Human Rho guanine nucleotide exchange factor 11 gene is associated with schizophrenia in a Japanese population

Genomic and Reverse Translational Analysis Discloses a Role for Small GTPase RhoA Signaling in the Pathogenesis of Schizophrenia: Rho-Kinase as a Novel Drug Target

Schizophrenia is one of the most serious psychiatric disorders and is characterized by reductions in both brain volume and spine density in the frontal cortex. RhoA belongs to the RAS homolog (Rho) family and plays critical roles in neuronal development and structural plasticity via Rho-kinase. RhoA activity is regulated by GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs). Several variants in GAPs and GEFs associated with RhoA have been reported to be significantly associated with schizophrenia. Moreover, several mouse models carrying schizophrenia-associated gene variants involved in RhoA/Rho-kinase signaling have been developed. In this review, we summarize clinical evidence showing that variants in genes regulating RhoA activity are associated with schizophrenia. In the last half of the review, we discuss preclinical evidence indicating that RhoA/Rho-kinase is a potential therapeutic target of schizophrenia. In particular, Rho-kinase inhibitors exhibit anti-psychotic-like effects not only in Arhgap10 S490P/NHEJ mice, but also in pharmacologic models of schizophrenia (methamphetamine- and MK-801-treated mice). Accordingly, we propose that Rho-kinase inhibitors may have antipsychotic effects and reduce cognitive deficits in schizophrenia despite the presence or absence of genetic variants in small GTPase signaling pathways.

In-depth investigations of the molecular basis underlying sex differences among middle-aged and elderly schizophrenia populations

Sex can influence almost all aspects of schizophrenia. However, the molecular mechanisms underlying sex differences in schizophrenia remain poorly understood. In this project, the dataset GSE107638 containing neuronal RNA-seq data and age/sex information of individuals with or without schizophrenia were retrieved. Schizophrenia samples were divided into young male (M-1), young female (F-1), middle-aged and elderly male (M-2) and middle-aged and elderly female (F-2) groups. Next, green/yellow/turquoise modules related to the M-2 trait and turquoise module correlated with the F-2 trait were identified by weighted correlation network analysis (WGCNA) analysis (soft thresholding power: 13; min module size: 200). Crucial genes in the M-2 green, M-2 turquoise and F-2 turquoise modules were identified by WGCNA, gene significance/module membership, and protein-protein interaction (PPI) analysis. Moreover, 2067 and 934 differentially expressed genes (|log2 fold-change| ≥0.58 and P-value < 0.05) in M-2 and F-2 schizophrenia subgroups versus same-age and same-sex counterparts were identified, respectively. Additionally, 82 core genes in the M-2 turquoise module and 4 hub genes in the F-2 turquoise module were differentially expressed in M-2 and F-2 schizophrenia subgroups versus their counterparts, respectively. Among the 82 hub genes, 15 genes were found to be correlated with neuronal development by the Kyoto Encyclopedia of Genes and Genomes enrichment analysis. Also, 2 potential PPI networks related to neuronal development were identified. Taken together, multiple potential hub genes and 2 potential neurobiological networks related to schizophrenia sex differences and disease progression were identified among middle-aged and elderly schizophrenia populations.

Molecular archaeology of human cognitive traits

The brains and minds of our human ancestors remain inaccessible for experimental exploration. Therefore, we reconstructed human cognitive evolution by projecting nonsynonymous/synonymous rate ratios (ω values) in mammalian phylogeny onto the anatomically modern human (AMH) brain. This atlas retraces human neurogenetic selection and allows imputation of ancestral evolution in task-related functional networks (FNs). Adaptive evolution (high ω values) is associated with excitatory neurons and synaptic function. It shifted from FNs for motor control in anthropoid ancestry (60-41 mya) to attention in ancient hominoids (26-19 mya) and hominids (19-7.4 mya). Selection in FNs for language emerged with an early hominin ancestor (7.4-1.7 mya) and was later accompanied by adaptive evolution in FNs for strategic thinking during recent (0.8 mya-present) speciation of AMHs. This pattern mirrors increasingly complex cognitive demands and suggests that co-selection for language alongside strategic thinking may have separated AMHs from their archaic Denisovan and Neanderthal relatives.

Mechanisms Underlying the Comorbidity of Schizophrenia and Type 2 Diabetes Mellitus

The mortality rate of patients with schizophrenia is high, and life expectancy is shorter by 10 to 20 years. Metabolic abnormalities including type 2 diabetes mellitus (T2DM) are among the main reasons. The prevalence of T2DM in patients with schizophrenia may be epidemiologically frequent because antipsychotics induce weight gain as a side effect and the cognitive dysfunction of patients with schizophrenia relates to a disordered lifestyle, poor diet, and low socioeconomic status. Apart from these common risk factors and risk factors unique to schizophrenia, accumulating evidence suggests the existence of common susceptibility genes between schizophrenia and T2DM. Functional proteins translated from common genetic susceptibility genes are known to regulate neuronal development in the brain and insulin in the pancreas through several common cascades. In this review, we discuss common susceptibility genes, functional cascades, and the relationship between schizophrenia and T2DM. Many genetic and epidemiological studies have reliably associated the comorbidity of schizophrenia and T2DM, and it is probably safe to think that common cascades and mechanisms suspected from common genes' functions are related to the onset of both schizophrenia and T2DM. On the other hand, even when genetic analyses are performed on a relatively large number of comorbid patients, the results are sometimes inconsistent, and susceptibility genes may carry only a low or moderate risk. We anticipate future directions in this field.

Loss of Arhgef11 in the Dahl Salt-Sensitive Rat Protects Against Hypertension-Induced Renal Injury

Arhgef11 is a Rho-guanine nucleotide exchange factor that was previously implicated in kidney injury in the Dahl salt-sensitive (SS) rat, a model of hypertension-related chronic kidney disease. Reduced Arhgef11 expression in an SS-Arhgef11^SHR-minimal congenic strain (spontaneously hypertensive rat allele substituted for S allele) significantly decreased proteinuria, fibrosis, and improved renal hemodynamics, without impacting blood pressure compared with the control SS (SS-wild type). Here, SS-Arhgef11^-/- and SS-wild type rats were placed on either low or elevated salt (0.3% or 2% NaCl) from 4 to 12 weeks of age. On low salt, starting at week 6 and through week 12, SS-Arhgef11^-/- animals demonstrated a 3-fold decrease in proteinuria compared with SS-wild type. On high salt, beginning at week 6, SS-Arhgef11^-/- animals demonstrated >2-fold lower proteinuria from weeks 8 to 12 and 30 mm Hg lower BP compared with SS-wild type. To better understand the molecular mechanisms of the renal protection from loss of Arhgef11, both RNA sequencing and discovery proteomics were performed on kidneys from week 4 (before onset of renal injury/proteinuria between groups) and at week 12 (low salt). The omics data sets revealed loss of Arhgef11 (SS-Arhgef11^-/-) initiates early transcriptome/protein changes in the cytoskeleton starting as early as week 4 that impact a number of cellular functions, including actin cytoskeletal regulation, mitochondrial metabolism, and solute carrier transporters. In summary, in vivo phenotyping coupled with a multi-omics approach provides strong evidence that increased Arhgef11 expression in the Dahl SS rat leads to actin cytoskeleton-mediated changes in cell morphology and cell function that promote kidney injury, hypertension, and decline in kidney function.

cAMP guided his way: a life for G protein-mediated signal transduction and molecular pharmacology-tribute to Karl H. Jakobs

Karl H. Jakobs, former editor-in-chief of Naunyn-Schmiedeberg's Archives of Pharmacology and renowned molecular pharmacologist, passed away in April 2018. In this article, his scientific achievements regarding G protein-mediated signal transduction and regulation of canonical pathways are summarized. Particularly, the discovery of inhibitory G proteins for adenylyl cyclase, methods for the analysis of receptor-G protein interactions, GTP supply by nucleoside diphosphate kinases, mechanisms in phospholipase C and phospholipase D activity regulation, as well as the development of the concept of sphingosine-1-phosphate as extra- and intracellular messenger will presented. His seminal scientific and methodological contributions are put in a general and timely perspective to display and honor his outstanding input to the current knowledge in molecular pharmacology.

Higher mortality and years of potential life lost of suicide in patients with schizophrenia

Patients with schizophrenia could have a higher risk of mortality. We compared the risk of mortality and the years of potential life lost (YPLL) associated with various causes of death between patients with schizophrenia and the general population. A total of 4,298 patients with schizophrenia were included. The cohort was linked to the Taiwan Death Register between 1998 and 2010 using personal identification numbers, which showed 367 patients with schizophrenia had died by the end of 2010. The standard mortality ratios (SMRs) and YPLL were analyzed by age, sex and cause of death. The overall SMR was significantly higher in patients with schizophrenia. Suicide had the most significantly greater SMR, and the SMRs for physical illnesses, accidents and injuries were all significantly greater in patients with schizophrenia. Suicide had the largest YPLL/deaths among all causes of mortality in patients with schizophrenia. Suicide had the most significantly greater risk of mortality among patients with schizophrenia as compared with the general population. Patients with schizophrenia are highly vulnerable in terms of increased mortality and require special attention.

Effects of the antipsychotics haloperidol, clozapine, and aripiprazole on the dendritic spine

Three types of antipsychotics, typical (e.g. haloperidol), atypical (e.g. clozapine), and dopamine partial agonist (e.g. aripiprazole), are administered for treatment of schizophrenia. These antipsychotics have different efficacy and side-effect profiles. We investigated whether aripiprazole, clozapine, and haloperidol differentially regulate the dendritic spine through the AKT-GSK-3 beta cascade. Dissociated cortical neurons from Sprague-Dawley rats were prepared and cultured for 28 days. Aripiprazole, clozapine, or haloperidol was administered to the rat cortical neurons. The levels of PSD95 protein and AKT-GSK-3 beta cascade-related proteins were investigated by Western blot. The number of spines and PSD95 puncta were investigated by immunofluorescence cell staining. Aripiprazole (1 µM or 10 µM) and clozapine (1 µM) increased the levels of PSD95 protein, the number of spines, phosphorylated Akt Thr308 and Ser473, and phosphorylated GSK-3 beta Ser9. On the other hand, haloperidol (1 µM or 10 µM) or an inappropriate concentration of clozapine (10 µM) decreased them. A GSK inhibitor also increased the levels of PSD-95 protein and caused the same morphology. Aripiprazole, clozapine, and haloperidol differentially regulate the dendritic spine, and this effect may occur through the AKT-GSK-3 beta cascade. Selection and appropriate dose of these antipsychotics may be important for the protection of dendritic spines in patients with schizophrenia.

Calcineurin is an important factor involved in glucose uptake in human adipocytes

Calcineurin inhibitors are used in immunosuppressive therapy applied after transplantation, but they are associated with major metabolic side effects including the development of new onset diabetes. Previously, we have shown that the calcineurin inhibiting drugs tacrolimus and cyclosporin A reduce adipocyte and myocyte glucose uptakes by reducing the amount of glucose transporter type 4 (GLUT4) at the cell surface, due to an increased internalization rate. However, this happens without alteration in total protein and phosphorylation levels of key proteins involved in insulin signalling or in the total amount of GLUT4. The present study evaluates possible pathways involved in the altered internalization of GLUT4 and consequent reduction of glucose uptake provoked by calcineurin inhibitors in human subcutaneous adipose tissue. Short- and long-term treatments with tacrolimus, cyclosporin A or another CNI deltamethrin (herbicide) decreased basal and insulin-dependent glucose uptake in adipocytes, without any additive effects observed when added together. However, no tacrolimus effects were observed on glucose uptake when gene transcription and protein translation were inhibited. Investigation of genes potentially involved in GLUT4 trafficking showed only a small effect on ARHGEF11 gene expression (p < 0.05). In conlusion, the specific inhibition of calcineurin, but not that of protein phosphatases, decreases glucose uptake in human subcutaneous adipocytes, suggesting that calcineurin is an important regulator of glucose transport. This inhibitory effect is mediated via gene transcription or protein translation; however, expression of genes potentially involved in GLUT4 trafficking and endocytosis appears not to be involved in these effects.

Human Rho Guanine Nucleotide Exchange Factor 11 (ARHGEF11) Regulates Dendritic Morphogenesis

Disturbances of synaptic connectivity during perinatal and adolescent periods have been hypothesized to be related to the pathophysiology of schizophrenia. Rho guanine nucleotide exchange factor 11 (ARHGEF11) is a specific guanine nucleotide exchange factors (GEF) for RhoA, which is a critical regulator of actin cytoskeleton dynamics and organization of dendritic spines and inhibitor of spine maintenance. ARHGEF11 variants are reported to be associated with a higher risk for the onset of schizophrenia in a Japanese population; however, how ARHGEF11 contributes to the pathogenesis of schizophrenia in dendritic spines is unknown. Therefore, we first studied the distribution, binding, and function of ARHGEF11 in the dendritic spines of the rat cerebral cortex. After subcellular fractionation of the rat cerebral cortex, ARHGEF11 was detected with synaptophysin and post-synaptic density protein 95 (PSD-95) in the P2 fractions including synaptosomal fractions containing presynaptic and postsynaptic density proteins. Endogenous ARHGEF11 was coimmunoprecipitated with synaptophysin or PSD-95. In cortical primary neurons at 28 days in vitro, immunostaining revealed that ARHGEF11 located in the dendrites and dendritic spines and colocalized with PSD-95 and synaptophysin. Overexpression of exogenous ARHGEF11 significantly decreased the number of spines (p = 0.008). These results indicate that ARHGEF11 is likely to be associated with synaptic membranes and regulation of spine.

Polygenic risk for type 2 diabetes mellitus among individuals with psychosis and their relatives

BACKGROUND

An elevated prevalence of Type 2 diabetes (T2D) has been observed in people with psychotic disorders and their relatives compared to the general population. It is not known whether this population also has increased genetic risk for T2D.

METHODS

Subjects included probands with schizophrenia, schizoaffective disorder, or psychotic bipolar I disorder, their first-degree relatives without psychotic disorders, and healthy controls, who participated in the Bipolar Schizophrenia Network for Intermediate Phenotypes study. We constructed sets of polygenic risk scores for T2D (PGRST2D) and schizophrenia (PGRSSCHIZ) using publicly available data from genome-wide association studies. We then explored the correlation of PGRST2D with psychiatric proband or relative status, and with self-reported diabetes. Caucasians and African-Americans were analyzed separately. We also evaluated correlations between PGRSSCHIZ and diabetes mellitus among Caucasian probands and their relatives.

RESULTS

In Caucasians, PGRST2D was correlated with self-reported diabetes mellitus within probands, but was not correlated with proband or relative status in the whole sample. In African-Americans, a PGRST2D based on selected risk alleles for T2D in this population did not correlate with proband or relative status. PGRSSCHIZ was not correlated with self-reported diabetes within Caucasian probands.

CONCLUSION

Differences in polygenic risk for T2D do not explain the increased prevalence of diabetes mellitus observed in psychosis probands and their relatives.

Allelic Variants in Arhgef11 via the Rho-Rock Pathway Are Linked to Epithelial-Mesenchymal Transition and Contributes to Kidney Injury in the Dahl Salt-Sensitive Rat

Previously, genetic analyses identified that variants in Arhgef11 may influence kidney injury in the Dahl salt-sensitive (S) rat, a model of hypertensive chronic kidney disease. To understand the potential mechanism by which altered expression and/or protein differences in Arhgef11 could play a role in kidney injury, stably transduced Arhgef11 knockdown cell lines as well as primary cultures of proximal tubule cells were studied. Genetic knockdown of Arhgef11 in HEK293 and NRK resulted in reduced RhoA activity, decreased activation of Rho-ROCK pathway, and less stress fiber formation versus control, similar to what was observed by pharmacological inhibition (fasudil). Primary proximal tubule cells (PTC) cultured from the S exhibited increased expression of Arhgef11, increased RhoA activity, and up regulation of Rho-ROCK signaling compared to control (small congenic). The cells were also more prone (versus control) to TGFβ-1 induced epithelial-mesenchymal transition (EMT), a hallmark feature of the development of renal interstitial fibrosis, and characterized by development of spindle shape morphology, gene expression changes in EMT markers (Col1a3, Mmp9, Bmp7, and Ocln) and increased expression of N-Cadherin and Vimentin. S derived PTC demonstrated a decreased ability to uptake FITC-albumin compared to the small congenic in vitro, which was confirmed by assessment of albumin re-uptake in vivo by infusion of FITC-albumin and immunofluorescence imaging. In summary, these studies suggest that genetic variants in the S form of Arhgef11 via increased expression and/or protein activity play a role in promoting kidney injury in the S rat through changes in cell morphology (Rho-Rock and/or EMT) that impact the function of tubule cells.