The recognition of carbohydrate moieties by cells of the innate immune system is emerging as an essential element in antifungal immunity, but despite the number and diversity of lectins expressed by innate immune cells, few carbohydrate receptors have been characterized. Mincle, a C-type lectin, is expressed predominantly on macrophages, and is here shown to play a role in macrophage responses to the yeast Candida albicans. After exposure to the yeast in vitro, Mincle localized to the phagocytic cup, but it was not essential for phagocytosis. In the absence of Mincle, production of TNF-α by macrophages was reduced, both in vivo and in vitro. In addition, mice lacking Mincle showed a significantly increased susceptibility to systemic candidiasis. Thus, Mincle plays a novel and nonredundant role in the induction of inflammatory signaling in response to C. albicans infection.

Ras signaling appears to be mediated in part by transcription factors that belong to the ets gene family. To identify downstream targets for the Ras signal transduction pathway, we have used Ras-transformed mouse fibroblasts to isolate a new member of the ets gene family, net. Net has sequence similarity in three regions with the ets factors Elkl and SAP1, which have been implicated in the serum response of the fos promoter. Net shares various properties with these proteins, including the ability to bind to ets DNA motifs through the Ets domain of the protein and form ternary complexes with the serum response factor SRF on the fos serum response element, SRE. However, Net differs from Elkl and SAP1 in a number of ways. The pattern of net RNA expression in adult mouse tissues is different. Net has negative effects on transcription in a number of assays, unlike Elkl. Strikingly, Ras, Src, and Mos expression switch Net activity to positive. The study of Net should help in understanding the interplay between Net and other members of the Elk subfamily and their contribution to signal transduction through Ras to the nucleus.

Background: C-type lectins play important roles in immunity and homeostasis.Results: CLECSF8 is expressed on neutrophils and monocytes and can mediate phagocytosis, the respiratory burst and inflammatory cytokine production, in part through association with a novel adaptor.Conclusion: CLECSF8 can trigger cellular activation.Significance: This study identifies a novel C-type lectin that can control immune cell function.

The ternary complex factors (TCFs) Net, Elk-1 and Sap-1 regulate immediate early genes through serum response elements (SREs) in vitro, but, surprisingly, their in vivo roles are unknown. Net is a repressor that is expressed in sites of vasculogenesis during mouse development. We have made gene-targeted mice that express a hypomorphic mutant of Net, Netd, which lacks the Ets DNA-binding domain. Strikingly, homozygous mutant mice develop a vascular defect and up-regulate an immediate early gene implicated in vascular disease, egr-1. They die after birth due to respiratory failure, resulting from the accumulation of chyle in the thoracic cage (chylothorax). The mice have dilated lymphatic vessels (lymphangiectasis) as early as E16.5. Interestingly, they express more egr-1 in heart and pulmonary arteries at E18.5. Net negatively regulates the egr-1 promoter and binds speci®-cally to SRE-5. Egr-1 has been associated with pathologies involving vascular stenosis (e.g. atherosclerosis), and here egr-1 dysfunction could possibly be associated with obstructions that ultimately affect the lymphatics. These results show that Net is involved in vascular biology and egr-1 regulation in vivo. Keywords: egr-1/Elk-3/ERP/Net/Sap-2 IntroductionThe ternary complex factors (TCFs) form a subfamily of Ets-domain transcription factors. The three TCFs, Elk-1, Sap-1 and Net/Sap-2/Erp/Elk-3 (Price et al., 1996;Wasylyk et al., 1998), have four conserved domains, A±D. A is the Ets DNA-binding domain (DBD). The B-box interacts with the serum response factor (SRF). C is a transcriptional activation domain that is stimulated by mitogen-activated protein (MAP) kinase phosphorylation. The D-domain is a MAP kinase-binding site and a nuclear localization signal. The TCFs are nuclear mediators of cellular responses to the activation of MAP kinase pathways. Net differs from the other TCFs in that in basal conditions, in which MAP kinases are not activated, it strongly inhibits transcription. Repression is mediated by two domains, the NID (Maira et al., 1996) and the CID (Criqui-Filipe et al., 1999). The TCFs form ternary complexes with SRF on serum response elements (SREs) of immediate early gene promoters, such as c-fos, egr-1 and jun-B. The SRE is constitutively occupied by factors, and extracellular signals are thought to lead to both phosphorylation of the complex and changes in its composition due to the exchange of TCFs.The in vivo role of the TCFs is poorly understood. They may regulate the expression of immediate early genes in response to various inductive stimuli. The TCFs are expressed in many cell types and tissues (Giovane et al., 1994;Lopez et al., 1994;Magnaghi-Jaulin et al., 1996;Nozaki et al., 1996;Sgambato et al., 1998), but their precise in vivo expression patterns are not well known. Net is expressed during mouse development at E7.5±8.5 in developing vascular primordia, including the yolk sac blood islands, allantoic vessels, heart endocardium and dorsal aortae (Ayadi et al., 2001). Vascular endothelial cell expression persists ...

The C-type lectin dendritic cell−specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN) mediates the innate immune recognition of microbial carbohydrates. We investigated the function of this molecule in the host response to pathogens in vivo, by generating mouse lines lacking the DC-SIGN homologues SIGNR1, SIGNR3, and SIGNR5. Resistance to Mycobacterium tuberculosis was impaired only in SIGNR3-deficient animals. SIGNR3 was expressed in lung phagocytes during infection, and interacted with M. tuberculosis bacilli and mycobacterial surface glycoconjugates to induce secretion of critical host defense inflammatory cytokines, including tumor necrosis factor (TNF). SIGNR3 signaling was dependent on an intracellular tyrosine-based motif and the tyrosine kinase Syk. Thus, the mouse DC-SIGN homologue SIGNR3 makes a unique contribution to protection of the host against a pulmonary bacterial pathogen.

Two overlapping genomic clones containing the murine granulocyte‐macrophage colony stimulating factor (GM‐CSF) gene have been isolated. On the basis of transfection experiments, we have established that a 9‐kb BamHI fragment from one of these recombinants encodes biologically active GM‐CSF. As deduced from nucleotide sequence analysis, the GM‐CSF gene comprises four exons encompassing 2.5 kb of genomic DNA. Primer extension analysis of GM‐CSF mRNA identifies a transcriptional initiation site 35 bp upstream of a single translational initiation codon in‐frame with the GM‐CSF coding sequences and 28 bp downstream of a TATA promoter consensus sequence. Pre‐GM‐CSF molecules encoded by mRNAs originating from this promoter would include a hydrophobic leader sequence typical for a secreted protein. Intriguingly, sequences present at the 5′ end of a GM‐CSF cDNA clone previously isolated in our laboratory are not contained within either of the genomic clones and must therefore be transcribed from a promoter located at least 10 kb 5′ of the main body of the gene. mRNAs transcribed from this alternative upstream promoter possess an additional initiating codon and potentially encode a pre‐GM‐CSF polypeptide with an atypical NH2‐terminal leader peptide. Comparison of the nucleotide sequence of the GM‐CSF gene with that of other haemopoietic growth factor genes has revealed a common decanucleotide (5′‐GPuGPuTTPyCAPy‐3′) within their respective 5′‐flanking regions which may be involved in their co‐ordinate regulation.

To investigate the role of mannose-binding lectin-A (MBL-A) in protection against infectious disease, MBL-A−/−-deficient mice were generated. Using a well-characterized mouse model of human filarial nematode infection, nematode survival and protective immune responses were tested in vivo. Blood-borne Brugia malayi microfilariae survived for significantly longer time periods in MBL-A−/− than in wild-type (WT) mice. However, no differences in either splenic cytokine responses or induction of leukocytes in the blood were observed. A profound abrogation of Ag-specific IgM levels was measured in B. malayi-infected MBL-A−/− mice, and some IgG isotypes were higher than those observed in WT animals. To establish whether there was a defect in Ab responses per se in MBL-A−/− mice or the effect was specific to filarial infection, we immunized these mice with OVA or a carbohydrate-free protein. Significantly, Ag-specific IgM responses were defective to both of these Ags, and Ag-specific IgG responses were largely unaffected. Furthermore, in naive mice, total IgM levels did not differ between MBL-A−/− and WT mice. This article describes the first demonstration that MBL-A may function independently of MBL-C and suggests that MBL-A, like other C-type lectins and members of the complement cascade, is intimately involved in the priming of the humoral Ab response.

The consortium for functional glycomics (CFG) was a large research initiative providing networking and resources for investigators studying the role of glycans and glycan-binding proteins in health and disease. Starting in 2001, six scientific cores were established to generate data, materials and new technologies. By the end of funding in 2011, the mouse phenotype core (MPC) submitted data to a website from the phenotype screen of 36 mutant mouse strains deficient in a gene for either a glycan-binding protein (GBP) or glycosyltransferase (GT). Each mutant strain was allotted three months for analysis and screened by standard phenotype assays used in the fields of immunology, histology, hematology, coagulation, serum chemistry, metabolism and behavior. Twenty of the deficient mouse strains had been studied in other laboratories, and additional tests were performed on these strains to confirm previous observations and discover new data. The CFG constructed 16 new homozygous mutant mouse strains and completed the initial phenotype screen of the majority of these new mutant strains. In total, >300 phenotype changes were observed, but considering the over 100 assays performed on each strain, most of the phenotypes were unchanged. Phenotype differences include abnormal testis morphology in GlcNAcT9- and Siglec-H-deficient mice and lethality in Pomgnt1-deficient mice. The numerous altered phenotypes discovered, along with the consideration of the significant findings of normality, will provide a platform for future characterization to understand the important roles of glycans and GBPs in the mechanisms of health and disease.