This work was supported by Inserm, University of Lille 2, MEDIALZ, LabEx (excellence laboratory, program invest for the future) and DISTALZ (Development of Innovative Strategies for a Transdisciplinary approach to Alzheimer's disease). F-J.F-G is currently a recipient fellowship of ANR (French National Research Agency/ NeuroSplice de Tau Projet ANR- 2010-BLAN-1114 01), but this work was also under the support of a grant from the JCCM (Spain).

1. Homogenization and Total Protein Extraction from Human and Mouse Brain Tissue
<ol>
	<li>Brain tissue homogenization. Homogenize the brain tissue 10% (w/v) in 8 M urea, 2 M thiourea and 1% w/v SDS buffer (UTS) using a potter glass (for human samples) or Teflon homogenizer (for mice samples). Sonicate at 60 Hz 30 pulses with a ultrasound generator applying 0.5 sec for total tissue disintegration13,14.
	<ol>
		<li>Determine protein concentration with Bradford assay, using BSA as standar...

<ol>
	<li>Collins, P. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Grand+challenges+in+global+mental+health.">Grand challenges in global mental health.</a> Nature. 475, 27-30 (2011).</li><li>De Deyn, P. P., Van Dam, D., Sergeant, N., Bu&#233;e, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Animal Models of Dementia Vol. 48 Neuromethods 449-468. , 449-468 (2011).</li><li>O'Farrell, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+resolution+two-dimensional+electrophoresis+of+proteins.">High resolution two-dimensional electrophoresis of proteins.</a> J Biol Chem. 250, 4007-4021 (1975).</li><li>Riederer, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Non-covalent+and+covalent+protein+labeling+in+two-dimensional+gel+electrophoresis.">Non-covalent and covalent protein labeling in two-dimensional gel electrophoresis.</a> J Proteomics. 71, 231-244 (2008).</li><li>Marouga, R., David, S., Hawkins, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+development+of+the+DIGE+system:+2D+fluorescence+difference+gel+analysis+technology.">The development of the DIGE system: 2D fluorescence difference gel analysis technology.</a> Anal Bioanal Chem. 382, 669-678 (2005).</li><li>Westermeier, R., Scheibe, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Difference+gel+electrophoresis+based+on+lys/cys+tagging.">Difference gel electrophoresis based on lys/cys tagging.</a> Methods Mol Biol. 424, 73-85 (2008).</li><li>Gong, L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+ventral+furrow+morphogenesis:+a+proteomic+analysis.">Drosophila ventral furrow morphogenesis: a proteomic analysis.</a> Development. 131, 643-656 (2004).</li><li>Gharbi, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+two-dimensional+differential+gel+electrophoresis+for+proteomic+expression+analysis+of+a+model+breast+cancer+cell+system.">Evaluation of two-dimensional differential gel electrophoresis for proteomic expression analysis of a model breast cancer cell system.</a> Mol Cell Proteomics. 1, 91-98 (2002).</li><li>Ando, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tau+pathology+modulates+Pin1+post-translational+modifications+and+may+be+relevant+as+biomarker.">Tau pathology modulates Pin1 post-translational modifications and may be relevant as biomarker.</a> Neurobiol Aging. 34, 757-769 (2013).</li><li>Bretteville, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+electrophoresis+of+tau+mutants+reveals+specific+phosphorylation+pattern+likely+linked+to+early+tau+conformational+changes.">Two-dimensional electrophoresis of tau mutants reveals specific phosphorylation pattern likely linked to early tau conformational changes.</a> PLoS One. 4, 4843 (2009).</li><li>Sergeant, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+characterization+of+paired+helical+filament-tau+from+Alzheimer's+disease:+demonstration+of+an+additional+74-kDa+component+and+age-related+biochemical+modifications.">Two-dimensional characterization of paired helical filament-tau from Alzheimer's disease: demonstration of an additional 74-kDa component and age-related biochemical modifications.</a> J Neurochem. 69, 834-844 (1997).</li><li>Sergeant, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Different+distribution+of+phosphorylated+tau+protein+isoforms+in+Alzheimer's+and+Pick's+diseases.">Different distribution of phosphorylated tau protein isoforms in Alzheimer's and Pick's diseases.</a> FEBS Lett. 412, 578-582 (1997).</li><li>Rabilloud, T., Luche, S., Santoni, V., Chevallet, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detergents+and+chaotropes+for+protein+solubilization+before+two-dimensional+electrophoresis.">Detergents and chaotropes for protein solubilization before two-dimensional electrophoresis.</a> Methods Mol Biol. 355, 111-119 (2007).</li><li>Wrobel, K., Caruso, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pretreatment+procedures+for+characterization+of+arsenic+and+selenium+species+in+complex+samples+utilizing+coupled+techniques+with+mass+spectrometric+detection.">Pretreatment procedures for characterization of arsenic and selenium species in complex samples utilizing coupled techniques with mass spectrometric detection.</a> Anal Bioanal Chem. 381, 317-331 (2005).</li><li>McCarthy, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carbamylation+of+proteins+in+2-D+electrophoresis--myth+or+reality.">Carbamylation of proteins in 2-D electrophoresis--myth or reality.</a> J Proteome Res. 2, 239-242 (2003).</li><li>Chafey, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Proteomic+analysis+of+beta-catenin+activation+in+mouse+liver+by+DIGE+analysis+identifies+glucose+metabolism+as+a+new+target+of+the+Wnt+pathway.">Proteomic analysis of beta-catenin activation in mouse liver by DIGE analysis identifies glucose metabolism as a new target of the Wnt pathway.</a> Proteomics. 9, 3889-3900 (2009).</li><li>Kahn, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparative+proteomic+analysis+of+blood+eosinophils+reveals+redox+signaling+modifications+in+patients+with+FIP1L1-PDGFRA-associated+chronic+eosinophilic+leukemia.">Comparative proteomic analysis of blood eosinophils reveals redox signaling modifications in patients with FIP1L1-PDGFRA-associated chronic eosinophilic leukemia.</a> J Proteome Res. 10, 1468-1480 (2011).</li><li>Pottiez, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+large-scale+electrophoresis-+and+chromatography-based+determination+of+gene+expression+profiles+in+bovine+brain+capillary+endothelial+cells+after+the+re-induction+of+blood-brain+barrier+properties.">A large-scale electrophoresis- and chromatography-based determination of gene expression profiles in bovine brain capillary endothelial cells after the re-induction of blood-brain barrier properties.</a> Proteome Sci. 8, 57 (2010).</li><li>Stochaj, W. R., Berkelman, T., Laird, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparative+2D+Gel+Electrophoresis+with+Immobilized+pH+Gradients:+IPG+Strip+Equilibration.">Preparative 2D Gel Electrophoresis with Immobilized pH Gradients: IPG Strip Equilibration.</a> CSH Protoc. , (2006).</li><li>Azimzadeh, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formalin-fixed+paraffin-embedded+(FFPE)+proteome+analysis+using+gel-free+and+gel-based+proteomics.">Formalin-fixed paraffin-embedded (FFPE) proteome analysis using gel-free and gel-based proteomics.</a> J Proteome Res. 9, 4710-4720 (2010).</li><li>Singh, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+the+p16-Arc+subunit+of+the+Arp+2/3+complex+as+a+substrate+of+MAPK-activated+protein+kinase+2+by+proteomic+analysis.">Identification of the p16-Arc subunit of the Arp 2/3 complex as a substrate of MAPK-activated protein kinase 2 by proteomic analysis.</a> J Biol Chem. 278, 36410-36417 (2003).</li><li>Rabilloud, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+thiourea+to+increase+the+solubility+of+membrane+proteins+in+two-dimensional+electrophoresis.">Use of thiourea to increase the solubility of membrane proteins in two-dimensional electrophoresis.</a> Electrophoresis. 19, 758-760 (1998).</li><li>Molloy, M. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extraction+of+membrane+proteins+by+differential+solubilization+for+separation+using+two-dimensional+gel+electrophoresis.">Extraction of membrane proteins by differential solubilization for separation using two-dimensional gel electrophoresis.</a> Electrophoresis. 19, 837-844 (1998).</li><li>Ericsson, C., Peredo, I., Nister, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimized+protein+extraction+from+cryopreserved+brain+tissue+samples.">Optimized protein extraction from cryopreserved brain tissue samples.</a> Acta Oncol. 46, 10-20 (2007).</li><li>Shaw, M. M., Riederer, B. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sample+preparation+for+two-dimensional+gel+electrophoresis.">Sample preparation for two-dimensional gel electrophoresis.</a> Proteomics. 3, 1408-1417 (2003).</li><li>Ye, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimization+of+protein+solubilization+for+the+analysis+of+the+CD14+human+monocyte+membrane+proteome+using+LC-MS/MS.">Optimization of protein solubilization for the analysis of the CD14 human monocyte membrane proteome using LC-MS/MS.</a> J Proteomics. 73, 112-122 (2009).</li><li>Centlow, M., Hansson, S. R., Welinder, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differential+proteome+analysis+of+the+preeclamptic+placenta+using+optimized+protein+extraction.">Differential proteome analysis of the preeclamptic placenta using optimized protein extraction.</a> J Biomed Biotechnol. 2010, 458-748 (2010).</li><li>Perdew, G. H., Schaup, H. W., Selivonchick, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+a+zwitterionic+detergent+in+two-dimensional+gel+electrophoresis+of+trout+liver+microsomes.">The use of a zwitterionic detergent in two-dimensional gel electrophoresis of trout liver microsomes.</a> Anal Biochem. 135, 453-455 (1983).</li><li>Schindowski, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alzheimer's+disease-like+tau+neuropathology+leads+to+memory+deficits+and+loss+of+functional+synapses+in+a+novel+mutated+tau+transgenic+mouse+without+any+motor+deficits.">Alzheimer's disease-like tau neuropathology leads to memory deficits and loss of functional synapses in a novel mutated tau transgenic mouse without any motor deficits.</a> Am J Pathol. 169, 599-616 (2006).</li><li>Veenstra, T. D., Marcus, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multidimensional+advancement+of+neuroproteomics.">Multidimensional advancement of neuroproteomics.</a> Expert Rev Proteomics. 5, 149-151 (2008).</li><li>Hernandez-Hernandez, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myotonic+dystrophy+CTG+expansion+affects+synaptic+vesicle+proteins,+neurotransmission+and+mouse.">Myotonic dystrophy CTG expansion affects synaptic vesicle proteins, neurotransmission and mouse.</a> 136, 957-970 (2013).</li><li>Deramecourt, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biochemical+staging+of+synucleinopathy+and+amyloid+deposition+in+dementia+with+Lewy+bodies.">Biochemical staging of synucleinopathy and amyloid deposition in dementia with Lewy bodies.</a> J Neuropathol Exp Neurol. 65, 278-288 (2006).</li><li>Tofaris, G. K., Razzaq, A., Ghetti, B., Lilley, K. S., Spillantini, M. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ubiquitination+of+alpha-synuclein+in+Lewy+bodies+is+a+pathological+event+not+associated+with+impairment+of+proteasome+function.">Ubiquitination of alpha-synuclein in Lewy bodies is a pathological event not associated with impairment of proteasome function.</a> J Biol Chem. 278, 44405-44411 (2003).</li><li>Sergeant, N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Truncated+beta-amyloid+peptide+species+in+pre-clinical+Alzheimer's+disease+as+new+targets+for+the+vaccination+approach.">Truncated beta-amyloid peptide species in pre-clinical Alzheimer's disease as new targets for the vaccination approach.</a> J Neurochem. 85, 1581-1591 (2003).</li><li>Le Freche, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tau+phosphorylation+and+sevoflurane+anesthesia:+an+association+to+postoperative+cognitive+impairment.">Tau phosphorylation and sevoflurane anesthesia: an association to postoperative cognitive impairment.</a> Anesthesiology. 116, 779-787 (2012).</li><li>Leboucher, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detrimental+effects+of+diet-induced+obesity+on+tau+pathology+are+independent+of+insulin+resistance+in+tau+transgenic+mice.">Detrimental effects of diet-induced obesity on tau pathology are independent of insulin resistance in tau transgenic mice.</a> Diabetes. 62, 1681-1688 (2013).</li><li>Deramecourt, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical,+neuropathological,+and+biochemical+characterization+of+the+novel+tau+mutation+P332S.">Clinical, neuropathological, and biochemical characterization of the novel tau mutation P332S.</a> J Alzheimers Dis. 31, 741-749 (2012).</li><li>Birdsill, A. C., Walker, D. G., Lue, L., Sue, L. I., Beach, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postmortem+interval+effect+on+RNA+and+gene+expression+in+human+brain+tissue.">Postmortem interval effect on RNA and gene expression in human brain tissue.</a> Cell Tissue Bank. 12, 311-318 (2011).</li><li>Bell, J. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Management+of+a+twenty-first+century+brain+bank:+experience+in+the+BrainNet+Europe+consortium.">Management of a twenty-first century brain bank: experience in the BrainNet Europe consortium.</a> Acta Neuropathol. 115, 497-507 (2008).</li><li>Crecelius, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessing+quantitative+post-mortem+changes+in+the+gray+matter+of+the+human+frontal+cortex+proteome+by+2-D+DIGE.">Assessing quantitative post-mortem changes in the gray matter of the human frontal cortex proteome by 2-D DIGE.</a> Proteomics. 8, 1276-1291 (2008).</li><li>Swatton, J. E., Prabakaran, S., Karp, N. A., Lilley, K. S., Bahn, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+profiling+of+human+postmortem+brain+using+2-dimensional+fluorescence+difference+gel+electrophoresis+(2-D+DIGE).">Protein profiling of human postmortem brain using 2-dimensional fluorescence difference gel electrophoresis (2-D DIGE).</a> Mol Psychiatry. 9, 128-143 (2004).</li><li>Viswanathan, S., Unlu, M., Minden, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+difference+gel+electrophoresis.">Two-dimensional difference gel electrophoresis.</a> Nat Protoc. 1, 1351-1358 (2006).</li><li>Tannu, N. S., Hemby, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+fluorescence+difference+gel+electrophoresis+for+comparative+proteomics+profiling.">Two-dimensional fluorescence difference gel electrophoresis for comparative proteomics profiling.</a> Nat Protoc. 1, 1732-1742 (2006).</li></ol>

Authors have no conflict of interest to declare.

Discovering pathological expression changes of proteins, search for biomarkers and the modulation of potential pathways for pharmacological targets are among the aims of the neuroproteomics approaches30. Amid the emerging tools, the 2DE field adds a promising expectative. Nevertheless, a consensus should be reached in order to minimize variability and increase reproducibility in the experiments. In line of this idea a standardized protocol to perform 2D-DIGE (Figure 2) and the subsequent 2DE i...

Mental and neurological disorders represent 13% of the global burden of disease, new challenges like pathophysiological mechanisms, risk factors and prodromal biomarkers must be explored1. In line with this objective, proteomics studies of the human brain become indispensable to uncover molecular pathways involved in processes like memory, behavior, emotions and neuronal plasticity for instance, not only for physiological but also for pathological conditions. Therefore, the use of animal models and more specifically the transgenic mice, brings a wide range of possibilities to mimic the etiology of human neurodegenerative disorders2.
Proteomics approaches are nowadays available in order to accomplish these new perspectives in the neuroscience field. Two-dimensional gel electrophoresis (2DE) is a potent and likely simple method that enables to compare the proteome of a wide range of samples. Moreover, it is also a powerful method to isolate a protein from a complex mixture in order to identify and further analyze by mass spectrometry. This technique essentially consists in two successive steps: 1) protein separation according to their isoelectric point (pI) by isoelectrofocusing (IEF). More precisely, an electric potential is applied across the immobiline acrylamide strips among a pH gradient and then proteins will migrate and focus on a determined pI in function of their global net charge. 2) Isoelectrically focused proteins are denatured and negatively charged by the addition of sodium dodecyl sulfate (SDS), thereby proteins in their first structure are separated depending on their apparent molecular weight (MW) by SDS-PAGE3. These two distinct properties allow us to tackle a double value to go further in the study of the proteome. On one hand this approach offers the possibility to perform a quantitative analysis using minimal dyes 2D-DIGE method, and on the other hand a qualitative analysis by mini-2DE coupled to western blotting.
Quantitative analysis by 2D-DIGE bestows protein expression changes all over the sample proteome. Briefly, samples are labeled with three cyanines (Cy2, Cy3 and Cy5) emitting at three distinct wavelengths (blue, green and red). These fluor minimal dyes containing N-hydroxy succinimidyl ester group react with the &#949;-amino group of lysines residues of proteins resulting in covalent amide bonds4. Lysine residues are labeled only between 1-3% and thus preventing multiple labels addition per protein and major net charge modifications5,6. Cy3 and Cy5 are often used to label two independent samples while Cy2 tags a mix of equal proportion of the samples to compare. The two main advantages are that all labeled samples are mixed and IEF and SDS-PAGE are carried out in one gel at once for each step, avoiding the inter variability among experiments due to gels comparison. Moreover, it presents a high detection threshold of around 1 femtomole of protein7. Gels are scanned and 2D software compares the 2D gel fluorescence images, where Cy2 serves as an internal standard allowing for identification of statistical differences among the spots for their posterior identification by mass spectrometry. The 2D analysis software using the internal standard achieves a fast detection of less than 10% of differences between samples with more than 95% of statistical confidence8.
Qualitative analysis by mini-2DE is a crucial step for protein characterization. The principle is the same as previously described for pI and MW separation, but in this case proteins are transferred from a small polyacrylamide gel to a membrane and immunoblotting is performed afterwards. While one dimension gel electrophoresis provides changes in protein expression for one or several protein epitopes in function of the antibody, the information of mini-2DE endows with two additional parameters. Firstly, the protein isovariants change in function of the pI, indicating that post-translational modifications might take place. Secondly, mass spectrometry identification may be indicative of plausible zymogens and catabolic products of proteins. Therefore, modifications observed by 2D-DIGE are likely indicative of the mechanisms underlying changes in global proteome profile. Alignments of immunoblots among several samples for the same protein epitope/s by mini-2DE may reflect acidity changes shedding light into post-translational variations slightly observed or even not by monodimensional immunoblotting9,10. Moreover, this analysis informs about the potential cleavage sites due to the knowledge of the pI and MW of the metabolic residues11,12.
The combination of these two techniques provides a complementary proteomics analysis. On one hand 2D-DIGE affords a type of differences allowing a precise isolation of polypeptides whose expression is different. These differences consist essentially into the appearance or disappearance of a spot or increase/decrease of intensity of a given one by software analysis of the fluorescent gels. However, these observations by themselves are unlikely to explain the nature of the modification observed. For these reasons, once the polypeptide is isolated and identified by mass spectrometry, the use of mini-2DE enables to precisely confirm 1) the identity of the protein isolated and 2) the nature of the difference: change in the isovariant/isoform level of expression, post-translational modifications and cleavage processes for instance. However, it is necessary to develop a starting lysis buffer both compatible with 2D-DIGE and with mini-2DE in order to limit the potential dispersions resulting from the use of extraction protocols that are very dissimilar.
In the present article, we described an adapted protocol for the preparation, extraction and performance of 2D-DIGE and mini-2DE techniques for brain proteins coming from human and mouse tissue.

<table border="0" cellpadding="0" cellspacing="0" width="709">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">CyDye DIGE FLUOR MIN KIT 5nmol 1 * 5 Nmo</td>
			<td style="width:113px;">GE Healtcare</td>
			<td style="width:119px;">25-8010-65</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">Immobiline DryStrip</td>
			<td style="width:113px;">GE Healtcare</td>
			<td style="width:119px;"></td>
			<td>Reference in function of the pH interval/size</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">IPG Buffer, pH X-X</td>
			<td style="width:113px;">GE Healtcare</td>
			<td style="width:119px;"></td>
			<td>Reference in function of the pH interval desired</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:311px;">AMBERLITE IRN-150L MIXED BED RESIN 1&#160;</td>
			<td style="width:113px;">GE Healtcare</td>
			<td style="width:119px;">551797N</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DRYSTRIP COVER FLUID IMMOBILINE 1 * 1 l</td>
			<td style="width:113px;">GE Healtcare</td>
			<td>17-1335-01</td>
			<td></td>
		</tr>
		<tr height="21">
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consensus brain-derived protein, extraction protocol for the study of human and murine brain proteome using both 2d-dige and mini 2de immunoblotting

Two-dimensional gel electrophoresis (2DE) is a powerful tool to uncover proteome modifications potentially related to different physiological or pathological conditions. Basically, this technique is based on the separation of proteins according to their isoelectric point in a first step, and secondly according to their molecular weights by SDS polyacrylamide gel electrophoresis (SDS-PAGE). In this report an optimized sample preparation protocol for little amount of human post-mortem and mouse brain tissue is described. This method enables to perform both two-dimensional fluorescence difference gel electrophoresis (2D-DIGE) and mini 2DE immunoblotting. The combination of these approaches allows one to not only find new proteins and/or protein modifications in their expression thanks to its compatibility with mass spectrometry detection, but also a new insight into markers validation. Thus, mini-2DE coupled to western blotting permits to identify and validate post-translational modifications, proteins catabolism and provides a qualitative comparison among different conditions and/or treatments. Herein, we provide a method to study components of protein aggregates found in AD and Lewy body dementia such as the amyloid-beta peptide and the alpha-synuclein. Our method can thus be adapted for the analysis of the proteome and insoluble proteins extract from human brain tissue and mice models too. In parallel, it may provide useful information for the study of molecular and cellular pathways involved in neurodegenerative diseases as well as potential novel biomarkers and therapeutic targets.

Proteomics on brain tissue remains challenging since no ideal buffer exists to recover 100% of proteins, especially membrane-associated or cytoskeleton proteins. The first set of experiments were focused on the search for a suitable lysis buffer compatible with the two approaches and which enables to recover a large panel of protein. Thus, three lysis buffers were assayed to determine the most appropriate one. Firstly, it was used the common biochemical and molecular biology buffer Tris-HCl20 at 10 mM with 1% ...

Watch this Scientific Journal Video about Consensus Brain-derived Protein, Extraction Protocol for the Study of Human and Murine Brain Proteome Using Both 2D-DIGE and Mini 2DE Immunoblotting at JoVE.c

Consensus Brain-derived Protein, Extraction Protocol for the Study of Human and Murine Brain Proteome Using Both 2D-DIGE and Mini 2DE Immunoblotting

A common protein extraction protocol using urea/thiourea/SDS buffer for human and mice brain tissue allows indentification of proteins by 2D-DIGE and their subsequent characterization by mini 2DE immunoblotting. This method enables one to obtain more reproducible and reliable results from human biopsies and experimental models.

Two-dimensional gel electrophoresis (2DE) is a powerful tool to uncover proteome modifications potentially related to different physiological or ...

consensus-brain-derived-protein-extraction-protocol-for-study-human

Research

JoVE Journal

Neuroscience

15.9K visualizações.  Inserm UMR 837.  Um protocolo de extração de proteínas comum utilizando tampão uréia / tiouréia / SDS para tecido cerebral humano e camundongos permite indentification de proteínas por 2D-DIGE e sua posterior caracterização por mini-immunoblotting 2DE. Este método permite a obtenção de resultados mais reprodutíveis e confiáveis ​​a partir de biópsias humanos e modelos experimentais. 

Vídeo: Consensus Brain-derived Protein, Extraction Protocol for the Study of Human and Murine Brain Proteome Using Both 2D-DIGE and Mini 2DE Immunoblotting