Kyla Pennington

Prominent synaptic and metabolic abnormalities revealed by proteomic analysis of the dorsolateral prefrontal cortex in schizophrenia and bipolar disorder

There is evidence for both similarity and distinction in the presentation and molecular characterization of schizophrenia and bipolar disorder. In this study, we characterized protein abnormalities in the dorsolateral prefrontal cortex in schizophrenia and bipolar disorder using two-dimensional gel electrophoresis. Tissue samples were obtained from 35 individuals with schizophrenia, 35 with bipolar disorder and 35 controls. Eleven protein spots in schizophrenia and 48 in bipolar disorder were found to be differentially expressed (P<0.01) in comparison to controls, with 7 additional spots found to be altered in both diseases. Using mass spectrometry, 15 schizophrenia-associated proteins and 51 bipolar disorder-associated proteins were identified. The functional groups most affected included synaptic proteins (7 of the 15) in schizophrenia and metabolic or mitochondrial-associated proteins (25 of the 51) in bipolar disorder. Six of seven synaptic-associated proteins abnormally expressed in bipolar disorder were isoforms of the septin family, while two septin protein spots were also significantly differentially expressed in schizophrenia. This finding represented the largest number of abnormalities from one protein family. All septin protein spots were upregulated in disease in comparison to controls. This study provides further characterization of the synaptic pathology present in schizophrenia and of the metabolic dysfunction observed in bipolar disorder. In addition, our study has provided strong evidence implicating the septin protein family of proteins in psychiatric disorders for the first time.

The Neuroproteomics of Schizophrenia

Proteomics is the study of global gene expression of an organ, body system, fluid, or cellular compartment at the protein level. Proteomic findings are reflective of complex gene × environment interactions, and the importance of this is increasingly appreciated in schizophrenia research. In this review, we outline the main proteomic methods available to researchers in this area and summarize, for the first time, the findings of the main quantitative neuroproteomic investigations of schizophrenia brain. Our review of these data revealed 16 gray matter proteins, and eight white matter proteins that were differentially expressed in the same direction in two or more investigations. Pathway analysis identified cellular assembly and organization as particularly disrupted in both gray and white matter, whereas the glycolysis-gluconeogenesis pathway was the major signaling pathway significantly altered in both. Reassuringly, these findings show remarkable convergence with functional pathways and positional candidate genes implicated from genomic studies. The specificity of schizophrenia proteomic findings are also addressed in the context of neuroproteomic investigations of neurodegenerative disorders and bipolar disorder. Finally, we discuss the major challenges in the field of neuroproteomics, such as the need for high throughput validation methods and optimal sample preparation. Future directions in the neuroproteomics of schizophrenia, including the use of blood-based biomarker work, the need to focus on subproteomes, and the increasing use of mass spectrometry-based methods are all discussed. This area of research is still in its infancy and offers huge potential to our understanding of schizophrenia on a cellular level.

Proteomic analysis reveals protein changes within layer 2 of the insular cortex in schizophrenia

Abnormalities in the size and activity of the insular cortex (IC), a brain region involved in auditory hallucinations and language, have been previously found in brain imaging studies in schizophrenia. In addition, cortical layer 2 has been shown to be abnormal in many brain regions in schizophrenia. In this study, 2‐D DIGE was used to quantitatively analyse protein expression in schizophrenia and control cases (n = 15/group) in microdissected layer 2 IC tissue. Proteomic analyses revealed 57 significantly differentially expressed (p<0.05) protein spots in schizophrenia. Validation of differential expression of two of the proteins differentially expressed was subsequently confirmed using Western blotting. This work provides evidence of abnormal protein expression in layer 2 of the IC in schizophrenia, supporting previous work of reduced neuronal size in this cortical layer in the IC. Over half of proteins abnormally expressed in this study have not been reported previously in proteomic studies investigating schizophrenia or neurodegenerative disorders. Proteins found to be abnormally expressed appear to collectively impact on neuronal plasticity through roles in neurite outgrowth, cellular morphogenesis and synaptic function.

Evidence for reduced neuronal somal size within the insular cortex in schizophrenia, but not in affective disorders

The insular cortex is a paralimbic area of the brain thought to have important roles in sensory integration, auditory hallucinations and language. Both structural and functional MRI studies have revealed that this brain area is abnormal in both size and activity in schizophrenia. Further investigation of this region at the cellular level in schizophrenia has not been carried out. In the current study, we conducted a stereological examination of neuronal and glial size and density in layers 2 and 3 of the dorso-caudal region of the insular cortex in 15 schizophrenic, 15 bipolar, 15 unipolar and 15 control patients. These cortical layers are candidate layers based on previous cytoarchitectual investigations. Statistical analysis (ANCOVA, correcting for pH, post-mortem interval and age) showed decreased neuronal volume in layer 2 in schizophrenia (p=0.0008, 16.2% mean reduction). No other significant changes were observed. This study thus provides the first evidence of cytoarchitectural abnormality of the insular cortex in the pathophysiology of schizophrenia but not mood disorders. Further work is needed to investigate the molecular basis for this neuronal abnormality in schizophrenia in order to elucidate its role in the pathophysiology of schizophrenia.

A proteomic investigation of similarities between conventional and herbal antidepressant treatments

Abstract Increasing clinical evidence for the effectiveness of herbal antidepressants has led to investigations at the molecular level. Using two-dimensional gel electrophoresis, this study investigated similarities in protein expression between clomipramine, St John’s wort and a Chinese herbal formula, xiao-yao-san, often used in mood disorder treatment. HT22 cells, derived from a mouse hippocampal cell line, were treated for 24 h, and protein expression was compared with that of the untreated cells (n = 4/group). Forty-three protein spots were found to be significantly differentially expressed (P < 0.05) in more than one of the treatment groups. Twenty-nine of these were identified using mass spectrometry. The most affected proteins were those involved in the cytoskeleton and energy metabolism, and an up-regulation of vimentin by all three treatments was confirmed by Western blotting. This study provides preliminary evidence for multiple common molecular targets between conventional and alternative antidepressants, which appear to collectively affect neuronal plasticity.

BSPR/EBI 2007 meeting report – Integrative Proteomics: From Molecules to Systems July 25–27, 2007 Wellcome Trust Conference Centre, Hinxton, UK

This report reviews the joint British Society for Proteome Research (BSPR) and European Bioinformatics Institute (EBI) 2007 meeting, ‘Integrative Proteomics: From Molecules to Systems’ which took place at the Wellcome Trust Conference Centre, Hinxton, UK, from 25th to 27th July. The aim of this years meeting was to explore how the integration of ‘omic’ technologies can lead to a comprehensive understanding of cellular organization, differentiation and signalling. Studies investigating protein–protein interactions and trafficking illustrated how the combination of proteomics and bioinformatics is allowing systems biology to develop as a discipline in its own right.

Book Reviews: Molecular Morphology in Human Tissues: Techniques and Applications. By Gerhard W. Hacker and Raymond Tubbs (Eds.)

world. The need to characterise genetic alterations is one of the highest priorities for the future of medicine. High density DNA microarray technology has played a key role in the analysis of whole genomes and their gene expression patterns. The ability to study many thousands of individual genes using oligonucleotide or cDNA arrays is now widespread with applications ranging from the profiling of gene expression patterns in whole organisms or tissues to the comparison of healthy and pathological samples. Additionally, the technology allows the rapid detection of point mutations, insertions or deletions, loss of heterozygosity, or gene amplification. Furthermore, alterations in DNA methylation patterns which may cause diseases can be studied by microarray analysis. However, despite the success of DNA microarrays, it is obvious that biological function is executed by biomolecules such as proteins. Therefore, protein biochips are emerging to follow DNA microarrays as a possible screening tool. Methods which are needed for identification and quantification, and for studying protein-protein interactions, enzyme-substrate interactions, and small molecule interactions are currently being developed. However, several requirements in diagnostics such as sensitivity, specificity, high throughput, cost effectiveness and turn-around time need to be improved. Joos and Fortina have assembled a collection of competent and leading contributors who give a comprehensive survey of the different technologies now in use and, additionally, provide detailed method sections enabling scientists in design and performance of microarray experiments. The first major part of the book is focused on DNA microarrays and comprises nine independent articles. Most of the methods are focused on the detection and analysis of single nucleotide polymorphisms (SNPs), which is of major interest in molecular medicine. Current medical and diagnostic questions such as SNPs in breast cancer, methylation profiles in normal and tumor cell lines or detection of severe acute respiratory syndrome (SARS) coronavirus infection are addressed. These molecular approaches fall into three different strategies: (1) target or whole genome amplification coupled with PCR; (2) probe amplification based on ligase chain reaction or rolling circle amplification; and (3) signal amplification using 3-D dendrimer labelling systems, enzymatic cascade reporters or invader assay. Several technology platforms such as the “Universal DNA Microarray”, Luminex, or the “Tag Array” are presented as examples of target and probe amplification strategies. These approaches show the flexibility to make the transition from clinical trial to diagnostic laboratory. Furthermore, highly sensitive methods based on signal amplification, which attend the requirements in clinical diagnostics were presented. Technical improvements concerning either probe preparation or experimental performance are also shown. The second part of the book comprises eight articles addressing the growing importance of aspects of the protein level such as tissue-specific protein expression, protein activity, protein-protein interactions, and antibody profiles. Protein arrays comprised of immobilised proteins is an emerging biochip format, which is used to determine antibody specificity and antibody profile from serum samples. An alternative way to profile proteins is the use of antibody arrays which correspond to an immunoassay in micro format. Antibody arrays are discussed as assay to profile the protein content in serum and as a tool for measuring protein expression levels. This section of the book is completed by elucidation of aspects of validation and quality control of protein microarray-based methods. The editors manage to cover the diverse DNA and protein microarraybased assays used in laboratories and research institutes. Presenting state-ofthe-art technologies with diagnostic focus combined with detailed step-bystep protocols, tips on troubleshooting and avoiding known pitfalls, the reader is enabled to design and perform microarray experiments for DNA and protein analysis. The choice of authors points towards the interdisciplinary character of microarray technology implicating the growing influence on clinical diagnostics.