohydrate metabolism and related to oligosaccharide metabolism was identified in colostrum we here corroborate the potential of goat milk as a natural source of lactose-derived oligosaccharides and for the development of functional foods.

Biosynthesis of milk fat, protein, and lactose: roles of transcriptional and posttranscriptional regulation

The demand for high-quality milk is increasing worldwide. The efficiency of milk synthesis can be improved by taking advantage of the accumulated knowledge of the transcriptional and posttranscriptional regulation of genes coding for proteins involved in the synthesis of fat, protein, and lactose in the mammary gland. Research in this area is relatively new, but data accumulated in the last 10 years provide a relatively clear picture. Milk fat synthesis appears to be regulated, at least in bovines, by an interactive network between SREBP1, PPARγ, and LXRα, with a potential role for other transcription factors, such as Spot14, ChREBP, and Sp1. Milk protein synthesis is highly regulated by insulin, amino acids, and amino acid transporters via transcriptional and posttranscriptional routes, with the insulin-mTOR pathway playing a central role. The transcriptional regulation of lactose synthesis is still poorly understood, but it is clear that glucose transporters play an important role. They can also cooperatively interact with amino acid transporters and the mTOR pathway. Recent data indicate the possibility of nutrigenomic interventions to increase milk fat synthesis by feeding long-chain fatty acids and milk protein synthesis by feeding amino acids. We propose a transcriptional network model to account for all available findings. This model encompasses a complex network of proteins that control milk synthesis with a cross talk between milk fat, protein, and lactose regulation, with mTOR functioning as a central hub.

What Have We Learned from Glycosyltransferase Knockouts in Mice?

There are five major classes of glycan including N- and O-glycans, glycosaminoglycans, glycosphingolipids, and glycophosphatidylinositol anchors, all expressed at the molecular frontier of each mammalian cell. Numerous biological consequences of altering the expression of mammalian glycans are understood at a mechanistic level, but many more remain to be characterized. Mouse mutants with deleted, defective, or misexpressed genes that encode activities necessary for glycosylation have led the way to identifying key functions of glycans in biology. However, with the advent of exome sequencing, humans with mutations in genes involved in glycosylation are also revealing specific requirements for glycans in mammalian development. The aim of this review is to summarize glycosylation genes that are necessary for mouse embryonic development, pathway-specific glycosylation genes whose deletion leads to postnatal morbidity, and glycosylation genes for which effects are mild, but perturbation of the organism may reveal functional consequences. General strategies for generating and interpreting the phenotype of mice with glycosylation defects are discussed in relation to human congenital disorders of glycosylation (CDG).

Mechanisms of fertilization elucidated by gene-manipulated animals

Capacitation and the acrosome reaction are key phenomena in mammalian fertilization. These phenomena were found more than 60 years ago. However, fundamental questions regarding the nature of capacitation and the timing of the acrosome reaction remain unsolved. Factors were postulated over time, but as their roles were not verified by gene-disruption experiments, widely accepted notions concerning the mechanism of fertilization are facing modifications. Today, although in vitro fertilization systems remain our central research tool, the importance of in vivo observations must be revisited. Here, primarily focusing on our own research, I summarize how in vivo observations using gene-manipulated animals have elucidated new concepts in the mechanisms of fertilization.

Role of aberrant IgG glycosylation in the pathogenesis of inflammatory bowel disease

The intestine is one of the most important organs associated with the immune system. It is thought that disruption of intestinal immunity causes inflammatory bowel disease (IBD). Recent advances in immune glycobiology have provided novel insights into many human diseases. For example, studies of glycosylation remodeling in mice have underscored the importance of oligosaccharides in the pathogenesis of IBD. Furthermore, aberrant glycosylation of IgG is a good serum marker of IBD activity. In this review, we examine current understanding of the role of aberrant glycosylation in the pathogenesis of IBD in terms of our original data and recent reports.

The Acrosome Reaction: A Historical Perspective

Acrosome reaction is often referred to as acrosomal exocytosis, but it differs significantly from normal exocytosis. While the vesicle membrane initially holding excreting molecules remains on the cell surface during exocytosis, the outer acrosomal membrane and plasma membrane are lost by forming vesicles during acrosome reaction. In this context, the latter process resembles a release of exosome. However, recent experimental data indicate that the most important roles of acrosome reaction lie not in the release of acrosomal contents (or "vesiculated" plasma and outer acrosomal membrane complexes) but rather in changes in sperm membrane. This review describes the mechanism of fertilization vis-a-vis sperm membrane change, with a brief historical overview of the half-century study of acrosome reaction.

The multiple roles of epidermal growth factor repeat O-glycans in animal development

The epidermal growth factor (EGF)-like repeat is a common, evolutionarily conserved motif found in secreted proteins and the extracellular domain of transmembrane proteins. EGF repeats harbor six cysteine residues which form three disulfide bonds and help generate the three-dimensional structure of the EGF repeat. A subset of EGF repeats harbor consensus sequences for the addition of one or more specific O-glycans, which are initiated by O-glucose, O-fucose or O-N-acetylglucosamine. These glycans are relatively rare compared to mucin-type O-glycans. However, genetic experiments in model organisms and cell-based assays indicate that at least some of the glycosyltransferases involved in the addition of O-glycans to EGF repeats play important roles in animal development. These studies, combined with state-of-the-art biochemical and structural biology experiments have started to provide an in-depth picture of how these glycans regulate the function of the proteins to which they are linked. In this review, we will discuss the biological roles assigned to EGF repeat O-glycans and the corresponding glycosyltransferases. Since Notch receptors are the best studied proteins with biologically-relevant O-glycans on EGF repeats, a significant part of this review is devoted to the role of these glycans in the regulation of the Notch signaling pathway. We also discuss recently identified proteins other than Notch which depend on EGF repeat glycans to function properly. Several glycosyltransferases involved in the addition or elongation of O-glycans on EGF repeats are mutated in human diseases. Therefore, mechanistic understanding of the functional roles of these carbohydrate modifications is of interest from both basic science and translational perspectives.

Challenge to the suppression of tumor growth by the β4-galactosyltransferase genes

It has been well established that structural changes in glycans attached to proteins and lipids are associated with malignant transformation of cells. We focused on galactose residues among the sugars since they are involved in the galectin-mediated biology, and many carbohydrate antigens are frequently expressed on this sugar. We found changes in the expression of the β4-galactosyltransferase (β4GalT) 2 and 5 genes in cancer cells: decreased expression of the β4GalT2 gene and increased expression of the β4GalT5 gene. The growth of mouse melanoma cells showing enhanced expression of the β4GalT2 gene or reduced expression of the β4GalT5 gene is inhibited remarkably in syngeneic mice. Tumor growth inhibition is probably caused by the induction of apoptosis, inhibition of angiogenesis, and/or reduced MAPK signals. Direct transduction of human β4GalT2 cDNA together with the adenovirus vector into human hepatocellular carcinoma cells grown in SCID mice results in marked growth retardation of the tumors. β4GalT gene-transfer appears to be a potential tool for cancer therapy.

Mannose supplements induce embryonic lethality and blindness in phosphomannose isomerase hypomorphic mice

Patients with congenital disorder of glycosylation (CDG), type Ib (MPI-CDG or CDG-Ib) have mutations in phosphomannose isomerase (MPI) that impair glycosylation and lead to stunted growth, liver dysfunction, coagulopathy, hypoglycemia, and intestinal abnormalities. Mannose supplements correct hypoglycosylation and most symptoms by providing mannose-6-P (Man-6-P) via hexokinase. We generated viable Mpi hypomorphic mice with residual enzymatic activity comparable to that of patients, but surprisingly, these mice appeared completely normal except for modest (~15%) embryonic lethality. To overcome this lethality, pregnant dams were provided 1-2% mannose in their drinking water. However, mannose further reduced litter size and survival to weaning by 40 and 66%, respectively. Moreover, ~50% of survivors developed eye defects beginning around midgestation. Mannose started at birth also led to eye defects but had no effect when started after eye development was complete. Man-6-P and related metabolites accumulated in the affected adult eye and in developing embryos and placentas. Our results demonstrate that disturbing mannose metabolic flux in mice, especially during embryonic development, induces a highly specific, unanticipated pathological state. It is unknown whether mannose is harmful to human fetuses during gestation; however, mothers who are at risk for having MPI-CDG children and who consume mannose during pregnancy hoping to benefit an affected fetus in utero should be cautious.

The cell biology of mammalian fertilization

Fertilization is the process by which eggs and spermatozoa interact, achieve mutual recognition, and fuse to create a zygote, which then develops to form a new individual, thus allowing for the continuity of a species. Despite numerous studies on mammalian fertilization, the molecular mechanisms underpinning the fertilization event remain largely unknown. However, as I summarize here, recent work using both gene-manipulated animals and in vitro studies has begun to elucidate essential sperm and egg molecules and to establish predictive models of successful fertilization.

Mice overexpressing β-1,4-Galactosyltransferase I are resistant to TNF-induced inflammation and DSS-induced colitis

Glycosylation is an essential post-translational modification, which determines the function of proteins and important processes such as inflammation. β-1,4-galactosyltransferase I (βGalT1) is a key enzyme involved in the addition of galactose moieties to glycoproteins. Intestinal mucins are glycoproteins that protect the gut barrier against invading pathogens and determine the composition of the intestinal microbiota. Proper glycosylation of mucus is important in this regard. By using ubiquitously expressing βGalT1 transgenic mice, we found that this enzyme led to strong galactosylation of mucus proteins, isolated from the gut of mice. This galactosylation was associated with a drastic change in composition of gut microbiota, as TG mice had a significantly higher Firmicutes to Bacteroidetes ratio. TG mice were strongly protected against TNF-induced systemic inflammation and lethality. Moreover, βGalT1 transgenic mice were protected in a model of DSS-induced colitis, at the level of clinical score, loss of body weight, colon length and gut permeability. These studies put βGalT1 forward as an essential protective player in exacerbated intestinal inflammation. Optimal galactosylation of N-glycans of mucus proteins, determining the bacterial composition of the gut, is a likely mechanism of this function.

2'-fucosyllactose: an abundant, genetically determined soluble glycan present in human milk

Lactose is the preeminent soluble glycan in milk and a significant source of energy for most newborn mammals. Elongation of lactose with additional monosaccharides gives rise to a varied repertoire of free soluble glycans such as 2'-fucosyllactose (2'-FL), which is the most abundant oligosaccharide in human milk. In infants, 2'-FL is resistant to digestion and reaches the colon where it is partially fermented, behaving as soluble prebiotic fiber. Evidence also suggests that portions of small soluble milk glycans, including 2'-FL, are absorbed, thus raising the possibility of systemic biological effects. 2'-FL bears an epitope of the Secretor histo-blood group system; approximately 70-80% of all milk samples contain 2'-FL, since its synthesis depends on a fucosyltransferase that is not uniformly expressed. The fact that some infants are not exposed to 2'-FL has helped researchers to retrospectively probe for biological activities of this glycan. This review summarizes the attributes of 2'-FL in terms of its occurrence in mammalian phylogeny, its postulated biological activities, and its variability in human milk.

Disruption of Smad4 expression in T cells leads to IgA nephropathy-like manifestations

The link between glomerular IgA nephropathy (IgAN) and T helper 2 (Th2) response has been implicated, however, the mechanisms are poorly defined because of the lack of an appropriate model. Here we report a novel murine model characterized by lineage-restricted deletion of the gene encoding MAD homologue 4 (Smad4) in T cells (Smad4(co/co;Lck-cre) ). Loss of Smad4 expression in T cells results in overproduction of Th2 cytokines and high serum IgA levels. We found that Smad4(co/co;Lck-cre) mice exhibited massive glomerular IgA deposition, increased albumin creatinine ratio, aberrant glycosylated IgA, IgA complexed with IgG1 and IgG2a, and polymeric IgA, all known features of IgAN in humans. Furthermore, we examined the β1, 4-galactosyltransferases (β4GalT) enzyme which is involved in the synthesis of glycosylated murine IgA, and we found reduced β4GalT2 and β4GalT4 mRNA levels in B cells. These findings indicate that Smad4(co/co;Lck-cre) mice could be a useful model for studying the mechanisms between IgAN and Th2 response, and further, disruption of Smad4-dependent signaling in T cells may play an important role in the pathogenesis of human IgAN and contributing to a Th2 T cell phenotype.

Generation of a mouse model with down-regulated U50 snoRNA (SNORD50) expression and its organ-specific phenotypic modulation

Box C/D-type small nucleolar RNAs (snoRNAs) are functional RNAs responsible for mediating 2'-O-ribose methylation of ribosomal RNAs (rRNAs) within the nucleolus. In the past years, evidence for the involvement of human U50 snoRNA in tumorigenesis has been accumulating. We previously identified U50HG, a non-protein-coding gene that hosted a box C/D-type U50 snoRNA, in a chromosomal breakpoint in a human B-cell lymphoma. Mouse genome analysis revealed four mouse U50 (mU50) host-genes: three mU50HG-a gene variants that were clustered in the genome and an mU50HG-b gene that we supposed to be the U50HG ortholog. In this study, to investigate the physiological importance of mU50 snoRNA and its involvement in tumorigenesis, we eliminated mU50 snoRNA sequences from the mU50HG-b gene. The established mouse line (ΔmU50(HG-b)) showed a significant reduction of mU50 snoRNA expression without alteration of the host-gene length and exon-intron structure, and the corresponding target rRNA methylation in various organs was reduced. Lifelong phenotypic monitoring showed that the ΔmU50(HG-b) mice looked almost normal without accelerated tumorigenicity; however, a notable difference was the propensity for anomalies in the lymphoid organs. Transcriptome analysis showed that dozens of genes, including heat shock proteins, were differentially expressed in ΔmU50(HG-b) mouse lymphocytes. This unique model of a single snoRNA knockdown with intact host-gene expression revealed further new insights into the discrete transcriptional regulation of multiple mU50 host-genes and the complicated dynamics involved in organ-specific processing and maintenance of snoRNAs.

The function of chaperone proteins in the assemblage of protein complexes involved in gamete adhesion and fusion processes

The remarkable complexity of the molecular events governing adhesion and fusion of the male and female gametes is becoming apparent. Novel research suggests that these highly specific cellular interactions are facilitated by multiprotein complexes that are delivered to and/or assembled on the surface of the gametes by molecular chaperones in preparation for sperm-egg interaction. While the activation of these molecular chaperones and the mechanisms by which they shuttle proteins to the surface of the cell remain the subject of ongoing investigation, a compelling suggestion is that these processes are augmented by dynamic membrane microdomains or lipid rafts that migrate to the apical region of the sperm head after capacitation. Preliminary studies of the oocyte plasma membrane have also revealed the presence of lipid rafts comprising several molecular chaperones, raising the possibility that similar mechanisms may be involved in the activation of maternal fusion machinery and the regulation of oocyte plasma membrane integrity. Despite these findings, the analysis of oocyte surface multiprotein complexes is currently lacking. Further analyses of the intermediary proteins that facilitate the expression of key players in sperm-egg fusion are likely to deliver important insights into this unique event, which culminates in the cytoplasmic continuity of the male and female gametes.

The maternal to zygotic transition in mammals

Prior to activation of the embryonic genome, the initiating events of mammalian development are under maternal control and include fertilization, the block to polyspermy and processing sperm DNA. Following gamete union, the transcriptionally inert sperm DNA is repackaged into the male pronucleus which fuses with the female pronucleus to form a 1-cell zygote. Embryonic transcription begins during the maternal to zygotic transfer of control in directing development. This transition occurs at species-specific times after one or several rounds of blastomere cleavage and is essential for normal development. However, even after activation of the embryonic genome, successful development relies on stored maternal components without which embryos fail to progress beyond initial cell divisions. Better understanding of the molecular basis of maternal to zygotic transition including fertilization, the activation of the embryonic genome and cleavage-stage development will provide insight into early human development that should translate into clinical applications for regenerative medicine and assisted reproductive technologies.

The molecular basis of gamete recognition in mice and humans

Successful fertilization heralds the onset of development and requires both gamete recognition and a definitive block to polyspermy. Sperm initially bind and penetrate the extracellular zona pellucida (ZP) that surrounds ovulated eggs, but are unable to bind the zona surrounding preimplantation embryos. The ZP of humans is composed of four (ZP1-4) and that of mouse three (ZP1-3) glycoproteins. Models for gamete recognition developed in mice had proposed that sperm bind to ZP3 glycans. However, phenotypes observed in genetically engineered mice are not consistent with this widely accepted model. More recently, taking advantage of the observation that human sperm do not bind to mouse eggs, human ZP2 was defined as the zona ligand in transgenic mouse models using gain-of-function assays. The sperm-binding site is an N-terminal domain of ZP2 that is cleaved by ovastacin, a metalloendoprotease released from egg cortical granules following fertilization. Proteolysis of this docking site provides a definitive block to polyspermy as sperm bind to uncleaved, but not cleaved ZP2 even after fertilization and cortical granule exocytosis. While progress has been made in defining the ZP ligand, less headway has been made in identifying the cognate sperm receptor. Although a number of sperm receptor candidates have been documented to interact with specific proteins in the ZP in vitro, continued fertility after genetic ablation of the cognate gene indicates that none are essential for gamete recognition. These on-going investigations inform reproductive medicine and suggest new therapies to improve fertility and/or provide contraception, thus expanding reproductive choices for human couples.

Large-scale identification of target proteins of a glycosyltransferase isozyme by Lectin-IGOT-LC/MS, an LC/MS-based glycoproteomic approach

Model organisms containing deletion or mutation in a glycosyltransferase-gene exhibit various physiological abnormalities, suggesting that specific glycan motifs on certain proteins play important roles in vivo. Identification of the target proteins of glycosyltransferase isozymes is the key to understand the roles of glycans. Here, we demonstrated the proteome-scale identification of the target proteins specific for a glycosyltransferase isozyme, β1,4-galactosyltransferase-I (β4GalT-I). Although β4GalT-I is the most characterized glycosyltransferase, its distinctive contribution to β1,4-galactosylation has been hardly described so far. We identified a large number of candidates for the target proteins specific to β4GalT-I by comparative analysis of β4GalT-I-deleted and wild-type mice using the LC/MS-based technique with the isotope-coded glycosylation site-specific tagging (IGOT) of lectin-captured N-glycopeptides. Our approach to identify the target proteins in a proteome-scale offers common features and trends in the target proteins, which facilitate understanding of the mechanism that controls assembly of a particular glycan motif on specific proteins.

Human sperm bind to the N-terminal domain of ZP2 in humanized zonae pellucidae in transgenic mice

Fertilization requires taxon-specific gamete recognition, and human sperm do not bind to zonae pellucidae (ZP1-3) surrounding mouse eggs. Using transgenesis to replace endogenous mouse proteins with human homologues, gain-of-function sperm-binding assays were established to evaluate human gamete recognition. Human sperm bound only to zonae pellucidae containing human ZP2, either alone or coexpressed with other human zona proteins. Binding to the humanized matrix was a dominant effect that resulted in human sperm penetration of the zona pellucida and accumulation in the perivitelline space, where they were unable to fuse with mouse eggs. Using recombinant peptides, the site of gamete recognition was located to a defined domain in the N terminus of ZP2. These results provide experimental evidence for the role of ZP2 in mediating sperm binding to the zona pellucida and support a model in which human sperm-egg recognition is dependent on an N-terminal domain of ZP2, which is degraded after fertilization to provide a definitive block to polyspermy.

Aberrant promoter methylation of beta-1,4 galactosyltransferase 1 as potential cancer-specific biomarker of colorectal tumors

Epigenetic alterations, such as CpG islands methylation and histone modifications, are recognized key characteristics of cancer. Glycogenes are a group of genes which epigenetic status was found to be changed in several tumors. In this study, we determined promoter methylation status of the glycogene beta-1,4-galactosyltransferase 1 (B4GALT1) in colorectal cancer patients. Methylation status of B4GALT1 was assessed in 130 colorectal adenocarcinomas, 13 adenomas, and in paired normal tissue using quantitative methylation specific PCR (QMSP). B4GALT1 mRNA expression was evaluated in methylated/unmethylated tumor and normal specimens. We also investigated microsatellite stability and microsatellite instability status and KRAS/BRAF mutations. Discriminatory power of QMSP was assessed by receiving operating curve (ROC) analysis on a training set of 24 colorectal cancers and paired mucosa. The area under the ROC curve (AUC) was 0.737 (95% confidence interval [CI]:0.591-0.881, P = 0.005) with an optimal cutoff value of 2.07 yielding a 54% sensitivity (95% CI: 35.1%-72.1%) and a specificity of 91.7% (95% CI: 74.1%-97.7%). These results were confirmed in an independent validation set where B4GALT1 methylation was detected in 52/106 patients. An inverse correlation was observed between methylation and B4GALT1 mRNA expression levels (r = -0.482, P = 0.037). Significant differences in methylation levels and frequencies was demonstrated in invasive lesions as compared with normal mucosa (P = 0.0001) and in carcinoma samples as compared with adenoma (P = 0.009). B4GALT1 methylation is a frequent and specific event in colorectal cancer and correlates with downregulation of mRNA expression. These results suggest that the glycogene B4GALT1 represent a valuable candidate biomarker of invasive phenotype of colorectal cancer.