A novel function for SNAP29 (synaptosomal-associated protein of 29 kDa) in mast cell phagocytosis

CCAAT/enhancer-binding protein α-dependent regulation of granule formation in mast cells by intestinal bacteria

The antiallergic effects of gut microbiota have been attracting attention in recent years, but the underlying cellular and molecular mechanisms have not yet been fully understood. In this study, we aimed to investigate these mechanisms specifically focusing on mast cells. Mast cells retain intracellular granules containing various inflammatory mediators such as histamine, which are released outside the cells upon IgE and allergen stimulation. We previously reported that increased expression of the transcription factor, CCAAT/enhancer-binding protein α (C/EBPα), suppresses granule formation in mast cells and that Lacticaseibacillus casei JCM1134T (LC) upregulates C/EBPα levels. Here, granule formation in mouse bone marrow-derived mast cells was suppressed in a MyD88-dependent manner after LC treatment due to C/EBPα-dependent downregulation of the genes encoding serglycin (SRGN) and mast cell protease 4 (Mcpt4). Furthermore, C/EBPα expression was regulated by DNA methylation in the 5' region far upstream of the transcription start site. LC suppressed DNA methylation of specific CpG motifs in the 5' region of the C/EBPα gene. These results conclude that specific gut microbial components, such as those from LC, suppress granule formation in mast cells by inhibiting SRGN and Mcpt4 expression via reduced C/EBPα gene methylation.

Post-translational suppression of the high affinity IgE receptor expression on mast cells by an intestinal bacterium

Mast cells, which express the high-affinity IgE receptor (FcεRI) on their surface, play a crucial role in inducing allergic inflammation. Since mast cells are activated by crosslinking of FcεRI with IgE and allergens, the cell surface expression level of FcεRI is an important factor in determining the sensitivity to allergens. Recently, the involvement of gut microbiota in the prevalence and regulation of allergy has attracted attention but the precise underlying mechanisms are not fully understood. In this study, the effect of intestinal bacteria on cell surface expression of FcεRI was examined. Bacteroides acidifaciens type A 43 specifically suppressed cell surface expression of FcεRI on mouse bone marrow-derived mast cells (BMMCs) without reduction in FcεRI α and β-chain mRNA and total protein expression. The suppressive effect required sustained exposure to this bacterium, with a corresponding reduction in Erk activation. Inhibition of Erk decreased cell surface distribution of FcεRI in BMMCs, at least in part, through facilitated endocytosis of FcεRI. These results indicate that B. acidifaciens type A 43 suppresses cell surface expression of FcεRI on mast cells in a post-translational manner via inhibition of Erk. The suppression of FcεRI expression on mast cells by specific bacteria might be the underlying mechanism involved in the regulation of allergy by gut microbiota.

SNARE-Mediated Exocytosis in Neuronal Development

The formation of the nervous system involves establishing complex networks of synaptic connections between proper partners. This developmental undertaking requires the rapid expansion of the plasma membrane surface area as neurons grow and polarize, extending axons through the extracellular environment. Critical to the expansion of the plasma membrane and addition of plasma membrane material is exocytic vesicle fusion, a regulated mechanism driven by soluble N-ethylmaleimide-sensitive factor attachment proteins receptors (SNAREs). Since their discovery, SNAREs have been implicated in several critical neuronal functions involving exocytic fusion in addition to synaptic transmission, including neurite initiation and outgrowth, axon specification, axon extension, and synaptogenesis. Decades of research have uncovered a rich variety of SNARE expression and function. The basis of SNARE-mediated fusion, the opening of a fusion pore, remains an enigmatic event, despite an incredible amount of research, as fusion is not only heterogeneous but also spatially small and temporally fast. Multiple modes of exocytosis have been proposed, with full-vesicle fusion (FFV) and kiss-and-run (KNR) being the best described. Whereas most in vitro work has reconstituted fusion using VAMP-2, SNAP-25, and syntaxin-1; there is much to learn regarding the behaviors of distinct SNARE complexes. In the past few years, robust heterogeneity in the kinetics and fate of the fusion pore that varies by cell type have been uncovered, suggesting a paradigm shift in how the modes of exocytosis are viewed is warranted. Here, we explore both classic and recent work uncovering the variety of SNAREs and their importance in the development of neurons, as well as historical and newly proposed modes of exocytosis, their regulation, and proteins involved in the regulation of fusion kinetics.

Mast cells exhibit intracellular microbicidal activity against Aggregatibacter actinomycetemcomitans

BACKGROUND AND OBJECTIVE

Several studies have demonstrated that mast cells are equipped with versatile tools to combat and kill bacteria. Additionally, mast cells produce and secrete a variety of mediators, which either regulate the host's immune system or directly attack bacteria. In this study, the intracellular microbicidal capacity of mast cells against Aggregatibacter actinomycetemcomitans was evaluated.

METHODS

Murine mast cells were challenged in vitro with A actinomycetemcomitans for 3, 5, 10, and 24 hours. Subsequently, the colony-forming units were counted. Additionally, the production and release of nitric oxide and hydrogen peroxide were analyzed by DAF-FM diacetate, the Griess reaction, and the Amplex Red kit, respectively. Cell death was evaluated using FITC Annexin V and propidium iodide staining.

RESULTS

Mast cells are able to efficiently eliminate periodontopathogen, with best results after 10 hours of intracellular challenge. The production/release of nitric oxide-and to a lesser extent of hydrogen peroxide-by mast cells was in agreement with its microbicidal capacity. Ninety percent of the mast cells  maintained their cellular viability even after 24 hours of bacterial challenge.

CONCLUSIONS

This is-to the best of our knowledge-the first report to describe the intracellular microbicidal activity of mast cells against A actinomycetemcomitans, concerning the production and release of potentially bactericidal substances. Further, the low number of cell deaths confirms that the decreased number of colony-forming units was due to the higher antimicrobial activity of mast cells. The results highlight the importance of these cells in the defense mechanisms of biofilm-induced periodontal disease.

Detection of Mast Cells and Basophils by Immunohistochemistry

Staining cells or tissues with basic dyes was the mainstay of mast cell and basophil detection methods for more than a century following the first identification of these cell types using such methods. These techniques have now been largely supplanted by immunohistochemical procedures with monoclonal antibodies directed against unique constituents of these cell types. Immunohistochemistry with antibodies specific for the granule protease tryptase provides a more sensitive and discriminating means for detecting mast cells than using the classical histochemical procedures, and using antibodies specific for products of basophils (2D7 antigen and basogranulin) has allowed detection of basophils that infiltrate into tissues. The application of immunohistochemistry to detect more than one marker in the same cell has underpinned concepts of mast cell heterogeneity based on differential expression of chymase and other proteases. The double labeling procedures employed have also provided a means for investigating the expression of cytokines and a range of other products. Protocols are here set out that have been used for immunohistochemical detection of mast cells and basophils and their subpopulations in human tissues. Consideration is given to pitfalls to avoid and to a range of alternative approaches.

In the line-up: deleted genes associated with DiGeorge/22q11.2 deletion syndrome: are they all suspects?

BACKGROUND

22q11.2 deletion syndrome (22q11DS), a copy number variation (CNV) disorder, occurs in approximately 1:4000 live births due to a heterozygous microdeletion at position 11.2 (proximal) on the q arm of human chromosome 22 (hChr22) (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011). This disorder was known as DiGeorge syndrome, Velo-cardio-facial syndrome (VCFS) or conotruncal anomaly face syndrome (CTAF) based upon diagnostic cardiovascular, pharyngeal, and craniofacial anomalies (McDonald-McGinn and Sullivan, Medicine 90:1-18, 2011; Burn et al., J Med Genet 30:822-4, 1993) before this phenotypic spectrum was associated with 22q11.2 CNVs. Subsequently, 22q11.2 deletion emerged as a major genomic lesion associated with vulnerability for several clinically defined behavioral deficits common to a number of neurodevelopmental disorders (Fernandez et al., Principles of Developmental Genetics, 2015; Robin and Shprintzen, J Pediatr 147:90-6, 2005; Schneider et al., Am J Psychiatry 171:627-39, 2014).

RESULTS

The mechanistic relationships between heterozygously deleted 22q11.2 genes and 22q11DS phenotypes are still unknown. We assembled a comprehensive "line-up" of the 36 protein coding loci in the 1.5 Mb minimal critical deleted region on hChr22q11.2, plus 20 protein coding loci in the distal 1.5 Mb that defines the 3 Mb typical 22q11DS deletion. We categorized candidates based upon apparent primary cell biological functions. We analyzed 41 of these genes that encode known proteins to determine whether haploinsufficiency of any single 22q11.2 gene-a one gene to one phenotype correspondence due to heterozygous deletion restricted to that locus-versus complex multigenic interactions can account for single or multiple 22q11DS phenotypes.

CONCLUSIONS

Our 22q11.2 functional genomic assessment does not support current theories of single gene haploinsufficiency for one or all 22q11DS phenotypes. Shared molecular functions, convergence on fundamental cell biological processes, and related consequences of individual 22q11.2 genes point to a matrix of multigenic interactions due to diminished 22q11.2 gene dosage. These interactions target fundamental cellular mechanisms essential for development, maturation, or homeostasis at subsets of 22q11DS phenotypic sites.

Endosomal and Phagosomal SNAREs

The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein family is of vital importance for organelle communication. The complexing of cognate SNARE members present in both the donor and target organellar membranes drives the membrane fusion required for intracellular transport. In the endocytic route, SNARE proteins mediate trafficking between endosomes and phagosomes with other endosomes, lysosomes, the Golgi apparatus, the plasma membrane, and the endoplasmic reticulum. The goal of this review is to provide an overview of the SNAREs involved in endosomal and phagosomal trafficking. Of the 38 SNAREs present in humans, 30 have been identified at endosomes and/or phagosomes. Many of these SNAREs are targeted by viruses and intracellular pathogens, which thereby reroute intracellular transport for gaining access to nutrients, preventing their degradation, and avoiding their detection by the immune system. A fascinating picture is emerging of a complex transport network with multiple SNAREs being involved in consecutive trafficking routes.

Mast cells at the crossroads of microbiota and IBD

The human gut harbors a wide range of microorganisms that play a fundamental role in the well-being of their host. A dysregulation of the microbial composition can lead to the development or exacerbation of gastrointestinal (GI) disorders. Emerging evidence supports the hypothesis that mast cells (MCs) play a role in host-microbiota communication, modulating the mutual influence between the host and its microbiota through changes in their activation state. The ability of some bacteria to specifically affect MC functions and activation has been extensively studied, with different and sometimes conflicting results, while only little is known about MC-fungi interactions. In this review, the most recent advances in the field of MC-bacteria and MC-fungi interactions will be discussed, with a particular focus on the role of these interactions in the onset of GI disorders such as inflammatory bowel diseases (IBD). Moreover, the connection between some MC-targeting drugs and IBD was discussed, suggesting probiotics as reasonable and promising therapy in the management of IBD patients.

Mrp1 is involved in lipid presentation and iNKT cell activation by Streptococcus pneumoniae

Invariant natural killer T cells (iNKT cells) are activated by lipid antigens presented by CD1d, but the pathway leading to lipid antigen presentation remains incompletely characterized. Here we show a whole-genome siRNA screen to elucidate the CD1d presentation pathway. A majority of gene knockdowns that diminish antigen presentation reduced formation of glycolipid-CD1d complexes on the cell surface, including members of the HOPS and ESCRT complexes, genes affecting cytoskeletal rearrangement, and ABC family transporters. We validated the role in vivo for the multidrug resistance protein 1 (Mrp1) in CD1d antigen presentation. Mrp1 deficiency reduces surface clustering of CD1d, which decreased iNKT cell activation. Infected Mrp1 knockout mice show decreased iNKT cell responses to antigens from Streptococcus pneumoniae and were associated with increased mortality. Our results highlight the unique cellular events involved in lipid antigen presentation and show how modification of this pathway can lead to lethal infection.

The CD1d pathway present lipid antigens resulting in the activation of iNKT cells but the complete pathway remains to be fully elucidated. Here, Chandra et al. use an siRNA screen and identify Mrp1 as crucial for CD1d lipid presentation and activation of iNKT in the context of Streptococcus pneumoniae infection.

Functional diversification of the NleG effector family in enterohemorrhagic Escherichia coli

The pathogenic strategy of Escherichia coli and many other gram-negative pathogens relies on the translocation of a specific set of proteins, called effectors, into the eukaryotic host cell during infection. These effectors act in concert to modulate host cell processes in favor of the invading pathogen. Injected by the type III secretion system (T3SS), the effector arsenal of enterohemorrhagic E. coli (EHEC) O157:H7 features at least eight individual NleG effectors, which are also found across diverse attaching and effacing pathogens. NleG effectors share a conserved C-terminal U-box E3 ubiquitin ligase domain that engages with host ubiquitination machinery. However, their specific functions and ubiquitination targets have remained uncharacterized. Here, we identify host proteins targeted for ubiquitination-mediated degradation by two EHEC NleG family members, NleG5-1 and NleG2-3. NleG5-1 localizes to the host cell nucleus and targets the MED15 subunit of the Mediator complex, while NleG2-3 resides in the host cytosol and triggers degradation of Hexokinase-2 and SNAP29. Our structural studies of NleG5-1 reveal a distinct N-terminal α/β domain that is responsible for interacting with host protein targets. The core of this domain is conserved across the NleG family, suggesting this domain is present in functionally distinct NleG effectors, which evolved diversified surface residues to interact with specific host proteins. This is a demonstration of the functional diversification and the range of host proteins targeted by the most expanded effector family in the pathogenic arsenal of E. coli.

How to use a multipurpose SNARE: The emerging role of Snap29 in cellular health

Despite extensive study, regulation of membrane trafficking is incompletely understood. In particular, the specific role of SNARE (Soluble NSF Attachment REceptor) proteins for distinct trafficking steps and their mechanism of action, beyond the core function in membrane fusion, are still elusive. Snap29 is a SNARE protein related to Snap25 that gathered a lot of attention in recent years. Here, we review the study of Snap29 and its emerging involvement in autophagy, a self eating process that is key to cell adaptation to changing environments, and in other trafficking pathways. We also discuss Snap29 role in synaptic transmission and in cell division, which might extend the repertoire of SNARE-mediated functions. Finally, we present evidence connecting Snap29 to human disease, highlighting the importance of Snap29 function in tissue development and homeostasis.

Role of Mast Cells in clearance of Leishmania through extracellular trap formation

Mast Cells (MCs) are one of the first immune cells encountered by invading pathogens. Their presence in large numbers in the superficial dermis, where Leishmania is encountered, suggests that they may play a critical role in immune responses to Leishmania. In this study the interactions of Leishmania donovani, the causative agent of visceral Leishmaniasis, and Leishmania tropica, the causative agent of cutaneous Leishmaniasis with MCs were studied. Co-culture of Leishmania with Peritoneal Mast Cells (PMCs) from BALB/c mice and Rat Basophilic Leukaemia (RBL-2H3) MCs led to significant killing of L. tropica and to a lesser extent of L. donovani. Also, while there was significant uptake of L. tropica by MCs, L. donovani was not phagocytosed. There was significant generation of Reactive Oxygen Species (ROS) by MCs on co-culture with these species of Leishmania which may contribute to their clearance. Interactions of MCs with Leishmania led to generation of MC extracellular traps comprising of DNA, histones and tryptase probably to ensnare these pathogens. These results clearly establish that MCs may contribute to host defences to Leishmania in a differential manner, by actively taking up these pathogens, and also by mounting effector responses for their clearance by extracellular means.

An essential step of kinetochore formation controlled by the SNARE protein Snap29

The kinetochore is an essential structure that mediates accurate chromosome segregation in mitosis and meiosis. While many of the kinetochore components have been identified, the mechanisms of kinetochore assembly remain elusive. Here, we identify a novel role for Snap29, an unconventional SNARE, in promoting kinetochore assembly during mitosis in Drosophila and human cells. Snap29 localizes to the outer kinetochore and prevents chromosome mis‐segregation and the formation of cells with fragmented nuclei. Snap29 promotes accurate chromosome segregation by mediating the recruitment of Knl1 at the kinetochore and ensuring stable microtubule attachments. Correct Knl1 localization to kinetochore requires human or Drosophila Snap29, and is prevented by a Snap29 point mutant that blocks Snap29 release from SNARE fusion complexes. Such mutant causes ectopic Knl1 recruitment to trafficking compartments. We propose that part of the outer kinetochore is functionally similar to membrane fusion interfaces.

Contribution of FcɛRI-associated vesicles to mast cell-macrophage communication following Francisella tularensis infection

Understanding innate immune intercellular communication following microbial infection remains a key biological issue. Using live cell imaging, we demonstrate that mast cells actively extend cellular projections to sample the macrophage periphery during Francisella tularensis LVS infection. Mast cell MHCII(hi) expression was elevated from less than 1% to 13% during LVS infection. Direct contact during co-culture with macrophages further increased mast cell MHCII(hi) expression to approximately 87%. Confocal analyses of the cellular perimeter revealed mast cell caspase-1 was localized in close proximity with FcɛRI in uninfected mast cells, and repositioned to clustered regions upon LVS infection. Importantly, mast cell FcɛRI-encompassed vesicles are transferred to macrophages by trogocytosis, and macrophage caspase-1 expression is further up-regulated upon direct contact with mast cells. Our study reveals direct cellular interactions between innate cells that may impact the function of caspase-1, a known sensor of microbial danger and requirement for innate defense against many pathogenic microbes including F. tularensis.

SNAP23 Regulates Endothelial Exocytosis of von Willebrand Factor

Endothelial exocytosis regulates vascular thrombosis and inflammation. The trafficking and release of endothelial vesicles is mediated by SNARE (Soluble NSF Attachment protein REceptors) molecules, but the exact identity of endothelial SNAREs has been unclear. Three SNARE molecules form a ternary complex, including isoforms of the syntaxin (STX), vesicle-associated membrane protein (VAMP), and synaptosomal-associated protein (SNAP) families. We now identify SNAP23 as the predominant endothelial SNAP isoform that mediates endothelial exocytosis of von Willebrand Factor (VWF). SNAP23 was localized to the plasma membrane. Knockdown of SNAP23 decreased endothelial exocytosis, suggesting it is important for endothelial exocytosis. SNAP23 interacted with the endothelial exocytic machinery, and formed complexes with other known endothelial SNARE molecules. Taken together, these data suggest that SNAP23 is a key component of the endothelial SNARE machinery that mediates endothelial exocytosis.

Roles and relevance of mast cells in infection and vaccination

In addition to their well-established role in allergy mast cells have been described as contributing to functional regulation of both innate and adaptive immune responses in host defense. Mast cells are of hematopoietic origin but typically complete their differentiation in tissues where they express immune regulatory functions by releasing diverse mediators and cytokines. Mast cells are abundant at mucosal tissues which are portals of entry for common infectious agents in addition to allergens. Here, we review the current understanding of the participation of mast cells in defense against infection. We also discuss possibilities of exploiting mast cell activation to provide adequate adjuvant activity that is needed in high-quality vaccination against infectious diseases.

Proteomic analysis of proteins surrounding occludin and claudin-4 reveals their proximity to signaling and trafficking networks

Tight junctions are complex membrane structures that regulate paracellular movement of material across epithelia and play a role in cell polarity, signaling and cytoskeletal organization. In order to expand knowledge of the tight junction proteome, we used biotin ligase (BioID) fused to occludin and claudin-4 to biotinylate their proximal proteins in cultured MDCK II epithelial cells. We then purified the biotinylated proteins on streptavidin resin and identified them by mass spectrometry. Proteins were ranked by relative abundance of recovery by mass spectrometry, placed in functional categories, and compared not only among the N- and C- termini of occludin and the N-terminus of claudin-4, but also with our published inventory of proteins proximal to the adherens junction protein E-cadherin and the tight junction protein ZO-1. When proteomic results were analyzed, the relative distribution among functional categories was similar between occludin and claudin-4 proximal proteins. Apart from already known tight junction- proteins, occludin and claudin-4 proximal proteins were enriched in signaling and trafficking proteins, especially endocytic trafficking proteins. However there were significant differences in the specific proteins comprising the functional categories near each of the tagging proteins, revealing spatial compartmentalization within the junction complex. Taken together, these results expand the inventory of known and unknown proteins at the tight junction to inform future studies of the organization and physiology of this complex structure.

Commensal bacteria directly suppress in vitro degranulation of mast cells in a MyD88-independent manner

The intestine harbors a substantial number of commensal bacteria that provide considerable benefits to the host. Epidemiologic studies have identified associations between alterations in the composition of the intestinal microbiota and the development of allergic disease. However, the cellular and molecular mechanisms underlying these effects remain to be determined. Here, we show that heat-killed commensal bacteria suppressed degranulation of mast cells in vitro in a MyD88-independent manner. In particular, Enterococcus faecalis showed the strongest suppression of degranulation through partial inhibition of Ca(2+) signaling upon the high affinity IgE receptor (FcεRI) cross-linking.

Drosophila SNAP-29 is an essential SNARE that binds multiple proteins involved in membrane traffic

Each membrane fusion event along the secretory and endocytic pathways requires a specific set of SNAREs to assemble into a 4-helical coiled-coil, the so-called trans-SNARE complex. Although most SNAREs contribute one helix to the trans-SNARE complex, members of the SNAP-25 family contribute two helixes. We report the characterization of the Drosophila homologue of SNAP-29 (dSNAP-29), which is expressed throughout development. Unlike the other SNAP-25 like proteins in fruit fly (i.e., dSNAP-25 and dSNAP-24), which form SDS-resistant SNARE complexes with their cognate SNAREs, dSNAP-29 does not participate in any SDS-resistant complexes, despite its interaction with dsyntaxin1 and dsyntaxin16 in vitro. Immunofluorescence studies indicated that dSNAP-29 is distributed in various tissues, locating in small intracellular puncta and on the plasma membrane, where it associates with EH domain-containing proteins implicated in the endocytic pathway. Overexpression and RNAi studies suggested that dSNAP-29 mediates an essential process in Drosophila development.

Escherichia coli exposure inhibits exocytic SNARE-mediated membrane fusion in mast cells

Mast cells orchestrate the allergic response through the release of proinflammatory mediators, which is driven by the fusion of cytoplasmic secretory granules with the plasma membrane. During this process, SNARE proteins including Syntaxin4, SNAP23 and VAMP8 play a key role. Following stimulation, the kinase IKKβ interacts with and phosphorylates the t-SNARE SNAP23. Phosphorylated SNAP23 then associates with Syntaxin4 and the v-SNARE VAMP8 to form a ternary SNARE complex, which drives membrane fusion and mediator release. Interestingly, mast cell degranulation is impaired following exposure to bacteria such as Escherichia coli. However, the molecular mechanism(s) by which this occurs is unknown. Here, we show that E. coli exposure rapidly and additively inhibits degranulation in the RBL-2H3 rat mast cell line. Following co-culture with E. coli, the interaction between IKKβ and SNAP23 is disrupted, resulting in the hypophosphorylation of SNAP23. Subsequent formation of the ternary SNARE complex between SNAP23, Syntaxin4 and VAMP8 is strongly reduced. Collectively, these results demonstrate that E. coli exposure inhibits the formation of VAMP8-containing exocytic SNARE complexes and thus the release of VAMP8-dependent granules by interfering with SNAP23 phosphorylation.

Detection of mast cells and basophils by immunohistochemistry

Staining cells or tissues with basic dyes was the mainstay of mast cell and basophil detection methods for more than a century following the first identification of these cell types using such methods. These techniques have now been largely supplanted by immunohistochemical procedures with monoclonal antibodies directed against unique constituents of these cell types. Immunohistochemistry with antibodies specific for the granule protease tryptase provides a more sensitive and discriminating means for detecting mast cells than using the classical histochemical procedures; and employing antibodies specific for products of basophils (2D7 antigen and basogranulin) has allowed detection of basophils that infiltrate into tissues. The application of immunohistochemistry to detect more than one marker in the same cell has underpinned concepts of mast cell heterogeneity based on differential expression of chymase and other proteases. The double-labelling procedures employed have also provided a means for investigating the expression of cytokines and a range of other products. Protocols are here set out that have been used for immunohistochemical detection of mast cells and basophils and their subpopulations in human tissues. Consideration is given to pitfalls to avoid and to a range of alternative approaches.

Multiple functions of the SNARE protein Snap29 in autophagy, endocytic, and exocytic trafficking during epithelial formation in Drosophila

How autophagic degradation is linked to endosomal trafficking routes is little known. Here we screened a collection of uncharacterized Drosophila mutants affecting membrane transport to identify new genes that also have a role in autophagy. We isolated a loss of function mutant in Snap29 (Synaptosomal-associated protein 29 kDa), the gene encoding the Drosophila homolog of the human protein SNAP29 and have characterized its function in vivo. Snap29 contains 2 soluble NSF attachment protein receptor (SNARE) domains and a asparagine-proline-phenylalanine (NPF motif) at its N terminus and rescue experiments indicate that both SNARE domains are required for function, whereas the NPF motif is in part dispensable. We find that Snap29 interacts with SNARE proteins, localizes to multiple trafficking organelles, and is required for protein trafficking and for proper Golgi apparatus morphology. Developing tissue lacking Snap29 displays distinctive epithelial architecture defects and accumulates large amounts of autophagosomes, highlighting a major role of Snap29 in autophagy and secretion. Mutants for autophagy genes do not display epithelial architecture or secretion defects, suggesting that the these alterations of the Snap29 mutant are unlikely to be caused by the impairment of autophagy. In contrast, we find evidence of elevated levels of hop-Stat92E (hopscotch-signal transducer and activator of transcription protein at 92E) ligand, receptor, and associated signaling, which might underlie the epithelial defects. In summary, our findings support a role of Snap29 at key steps of membrane trafficking, and predict that signaling defects may contribute to the pathogenesis of cerebral dysgenesis, neuropathy, ichthyosis, and palmoplantar keratoderma (CEDNIK), a human congenital syndrome due to loss of Snap29.

A genome-wide association study for somatic cell score using the Illumina high-density bovine beadchip identifies several novel QTL potentially related to mastitis susceptibility

Mastitis is an inflammation-driven disease of the bovine mammary gland that occurs in response to physical damage or infection and is one of the most costly production-related diseases in the dairy industry worldwide. We performed a genome-wide association study (GWAS) to identify genetic loci associated with somatic cell score (SCS), an indicator trait of mammary gland inflammation. A total of 702 Holstein-Friesian bulls were genotyped for 777,962 single nucleotide polymorphisms (SNPs) and associated with SCS phenotypes. The SCS phenotypes were expressed as daughter yield deviations (DYD) based on a large number of progeny performance records. A total of 138 SNPs on 15 different chromosomes reached genome-wide significance (corrected p-value ≤ 0.05) for association with SCS (after correction for multiple testing). We defined 28 distinct QTL regions and a number of candidate genes located in these QTL regions were identified. The most significant association (p-value = 1.70 × 10⁻⁷) was observed on chromosome 6. This QTL had no known genes annotated within it, however, the Ensembl Genome Browser predicted the presence of a small non-coding RNA (a Y RNA gene) in this genomic region. This Y RNA gene was 99% identical to human RNY4. Y RNAs are a rare type of non-coding RNA that were originally discovered due to their association with the autoimmune disease, systemic lupus erythematosus. Examining small-RNA sequencing (RNAseq) data being generated by us in multiple different mastitis-pathogen challenged cell-types has revealed that this Y RNA is expressed (but not differentially expressed) in these cells. Other QTL regions identified in this study also encoded strong candidate genes for mastitis susceptibility. A QTL region on chromosome 13, for example, was found to contain a cluster of β-defensin genes, a gene family with known roles in innate immunity. Due to the increased SNP density, this study also refined the boundaries for several known QTL for SCS and mastitis.