GPI-anchor Biosynthesis Research Articles

Identification of CNTN2 as a genetic modifier of PIGA-CDG through pedigree analysis of a family with incomplete penetrance and functional testing in Drosophila.

Loss of function mutations in the X-linked PIGA gene lead to PIGA-CDG, an ultra-rare congenital disorder of glycosylation (CDG), typically presenting with seizures, hypotonia, and neurodevelopmental delay. We identified two brothers (probands) with PIGA-CDG, presenting with epilepsy and mild developmental delay. Both probands carry PIGA S132C , an ultra-rare variant predicted to be damaging. Strikingly, the maternal grandfather and a great-uncle also carry PIGA S132C , but neither presents with symptoms associated with PIGA-CDG. We hypothesized genetic modifiers may contribute to this reduced penetrance. Using whole genome sequencing and pedigree analysis, we identified possible susceptibility variants found in the probands and not in carriers and possible protective variants found in the carriers and not in the probands. Candidate variants included heterozygous, damaging variants in three genes also involved directly in GPI-anchor biosynthesis and a few genes involved in other glycosylation pathways or encoding GPI-anchored proteins. We functionally tested the predicted modifiers using a Drosophila eye-based model of PIGA-CDG. We found that loss of CNTN2 , a predicted protective modifier, rescues loss of PIGA in Drosophila eye-based model, like what we predict in the family. Further testing found that loss of CNTN2 also rescues patient-relevant phenotypes, including seizures and climbing defects in Drosophila neurological models of PIGA-CDG. By using pedigree information, genome sequencing, and in vivo testing, we identified CNTN2 as a strong candidate modifier that could explain the incomplete penetrance in this family. Identifying and studying rare disease modifier genes in human pedigrees may lead to pathways and targets that may be developed into therapies.

Glycosylphosphatidylinositol anchor biosynthesis pathway-based biomarker identification with machine learning for prognosis and T cell exhaustion status prediction in breast cancer.

As the primary component of anti-tumor immunity, T cells are prone to exhaustion and dysfunction in the tumor microenvironment (TME). A thorough understanding of T cell exhaustion (TEX) in the TME is crucial for effectively addressing TEX in clinical settings and promoting the efficacy of immune checkpoint blockade therapies. In eukaryotes, numerous cell surface proteins are tethered to the plasma membrane via Glycosylphosphatidylinositol (GPI) anchors, which play a crucial role in facilitating the proper translocation of membrane proteins. However, the available evidence is insufficient to support any additional functional involvement of GPI anchors. Here, we investigate the signature of GPI-anchor biosynthesis in the TME of breast cancer (BC)patients, particularly its correlation with TEX. GPI-anchor biosynthesis should be considered as a prognostic risk factor for BC. Patients with high GPI-anchor biosynthesis showed more severe TEX. And the levels of GPI-anchor biosynthesis in exhausted CD8 T cells was higher than normal CD8 T cells, which was not observed between malignant epithelial cells and normal mammary epithelial cells. In addition, we also found that GPI -anchor biosynthesis related genes can be used to diagnose TEX status and predict prognosis in BC patients, both the TEX diagnostic model and the prognostic model showed good AUC values. Finally, we confirmed our findings in cells and clinical samples. Knockdown of PIGU gene expression significantly reduced the proliferation rate of MDA-MB-231 and MCF-7 cell lines. Immunofluorescence results from clinical samples showed reduced aggregation of CD8 T cells in tissues with high expression of GPAA1 and PIGU.

The GPI-anchor biosynthesis pathway is critical for syncytiotrophoblast differentiation and placental development

The glycosylphosphatidylinositol (GPI) biosynthetic pathway in the endoplasmic reticulum (ER) is crucial for generating GPI-anchored proteins (GPI-APs), which are translocated to the cell surface and play a vital role in cell signaling and adhesion. This study focuses on two integral components of the GPI pathway, the PIGL and PIGF proteins, and their significance in trophoblast biology. We show that GPI pathway mutations impact on placental development impairing the differentiation of the syncytiotrophoblast (SynT), and especially the SynT-II layer, which is essential for the establishment of the definitive nutrient exchange area within the placental labyrinth. CRISPR/Cas9 knockout of Pigl and Pigf in mouse trophoblast stem cells (mTSCs) confirms the role of these GPI enzymes in syncytiotrophoblast differentiation. Mechanistically, impaired GPI-AP generation induces an excessive unfolded protein response (UPR) in the ER in mTSCs growing in stem cell conditions, akin to what is observed in human preeclampsia. Upon differentiation, the impairment of the GPI pathway hinders the induction of WNT signaling for early SynT-II development. Remarkably, the transcriptomic profile of Pigl- and Pigf-deficient cells separates human patient placental samples into preeclampsia and control groups, suggesting an involvement of Pigl and Pigf in establishing a preeclamptic gene signature. Our study unveils the pivotal role of GPI biosynthesis in early placentation and uncovers a new preeclampsia gene expression profile associated with mutations in the GPI biosynthesis pathway, providing novel molecular insights into placental development with implications for enhanced patient stratification and timely interventions.

Abstract LB330: CWH43 as a prognostic marker and therapeutic target in colorectal cancer

Abstract Colorectal cancer (CRC) remains a significant global health issue, particularly challenging due to the poor prognosis of its metastatic form. This highlights the critical need for novel and effective therapeutic targets to manage disease progression. A key focus of our research is the Cell Wall Biogenesis 43 C-Terminal Homolog (CWH43), which plays an essential role in GPI anchor biosynthesis and lipid remodeling, crucial for attaching membrane proteins to cell membranes. Our study aimed to clarify the function of CWH43 in CRC progression and evaluate its potential as a therapeutic target. Through an integrated bioinformatics analysis using public cancer databases, coupled with experimental validations in CRC cell models, we noted a conspicuous decrease in CWH43 mRNA levels in CRC tissues compared to normal tissue. This decrease in CWH43 expression correlated with poorer prognoses in CRC patients. In our experimental findings, we discovered that suppressing CWH43 led to increased proliferation, migration, and invasiveness of CRC cells, whereas its overexpression inhibited these processes. Notably, we observed elevated levels of CWH43 in CRC patients who showed a lower response to chemotherapy. Particularly in advanced-stage CRC patients (T4 and N2), high CWH43 expression correlated with reduced overall survival and shorter progression-free intervals, suggesting a potential association with chemotherapy resistance. In our cellular experiments, overexpression of CWH43 in CRC cells resulted in decreased sensitivity to chemotherapy drugs like CPT11, 5-FU, and oxaliplatin, which was consistent with a reduction in the expression of apoptosis-related markers. Additionally, there was a notable negative correlation between CWH43 expression and radiation sensitivity. Our Gene Set Enrichment Analysis (GSEA) revealed a significant connection between CWH43 and pathways involved in oxidative phosphorylation and fatty acid metabolism, indicating its role in regulating ferroptosis. We also demonstrated that overexpressing CWH43 in CRC cells increases the levels of multiple ferroptosis suppressors. Importantly, the use of ferroptosis inducers appeared to counteract the chemotherapy resistance influenced by CWH43. Based on these findings, we propose that CWH43 plays a role in inhibiting ferroptosis, contributing to therapeutic resistance in CRC. Therefore, targeting CWH43 could be a promising strategy for developing ferroptosis-inducing therapies, offering a new avenue for the treatment of CRC, especially in cases resistant to traditional therapies. Citation Format: Cheng-Chin Lee, Yu-Jia Chang, Chien-Yu Huang. CWH43 as a prognostic marker and therapeutic target in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB330.

Phosphatidylethanolamine (18:2e/18:2) may inhibit adipose tissue wasting in patients with cancer cachexia by increasing lysophosphatidic acid receptor 6

BackgroundCancer associated cachexia is characterized by the significant loss of adipose tissue, leading to devastating weight loss and muscle wasting in the majority of cancer patients. The effects and underlying mechanisms of degradation metabolites on adipocytes in cachectic patients remain poorly understood. To address this knowledge gap, we conducted a comprehensive study combining lipidomic analysis of subcutaneous and visceral adipose tissue with transcriptomics data from the database to investigate the mechanisms of lipid regulation in adipocytes. MethodsWe collected subcutaneous and visceral adipose tissue samples from cachectic and noncachectic cancer patients. Lipidomic analysis was performed to identify differentially expressed lipids in both types of adipose tissue. Additionally, transcriptomics data from the GEO database were analyzed to explore gene expression patterns in adipocytes. Bioinformatics analysis was employed to determine the enrichment of differentially expressed genes in specific pathways. Furthermore, molecular docking studies were conducted to predict potential protein targets of specific lipids, with a focus on the PI3K-Akt signaling pathway. Western blot analysis was used to validate protein levels of the identified target gene, lysophosphatidic acid receptor 6 (LPAR6), in subcutaneous and visceral adipose tissue from cachectic and noncachectic patients. ResultsSignificant lipid differences in subcutaneous and visceral adipose tissue between cachectic and noncachectic patients were identified by multivariate statistical analysis. Cachectic patients exhibited elevated Ceramides levels and reduced CerG2GNAc1 levels (P < 0.05). A total of 10 shared lipids correlated with weight loss and IL-6 levels, enriched in Sphingolipid metabolism, GPI-anchor biosynthesis, and Glyceropholipid metabolism pathways. LPAR6 expression was significantly elevated in both adipose tissues of cachectic patients (P < 0.05). Molecular docking analysis indicated strong binding of Phosphatidylethanolamine (PE) (18:2e/18:2) to LPAR6. ConclusionsOur findings suggest that specific lipids, including PE(18:2e/18:2), may mitigate adipose tissue wasting in cachexia by modulating the expression of LPAR6 through the PI3K-Akt signaling pathway. The identification of these potential targets and mechanisms provides a foundation for future investigations and therapeutic strategies to combat cachexia. By understanding the underlying lipid regulation in adipocytes, we aim to develop targeted interventions to ameliorate the devastating impact of cachexia on patient outcomes and quality of life. Nevertheless, further studies and validation are warranted to fully elucidate the intricate mechanisms involved and translate these findings into effective clinical interventions.

The combination of manogepix and itraconazole is synergistic and inhibits the growth of Madurella mycetomatis in vitro but not in vivo.

Mycetoma is a neglected tropical disease commonly caused by the fungus Madurella mycetomatis. Standard treatment consists of extensive treatment with itraconazole in combination with surgical excision of the infected tissue, but has a low success rate. To improve treatment outcomes, novel treatment strategies are needed. Here, we determined the potential of manogepix, a novel antifungal agent that targets the GPI-anchor biosynthesis pathway by inhibition of the GWT1 enzyme. Manogepix was evaluated by determining the minimal inhibitory concentrations (MICs) according to the CLSI-based in vitro susceptibility assay for 22M. mycetomatis strains and by in silico protein comparison of the target protein. The synergy between manogepix and itraconazole was determined using a checkerboard assay. The efficacy of clinically relevant dosages was assessed in an in vivo grain model in Galleria mellonella larvae. MICs for manogepix ranged from<0.008 to >8mg/l and 16/22M. mycetomatis strains had an MIC ≥4mg/ml. Differences in MICs were not related to differences observed in the GWT1 protein sequence. For 70% of the tested isolates, synergism was found between manogepix and itraconazole in vitro. In vivo, enhanced survival was not observed upon admission of 8.6mg/kg manogepix, nor in combination treatment with 5.7mg/kg itraconazole. MICs of manogepix were high, but the in vitro antifungal activity of itraconazole was enhanced in combination therapy. However, no efficacy of manogepix was found in an in vivo grain model using clinically relevant dosages. Therefore, the therapeutic potential of manogepix in mycetoma caused by M. mycetomatis seems limited.

The genes regulating sensitivity of tumor cells to T cell-mediated killing: could they be potential personalized immunotherapeutic targets in head and neck squamous cell carcinoma?

ObjectiveTo identify the pivotal genes, specifically the STTK genes, that govern the sensitivity of tumor cells to T cell-mediated killing in Head and Neck Squamous Cell Carcinoma (HNSC).MethodsThe differentially expressed genes (DEGs) in HNSC and STTK genes were overlapped to obtain the DE-STTK genes. Univariate and LASSO regression analyses were conducted to identify the pivotal DE-STTK genes that serve as hubs in HNSC (i.e., hub DE-STTK genes). The risk model was established to divide HNSC tumor samples into high- and low-risk groups based on the hub DE-STTK genes. Further investigations were carried out by examing the expression level, prognostic values, diagnostic values, enriched signaling pathways, correlation with tumor mutation burden (TMB), and association with tumor immune infiltration cells (TIICs).ResultsA total of 71 genes were found to be overlapped between DEGs in HNSC and STTK genes. Lasso regression analysis identified 9 hub genes which were MYF6, AATF, AURKA, CXCL9, DPM2, MYO1B, NCBP2, TNFRSF12A, and TRAF1. The network analysis of hub DE-STTK genes-pathway reveals that these 9 hub genes exhibit enrichment in multiple signaling pathways, including toll-like receptor signaling, TNF signaling, NF-kappa B signaling, cytokine-cytokine receptor interaction, spliceosome, mRNA surveillance pathway, nucleocytoplasmic transport, GPI-anchor biosynthesis, as well as N-Glycan biosynthesis. The Pearson correlation analysis showed that the majority of correlations between 9 hub DE-STTK genes and immune cells were positive.ConclusionThe 9 identified hub DE-STTK genes (MYF6, AATF, AURKA, CXCL9, DPM2, MYO1B, NCBP2, TNFRSF12A, and TRAF1) are presumptively implicated in the modulation of tumor immunity in HNSC. These genes, along with their enriched pathways, hold promise as potential personalized immunotherapeutic targets for the treatment of HNSC, thereby offering novel avenues for therapeutic intervention in this malignancy.

THU082 Longitudinal Multiomics Characterization Of Paired Primary And Recurrent Aggressive Pituitary Tumors From The Same Patient Reveals Genomic Stability And Transcriptomic And Epigenetic Heterogeneity With Metabolic Pathways Alterations

Abstract Disclosure: K. Taniguchi-Ponciano: None. A. Chavez-Santoscoy: None. S. Hinojosa-Alvarez: None. J. Hernandez-Perez: None. A. Valenzuela-Perez: None. S. Vela-Patiño: None. S. Andonegui-Elguera: None. A. Cano-Zaragoza: None. F. Martinez-Mendoza: None. J. Kerbel: None. Z. Zhang: None. G. Smith: None. A. Rubenstein: None. W. Cheng: None. N. Mendelev: None. M. Amper: None. M. Zamojski: None. E. Zaslavsky: None. F.M. Ruf-Zamojski: None. S.C. Sealfon: None. M. Mercado: None. D. Marrero-Rodríguez: None. Pituitary tumors (PT) represent 20% of all intracranial neoplasms. Some behave aggressively, growing rapidly and invading surrounding tissues, with high recurrence rates and are frequently resistant to conventional therapies. We performed exome and transcriptome sequencing, as well as methylation profiling of primary and recurrent PT of the same patient. The cohort consisted of patients with GH- and gonadotropin-producing PT and a patient with an ACTH carcinoma. We sought genome evolution as well as transcriptomic and methylomic changes trough time, trying to identify molecular markers of recurrence. We performed scRNAseq to identify tumor cell populations. Compared to the primary PT, recurrent lesions showed less than 5% genomic changes in the SNV profile. The gonadotrophin-PT did not show common variants between patients or between primary and recurrent lesions. The ACTH-carcinoma showed USP8, TP53 and EGFR variants in both tumor samples, but no genomic changes between tumors despite a Ki67 of 80% in the recurrent lesion. A GH-tumor showed an AIP variant with high genetic heterogeneity. No CNV between the primary and recurrent tumors were observed. Regardless of their lineage, all PT showed different degrees of transcriptomic and methylomic heterogeneity between the primary and the recurrent lesions. Primary and recurrent tumors clustered separately from each other but together among themselves. Interestingly the differentially expressed and methylated genes in gonadotropin-producing PT are related to fatty acid biosynthesis and metabolism, GPI-anchor biosynthesis, and other metabolic pathways. ACTH-carcinoma differs significantly from the silent corticotrope in gene expression and methylation patterns. The ACTH-carcinoma showed alteration in N-Glycan biosynthesis, glycerophospholipid metabolism, purine and pyrimidine metabolism, whereas the silent corticotrope showed one carbon pool by folate, inositol phosphate metabolism, carbohydrate digestion and absorption and biosynthesis of unsaturated fatty acids. The GH-tumor showed alteration in pyruvate metabolism, propanoate metabolism, insulin secretion, and aldosterone synthesis and secretion. Our results suggest that there are several clones conforming a PT and some of them remain after surgical resection and can re-grow, this was confirmed by our scRNAseq analysis and immunofluorescence assays. We conclude that PT are genomically stable trough time, indicating that mechanisms other than somatic mutations are involved in pituitary tumorigenesis and that their biology could be driven by transcriptomically and epigenetically heterogeneous clones within the tumor itself. Presentation: Thursday, June 15, 2023

Variant-to-gene mapping followed by cross-species genetic screening identifies GPI-anchor biosynthesis as a regulator of sleep.

Genome-wide association studies (GWAS) in humans have identified loci robustly associated with several heritable diseases or traits, yet little is known about the functional roles of the underlying causal variants in regulating sleep duration or quality. We applied an ATAC-seq/promoter focused Capture C strategy in human iPSC-derived neural progenitors to carry out a "variant-to-gene" mapping campaign that identified 88 candidate sleep effector genes connected to relevant GWAS signals. To functionally validate the role of the implicated effector genes in sleep regulation, we performed a neuron-specific RNA interference screen in the fruit fly, Drosophila melanogaster, followed by validation in zebrafish. This approach identified a number of genes that regulate sleep including a critical role for glycosylphosphatidylinositol (GPI)-anchor biosynthesis. These results provide the first physical variant-to-gene mapping of human sleep genes followed by a model organism-based prioritization, revealing a conserved role for GPI-anchor biosynthesis in sleep regulation.

Systematic Interrogation of Tumor Cell Resistance to Chimeric Antigen Receptor T-cell Therapy in Pancreatic Cancer.

The identification and validation of key determinants of CAR T-cell response in pancreatic cancer provide insights into the landscape of tumor cell intrinsic resistance mechanisms and into approaches to improve therapeutic efficacy.

Calcineurin Inhibitors Synergize with Manogepix to Kill Diverse Human Fungal Pathogens.

Invasive fungal infections have mortality rates of 30–90%, depending on patient co-morbidities and the causative pathogen. The frequent emergence of drug resistance reduces the efficacy of currently approved treatment options, highlighting an urgent need for antifungals with new modes of action. Addressing this need, fosmanogepix (N-phosphonooxymethylene prodrug of manogepix; MGX) is the first in a new class of gepix drugs, and acts as a broad-spectrum, orally bioavailable inhibitor of the essential fungal glycosylphosphatidylinositol (GPI) acyltransferase Gwt1. MGX inhibits the growth of diverse fungal pathogens and causes accumulation of immature GPI-anchored proteins in the fungal endoplasmic reticulum. Relevant to the ongoing clinical development of fosmanogepix, we report a synergistic, fungicidal interaction between MGX and inhibitors of the protein phosphatase calcineurin against important human fungal pathogens. To investigate this synergy further, we evaluated a library of 124 conditional expression mutants covering 95% of the genes encoding proteins involved in GPI-anchor biosynthesis or proteins predicted to be GPI-anchored. Strong negative chemical-genetic interactions between the calcineurin inhibitor FK506 and eleven GPI-anchor biosynthesis genes were identified, indicating that calcineurin signalling is required for fungal tolerance to not only MGX, but to inhibition of the GPI-anchor biosynthesis pathway more broadly. Depletion of these GPI-anchor biosynthesis genes, like MGX treatment, also exposed fungal cell wall (1→3)-β-D-glucans. Taken together, these findings suggest the increased risk of invasive fungal infections associated with use of calcineurin inhibitors as immunosuppressants may be mitigated by their synergistic fungicidal interaction with (fos)manogepix and its ability to enhance exposure of immunostimulatory glucans.

Gut microbiota alternation under the intestinal epithelium-specific knockout of mouse Piga gene

Crosstalk between the gut microbiota and intestinal epithelium shapes the gut environment and profoundly influences the intestinal immune homeostasis. Glycosylphosphatidylinositol anchored proteins (GPI – APs) contribute to a variety of gut-associated immune functions, including microbial surveillance and defense, and epithelial cell polarity. Properly polarised epithelial cells are essential for the establishment of the barrier function of gut epithelia. The Piga gene is one among seven genes that encode for an enzyme which is involved in the first step of GPI-anchor biosynthesis. This is the first study reporting a knockout of the intestinal epithelial cell-specific Piga gene (Piga-/-) and its association with the gut microbiota in mice using a whole metagenome shotgun-based sequencing approach. An overall reduced microbiota diversity has been observed in the Piga-/- group as compared to the control group (ANOVA p = 0.34). The taxonomic biomarkers, namely: Gammaproteobacteria (class), Enterobacterales (order), Enterobacteriaceae (family), Escherichia (genus), Proteus (genus) and Escherichia coli (species), increased more in the Piga-/- mice as compared to in the control group. Further, the pathogenic E. coli strains, namely E. coli O157:H7 str. EDL 933 (EHEC), E. coli CFT073 (UPEC) and E. coli 536 (UPEC), were found in the Piga-/- mice which also harbored virulence factor transporters. In addition, the taxa responsible for short chain fatty acid production were decreased in the Piga-/- group. The Piga-/- mice gut harbored an increased number of microbial functions responsible for the survival of pathogens in the inflamed gut environment. Our observations clearly indicate that the Piga-/- mice gut might have an overall enhancement in pathogenic behaviour and reduced capabilities beneficial to health.

C18orf32 loss-of-function is associated with a neurodevelopmental disorder with hypotonia and contractures.

Glycosylphosphatidylinositol(GPI) functions to anchor certain proteins to the cell surface. Although defects in GPI biosynthesis can result in a wide range of phenotypes, most affected patients present with neurological abnormalities and their diseases are grouped as inherited-GPI deficiency disorders. We present two siblings with global developmental delay, brain anomalies, hypotonia, and contractures. Exome sequencing revealed a homozygous variant, NM_001035005.4:c.90dupC (p.Phe31Leufs*3) in C18orf32, a gene not previously associated with any disease in humans. The encoded protein is known to be important for GPI-inositol deacylation. Knockout of C18orf32 in HEK293 cells followed by a transfection rescue assay revealed that the PIPLC (Phosphatidylinositol-Specific Phospholipase C) sensitivity of GPI-APs (GPI-anchored proteins) was restored only by the wild type and not the mutant C18orf32. Immunofluorescence revealed that the mutant C18orf32 was localized to the endoplasmic reticulum and was also found as aggregates in the nucleus. In conclusion, we identified a pathogenic variant in C18orf32 as the cause of a novel autosomal recessive neurodevelopmental disorder with hypotonia and contractures. Our results demonstrate the importance of C18orf32 in the biosynthesis of GPI-anchors, the molecular impact of the variant on the protein function, and add a novel candidate gene to the existing repertoire of genes implicated in neurodevelopmental disorders.

Flow cytometry-based quantification of targeted knock-in events in human cell lines using a GPI-anchor biosynthesis gene PIGP.

Targeted knock-in supported by the CRISPR/Cas systems enables the insertion, deletion, and substitution of genome sequences exactly as designed. Although this technology is considered to have wide range of applications in life sciences, one of its prerequisites for practical use is to improve the efficiency, precision, and specificity achieved. To improve the efficiency of targeted knock-in, there first needs to be a reporter system that permits simple and accurate monitoring of targeted knock-in events. In the present study, we created such a system using the PIGP gene, an autosomal gene essential for GPI-anchor biosynthesis, as a reporter gene. We first deleted a PIGP allele using Cas9 nucleases and then incorporated a truncating mutation into the other PIGP allele in two near-diploid human cell lines. The resulting cell clones were used to monitor the correction of the PIGP mutations by detecting GPI anchors distributed over the cell membrane via flow cytometry. We confirmed the utility of these reporter clones by performing targeted knock-in in these clones via a Cas9 nickase-based strategy known as tandem paired nicking, as well as a common process using Cas9 nucleases, and evaluating the efficiencies of the achieved targeted knock-in. We also leveraged these reporter clones to test a modified procedure for tandem paired nicking and demonstrated a slight increase in the efficiency of targeted knock-in by the new procedure. These data provide evidence for the utility of our PIGP-based assay system to quantify the efficiency of targeted knock-in and thereby help improve the technology of targeted knock-in.

First insights into the honey bee (Apis mellifera) brain lipidome and its neonicotinoid-induced alterations associated with reduced self-grooming behavior

IntroductionHoney bees (Apis mellifera) play key roles in food production performing complex behaviors, like self-grooming to remove parasites. However, the lipids of their central nervous system have not been examined, even though they likely play a crucial role in the performance of cognitive process to perform intricate behaviors. Lipidomics has greatly advanced our understanding of neuropathologies in mammals and could provide the same for honey bees. ObjectivesThe objectives of this study were to characterize the brain lipidome of adult honey bees and to assess the effect of clothianidin (a neurotoxic insecticide) on the brain lipid composition, gene expression, and performance of self-grooming behavior under controlled conditions (cage experiments). MethodsAfter seven days of exposure to oral sublethal doses of clothianidin, the bees were assessed for self-grooming behavior; their brains were dissected to analyze the lipidome using an untargeted lipidomics approach and to perform a high throughput RNAseq analysis. ResultsCompared to all other organisms, healthy bee brain lipidomes contain unusually high levels of alkyl-ether linked (plasmanyl) phospholipids (51.42%) and low levels of plasmalogens (plasmenyl phospholipids; 3.46%). This could make it more susceptible to the effects of toxins in the environment. A positive correlation between CL 18:3/18:1/14:0/22:6, TG 6:0/11:2/18:1, LPE 18:0e and intense self-grooming was found. Sublethal doses of a neonicotinoid altered PC 20:3e/15:0, PC 16:0/18:3, PA 18:0/24:1, and TG 18:1/18:1/18/1 levels, and affected gene expression linked to GPI-anchor biosynthesis pathway and energy metabolism that may be partially responsible for the altered lipid composition. ConclusionThis study showed that lipidomics can reveal honey bee neuropathologies associated with reduced grooming behavior due to sublethal neonicotinoid exposure. The ease of use, unusual brain lipidome as well as characterized behaviors that are affected by the environment make honey bees a promising model organism for studying the neurolipidome and associations with neurobehavioral disorders.

Computational prediction of the effects of non-synonymous single nucleotide polymorphisms on the GPI-anchor transamidase subunit GPI8p of Plasmodium falciparum

Drug resistance is increasingly evolving in malaria parasites; hence, it is important to discover and establish alternative drug targets. In this context, GPI-anchor transamidase (GPI-T) is a potential drug target primarily of its crucial role in the development and survival of the parasite in the GPI anchor biosynthesis pathway. The present investigation was undertaken to explore the plausible effects of nsSNP on the structure and functions of GPI-T subunit GPI8p of Plasmodium falciparum. The GPI8p (PF3D7_1128700) was analyzed using various sequence-based and structure-based computational tools such as SIFT, PROVEAN, PredictSNP, SNAP2, I-Mutant, MuPro, ConSurf, NetSurfP, MUSTER, COACH server and STRING server. Of the 34 nsSNPs submitted for functional analysis, 18 nsSNPs (R124 L, N143 K, Y145 F, V157I, T195S, K379E, I392 K, I437 T, Y438H, N439D, Y441H, N442D, N448D, N451D, D457A, D457Y, I458 L and N460 K) were predicted to have deleterious effects on the protein GPI8p. Additionally, I-Mutant 2.0 and MuPro both showed a decrease in stability after mutation as a result of these nsSNPs, suggesting the destabilization of protein. ConSurf findings suggest that most of the regions were highly conserved. In addition, COACH server was used to predict the ligand binding sites. It was found that no mutation was present at the predicted ligand binding site. The results of the STRING database showed that the protein GPI8p interacts with those proteins which either involve the biosynthetic process of attaching GPI anchor to protein or GPI anchor. The present study suggested that the GPI8p could be a novel target for anti-malarial drugs, which provides significant details for further experimentation.

The Glycosylphosphatidylinositol Anchor Regulates T Cell Antigen Receptor Induced IL-2 Production

Differential contributions of the glycosylphosphatidylinositol (GPI)-anchor and GPI-anchored proteins (GPI-AP) to signalling remain poorly understood. Here we show that GPI-AP deficient murine clones produce on average 18 and 181-fold more IL-2 mRNA and protein, respectively, upon T cell receptor (TCR) stimulation, in a cell-intrinsic fashion. This phenotype is formally attributed to a mutation within the transferase complex that predicates the initial step in GPI-anchor biosynthesis. Conditional disruption of the transferase complex enabled the generation of primary GPI-AP deficient CD4+ T cells, which produce on average 10- and 23-fold more IL-2 mRNA and protein, respectively, upon TCR stimulation. Conditional disruption of the transamidase complex yields GPI-sufficient, GPI-AP deficient primary CD4+ T cells. TCR stimulation of these cells yields levels of IL-2 mRNA and protein ranging from 1 - 3 and 3-fold, respectively, of controls. These results provide the first evidence of a profound impact of GPI in the regulation of TCR signalling.

Leveraging Whole Genome Sequencing to Define the Mutational Landscape in Paroxysmal Nocturnal Hemoglobinuria

Background: Paroxysmal nocturnal hemoglobinuria (PNH) is a prototypic disorder of hematopoietic stem cells leading to recurrent complement-mediated intravascular hemolysis. The development of PNH has been linked to somatic mutations in the PIGA gene, coding for an enzyme critically involved in GPI anchor synthesis. While mutations in PIGA are pathognomonic for PNH, other mutations of GPI biosynthetic pathways have been described in isolated cases. Moreover, additional genetic determinants of clonal advantage and other genetic modifiers of the clinical course have not been sufficiently clarified. Aim: This study was performed to investigate the molecular pathogenesis of PNH in a large patient cohort. Methods: Using a typical myeloid targeted panel, mutations in PIGA gene can be identified 60-70% of cases and thus we performed whole genome sequencing (WGS, mean. coverage 100x). To further clarify the molecular pathogenesis of PIGA WT cases. A cohort of 94 patients (irrespective of PIGA mutations) with a confirmed hemolytic PNH, primary or evolved from antecedent AA was studied. The average clone size at diagnosis was 73.5%, measured by granulocyte flow cytometry. Before extracting all exomic variants, including small variants and large-scale insertions/deletions, primary analysis was performed for initial variant calling and filtering of putative sequencing artifacts (1A). Results: As expected the majority of these patients (73.4%) harbored genetic lesions or mutations in PIGA with a mean variant allele frequency (VAF) of 29% and clone size of 69% by flow. Of these, 45% carried frameshift mutations, while 19% had splice variants and 14.5% carried missense mutations. Lastly, 14.5% of these mutations were based on gained stop codons or in-frame deletions while in 7% large scale genomic deletions in the PIGA locus were found (1B). The majority of these patients (67%) harbored a single genetic lesion, but &amp;gt;1 mutation was found in 23% of patients. Thus flow cytometric clone size may be a result of multiple genetically diverse PIGA mutant clones as indicated by the correlation between PNH clone size and number of PIGA mutants (P=4.14x10-7) (1C). In patients with PNH in whom PIGA mutations were not found, the average clone size was smaller (average 15.0%). We thus subjected them to targeted deep sequencing (coverage mean 1000x) to ascertain that inability to detect mutations was not due to technical sensitivity. Indeed, 8/25 cases turned out to have a PIGA mutation. In addition we studied expression of PIGA in PIGAmut versus WT cases, but no significant decrease in PIGA RNA was found. To further clarify the pathogenesis, we analyzed a gene panel of 33 proteins currently known to be involved in GPI anchor biosynthesis. We found a PIGO nonsense mutation (c.2593C&amp;gt;T) and a PIGV missense variant (c.467G&amp;gt;A) in two WT patients. These two variants were unique in PNH compared to a large cohort of myeloid neoplasias (N=2630) and appeared to be functionally consequential according to stringent in silico predictor and quality filter pipelines. Since the progression of PNH into frank myeloid neoplasia can occur and the dynamics of the expansion of PNH clones is unpredictable and thus may be influenced by additional hits, we queried if additional lesions could explain these two phenomena. We also investigated the concomitant presence of myeloid mutation in these cases. We found additional somatic mutations (panel of 77 genes) in 47.8% of all PNH patients including ASXL1 (N=10), BCOR (N=8), KMT2D (N=6), and RUNX1 (N=4) (1D). Analyzing the VAF revealed that the majority of these events were subclonal in relation to PIGA mutations. Since we studied the patients with already highly expanded clones and due to assertion bias no difference in clone size and additional mutations was found but an ongoing study in early PNH will determine whether subclonal hits predict progression to full blown PNH (1E). Conclusion: Our study shows that WGS can faithfully detect PIGA defects in a majority of PNH patients but this detection may be low in patients with smaller clones. Second, subclonal mutations linked to myeloid neoplasia are frequent events in PNH. Lastly we found two novel mutations in GPI synthetic pathway. Since none of these genes have been implicated in the pathogenesis of PNH, these findings extend our understanding of the pathogenesis of PNH and make the case for a targeted PIG pathway-wide sequencing of affected patients. Disclosures Maciejewski: Alexion, BMS: Speakers Bureau; Novartis, Roche: Consultancy, Honoraria.

Molecular analysis of GPI-anchor biosynthesis pathway genes in rat strains used for the Pig-a gene mutation assay

Recent studies support the assumption that mutation of the X-linked Pig-a gene is most likely responsible for the mutant phenotype of the cells deficient in glycosylphosphatidylinositol (GPI)-anchored proteins quantified in the rodent Pig-a gene mutation assay. In humans, however, mutations in both alleles of one of the 30 other genes involved in GPI-anchor synthesis, e.g., PIG-L and PIG-O, cause reduced expression of surface GPI-anchored proteins. Here, we investigated the possibility that the loss of the GPI-anchor detected by the rat Pig-a assay also could be caused by mutation in other GPI-biosynthesis genes. 31 samples were obtained from 8 inbred and outbred rat strains commonly used for genetic toxicology assays. In order to investigate possible sources of variation in the Pig-a assay, variant DNA sequences were evaluated in Cd59 and 24 GPI-biosynthesis genes. In some genes, such as Pig-n and Pig-u, homozygous variations occurred in all animals, suggesting that these variations are due to deviations in the reference genome. Heterozygous Pig-s, Pig-w, Pig-o, Pig-c, Pgap1, Pgap2, Pig-k and Pig-t variations were found, however, indicating that these genes could serve as targets for mutation in the assay. Protein alignment for these altered genes was conducted with possible human, mouse and rat phenotypic mutants from the literature; this analysis demonstrated that many of the variations that we detected were in non-conserved sequences and that no phenotypes for any of these variants could be inferred from known mutants from the literature. All heterozygous variants were in outbred rats. Overall, the findings of this study cannot totally rule out the possibility that mutations in GPI-biosynthesis genes other than Pig-a are detected in the Pig-a assay, but suggest that if it occurs, it must occur only rarely and therefore mutations in genes other than Pig-a have little impact on rat-based experiments.

AtPIG-S, a predicted Glycosylphosphatidylinositol Transamidase subunit, is critical for pollen tube growth in Arabidopsis

BackgroundGlycosylphosphatidylinositol (GPI) addition is one of the several post-translational modifications to proteins that increase their affinity for membranes. In eukaryotes, the GPI transamidase complex (GPI-T) catalyzes the attachment of pre-assembled GPI anchors to GPI-anchored proteins (GAPs) through a transamidation reaction. A mutation in AtGPI8 (gpi8–2), the putative catalytic subunit of GPI-T in Arabidopsis, is transmitted normally through the female gametophyte (FG), indicating the FG tolerates loss of GPI transamidation. In contrast, gpi8–2 almost completely abolishes male gametophyte (MG) function. Still, the unexpected finding that gpi8–2 FGs function normally requires further investigation. Additionally, specific developmental defects in the MG caused by loss of GPI transamidation remain poorly characterized.ResultsHere we investigated the effect of loss of AtPIG-S, another GPI-T subunit, in both gametophytes. Like gpi8–2, we showed that a mutation in AtPIG-S (pigs-1) disrupted synergid localization of LORELEI (LRE), a putative GAP critical for pollen tube reception by the FG. Still, pigs-1 is transmitted normally through the FG. Conversely, pigs-1 severely impaired male gametophyte (MG) function during pollen tube emergence and growth in the pistil. A pPIGS:GFP-PIGS transgene complemented these MG defects and enabled generation of pigs-1/pigs-1 seedlings. However, the pPIGS:GFP-PIGS transgene seemingly failed to rescue the function of AtPIG-S in the sporophyte, as pigs-1/pigs-1, pPIGS:GFP-PIGS seedlings died soon after germination.ConclusionsCharacterization of pigs-1 provided further evidence that the FG tolerates loss of GPI transamidation more than the MG and that the MG compared to the FG may be a better haploid system to study the role of GPI-anchoring. Pigs-1 pollen develops normally and thus represent a tool in which GPI anchor biosynthesis and transamidation of GAPs have been uncoupled, offering a potential way to study free GPI in plant development. While previously reported male fertility defects of GPI biosynthesis mutants could have been due either to loss of GPI or GAPs lacking the GPI anchor, our results clarified that the loss of mature GAPs underlie male fertility defects of GPI-deficient pollen grains, as pigs-1 is defective only in the downstream transamidation step.