Drosophila melanogaster Models of Metal-Related Human Diseases and Metal Toxicity

Iron, copper and zinc are transition metals essential for life because they are required in a multitude of biological processes. Organisms have evolved to acquire metals from nutrition and to maintain adequate levels of each metal to avoid damaging effects associated with its deficiency, excess or misplacement. Interestingly, the main components of metal homeostatic pathways are conserved, with many orthologues of the human metal-related genes having been identified and characterized in Drosophila melanogaster. Drosophila has gained appreciation as a useful model for studying human diseases, including those caused by mutations in pathways controlling cellular metal homeostasis. Flies have many advantages in the laboratory, such as a short life cycle, easy handling and inexpensive maintenance. Furthermore, they can be raised in a large number. In addition, flies are greatly appreciated because they offer a considerable number of genetic tools to address some of the unresolved questions concerning disease pathology, which in turn could contribute to our understanding of the metal metabolism and homeostasis. This review recapitulates the metabolism of the principal transition metals, namely iron, zinc and copper, in Drosophila and the utility of this organism as an experimental model to explore the role of metal dyshomeostasis in different human diseases. Finally, a summary of the contribution of Drosophila as a model for testing metal toxicity is provided

Using gene expression and systems biology to interrogate auditory hallucinations in schizophrenic patients

Schizophrenia is a severe mental disorder affecting around 1% of the opulation. This disease presents a complex aetiology that has not been completely unveiled yet. Auditory hallucinations are a very significant and disruptive symptom of schizophrenia affecting between 60% and 80% of schizophrenic patients. In this paper we have used a network-based transcriptomic analysis aiming to identify differences in gene expression between schizophrenic patients with and without auditory hallucinations. Gene expression data from blood samples drained from 30 schizophrenia patients were generated using Affymetrix Human Gene 2.0 ST Genechips. Affymetrix Expression console was used for normalization and quality control purposes. The RMA normalization method was applied for gene summarization and then a filter applied to keep only the most variably expressed probesets (4,508). These dataset was analysed using the weighted gene co-expression network analysis (WGCNA) package in R. The gene co-expression network analyses allowed us to identify eleven different gene modules based on their topological overlap. These modules were related to the relevant phenotypic information and allowing us to identify modules related with different phenotypic traits of interest. Gene co-expression network analysis is a useful tool for the analysis of gene expression analysis. Its application in the analysis of schizophrenia gene expression provides an insight on the molecular mechanisms related with this disease and the differences at the molecular level between patients presenting auditory hallucinations and those that do not. In our analysis we have been able to identify different gene modules containing genes expression profiles that can be related with clinically relevant phenotypes. These gene modules could be functionally annotated and related with different pathways and gene ontology terms that are relevant in the context of this analysis

Time dependent expression of the blood biomarkers EIF2D and TOX in patients with schizophrenia

Background During last years, there has been an intensive search for blood biomarkers in schizophrenia to assist in diagnosis, prognosis and clinical management of the disease. Methods In this study, we first conducted a weighted gene coexpression network analysis to address differentially expressed genes in peripheral blood from patients with chronic schizophrenia (n?=?30) and healthy controls (n?=?15). The discriminating performance of the candidate genes was further tested in an independent cohort of patients with first-episode schizophrenia (n?=?124) and healthy controls (n?=?54), and in postmortem brain samples (cingulate and prefrontal cortices) from patients with schizophrenia (n?=?34) and healthy controls (n?=?35). Results The expression of the Eukaryotic Translation Initiation Factor 2D (EIF2D) gene, which is involved in protein synthesis regulation, was increased in the chronic patients of schizophrenia. On the contrary, the expression of the Thymocyte Selection-Associated High Mobility Group Box (TOX) gene, involved in immune function, was reduced. EIF2D expression was also altered in first-episode schizophrenia patients, but showing reduced levels. Any of the postmortem brain areas studied did not show differences of expression of both genes. Conclusions EIF2D and TOX are putative blood markers of chronic patients of schizophrenia, which expression change from the onset to the chronic disease, unraveling new biological pathways that can be used for the development of new intervention strategies in the diagnosis and prognosis of schizophrenia disease.Acknowledgments: This work was supported by Fondo de Investigación Sanitaria, Ministerio de Economía y Competitividad, Spain (PI10/01399, PI13/00447; PI17/00402, co-financed by FEDER) to J. Sanjuan and M.D. Moltó; Generalitat Valenciana PROMETEO Excellence Program, Spain (PROMETEO2016/082) to J Sanjuán. J Gilabert-Juan and N. Sebastiá-Ortega were recipients of research contracts from CIBERSAM, Spain. The RNA samples donated bythe Stanley Medical Research Institute Brain Collection were courtesy of Drs. Michael B. Knable, E. Fuller Torrey, Maree J. Webster, and Robert H. Yolken. The authors also thank the collaboration of the staff members of the hospitals

FOXP2 expression and gray matter density in the male brains of patients with schizophrenia

Common genetic variants of FOXP2 may contribute to schizophrenia vulnerability, but controversial results have been reported for this proposal. Here we evaluated the potential impact of the common FOXP2 rs2396753 polymorphism in schizophrenia. It was previously reported to be part of a risk haplotype for this disease and to have significant effects on gray matter concentration in the patients. We undertook the first examination into whether rs2396753 affects the brain expression of FOXP2 and a replication study of earlier neuroimaging findings of the influence of this genetic variant on brain structure. FOXP2 expression levels were measured in postmortem prefrontal cortex samples of 84 male subjects (48 patients and 36 controls) from the CIBERSAM Brain and the Stanley Foundation Array Collections. High-resolution anatomical magnetic resonance imaging was performed on 79 male subjects (61 patients, 18 controls) using optimized voxel-based morphometry. We found differences in FOXP2 expression and brain morphometry depending on the rs2396753, relating low FOXP2 mRNA levels with reduction of gray matter density. We detected an interaction between rs2396753 and the clinical groups, showing that heterozygous patients for this polymorphism have gray matter density decrease and low FOXP2 expression comparing with the heterozygous controls.This study shows the importance of independent replication of neuroimaging genetic studies of FOXP2 as a candidate gene in schizophrenia. Furthermore, our results suggest that the FOXP2 rs2396753 affects mRNA levels, thus providing new knowledge about its significance as a potential susceptibility polymorphism in schizophrenia

Time dependent expression of the blood biomarkers EIF2D and TOX in patients with schizophrenia

Background: During last years, there has been an intensive search for blood biomarkers in schizophrenia to assist in diagnosis, prognosis and clinical management of the disease. Methods: In this study, we first conducted a weighted gene coexpression network analysis to address differentially expressed genes in peripheral blood from patients with chronic schizophrenia (n = 30) and healthy controls (n = 15). The discriminating performance of the candidate genes was further tested in an independent cohort of patients with first-episode schizophrenia (n = 124) and healthy controls (n = 54), and in postmortem brain samples (cingulate and prefrontal cortices) from patients with schizophrenia (n = 34) and healthy controls (n = 35). Results: The expression of the Eukaryotic Translation Initiation Factor 2D (EIF2D) gene, which is involved in protein synthesis regulation, was increased in the chronic patients of schizophrenia. On the contrary, the expression of the Thymocyte Selection-Associated High Mobility Group Box (TOX) gene, involved in immune function, was reduced. EIF2D expression was also altered in first-episode schizophrenia patients, but showing reduced levels. Any of the postmortem brain areas studied did not show differences of expression of both genes. Conclusions: EIF2D and TOX are putative blood markers of chronic patients of schizophrenia, which expression change from the onset to the chronic disease, unraveling new biological pathways that can be used for the development of new intervention strategies in the diagnosis and prognosis of schizophrenia disease