Seizure-suppressor genes: can they help spearhead the discovery of novel therapeutic targets for epilepsy?

INTRODUCTION: Epilepsies are disorders of neuronal excitability characterized by spontaneously recurrent focal and generalized seizures, some of which result from genetic mutations. Despite the availability of antiseizure medications, pharmaco-resistant epilepsy is seen in about 23% of epileptic patients worldwide. Therefore, there is an urgent need to develop novel therapeutic strategies for epilepsies. Several epilepsy-associated genes have been found in humans. Seizure susceptibility can also be induced in Drosophila mutants, some showing features resembling human epilepsies. Interestingly, several second-site mutation gene products have been found to suppress seizure susceptibility in the seizure genetic model Drosophila. Thus, these so-called 'seizure-suppressor' gene variants may lead to developing a novel class of antiseizure medications. AREA COVERED: This review evaluates the potential therapeutic of seizure-suppressor gene variants. EXPERT OPINION: Studies on epilepsy-associated genes have allowed analyses of mutations linked to human epilepsy by reproducing these mutations in Drosophila using reverse genetics to generate potential antiseizure therapeutics. As a result, about fifteen seizure-suppressor gene mutants have been identified. Furthermore, some of these epilepsy gene mutations affect ligand-and voltage-gated ion channels. Therefore, a better understanding of the antiseizure activity of seizure-suppressor genes is essential in advancing gene therapy and precision medicine for epilepsy.

Identification of tumor-suppressor genes in lung squamous cell carcinoma through integrated bioinformatics analyses.

Lung cancer is a prevalent malignancy, and fatalities of the disease exceed 400,000 cases worldwide. Lung squamous cell carcinoma (LUSC) has been recognized as the most common pathological form of lung cancer. The comprehensive understanding of molecular features related to LUSC progression has great significance in LUSC prognosis assessment and clinical management. In this study, we aim to identify a panel of signature genes closely associated with LUSC, which can provide novel insights into the progression of LUSC. Gene expression profiles were retrieved from public resources including gene expression omnibus (GEO) and the cancer genome atlas (TCGA) database. Differentially expressed genes (DEGs) between LUSC specimens and normal lung tissues were identified by bioinformatics analyses. A total of 66 DEGs were identified based on two cohorts of data. CytoHubba plugin of Cytoscape software was utilized for the further analyses of the top 10 candidate hub genes including OGN, ABI3BP, MAMDC2, FGF7, FAM107A, SPARCL1, DCN, COL14A1, and MFAP4 and CHRDL1, which showed significant downregulation in LUSC. Two LUSC cell lines were used to validate the functions of CHRDL1 and FAM107A through overexpression experiment. Together, our data revealed novel candidate tumor-suppressor genes in LUSC, suggesting previously unappreciated mechanisms in the progression of LUSC.

Differential expression profiling of onco and tumor-suppressor genes from major-signaling pathways in Wilms' tumor.

PURPOSE: Wilms' tumor is the most-frequent malignant-kidney tumor in children under 3-4 years of age and is caused by genetic alterations of oncogenes (OG) and tumor-suppressor genes (TG). Wilms' tumor has been linked to many OG-&-TG. However, only WT1 has a proven role in the development of this embryonic-tumor. METHODS: The study investigates the level of mRNA expression of 16 OGs and 20 TGs involved in key-signaling pathways, including chromatin modification; RAS; APC; Cell Cycle/Apoptosis; Transcriptional Regulation; PI3K; NOTCH-&-HH; PI3K & RAS of 24-fresh Wilms'-tumor cases by capture-and-reporter probe Code-Sets chemistry, as CNVs in these pathway genes have been reported. RESULTS: Upon extensively investigating, MEN1, MLL2, MLL3, PBRM1, PRDM1, SMARCB1, SETD2, WT1, PTPN11, KRAS, HRAS, NF1, APC, RB1, FUBP1, BCOR, U2AF1, PIK3CA, PTEN, EBXW7, SMO, ALK, CBL, EP300-and-GATA1 were found to be significantly up-regulated in 58.34, 62.5, 79.17, 91.67, 58, 66.66,54, 58.34, 66.67, 75, 62.5, 62.5, 58, 79.17, 79.17, 75, 70.84, 50, 50, 75, 66.66, 62.50, 61.66, 58.34-and-62.50% of cases respectively, whereas BRAF, NF2, CDH1, BCL2, FGFR3, ERBB2, MET, RET, EGFR-and-GATA2 were significantly down regulated in 58, 87.50, 79.16, 54.16, 79.17, 91.66, 66.66, 58.33, 91.66-and-62.50% of cases, respectively. Interestingly, the WT1 gene was five-fold down regulated in 41.66% of cases only. CONCLUSION: Hence, extensive profiling of OGs and TGs association of major-signaling pathways in Wilms' tumor cases may aid in disease diagnosis. PBRM1 (up-regulated in 91.67% of cases), ERBB2 and EGFR (down-regulated in 91.66 and 91.66% of cases, respectively) could be marker genes. However, validation of all relevant results in a larger number of samples is required.

P53 Suppressor Gene Tissue Microarray-based Protein Expression Analysis in Meningiomas.

BACKGROUND/AIM: Meningiomas represent the main intracranial primary central nervous system (CNS) tumour in adults worldwide. Oncogenes' over-activation combined with suppressor genes' silencing affect negatively the biological behavior of these neoplasms. This study aimed to explore the impact of p53 suppressor gene expression in meningiomas' clinic-pathological features based on a combination of sophisticated techniques. MATERIALS AND METHODS: Fifty (n=50) meningiomas were included in the study, comprising a broad spectrum of histopathological subtypes. An immunohistochemistry assay was applied on tissue microarray cores followed by digital image analysis. RESULTS: p53 protein over-expression (high staining intensity levels) was observed in 27/50 (54%) cases, whereas the rest (23/50-/46%) demonstrated moderate to low levels of the protein. p53 over-expression was statistically significantly correlated to the mitotic index of the examined cases (p-value=0.001). Interestingly, the atypical/anaplastic group of histotypes demonstrated the strongest p53 expression rates compared to the others (p-value=0.001). CONCLUSION: p53 overexpression is observed in a broad spectrum of meningiomas. High expression levels lead to an aggressive biological behavior of the malignancy (combined with increased mitotic rates), especially in atypical and anaplastic sub-types that also have a high recurrence rate.

Significance of Hypermethylation of Tumor-Suppressor Genes PTGER4 and ZNF43 at CpG Sites in the Prognosis of Colorectal Cancer.

The status of DNA methylation in primary tumor tissue and adjacent tumor-free tissue is associated with the occurrence of aggressive colorectal cancer (CRC) and can aid personalized cancer treatments at early stages. Tumor tissue and matched adjacent nontumorous tissue were extracted from 208 patients with CRC, and the correlation between the methylation levels of PTGER4 and ZNF43 at certain CpG loci and the prognostic factors of CRC was determined using the MassARRAY System testing platform. The Wilcoxon signed-rank test, a Chi-square test, and McNemar's test were used for group comparisons, and Kaplan-Meier curves and a log-rank test were used for prediction. The hypermethylation of PTGER4 at the CpG_4, CpG_5, CpG_15, and CpG_17 tumor tissue sites was strongly correlated with shorter recurrence-free survival (RFS), progression-free survival (PFS), and overall survival (OS) [hazard ratio (HR) = 3.26, 95% confidence interval (CI) = 1.38-7.73 for RFS, HR = 2.35 and 95% CI = 1.17-4.71 for PFS, HR = 4.32 and 95% CI = 1.8-10.5 for OS]. By contrast, RFS and PFS were significantly longer in the case of increased methylation of ZNF43 at the CpG_5 site of normal tissue [HR = 2.33, 95% CI = 1.07-5.08 for RFS, HR = 2.42 and 95% CI = 1.19-4.91 for PFS]. Aberrant methylation at specific CpG sites indicates tissue with aggressive behavior. Therefore, the differential methylation of PTGER4 and ZNF43 at specific loci can be employed for the prognosis of patients with CRC.

MicroRNA-139-5p acts as a suppressor gene for depression by targeting nuclear receptor subfamily 3, group C, member 1.

MicroRNA-139-5p (miR-139-5p) is one of the most differentially expressed miRNAs in the brain between healthy people and depressed patients. However, its function in depression is unclear. Therefore, we investigated the function of miR-139-5p in depression. Here, miR-139-5p expression was found to be upregulated in the model group. MiR-139-5p inhibition could increase sucrose preference and decrease mice immobility time after chronic corticosterone (CORT) injection. Furthermore, compared with the antago-NC group, 3 weeks of antagomiR-139-5p treatment significantly decreased miR-139-5p level in model group hippocampus, increased sucrose preference index, reduced neuron damages, and enhanced the levels of nuclear receptor subfamily 3 group C member 1 (NR3C1), brain-derived neurotrophic factor (BDNF), phosphorylated/total tyrosine kinase receptor B (p-TrkB/TrkB), phosphorylated/total cAMP-response element-binding protein (p-CREB/CREB) and phosphorylated/total extracellular regulated protein kinases (p-ERK/ERK). Moreover, as a potential target for miR-139-5p, NR3C1 level was reduced by miR-139-5p mimic. Altogether, by activating the BDNF-TrkB signaling pathway, miR-139-5p inhibition plays an antidepressant-like role and might serve as an effective depression target (Fig. graphical abstract).

SPINK5 is a Tumor-Suppressor Gene Involved in the Progression of Nonsmall Cell Lung Carcinoma through Negatively Regulating PSIP1.

This study aimed to elucidate how SPINK5 affects the malignant phenotypes of NSCLC and the molecular mechanism. NSCLC and adjacent normal tissues were collected to detect the differential level of SPINK5. The influence of SPINK5 on pathological indicators of NSCLC was analyzed. Cellular functions of NSCLC cells overexpressing SPINK5 were assessed by CCK-8, EdU, and transwell assay. By confirming the downstream target of SPINK5, its molecular mechanism on regulating NSCLC was finally explored through rescue experiments. SPINK5 was lowly expressed in NSCLC tissues, and it predicted tumor staging and lymphatic metastasis. In vitro overexpression of SPINK5 declined proliferative and migratory rates in NSCLC cells. PSIP1 was verified as the target gene binding SPINK5, and they displayed a negative correlation in NSCLC tissues. Overexpression of PSIP1 was able to reverse the inhibited proliferative and migratory potentials in NSCLC cells overexpressing SPINK5. SPINK5 level has a close relation to tumor staging and lymphatic metastasis in NSCLC. It serves as a tumor-suppressor gene that inhibits proliferation and migration of NSCLC through negatively regulating PSIP1.

Atypical molecular features of RNA silencing against the phloem-restricted polerovirus TuYV.

In plants and some animal lineages, RNA silencing is an efficient and adaptable defense mechanism against viruses. To counter it, viruses encode suppressor proteins that interfere with RNA silencing. Phloem-restricted viruses are spreading at an alarming rate and cause substantial reduction of crop yield, but how they interact with their hosts at the molecular level is still insufficiently understood. Here, we investigate the antiviral response against phloem-restricted turnip yellows virus (TuYV) in the model plant Arabidopsis thaliana. Using a combination of genetics, deep sequencing, and mechanical vasculature enrichment, we show that the main axis of silencing active against TuYV involves 22-nt vsiRNA production by DCL2, and their preferential loading into AGO1. Moreover, we identify vascular secondary siRNA produced from plant transcripts and initiated by DCL2-processed AGO1-loaded vsiRNA. Unexpectedly, and despite the viral encoded VSR P0 previously shown to mediate degradation of AGO proteins, vascular AGO1 undergoes specific post-translational stabilization during TuYV infection. Collectively, our work uncovers the complexity of antiviral RNA silencing against phloem-restricted TuYV and prompts a re-assessment of the role of its suppressor of silencing P0 during genuine infection.

Identification of fibronectin 1 as a candidate genetic modifier in a Col4a1 mutant mouse model of Gould syndrome.

Collagen type IV alpha 1 and alpha 2 (COL4A1 and COL4A2) are major components of almost all basement membranes. COL4A1 and COL4A2 mutations cause a multisystem disorder that can affect any organ but typically involves the cerebral vasculature, eyes, kidneys and skeletal muscles. In recent years, patient advocacy and family support groups have united under the name of Gould syndrome. The manifestations of Gould syndrome are highly variable, and animal studies suggest that allelic heterogeneity and genetic context contribute to the clinical variability. We previously characterized a mouse model of Gould syndrome caused by a Col4a1 mutation in which the severities of ocular anterior segment dysgenesis (ASD), myopathy and intracerebral hemorrhage (ICH) were dependent on genetic background. Here, we performed a genetic modifier screen to provide insight into the mechanisms contributing to Gould syndrome pathogenesis and identified a single locus [modifier of Gould syndrome 1 (MoGS1)] on Chromosome 1 that suppressed ASD. A separate screen showed that the same locus ameliorated myopathy. Interestingly, MoGS1 had no effect on ICH, suggesting that this phenotype could be mechanistically distinct. We refined the MoGS1 locus to a 4.3 Mb interval containing 18 protein-coding genes, including Fn1, which encodes the extracellular matrix component fibronectin 1. Molecular analysis showed that the MoGS1 locus increased Fn1 expression, raising the possibility that suppression is achieved through a compensatory extracellular mechanism. Furthermore, we found evidence of increased integrin-linked kinase levels and focal adhesion kinase phosphorylation in Col4a1 mutant mice that is partially restored by the MoGS1 locus, implicating the involvement of integrin signaling. Taken together, our results suggest that tissue-specific mechanistic heterogeneity contributes to the variable expressivity of Gould syndrome and that perturbations in integrin signaling may play a role in ocular and muscular manifestations.

SMC complexes are guarded by the SUMO protease Ulp2 against SUMO-chain-mediated turnover.

Structural maintenance of chromosomes (SMCs) complexes, cohesin, condensin, and Smc5/6, are essential for viability and participate in multiple processes, including sister chromatid cohesion, chromosome condensation, and DNA repair. Here we show that SUMO chains target all three SMC complexes and are antagonized by the SUMO protease Ulp2 to prevent their turnover. We uncover that the essential role of the cohesin-associated subunit Pds5 is to counteract SUMO chains jointly with Ulp2. Importantly, fusion of Ulp2 to kleisin Scc1 supports viability of PDS5 null cells and protects cohesin from proteasomal degradation mediated by the SUMO-targeted ubiquitin ligase Slx5/Slx8. The lethality of PDS5-deleted cells can also be bypassed by simultaneous loss of the proliferating cell nuclear antigen (PCNA) unloader, Elg1, and the cohesin releaser, Wpl1, but only when Ulp2 is functional. Condensin and Smc5/6 complex are similarly guarded by Ulp2 against unscheduled SUMO chain assembly, which we propose to time the availability of SMC complexes on chromatin.

High-throughput suppressor screen demonstrates that RcsF monitors outer membrane integrity and not Bam complex function.

The regulator of capsule synthesis (Rcs) is a complex signaling cascade that monitors gram-negative cell envelope integrity. The outer membrane (OM) lipoprotein RcsF is the sensory component, but how RcsF functions remains elusive. RcsF interacts with the ß-barrel assembly machinery (Bam) complex, which assembles RcsF in complex with OM proteins (OMPs), resulting in RcsF's partial cell surface exposure. Elucidating whether RcsF/Bam or RcsF/OMP interactions are important for its sensing function is challenging because the Bam complex is essential, and partial loss-of-function mutations broadly compromise the OM biogenesis. Our recent discovery that, in the absence of nonessential component BamE, RcsF inhibits function of the central component BamA provided a genetic tool to select mutations that specifically prevent RcsF/BamA interactions. We employed a high-throughput suppressor screen to isolate a collection of such rcsF and bamA mutants and characterized their impact on RcsF/OMP assembly and Rcs signaling. Using these mutants and BamA inhibitors MRL-494L and darobactin, we provide multiple lines of evidence against the model in which RcsF senses Bam complex function. We show that Rcs activation in bam mutants results from secondary OM and lipopolysaccharide defects and that RcsF/OMP assembly is required for this activation, supporting an active role of RcsF/OMP complexes in sensing OM stress.

Moderate levels of 5-fluorocytosine cause the emergence of high frequency resistance in cryptococci.

The antifungal agent 5-fluorocytosine (5-FC) is used for the treatment of several mycoses, but is unsuitable for monotherapy due to the rapid development of resistance. Here, we show that cryptococci develop resistance to 5-FC at a high frequency when exposed to concentrations several fold above the minimal inhibitory concentration. The genomes of resistant clones contain alterations in genes relevant as well as irrelevant for 5-FC resistance, suggesting that 5-FC may be mutagenic at moderate concentrations. Mutations in FCY2 (encoding a known permease for 5-FC uptake), FCY1, FUR1, UXS1 (encoding an enzyme that converts UDP-glucuronic acid to UDP-xylose) and URA6 contribute to 5-FC resistance. The uxs1 mutants accumulate UDP-glucuronic acid, which appears to down-regulate expression of permease FCY2 and reduce cellular uptake of the drug. Additional mutations in genes known to be required for UDP-glucuronic acid synthesis (UGD1) or a transcriptional factor NRG1 suppress UDP-glucuronic acid accumulation and 5-FC resistance in the uxs1 mutants.

A multifaceted module of BRI1 ETHYLMETHANE SULFONATE SUPRESSOR1 (BES1)-MYB88 in growth and stress tolerance of apple.

The R2R3 transcription factor MdMYB88 has previously been reported to function in biotic and abiotic stress responses. Here, we identify BRI1 ETHYLMETHANE SULFONATE SUPRESSOR1 (MdBES1), a vital component of brassinosteroid (BR) signaling in apple (Malus × domestica) that directly binds to the MdMYB88 promoter, regulating the expression of MdMYB88 in a dynamic and multifaceted mode. MdBES1 positively regulated expression of MdMYB88 under cold stress and pathogen attack, but negatively regulated its expression under control and drought conditions. Consistently, MdBES1 was a positive regulator for cold tolerance and disease resistance in apple, but a negative regulator for drought tolerance. In addition, MdMYB88 participated in BR biosynthesis by directly regulating the BR biosynthetic genes DE ETIOLATED 2 (MdDET2), DWARF 4 (MdDWF4), and BRASSINOSTEROID 6 OXIDASE 2 (MdBR6OX2). Applying exogenous BR partially rescued the erect leaf and dwarf phenotypes, as well as defects in stress tolerance in MdMYB88/124 RNAi plants. Moreover, knockdown of MdMYB88 in MdBES1 overexpression (OE) plants decreased resistance to a pathogen and C-REPEAT BINDING FACTOR1 expression, whereas overexpressing MdMYB88 in MdBES1 OE plants increased expression of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 3 （MdSPL3） and BR biosynthetic genes, suggesting that MdMYB88 contributes to MdBES1 function during BR biosynthesis and the stress response. Taken together, our results reveal multifaceted regulation of MdBES1 on MdMYB88 in BR biosynthesis and stress tolerance.

Allele-specific suppression in Caenorhabditis elegans reveals details of EMS mutagenesis and a possible moonlighting interaction between the vesicular acetylcholine transporter and ERD2 receptors.

A missense mutant, unc-17(e245), which affects the Caenorhabditis elegans vesicular acetylcholine transporter UNC-17, has a severe uncoordinated phenotype, allowing efficient selection of dominant suppressors that revert this phenotype to wild-type. Such selections permitted isolation of numerous suppressors after EMS (ethyl methanesulfonate) mutagenesis, leading to demonstration of delays in mutation fixation after initial EMS treatment, as has been shown in T4 bacteriophage but not previously in eukaryotes. Three strong dominant extragenic suppressor loci have been defined, all of which act specifically on allele e245, which causes a G347R mutation in UNC-17. Two of the suppressors (sup-1 and sup-8/snb-1) have previously been shown to encode synaptic proteins able to interact directly with UNC-17. We found that the remaining suppressor, sup-2, corresponds to a mutation in erd-2.1, which encodes an endoplasmic reticulum retention protein; sup-2 causes a V186E missense mutation in transmembrane helix 7 of ERD-2.1. The same missense change introduced into the redundant paralogous gene erd-2.2 also suppressed unc-17(e245). Suppression presumably occurred by compensatory charge interactions between transmembrane helices of UNC-17 and ERD-2.1 or ERD-2.2, as previously proposed in work on suppression by SUP-1(G84E) or SUP-8(I97D)/synaptobrevin. erd-2.1(V186E) homozygotes were fully viable, but erd-2.1(V186E); erd-2.2(RNAi) exhibited synthetic lethality [like erd-2.1(RNAi); erd-2.2(RNAi)], indicating that the missense change in ERD-2.1 impairs its normal function in the secretory pathway but may allow it to adopt a novel moonlighting function as an unc-17 suppressor.

RCB initiates Arabidopsis thermomorphogenesis by stabilizing the thermoregulator PIF4 in the daytime.

Daytime warm temperature elicits thermomorphogenesis in Arabidopsis by stabilizing the central thermoregulator PHYTOCHROME INTERACTING transcription FACTOR 4 (PIF4), whose degradation is otherwise promoted by the photoreceptor and thermosensor phytochrome B. PIF4 stabilization in the light requires a transcriptional activator, HEMERA (HMR), and is abrogated when HMR's transactivation activity is impaired in hmr-22. Here, we report the identification of a hmr-22 suppressor mutant, rcb-101, which surprisingly carries an A275V mutation in REGULATOR OF CHLOROPLAST BIOGENESIS (RCB). rcb-101/hmr-22 restores thermoresponsive PIF4 accumulation and reverts the defects of hmr-22 in chloroplast biogenesis and photomorphogenesis. Strikingly, similar to hmr, the null rcb-10 mutant impedes PIF4 accumulation and thereby loses the warm-temperature response. rcb-101 rescues hmr-22 in an allele-specific manner. Consistently, RCB interacts directly with HMR. Together, these results unveil RCB as a novel temperature signaling component that functions collaboratively with HMR to initiate thermomorphogenesis by selectively stabilizing PIF4 in the daytime.

Co-Translational Folding of the First Transmembrane Domain of ABC-Transporter CFTR is Supported by Assembly with the First Cytosolic Domain.

ABC transporters transport a wealth of molecules across membranes and consist of transmembrane and cytosolic domains. Their activity cycle involves a tightly regulated and concerted domain choreography. Regulation is driven by the cytosolic domains and function by the transmembrane domains. Folding of these polytopic multidomain proteins to their functional state is a challenge for cells, which is mitigated by co-translational and sequential events. We here reveal the first stages of co-translational domain folding and assembly of CFTR, the ABC transporter defective in the most abundant rare inherited disease cystic fibrosis. We have combined biosynthetic radiolabeling with protease-susceptibility assays and domain-specific antibodies. The most N-terminal domain, TMD1 (transmembrane domain 1), folds both its hydrophobic and soluble helices during translation: the transmembrane helices pack tightly and the cytosolic N- and C-termini assemble with the first cytosolic helical loop ICL1, leaving only ICL2 exposed. This N-C-ICL1 assembly is strengthened by two independent events: (i) assembly of ICL1 with the N-terminal subdomain of the next domain, cytosolic NBD1 (nucleotide-binding domain 1); and (ii) in the presence of corrector drug VX-809, which rescues cell-surface expression of a range of disease-causing CFTR mutants. Both lead to increased shielding of the CFTR N-terminus, and their additivity implies different modes of action. Early assembly of NBD1 and TMD1 is essential for CFTR folding and positions both domains for the required assembly with TMD2. Altogether, we have gained insights into this first, nucleating, VX-809-enhanced domain-assembly event during and immediately after CFTR translation, involving structures conserved in type-I ABC exporters.

Extracellular Release of ILEI/FAM3C and Amyloid-ß Is Associated with the Activation of Distinct Synapse Subpopulations.

BACKGROUND: Brain amyloid-ß (Aß) peptide is released into the interstitial fluid (ISF) in a neuronal activity-dependent manner, and Aß deposition in Alzheimer's disease (AD) is linked to baseline neuronal activity. Although the intrinsic mechanism for Aß generation remains to be elucidated, interleukin-like epithelial-mesenchymal transition inducer (ILEI) is a candidate for an endogenous Aß suppressor. OBJECTIVE: This study aimed to access the mechanism underlying ILEI secretion and its effect on Aß production in the brain. METHODS: ILEI and Aß levels in the cerebral cortex were monitored using a newly developed ILEI-specific ELISA and in vivo microdialysis in mutant human Aß precursor protein-knockin mice. ILEI levels in autopsied brains and cerebrospinal fluid (CSF) were measured using ELISA. RESULTS: Extracellular release of ILEI and Aß was dependent on neuronal activation and specifically on tetanus toxin-sensitive exocytosis of synaptic vesicles. However, simultaneous monitoring of extracellular ILEI and Aß revealed that a spontaneous fluctuation of ILEI levels appeared to inversely mirror that of Aß levels. Selective activation and inhibition of synaptic receptors differentially altered these levels. The evoked activation of AMPA-type receptors resulted in opposing changes to ILEI and Aß levels. Brain ILEI levels were selectively decreased in AD. CSF ILEI concentration correlated with that of Aß and were reduced in AD and mild cognitive impairment. CONCLUSION: ILEI and Aß are released from distinct subpopulations of synaptic terminals in an activity-dependent manner, and ILEI negatively regulates Aß production in specific synapse types. CSF ILEI might represent a surrogate marker for the accumulation of brain Aß.

Identification of Novel Molecular Regulators Modulating Ethylene Biosynthesis Using EMS-Based Genetic Screening.

The gaseous hormone ethylene regulates a diverse range of plant development and stress responses. Ethylene biosynthesis is tightly regulated by the transcriptional and posttranscriptional regulation of ethylene biosynthetic enzymes. ACC synthase (ACS) is the rate-limiting enzyme that controls the speed of ethylene biosynthesis in plant tissues, thus serving as a primary target for biotic and abiotic stresses to modulate ethylene production. Despite the critical role of ACS in ethylene biosynthesis, only a few regulatory components regulating ACS stability or ACS transcript levels have been identified and characterized. Here we show a genetic approach for identifying novel regulatory components in ethylene biosynthesis by screening EMS-mutagenized Arabidopsis seeds.

Patient-specific Alzheimer-like pathology in trisomy 21 cerebral organoids reveals BACE2 as a gene dose-sensitive AD suppressor in human brain.

A population of more than six million people worldwide at high risk of Alzheimer's disease (AD) are those with Down Syndrome (DS, caused by trisomy 21 (T21)), 70% of whom develop dementia during lifetime, caused by an extra copy of ß-amyloid-(Aß)-precursor-protein gene. We report AD-like pathology in cerebral organoids grown in vitro from non-invasively sampled strands of hair from 71% of DS donors. The pathology consisted of extracellular diffuse and fibrillar Aß deposits, hyperphosphorylated/pathologically conformed Tau, and premature neuronal loss. Presence/absence of AD-like pathology was donor-specific (reproducible between individual organoids/iPSC lines/experiments). Pathology could be triggered in pathology-negative T21 organoids by CRISPR/Cas9-mediated elimination of the third copy of chromosome 21 gene BACE2, but prevented by combined chemical ß and γ-secretase inhibition. We found that T21 organoids secrete increased proportions of Aß-preventing (Aß1-19) and Aß-degradation products (Aß1-20 and Aß1-34). We show these profiles mirror in cerebrospinal fluid of people with DS. We demonstrate that this protective mechanism is mediated by BACE2-trisomy and cross-inhibited by clinically trialled BACE1 inhibitors. Combined, our data prove the physiological role of BACE2 as a dose-sensitive AD-suppressor gene, potentially explaining the dementia delay in ~30% of people with DS. We also show that DS cerebral organoids could be explored as pre-morbid AD-risk population detector and a system for hypothesis-free drug screens as well as identification of natural suppressor genes for neurodegenerative diseases.

A selective transmembrane recognition mechanism by a membrane-anchored ubiquitin ligase adaptor.

While it is well-known that E3 ubiquitin ligases can selectively ubiquitinate membrane proteins in response to specific environmental cues, the underlying mechanisms for the selectivity are poorly understood. In particular, the role of transmembrane regions, if any, in target recognition remains an open question. Here, we describe how Ssh4, a yeast E3 ligase adaptor, recognizes the PQ-loop lysine transporter Ypq1 only after lysine starvation. We show evidence of an interaction between two transmembrane helices of Ypq1 (TM5 and TM7) and the single transmembrane helix of Ssh4. This interaction is regulated by the conserved PQ motif. Strikingly, recent structural studies of the PQ-loop family have suggested that TM5 and TM7 undergo major conformational changes during substrate transport, implying that transport-associated conformational changes may determine the selectivity. These findings thus provide critical information concerning the regulatory mechanism through which transmembrane domains can be specifically recognized in response to changing environmental conditions.