Preservation of dendritic spine morphology and postsynaptic signaling markers after treatment with solid lipid curcumin particles in the 5xFAD mouse model of Alzheimer's amyloidosis

BACKGROUND

Synaptic failure is one of the principal events associated with cognitive dysfunction in Alzheimer's disease (AD). Preservation of existing synapses and prevention of synaptic loss are promising strategies to preserve cognitive function in AD patients. As a potent natural anti-oxidant, anti-amyloid, and anti-inflammatory polyphenol, curcumin (Cur) shows great promise as a therapy for AD. However, hydrophobicity of natural Cur limits its solubility, stability, bioavailability, and clinical utility for AD therapy. We have demonstrated that solid lipid curcumin particles (SLCP) have greater therapeutic potential than natural Cur in vitro and in vivo models of AD. In the present study, we have investigated whether SLCP has any preservative role on affected dendritic spines and synaptic markers in 5xFAD mice.

METHODS

Six- and 12-month-old 5xFAD and age-matched wild-type mice received oral administration of SLCP (100 mg/kg body weight) or equivalent amounts of vehicle for 2 months. Neuronal morphology, neurodegeneration, and amyloid plaque load were investigated from prefrontal cortex (PFC), entorhinal cortex (EC), CA1, CA3, and the subicular complex (SC). In addition, the dendritic spine density from apical and basal branches was studied by Golgi-Cox stain. Further, synaptic markers, such as synaptophysin, PSD95, Shank, Homer, Drebrin, Kalirin-7, CREB, and phosphorylated CREB (pCREB) were studied using Western blots. Finally, cognitive and motor functions were assessed using open-field, novel object recognition (NOR) and Morris water maze (MWM) tasks after treatment with SLCP.

RESULTS

We observed an increased number of pyknotic and degenerated cells in all these brain areas in 5xFAD mice and SLCP treatment partially protected against those losses. Decrease in dendritic arborization and dendritic spine density from primary, secondary, and tertiary apical and basal branches were observed in PFC, EC, CA1, and CA3 in both 6- and 12-month-old 5xFAD mice, and SLCP treatments partially preserved the normal morphology of these dendritic spines. In addition, pre- and postsynaptic protein markers were also restored by SLCP treatment. Furthermore, SLCP treatment improved NOR and cognitive function in 5xFAD mice.

CONCLUSIONS

Overall, these findings indicate that use of SLCP exerts neuroprotective properties by decreasing amyloid plaque burden, preventing neuronal death, and preserving dendritic spine density and synaptic markers in the 5xFAD mice.

Inherited platelet diseases with normal platelet count: phenotypes, genotypes and diagnostic strategy

Inherited platelet disorders resulting from platelet function defects and a normal platelet count cause a moderate or severe bleeding diathesis. Since the description of Glanzmann thrombasthenia resulting from defects of ITGA2B and ITGB3, new inherited platelet disorders have been discovered, facilitated by the use of high throughput sequencing and genomic analyses. Defects of RASGRP2 and FERMT3 responsible for severe bleeding syndromes and integrin activation have illustrated the critical role of signaling molecules. Important are mutations of P2RY12 encoding the major ADP receptor causal for an inherited platelet disorder with inheritance characteristics that depend on the variant identified. Interestingly, variants of GP6 encoding the major subunit of the collagen receptor GPVI/FcRγ associate only with mild bleeding. The numbers of genes involved in dense granule defects including Hermansky-Pudlak and Chediak Higashi syndromes continue to progress and are updated. The ANO6 gene encoding a Ca2+-activated ion channel required for phospholipid scrambling is responsible for the rare Scott syndrome and decreased procoagulant activity. A novel EPHB2 defect in a familial bleeding syndrome demonstrates a role for this tyrosine kinase receptor independent of the classical model of its interaction with ephrins. Such advances highlight the large diversity of variants affecting platelet function but not their production, despite the difficulties in establishing a clear phenotype when few families are affected. They have provided insights into essential pathways of platelet function and have been at the origin of new and improved therapies for ischemic disease. Nevertheless, many patients remain without a diagnosis and requiring new strategies that are now discussed.

CLEM Characterization of Rab8 and Associated Membrane Trafficking Regulators at Primary Cilium Structures

Correlative light and electron microscopy (CLEM) enables determination of high-resolution structural information for proteins of interest within their biological context through the combination of electron and fluorescence microscopies. Numerous electron microscopy (EM) studies of primary cilia have provided ultrastructural details about these antennal-like organelles that extend from the surface of the cell. The core structure of the cilium includes a microtubule-based axoneme, a basal body derived from the mother centriole, and the ciliary membrane, which is connected to the plasma membrane. The small GTPase Rab8 localizes to the ciliary membrane and is important for ciliogenesis, and Rab11 transports the Rab8 guanine nucleotide exchange factor (GEF) Rabin8 to the mother centriole to activate Rab8-dependent ciliary membrane growth. Some primary cilia have a ciliary pocket membrane (CPM) which is observed as an involution from the plasma membrane to the base of the cilia membrane. The Rab11- and Rab8-assocaited membrane trafficking regulator Eps15 Homology Domain-containing protein 1 (EHD1) and EHD3 also function in early stages of ciliogenesis; however, they localize to the CPM. These ciliary localizations of Rab8 and EHD1 can be resolved using CLEM with conventional fluorescence microscopy and transmission electron microscopy (TEM) imaging. Here, we describe in detail the protocol for this CLEM method applicable for ciliary proteins and proteins in other cellular organelles.

Association of a Novel Intronic Variant in RPGR With Hypomorphic Phenotype of X-Linked Retinitis Pigmentosa

Importance

Pathogenic variants in retinitis pigmentosa GTPase regulator (RPGR) gene typically lead to a severe form of X-linked retinitis pigmentosa, which is associated with early severe vision loss.

Objective

To investigate an X-linked retinal degeneration family with atypical preservation of visual acuity in the presence of a novel deep intronic splice site RPGR c.779-5T>G variant.

Design, Setting, and Participants

In this case series, 3 members of an X-linked retinal degeneration family were studied by in-depth phenotyping and genetic screening at a single center. Data were collected and analyzed from November 2018 to March 2020.

Main Outcomes and Measures

Data were collected on full ophthalmic history, examination, and retinal imaging. A full retinitis pigmentosa gene panel was analyzed by next-generation sequencing. The pathogenicity of the RPGR c.779-5T>G variant was assessed by in silico splice prediction tools and by purpose-designed in vitro splicing assay.

Results

An 84-year-old man was referred with clinical diagnosis of choroideremia and possible inclusion into a gene therapy trial. He presented with late-stage retinal degeneration and unusually preserved visual acuity (78 and 68 ETRDS letters) that clinically resembled choroideremia. His 23-year-old grandson was still in early stages of degeneration but showed a very different clinical picture, typical of retinitis pigmentosa. Next-generation sequencing identified a sole RPGR c.779-5T>G variant of undetermined pathogenicity in both cases. The daughter of the proband showed an RPGR carrier phenotype and was confirmed to carry the same variant. The molecular analysis confirmed that the RPGR c.779-5T>G variation reduced the efficiency of intron splicing compared with wild type, leading to a population of mutant and normal transcripts. The predicted consequences of the pathogenic variant are potential use of an alternative splice acceptor site or complete skipping of exon 8, resulting in truncated forms of the RPGR protein with different levels of glutamylation.

Conclusions and Relevance

These results support the importance of careful interpretation of inconsistent clinical phenotypes between family members. Using a molecular splicing assay, a new pathogenic variant in a noncoding region of RPGR was associated with a proportion of normal and hypomorphic RPGR, where cones are likely to survive longer than expected, potentially accounting for the preserved visual acuity observed in this family.

Better understanding the neurobiology of primary lateral sclerosis

Primary lateral sclerosis (PLS) is a rare neurodegenerative disease characterized by progressive degeneration of upper motor neurons (UMNs). Recent studies shed new light onto the cellular events that are particularly important for UMN maintenance including intracellular trafficking, mitochondrial energy homeostasis and lipid metabolism. This review summarizes these advances including the role of Alsin as a gene linked to atypical forms of juvenile PLS, and discusses wider aspects of cellular pathology that have been observed in adult forms of PLS. The review further discusses the prospects of new transgenic upper motor neuron reporter mice, human stem cell-derived UMN cultures, cerebral organoids and non-human primates as future model systems to better understand and ultimately treat PLS.

Association of coronary calcium score with endothelial dysfunction and arterial stiffness

BACKGROUND AND AIMS

The aim of the study was to determine potential associations between endothelial dysfunction and arterial stiffness, measured by peripheral arterial tonometry, and coronary artery calcium score (CACS) assessed by computed tomography (CT).

METHODS AND RESULTS

The BIG3 study is a prospective longitudinal, non-interventional, pulmonary-cardiovascular cohort study exploring the three major smoking-induced diseases: cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer, in a 45-75 aged cohort (mean 62 years), enriched in smokers. Computed tomography of the chest with assessment of CACS was performed in a selected subset of the participants (n = 2080). Peripheral arterial tonometry (EndoPAT) was used to assess endothelial function and arterial stiffness measured as reactive hyperaemia index (RHI) and augmentation index (AI), respectively. We observed significant associations of CACS, endothelial dysfunction, and arterial stiffness with several risk factors for coronary heart disease including age, sex, BMI, diabetes mellitus, and blood pressure. There was significant association of CACS, classified into three levels of severity, with RHI and AI (p = 0.0005 and p = 0.0009, respectively). For groups of increasing CACS (0, 1-400 and > 400 Agatston score), RHI decreased from median 1.89 (1.58-2.39), and 1.93 (1.62-2.41) to 1.77 (1.51-2.10). AI increased from median 14.3 (5.7-25.2), and 16.4 (8.1-27.6) to 18.0 (9.1-29.2). RHI, but not AI, remained significantly associated with CACS after risk factors adjustment.

CONCLUSIONS

In this large study of coronary artery calcium and vascular function, we found an association between CACS and both endothelial dysfunction and arterial stiffness, indicating that they may reflect similar mechanisms for development of cardiovascular disease.

[miR-93-5p promotes invasion and migration of triple negative breast cancer cells by targeting FGD5]

Objective To investigate the molecular mechanism by which miR-93-5p promotes the invasion and migration of triple negative breast cancer (TNBC) cells. Methods The miR-93-5p and faciogenital dysplasia-5 (FGD5) were screened out by Gene Expression Omnibus (GEO). Bioinformatics software was used to predict the candidate target genes for miR-93-5p. The relative expression of miR-93-5p in cells was detected by real-time quantitative PCR. Western blot was used to detect the relative expression of FGD5. Transwell^TM assay was performed to detect the effects of miR-93-5p on the invasion and migration of MDA-MB-231 cells. The expression of FGD5 and survival curve in breast cancer and the correlation between miR-93-5p and FGD5 were analyzed by bioinformatics database. Dual luciferase reporter gene experiment was employed to verify the targeting relationship between miR-93-5p and FGD5. Results The miR-93-5p was highly expressed in TNBC tissues and cell lines. The higher the expression of miR-93-5p was, the worse the prognosis of breast cancer patients were. Knockdown of miR-93-5p inhibited the invasion and migration ability of MDA-MB-231 cells. Bioinformatics analysis showed that there were complementary sequences between miR-93-5p and FGD5. FGD5 presented low expression in breast cancer tissues and lower FGD5 expression in breast cancer patients corresponded to poorer prognosis. The expression levels between miR-93-5p and FGD5 were negatively correlated. Transfection of miR-93-5p inhibitor plasmid up-regulated the expression of FGD5 in TNBC cells. Dual luciferase reporter gene experiments confirmed that miR-93-5p could down-regulate the luciferase activity of wild-type FGD5. Conclusion The miR-93-5p can promote the invasion and migration of TNBC cells by targeting FGD5.

Cdc24 interacts with septins to create a positive feedback loop during bud site assembly in yeast

Yeast cells select the position of their new bud at the beginning of each cell cycle. The recruitment of septins to this prospective bud site is one of the critical events in a complex assembly pathway that culminates in the outgrowth of a new daughter cell. During recruitment, septin rods follow the high concentration of Cdc42GTP that is generated by the focused localization of the Cdc42 guanine-nucleotide-exchange factor Cdc24. We show that, shortly before budding, Cdc24 not only activates Cdc42 but also transiently interacts with Cdc11, the septin subunit that caps both ends of the septin rods. Mutations in Cdc24 that reduce affinity to Cdc11 impair septin recruitment and decrease the stability of the polarity patch. The interaction between septins and Cdc24 thus reinforces bud assembly at sites where septin structures are formed. Once the septins polymerize to form the septin ring, Cdc24 is found at the cortex of the bud and directs further outgrowth from this position.

Involvement of D2 receptor in the NAc in chronic unpredictable stress-induced depression-like behaviors

D2 receptors (D2Rs) located in both pre- and postsynaptic membranes of medium spiny neurons (MSNs) in the nucleus accumbens (NAc) are involved in the stress response and associated behaviors. The role of D2Rs in chronic unpredictable stress (CUS)-induced depression-like behaviors is not clear. Quinpirole (a D2R agonist) and eticlopride (a D2R antagonist) were stereotactically delivered into the NAc before Sprague Dawley rats underwent CUS. CUS-induced depression-like behaviors were accompanied by a significant decrease in both the dopamine (DA) level and D2R expression in the NAc. Eticlopride reversed CUS-induced depression-like behavior and rescued the DA levels in the NAc, and microinjection of DA into the NAc of CUS individuals had the same effect as eticlopride. By contrast, delivery of quinpirole into the NAc of control animals induced depression-like behaviors accompanied by a decrease in the DA level in the NAc. These results show that DA plays a key role in CUS-induced depression-like behaviors and the D2R exerts a presynaptic negative feedback on DA levels during CUS. Microinjection of quinpirole into the NAc also decreased the level of the kalirin-7 protein in the NAc of both control and stressed animals, while eticlopride increased its level in the NAc of rats. In agreement with these results, intraperitoneal injection of eticlopride in mice also caused an increase in both the kalirin-7 protein level in the NAc and spine density in MSNs, while quinpirole reduced them. These results suggest that regulation of kalirin-7 through D2R in the NAc is a general pathway in rats and mice, and is involved in CUS-induced depression-like behaviors. Kalirin-7 may be directly regulated through the D2R postsynaptic pathway or indirectly through the presynaptic pathway in the NAc. The interaction between D2R and kalirin-7 needs to be investigated further.

Subcellular localization of Rap1 GTPase activator CalDAG-GEFI is orchestrated by interaction of its atypical C1 domain with membrane phosphoinositides

BACKGROUND

The small GTPase Rap1 and its guanine nucleotide exchange factor, CalDAG-GEFI (CDGI), are critical for platelet function and hemostatic plug formation. CDGI function is regulated by a calcium binding EF hand regulatory domain and an atypical C1 domain with unknown function.

OBJECTIVE

Here, we investigated whether the C1 domain controls CDGI subcellular localization, both in vitro and in vivo.

METHODS

CDGI interaction with phosphoinositides was studied by lipid co-sedimentation assays and molecular dynamics simulations. Cellular localization of CDGI was studied in heterologous cells by immunofluorescence and subcellular fractionation assays.

RESULTS

Lipid co-sedimentation studies demonstrated that the CDGI C1 domain associates with membranes through exclusive recognition of phosphoinositides, phosphatidylinositol (4,5)-biphosphate (PIP2) and phosphatidylinositol (3,4,5)-triphosphate (PIP3). Molecular dynamics simulations identified a phospholipid recognition motif consisting of residues exclusive to the CDGI C1 domain. Mutation of those residues abolished co-sedimentation of the C1 domain with lipid vesicles and impaired membrane localization of CDGI in heterologous cells.

CONCLUSION

Our studies identify a novel interaction between an atypical C1 domain and phosphatidylinositol (4,5)-biphosphate and phosphatidylinositol (3,4,5)-triphosphate in cellular membranes, which is critical for Rap1 signaling in health and disease.

Prime Time for Dimeric Cytohesins: Surveying the Membrane with One Foot at a Time

In this issue of Structure, Das et al. (2019) probe the structure and dynamics of dimeric cytohesins (guanine nucleotide exchange factors for ADP-ribosylation factors), in solution and on membranes. Unleashing an arsenal of methods, they demonstrate that a pleckstrin-homology domain-mediated membrane recruitment promotes conformational changes that prime cytohesins for allosteric activation.

Identification of alternative splicing and lncRNA genes in pathogenesis of small cell lung cancer based on their RNA sequencing

BACKGROUND

The molecular mechanisms involved in small-cell lung cancer (SCLC) are largely unknown. Recent studies have suggested that long non-coding RNAs (lncRNAs) are likely to play a critical role.

OBJECTIVES

There is an urgent need for suitable molecular biomarkers for SCLC diagnosis and for assessing patient prognosis.

MATERIAL AND METHODS

In this study, we used public databases to identify mRNA-like candidate lncRNAs. A multi-step computational approach was used to construct a functional SCLC lncRNAs-mediated competing with endogenous RNA (ceRNA) network (LMCN) by integrating genome-wide lncRNAs and mRNA expression profiles, miRNA-target interactions, functional analyses, and clinical survival analyses.

RESULTS

The results revealed the significance of lncRNAs interactions with ceRNAs in SCLC, indicating that integration of expression profiles and alternative splicing could be used to identify biomarkers and the underlying pathological changes. The following genes: EPB41L4A-AS1, HOXA-AS2, XIST, DLEU2, FGD5-AS1, ALMS1-IT1, SNHG12, MIR17HG, MIR4720, and SCARNA10 in cluster, as well as shared alternative splicing events, were considered to be critical genes.

CONCLUSIONS

Olfactory transduction and endocytosis were the top-enriched pathways in SCLC. The selected cluster, including critical genes, might also be a potential pathway of SCLC pathogenesis. As a result, this research provides the perspective information to explore the potential critical genes and its pathways in SCLC therapy.

A novel mutation causes Hermansky-Pudlak syndrome type 4 with pulmonary fibrosis in 2 siblings from China

Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive multisystem disorder characterized by oculocutaneous albinism (OCA) and bleeding diathesis, although it displays both genetic and phenotypic heterogeneity. Several genetic subtypes of HPS have been identified in human; however, the characterizations of HPS type 4 (HPS-4) genotype and phenotype remain unclear. This study was aimed to identify gene mutation responsible for HPS-4 with pulmonary fibrosis (PF).Two Chinese siblings in their 50 s afflicted with OCA and progressive dyspnea were recruited and underwent clinical and genetic examinations. In both patients, chest high-resolution computerized tomography showed severe interstitial PF in bilateral lung fields, and the pulmonary function test indicated restrictive lung disease. A novel homozygous frameshift mutation (NM_022081: c.630dupC; p.A211fs) in the HPS4 gene was identified by whole-exome sequencing analysis followed by Sanger DNA sequencing, and it segregated with the phenotypes. The c.630dupC mutation was not found in unaffected healthy controls. The patients were considered as HPS-4 with interstitial PF and eventually died of respiratory failure.This is the first report on the genotype and clinical phenotype of HPS-4 in China. Our results demonstrate the association between a novel frameshift mutation in HPS4 and severe PF with poor prognosis in HPS is presented.

[The clinical characteristics and molecular pathogenesis of a variant Glanzmann's thrombasthenia-like pedigree]

Objective: To review the clinical characteristics of a pedigree with inherited hemorrhagic disease to explore its molecular pathogenesis. Methods: The clinical data of the pedigree with inherited hemorrhagic disease were collected. After extracting DNA, next generation sequencing was utilized to detect the potential gene mutation. The changes of RASGRP2 transcript of this proband and his parents were detected using RT-PCR to compare with normal control. Results: The phenotype of the proband in this pedigree with inherited platelet dysfunction and bleeding disorder was similar to variant Glanzmann's thrombasthenia, the maximum aggregations of platelet in response to the physiological agonists including ADP, epinephrine and arachidonic acid were significantly lower, leading to severe spontaneous mucosal bleeding. Integrin αIIbβ3 gene mutation was not detected, but another gene mutation RASGRP2 IVS3-1 stood out. The mutation was homozygous in the proband and heterozygosis in both of his parents. Two transcript types were detected in the proband, without transcripts coding functional RASGRP2 protein, however, his parents had functional transcripts and abnormal transcripts, with the normal transcripts in the majority. Conclusions: The RASGRP2 IVS3-1 gene mutation was responsible for the inherited hemorrhagic disease. The RASGRP2 IVS3-1 gene mutation led to abnormal alternative splicing, without formation of functional RASGRP2 protein. The RASGRP2 protein is at the nexus of calcium-dependent platelet activation and hemostasis after damage of blood vessels. Spontaneous mucosal bleeding was a result of the lack of the functional RASGRP2 protein. This was the first report of RASGRP2 gene mutation resulting in bleeding disorder in China, and also the first report of the mutation type of RASGRP2 IVS3-1.

Multicopy suppressors of temperature-sensitive mutations of yeast mRNA capping enzyme

We have isolated three Saccharomyces cerevisiae genes-CES1, CES2, and CES3-- that, when present in high copy, suppress the ts growth defect caused by mutations in the CEG1 gene encoding mRNA guanylyltransferase (capping enzyme). Molecular characterization of the capping enzyme suppressor genes reveals the following. CES2 is identical to ESP1, a gene required for proper nuclear division. We show by deletion analysis that the 1573-amino acid ESP1 polypeptide is composed of distinct functional domains. The C-terminal portion of ESP1 is essential for cell growth, but dispensable for CES2 activity. The N-terminal half of ESP1, which is sufficient for CES2 function, displays local sequence similarity to the small subunit of the vaccinia virus RNA capping enzyme. This suggests a basis for suppression by physical or functional interaction between the CES2 domain of ESP1 and the yeast guanylyltransferase. CES1 encodes a novel hydrophilic 915-amino acid protein. The amino acid sequence of CES1 is uninformative, except for its extensive similarity to another yeast gene product of unknown function. The CES1 homologue (designated CES4) is also a multicopy suppressor of capping enzyme ts mutations. Neither CES1 nor CES4 is essential for cell growth, and a double deletion mutant is viable. CES3 corresponds to BUD5, which encodes a putative guanine nucleotide exchange factor. We hypothesize that CES1, CES4, and BUD5 may impact on RNA transactions downstream of cap synthesis that are cap dependent in vivo.

B Cell Defects Observed in Nod2 Knockout Mice Are a Consequence of a Dock2 Mutation Frequently Found in Inbred Strains

Phenotypic differences among substrains of laboratory mice due to spontaneous mutations or pre-existing genetic variation confound the interpretation of targeted mutagenesis experiments and contribute to challenges with reproducibility across institutions. Notably, C57BL/6 Hsd mice and gene-targeted mice that have been backcrossed to this substrain have been reported to harbor a duplication in exons 28 and 29 of Dock2 In this study, we demonstrate the presence of this Dock2 variant in the widely used Nod2-/- mice. Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) is a cytosolic innate immune receptor associated with inflammatory bowel disease susceptibility. Consistent with a role of NOD2 in an immunological disorder, Nod2-/- mice bred at our institution displayed multiple B cell defects including deficiencies in recirculating B cells, marginal zone B cells, and B1a cells in vivo, as well as defects in class switch recombination in vitro. However, we found that these effects are due to the Dock2 variant and are independent of Nod2 deletion. Despite originating from the same gene-targeted founder mice, Nod2-/- mice from another source did not harbor the Dock2 variant or B cell defects. Finally, we show that Dock2-/- mice display the same B cell defects as mice harboring the Dock2 variant, confirming that the variant is a loss-of-function mutation and is sufficient to explain the alterations to the B cell compartment observed in Nod2-/- mice. Our findings highlight the effects of confounding mutations from widely used inbred strains on gene-targeted mice and reveal new functions of DOCK2 in B cells.

Microgravity simulation activates Cdc42 via Rap1GDS1 to promote vascular branch morphogenesis during vasculogenesis

Gravity plays an important role in normal tissue maintenance. The ability of stem cells to repair tissue loss in space through regeneration and differentiation remains largely unknown. To investigate the impact of microgravity on blood vessel formation from pluripotent stem cells, we employed the embryoid body (EB) model for vasculogenesis and simulated microgravity by clinorotation. We first differentiated mouse embryonic stem cells into cystic EBs containing two germ layers and then analyzed vessel formation under clinorotation. We observed that endothelial cell differentiation was slightly reduced under clinorotation, whereas vascular branch morphogenesis was markedly enhanced. EB-derived endothelial cells migrated faster, displayed multiple cellular processes, and had higher Cdc42 and Rac1 activity when subjected to clinorotation. Genetic analysis and rescue experiments demonstrated that Cdc42 but not Rac1 is required for microgravity-induced vascular branch morphogenesis. Furthermore, affinity pull-down assay and mass spectrometry identified Rap1GDS1 to be a Cdc42 guanine nucleotide exchange factor, which was upregulated by clinorotation. shRNA-mediated knockdown of Rap1GDS1 selectively suppressed Cdc42 activation and inhibited both baseline and microgravity-induced vasculogenesis. This was rescued by ectopic expression of constitutively active Cdc42. Taken together, these results support the notion that simulated microgravity activates Cdc42 via Rap1GDS1 to promote vascular branch morphogenesis.

Genetic analysis in UK Biobank links insulin resistance and transendothelial migration pathways to coronary artery disease

UK Biobank is among the world's largest repositories for phenotypic and genotypic information in individuals of European ancestry. We performed a genome-wide association study in UK Biobank testing ∼9 million DNA sequence variants for association with coronary artery disease (4,831 cases and 115,455 controls) and carried out meta-analysis with previously published results. We identified 15 new loci, bringing the total number of loci associated with coronary artery disease to 95 at the time of analysis. Phenome-wide association scanning showed that CCDC92 likely affects coronary artery disease through insulin resistance pathways, whereas experimental analysis suggests that ARHGEF26 influences the transendothelial migration of leukocytes.

Genetic association analysis of polymorphisms in PSD3 gene with obesity, type 2 diabetes, and HDL cholesterol

BACKGROUND

The pleckstrin and Sec7 domain-containing 3 (PSD3) gene has been linked to immune diseases. We examined whether the genetic variants within the PSD3 gene are associated with obesity, type 2 diabetes (T2D), and high-density lipoprotein (HDL) cholesterol level.

METHODS

Multiple logistic regression model and linear regression model were used to examine the associations of 259 single nucleotide polymorphisms (SNPs) within the PSD3 gene with obesity and T2D as binary traits, and HDL level as a continuous trait using the Marshfield data, respectively. A replication study of obesity was conducted using the Health Aging and Body Composition (Health ABC) sample.

RESULTS

23SNPs were associated with obesity (p<0.05) in the Marshfield sample and rs4921966 revealed the strongest association (p=3.97×10^-6). Of the 23SNPs, 20 were significantly associated with obesity in the meta-analysis of two samples (p<0.05). Furthermore, 6SNPs revealed associations with T2D in the Marshfield data (top SNP rs12156368 with p=3.05×10^-3); while two SNPs (rs6983992 and rs7843239) were associated with both obesity and T2D (p=0.0188 and 0.023 for obesity and p=8.47×10^-3 and 0.0128 for T2D, respectively). Furthermore, 11SNPs revealed associations with HDL level (top SNP rs13254772 with p=2.79×10^-3) in the Marshfield data; meanwhile rs7009615 was associated with both T2D (p=0.038) and HDL level (p=4.44×10^-3). In addition, haplotype analyses further supported the results of single SNP analysis.

CONCLUSIONS

Common variants in PSD3 were associated with obesity, T2D and HDL level. These findings add important new insights into the pathogenesis of obesity, T2D and HDL cholesterol.

GALNT14 promotes lung-specific breast cancer metastasis by modulating self-renewal and interaction with the lung microenvironment

Some polypeptide N-acetyl-galactosaminyltransferases (GALNTs) are associated with cancer, but their function in organ-specific metastasis remains unclear. Here, we report that GALNT14 promotes breast cancer metastasis to the lung by enhancing the initiation of metastatic colonies as well as their subsequent growth into overt metastases. Our results suggest that GALNT14 augments the self-renewal properties of breast cancer cells (BCCs). Furthermore, GALNT14 overcomes the inhibitory effect of lung-derived bone morphogenetic proteins (BMPs) on self-renewal and therefore facilitates metastasis initiation within the lung microenvironment. In addition, GALNT14 supports continuous growth of BCCs in the lung by not only inducing macrophage infiltration but also exploiting macrophage-derived fibroblast growth factors (FGFs). Finally, we identify KRAS-PI3K-c-JUN signalling as an upstream pathway that accounts for the elevated expression of GALNT14 in lung-metastatic BCCs. Collectively, our findings uncover an unprecedented role for GALNT14 in the pulmonary metastasis of breast cancer and elucidate the underlying molecular mechanisms.

Epileptic Encephalopathy Caused by Mutations in the Guanine Nucleotide Exchange Factor DENND5A

Epileptic encephalopathies are a catastrophic group of epilepsies characterized by refractory seizures and cognitive arrest, often resulting from abnormal brain development. Here, we have identified an epileptic encephalopathy additionally featuring cerebral calcifications and coarse facial features caused by recessive loss-of-function mutations in DENND5A. DENND5A contains a DENN domain, an evolutionarily ancient enzymatic module conferring guanine nucleotide exchange factor (GEF) activity to multiple proteins serving as GEFs for Rabs, which are key regulators of membrane trafficking. DENND5A is detected predominantly in neuronal tissues, and its highest levels occur during development. Knockdown of DENND5A leads to striking alterations in neuronal development. Mechanistically, these changes appear to result from upregulation of neurotrophin receptors, leading to enhanced downstream signaling. Thus, we have identified a link between a DENN domain protein and neuronal development, dysfunction of which is responsible for a form of epileptic encephalopathy.

Gene Signature of High White Blood Cell Count in B-Precursor Acute Lymphoblastic Leukemia

In this study we sought to identify genetic factors associated with the presenting white blood cell (WBC) count in B-precursor acute lymphoblastic leukemia (BP-ALL). Using ETV6-RUNX1-positive BP-ALL patient samples, a homogeneous subtype, we identified 16 differentially expressed genes based on the presenting WBC count (< 50,000/cumm vs > 50,000). We further confirmed that IL1R1, BCAR3, KCNH2, PIR, and ZDHHC23 were differentially expressed in a larger cohort of ETV6-RUNX1-negative BP-ALL patient samples. Statistical analysis demonstrated that expression levels of these genes could accurately categorize high and low WBC count subjects using two independent patient sets, representing positive and negative ETV6-RUNX1 cases. Further studies in leukemia cell line models will better delineate the role of these genes in regulating the white blood cell count and potentially identify new therapeutic targets.

Transcriptome analysis of cortical tissue reveals shared sets of downregulated genes in autism and schizophrenia

Autism (AUT), schizophrenia (SCZ) and bipolar disorder (BPD) are three highly heritable neuropsychiatric conditions. Clinical similarities and genetic overlap between the three disorders have been reported; however, the causes and the downstream effects of this overlap remain elusive. By analyzing transcriptomic RNA-sequencing data generated from post-mortem cortical brain tissues from AUT, SCZ, BPD and control subjects, we have begun to characterize the extent of gene expression overlap between these disorders. We report that the AUT and SCZ transcriptomes are significantly correlated (P<0.001), whereas the other two cross-disorder comparisons (AUT-BPD and SCZ-BPD) are not. Among AUT and SCZ, we find that the genes differentially expressed across disorders are involved in neurotransmission and synapse regulation. Despite the lack of global transcriptomic overlap across all three disorders, we highlight two genes, IQSEC3 and COPS7A, which are significantly downregulated compared with controls across all three disorders, suggesting either shared etiology or compensatory changes across these neuropsychiatric conditions. Finally, we tested for enrichment of genes differentially expressed across disorders in genetic association signals in AUT, SCZ or BPD, reporting lack of signal in any of the previously published genome-wide association study (GWAS). Together, these studies highlight the importance of examining gene expression from the primary tissue involved in neuropsychiatric conditions-the cortical brain. We identify a shared role for altered neurotransmission and synapse regulation in AUT and SCZ, in addition to two genes that may more generally contribute to neurodevelopmental and neuropsychiatric conditions.

HLB1 Is a Tetratricopeptide Repeat Domain-Containing Protein That Operates at the Intersection of the Exocytic and Endocytic Pathways at the TGN/EE in Arabidopsis

The endomembrane system plays essential roles in plant development, but the proteome responsible for its function and organization remains largely uncharacterized in plants. Here, we identified and characterized the HYPERSENSITIVE TO LATRUNCULIN B1 (HLB1) protein isolated through a forward-genetic screen in Arabidopsis thaliana for mutants with heightened sensitivity to actin-disrupting drugs. HLB1 is a plant-specific tetratricopeptide repeat domain-containing protein of unknown function encoded by a single Arabidopsis gene. HLB1 associated with the trans-Golgi network (TGN)/early endosome (EE) and tracked along filamentous actin, indicating that it could link post-Golgi traffic with the actin cytoskeleton in plants. HLB1 was found to interact with the ADP-ribosylation-factor guanine nucleotide exchange factor, MIN7/BEN1 (HOPM INTERACTOR7/BREFELDIN A-VISUALIZED ENDOCYTIC TRAFFICKING DEFECTIVE1) by coimmunoprecipitation. The min7/ben1 mutant phenocopied the mild root developmental defects and latrunculin B hypersensitivity of hlb1, and analyses of ahlb1/ min7/ben1 double mutant showed that hlb1 and min7/ben1 operate in common genetic pathways. Based on these data, we propose that HLB1 together with MIN7/BEN1 form a complex with actin to modulate the function of the TGN/EE at the intersection of the exocytic and endocytic pathways in plants.