The identification and validation of gene–gene interactions is a major challenge in human studies. Here, we explore an approach for studying epistasis in humans using a Drosophila melanogaster model of neonatal diabetes mellitus. Expression of the mutant preproinsulin (hINSC96Y) in the eye imaginal disc mimics the human disease: it activates conserved stress-response pathways and leads to cell death (reduction in eye area). Dominant-acting variants in wild-derived inbred lines from the Drosophila Genetics Reference Panel produce a continuous, highly heritable distribution of eye-degeneration phenotypes in a hINSC96Y background. A genome-wide association study (GWAS) in 154 sequenced lines identified a sharp peak on chromosome 3L, which mapped to a 400-bp linkage block within an intron of the gene sulfateless (sfl). RNAi knockdown of sfl enhanced the eye-degeneration phenotype in a mutant-hINS-dependent manner. RNAi against two additional genes in the heparan sulfate (HS) biosynthetic pathway (ttv and botv), in which sfl acts, also modified the eye phenotype in a hINSC96Y-dependent manner, strongly suggesting a novel link between HS-modified proteins and cellular responses to misfolded proteins. Finally, we evaluated allele-specific expression difference between the two major sfl-intronic haplotypes in heterozygtes. The results showed significant heterogeneity in marker-associated gene expression, thereby leaving the causal mutation(s) and its mechanism unidentified. In conclusion, the ability to create a model of human genetic disease, map a QTL by GWAS to a specific gene, and validate its contribution to disease with available genetic resources and the potential to experimentally link the variant to a molecular mechanism demonstrate the many advantages Drosophila holds in determining the genetic underpinnings of human disease.
Vitiligo is a T-cell mediated skin disorder characterized by progressive loss of skin color. In individuals genetically predisposed to the disease, various triggers contribute to the initiation of vitiligo. Precipitating factors can stress the skin, leading to T-cell activation and recruitment. Though hereditary factors are implicated in the pathogenesis of vitiligo, it is unknown whether precipitating, stressful events play a role in vitiligo. To understand this, we utilized a validated perceived stress scale (PSS) to measure this parameter in vitiligo patients compared to persons without vitiligo. Additionally, we probed a clinical database, using a knowledge linking software called ROCKET, to gauge stress-related conditions in the vitiligo patient population. From a pool of patients in an existing database, a hundred individuals with vitiligo and twenty-five age-and sex-matched comparison group of individuals without vitiligo completed an online survey to quantify their levels of perceived stress. In parallel, patients described specifics of their disease condition, including the affected body sites, the extent, duration and activity of their vitiligo. Perceived stress was significantly higher among vitiligo individuals compared to those without vitiligo. ROCKET analyses suggested signs of metabolic-related disease (i.e., 'stress') preceding vitiligo development. No correlation was found between perceived stress and the stage or the extent of disease, suggesting that elevated stress may not be a consequence of pigment loss alone. The data provide further support for stress as a precipitating factor in vitiligo development.
Drosophila melanogaster has been widely used as a model of human Mendelian disease, but its value in modeling complex disease has received little attention. Fly models of complex disease would enable high-resolution mapping of disease-modifying loci and the identification of novel targets for therapeutic intervention. Here, we describe a fly model of permanent neonatal diabetes mellitus and explore the complexity of this model. The approach involves the transgenic expression of a misfolded mutant of human preproinsulin, hINSC96Y, which is a cause of permanent neonatal diabetes. When expressed in fly imaginal discs, hINSC96Y causes a reduction of adult structures, including the eye, wing, and notum. Eye imaginal discs exhibit defects in both the structure and the arrangement of ommatidia. In the wing, expression of hINSC96Y leads to ectopic expression of veins and mechano-sensory organs, indicating disruption of wild-type signaling processes regulating cell fates. These readily measurable “disease” phenotypes are sensitive to temperature, gene dose, and sex. Mutant (but not wild-type) proinsulin expression in the eye imaginal disc induces IRE1-mediated XBP1 alternative splicing, a signal for endoplasmic reticulum stress response activation, and produces global change in gene expression. Mutant hINS transgene tester strains, when crossed to stocks from the Drosophila Genetic Reference Panel, produce F1 adults with a continuous range of disease phenotypes and large broad-sense heritability. Surprisingly, the severity of mutant hINS-induced disease in the eye is not correlated with that in the notum in these crosses, nor with eye reduction phenotypes caused by the expression of two dominant eye mutants acting in two different eye development pathways, Drop (Dr) or Lobe (L), when crossed into the same genetic backgrounds. The tissue specificity of genetic variability for mutant hINS-induced disease has, therefore, its own distinct signature. The genetic dominance of disease-specific phenotypic variability in our model of misfolded human proinsulin makes this approach amenable to genome-wide association study in a simple F1 screen of natural variation.
Previous data demonstrate that Epstein-Barr Virus Latent Membrane Protein 2A (LMP2A) enhances IL-10 to promote the survival of LMP2A-expressing B cell lymphomas. Since STAT3 is an important regulator of IL-10 production, we hypothesized that LMP2A activates a signal transduction cascade that increases STAT3 phosphorylation to enhance IL-10. Using LMP2A-negative and –positive B cell lines, the data indicate that LMP2A requires the early signaling molecules of the Syk/RAS/PI3K pathway to increase IL-10. Additional studies indicate that the PI3K-regulated kinase, BTK, is responsible for phosphorylating STAT3, which ultimately mediates the LMP2A-dependent increase in IL-10. These data are the first to show that LMP2A signaling results in STAT3 phosphorylation in B cells through a PI3K/BTK-dependent pathway. With the use of BTK and STAT3 inhibitors to treat B cell lymphomas in clinical trials, these findings highlight the possibility of using new pharmaceutical approaches to treat EBV-associated lymphomas that express LMP2A.
SUMMARY In mature neurons, postsynaptic N-methyl-D-aspartate receptors (NMDARs) are segregated into two populations, synaptic and extrasynaptic, which differ in localization, function, and associated intracellular cascades. These two pools are connected via lateral diffusion, and receptor exchange between them modulates synaptic NMDAR content. Here, we identify the phosphorylation of the PDZ-ligand of the GluN2B subunit of NMDARs (at S1480) as a critical determinant in dynamically controlling NMDAR synaptic content. We find that phosphorylation of GluN2B at S1480 maintains NMDARs at extrasynaptic membranes as part of a protein complex containing protein phosphatase 1 (PP1). Global activation of NMDARs leads to the activation of PP1, which mediates dephosphorylation of GluN2B at S1480 to promote an increase in synaptic NMDAR content. Thus, PP1-mediated dephosphorylation of the GluN2B PDZ-ligand modulates the synaptic expression of NMDARs in mature neurons in an activity-dependent manner, a process with profound consequences for synaptic and structural plasticity, metaplasticity, and synaptic neurotransmission.
Objective: Dravet syndrome is a severe developmental and epileptic encephalopathy (DEE) most often caused by de novo pathogenic variants in SCN1A.Individuals with Dravet syndrome rarely achieve seizure control and have significantly elevated risk for sudden unexplained death in epilepsy (SUDEP).Heterozygous deletion of Scn1a in mice (Scn1a +/− ) recapitulates several core phenotypes, including temperature-dependent and spontaneous seizures, SUDEP, and behavioral abnormalities. Furthermore, Scn1a +/− mice exhibit a similar clinical response to standard anticonvulsants. Cholesterol 24-hydroxlase (CH24H) is a brain-specific enzyme responsible for cholesterol catabolism. Recent research has indicated the therapeutic potential of CH24H inhibition for diseases associated with neural excitation, including seizures.Methods:In this study, the novel compound soticlestat, a CH24H inhibitor, was administered to Scn1a +/− mice to investigate its ability to improve Dravet-like phenotypes in this preclinical model. Results: Soticlestat treatment reduced seizure burden, protected against hyperthermia-induced seizures, and completely prevented SUDEP in Scn1a +/− mice. Video-electroencephalography (EEG) analysis confirmed the ability of soticlestat to reduce occurrence of electroclinical seizures.Significance: This study demonstrates that soticlestat-mediated inhibition of CH24H provides therapeutic benefit for the treatment of Dravet syndrome in mice and has the potential for treatment of DEEs.
An immunotherapeutic strategy is discussed supporting anti-tumor activity toward malignancies overexpressing ganglioside D3. GD3 can be targeted by NKT cells when derived moieties are presented in the context of CD1d. NKT cells can support anti-tumor responses by secreting inflammatory cytokines and through cytotoxicity toward CD1dGD3 tumors. To overexpress GD3, we generated expression vector DNA and an adenoviral vector encoding the enzyme responsible for generating GD3 from its ubiquitous precursor GM3. We show that DNA encoding α-N-acetyl-neuraminide α-2,8-sialyltransferase 1 (SIAT8) introduced by gene gun vaccination in vivo leads to overexpression of GD3 and delays tumor growth. Delayed tumor growth is dependent on CD1d expression by host immune cells, as shown in experiments engaging CD1d knockout mice. A trend toward greater NKT cell populations among tumor-infiltrating lymphocytes is associated with SIAT8 vaccination. A single adenoviral vaccination introduces anti-tumor activity similarly to repeated vaccination with naked DNA. Here, greater NKT tumor infiltrates were accompanied by marked overexpression of IL-17 in the tumor, later switching to IL-4. Our results suggest that a single intramuscular adenoviral vaccination introduces overexpression of GD3 by antigen-presenting cells at the injection site, recruiting NKT cells that provide an inflammatory anti-tumor environment. We propose adenoviral SIAT8 (AdV-SIAT8) can slow the growth of GD3 expressing tumors in patients.
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