We are particularly grateful to Dr. Barry Ganetzky, in who&#39;s lab the genetic screen was performed, allowing the identification and characterization of brat as a neuroprotective gene. We thank Dr. Steven Robinow for kindly providing the collection of ENU-mutagenized flies used in the genetic screen presented in this article. We thank the members of Ganetzky lab, Drs. Grace Boekhoff-Falk and David Wassarman for helpful discussions throughout the duration of this project, Ling Ling Ho and Bob Kreber for technical assistance, Dr. Aki Ikeda for the use of his microtome facility at the University of Wisconsin and Dr. Kim Lackey and the Optical Analysis Facility at the University of Alabama.

1. Preparation and Aging of Flies
<ol>
	<li>Obtain or generate6 a collection of Drosophila mutants that will be used for the genetic screen. Here, ENU-mutagenized lines mapped to the second chromosome and balanced over CyO are used.</li>
	<li>Amplify experimental genotype lines in an incubator set at 25 &#176;C, 12 h light/dark cycle on cornmeal-molasses medium.</li>
	<li>Collect around 20 homozygous progeny between 0-2 days of adult eclosion from each experimental genotype. El...

<ol>
	<li>Frade, J. M., Ovejero-Benito, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuronal+cell+cycle:+the+neuron+itself+and+its+circumstances.">Neuronal cell cycle: the neuron itself and its circumstances.</a> Cell Cycle. 14 (5), 712-720 (2015).</li><li>Aranda-Anzaldo, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+post-mitotic+state+in+neurons+correlates+with+a+stable+nuclear+higher-order+structure.">The post-mitotic state in neurons correlates with a stable nuclear higher-order structure.</a> Communicative &amp; Integrative Biology. 5 (2), 134-139 (2012).</li><li>Haelterman, N. 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=Large-scale+identification+of+chemically+induced+mutations+in+Drosophila+melanogaster.">Large-scale identification of chemically induced mutations in Drosophila melanogaster.</a> Genome Res. 24 (10), 1707-1718 (2014).</li><li>Moresco, E. M., Li, X., Beutler, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Going+forward+with+genetics:+recent+technological+advances+and+forward+genetics+in+mice.">Going forward with genetics: recent technological advances and forward genetics in mice.</a> The American Journal of Pathology. 182 (5), 1462-1473 (2013).</li><li>St Johnston, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+art+and+design+of+genetic+screens:+Drosophila+melanogaster.">The art and design of genetic screens: Drosophila melanogaster.</a> Nature Reviews Genetics. 3 (3), 176-188 (2002).</li><li>Greenspan, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Fly pushing: The theory and practice of Drosophila genetics. , (2004).</li><li>Reiter, L. T., Potocki, L., Chien, S., Gribskov, M., Bier, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+systematic+analysis+of+human+disease-associated+gene+sequences+in+Drosophila+melanogaster.">A systematic analysis of human disease-associated gene sequences in Drosophila melanogaster.</a> Genome Research. 11 (6), 1114-1125 (2001).</li><li>Rubin, G. M., 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+genomics+of+the+eukaryotes.">Comparative genomics of the eukaryotes.</a> Science. 287 (5461), 2204-2215 (2000).</li><li>Nichols, C. D., Becnel, J., Pandey, U. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Methods+to+assay+Drosophila+behavior.">Methods to assay Drosophila behavior.</a> Journal of Visualized Experiments. (61), (2012).</li><li>Ali, Y. O., Escala, W., Ruan, K., Zhai, R. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assaying+locomotor,+learning,+and+memory+deficits+in+Drosophila+models+of+neurodegeneration.">Assaying locomotor, learning, and memory deficits in Drosophila models of neurodegeneration.</a> Journal of Visualized Experiments. (49), (2011).</li><li>Karres, J. S., Hilgers, V., Carrera, I., Treisman, J., Cohen, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+conserved+microRNA+miR-8+tunes+atrophin+levels+to+prevent+neurodegeneration+in+Drosophila.">The conserved microRNA miR-8 tunes atrophin levels to prevent neurodegeneration in Drosophila.</a> Cell. 131 (1), 136-145 (2007).</li><li>Helfrich, C., Engelmann, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Circadian-Rhythm+of+the+Locomotor-Activity+in+Drosophila-Melanogaster+and+Its+Mutants+Sine+Oculis+and+Small+Optic+Lobes.">Circadian-Rhythm of the Locomotor-Activity in Drosophila-Melanogaster and Its Mutants Sine Oculis and Small Optic Lobes.</a> Physiological Entomology. 8 (3), 257-272 (1983).</li><li>R Development Core Team. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> R: A language and environment for statistical computing. , (2008).</li><li>Bokel, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EMS+screens+:+from+mutagenesis+to+screening+and+mapping.">EMS screens : from mutagenesis to screening and mapping.</a> Methods in Molecular Bioogyl. 420, 119-138 (2008).</li><li>Lindsley, D. L., Zimm, G. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Genome of Drosophila Melanogaster. , (1992).</li><li>Cook, R. 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=The+generation+of+chromosomal+deletions+to+provide+extensive+coverage+and+subdivision+of+the+Drosophila+melanogaster+genome.">The generation of chromosomal deletions to provide extensive coverage and subdivision of the Drosophila melanogaster genome.</a> Genome Biology. 13 (3), R21 (2012).</li><li>Loewen, C., Boekhoff-Falk, G., Ganetzky, B., Chtarbanova, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Novel+Mutation+in+Brain+Tumor+Causes+Both+Neural+Over-Proliferation+and+Neurodegeneration+in+Adult+Drosophila.">A Novel Mutation in Brain Tumor Causes Both Neural Over-Proliferation and Neurodegeneration in Adult Drosophila.</a> Genes Genomes Genetics G3 (Bethesda). 8 (10), 3331-3346 (2018).</li><li>Gloor, G. B., 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=Type+I+repressors+of+P+element+mobility.">Type I repressors of P element mobility.</a> Genetics. 135 (1), 81-95 (1993).</li><li>Komori, H., Xiao, Q., McCartney, B. M., Lee, C. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brain+tumor+specifies+intermediate+progenitor+cell+identity+by+attenuating+beta-catenin/Armadillo+activity.">Brain tumor specifies intermediate progenitor cell identity by attenuating beta-catenin/Armadillo activity.</a> Development. 141 (1), 51-62 (2014).</li><li>Kretzschmar, D., Hasan, G., Sharma, S., Heisenberg, M., Benzer, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+swiss+cheese+mutant+causes+glial+hyperwrapping+and+brain+degeneration+in+Drosophila.">The swiss cheese mutant causes glial hyperwrapping and brain degeneration in Drosophila.</a> The Journal of Neuroscience. 17 (19), 7425-7432 (1997).</li><li>Kang, K. H., Reichert, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Control+of+neural+stem+cell+self-renewal+and+differentiation+in+Drosophila.">Control of neural stem cell self-renewal and differentiation in Drosophila.</a> Cell and Tissue Research. 359 (1), 33-45 (2015).</li><li>Brand, A. H., Perrimon, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeted+Gene-Expression+as+a+Means+of+Altering+Cell+Fates+and+Generating+Dominant+Phenotypes.">Targeted Gene-Expression as a Means of Altering Cell Fates and Generating Dominant Phenotypes.</a> Development. 118 (2), 401-415 (1993).</li><li>Loewen, C. A., Ganetzky, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mito-Nuclear+Interactions+Affecting+Lifespan+and+Neurodegeneration+in+a+Drosophila+Model+of+Leigh+Syndrome.">Mito-Nuclear Interactions Affecting Lifespan and Neurodegeneration in a Drosophila Model of Leigh Syndrome.</a> Genetics. 208 (4), 1535-1552 (2018).</li><li>Cao, Y., Chtarbanova, S., Petersen, A. J., Ganetzky, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dnr1+mutations+cause+neurodegeneration+in+Drosophila+by+activating+the+innate+immune+response+in+the+brain.">Dnr1 mutations cause neurodegeneration in Drosophila by activating the innate immune response in the brain.</a> Proceedings of the National Academy of Sciences of the United States of America. 110 (19), E1752-E1760 (2013).</li><li>Lessing, D., Bonini, N. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Maintaining+the+brain:+insight+into+human+neurodegeneration+from+Drosophila+melanogaster+mutants.">Maintaining the brain: insight into human neurodegeneration from Drosophila melanogaster mutants.</a> Nature Reviews Genetics. 10 (6), 359-370 (2009).</li><li>Peng, F., 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=Loss+of+Polo+ameliorates+APP-induced+Alzheimer's+disease-like+symptoms+in+Drosophila.">Loss of Polo ameliorates APP-induced Alzheimer's disease-like symptoms in Drosophila.</a> Scientific Reports. 5, 16816 (2015).</li><li>Venken, K. J., Bellen, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+mutagens,+transposons,+and+transgenes+to+interrogate+gene+function+in+Drosophila+melanogaster.">Chemical mutagens, transposons, and transgenes to interrogate gene function in Drosophila melanogaster.</a> Methods. 68 (1), 15-28 (2014).</li><li>Gonzalez, M. 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=Whole+Genome+Sequencing+and+a+New+Bioinformatics+Platform+Allow+for+Rapid+Gene+Identification+in+D.+melanogaster+EMS+Screens.">Whole Genome Sequencing and a New Bioinformatics Platform Allow for Rapid Gene Identification in D. melanogaster EMS Screens.</a> Biology (Basel). 1 (3), 766-777 (2012).</li><li>Palladino, M. J., Hadley, T. J., Ganetzky, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temperature-sensitive+paralytic+mutants+are+enriched+for+those+causing+neurodegeneration+in+drosophila.">Temperature-sensitive paralytic mutants are enriched for those causing neurodegeneration in drosophila.</a> Genetics. 161 (3), 1197-1208 (2002).</li></ol>

The authors declare no conflicts of interest.

Forward genetic screens in Drosophila have been an effective approach to identify genes involved in different biological processes, including age-dependent neuroprotection5,23,24,25. Using this strategy, we were successful in identifying brat as a novel neuroprotective gene17.
One critical step in this protocol involves the p...

Neurons are for the most part post-mitotic and incapable of dividing1,2. In most animals, neuroprotective mechanisms exist to maintain these cells throughout the organism&#39;s lifespan, especially at old age when neurons are most vulnerable to damage. Genes underlying these mechanisms can be identified in mutants exhibiting neurodegeneration, a phenotypic indicator for the loss of neuroprotection, using a forward genetic protocol. Forward genetic screens using chemical mutagens such as ethyl methanesulfonate (EMS) or N-ethyl-N-nitrosourea (ENU) are particularly useful due to the random point mutations they induce, resulting in an inherently unbiased approach that has shed light on numerous gene functions in eukaryotic model organisms3,4,5 (in contrast, X-ray mutagenesis creates DNA breaks and can result in rearrangement rather than point mutations6).
The common fruit fly Drosophila melanogaster is an ideal subject for these screens due to its high quality, well annotated genome sequence, its long history as a model organism with highly developed genetic tools, and most significantly, its shared evolutionary history with humans7,8. A limiting factor in the applicability of this protocol is early lethality caused by the mutated genes, which would prevent testing at old age9. However, for non-lethal mutations, a climbing assay, which takes advantage of negative geotaxis, is a simple, although extensive, method of quantifying impaired motor functioning10. To exhibit sufficient locomotor reactivity, flies depend on neural functions to determine direction, sense its position, and coordinate movement. The inability of flies to sufficiently climb in response to stimuli can therefore indicate neurological defects11. Once a particular defective climbing phenotype is identified, further testing using a secondary screen such as histological analysis of brain tissue, can be used to identify neurodegeneration in climbing-defective flies. Subsequent gene mapping can then be used to reveal the genomic region on the chromosome carrying the defective neuroprotective gene of interest. To narrow down the chromosomal region of interest, meiotic mapping using mutant fly lines carrying dominant marker genes with known locations on the chromosome can be performed. The marker genes serve as a reference point for the mutation as the frequency of recombination between two loci provides a measurable distance that can be used to map the approximate location of a gene. Finally, crossing the mutant lines with lines carrying balanced deficiencies on the meiotically mapped chromosomal region of interest creates a complementation test in which the gene of interest can be verified if its known phenotype is expressed5. Polymorphic nucleotide sequences in the identified gene, possibly resulting in an altered amino acid sequences, can be evaluated by sequencing the gene and comparing it to the Drosophila genome sequence. Subsequent characterization of the gene of interest can include testing of additional mutant alleles, mutation rescue experiments and examination of additional phenotypes.

<table border="0" cellpadding="0" cellspacing="0" style="width:743px;" width="743">
	<tbody>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:743px;">Major equipment</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Fume hood for histology</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Light Microscope</td>
			<td style="width:195px;">Nikon</td>
			<td style="width:123px;">Eclipe E100</td>
			<td style="width:171px;">Preferred objective for imaging is X20</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Imaging software</td>
			<td style="width:195px;">Nikon</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Microscope Camera</td>
			<td style="width:195px;">Nikon</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Thermal cycler</td>
			<td style="width:195px;">Eppendorf</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:743px;">Fly pushing and climbing assay</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">VWR&#174; Drosophila Vial, Narrow</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;">75813-160</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">VWR&#174; General-Purpose Laboratory Labeling Tape</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;">89097-912</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Standard mouse pad</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Stereoscope</td>
			<td style="width:195px;">Motic</td>
			<td style="width:123px;"></td>
			<td>Model SMZ-168</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">CO2 anesthesia station (Blowgun, foot valve, Ultimate Flypad)</td>
			<td style="width:195px;">Genesee Scientific</td>
			<td style="width:123px;">54-104, 59-121, 59-172</td>
			<td>Doesn&#8217;t iinclude CO2 tank</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Fine-Tip Brushes</td>
			<td style="width:195px;">SOLO HORTON BRUSHES, INC.</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Drosophila Incubator</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;">89510-750</td>
			<td></td>
		</tr>
		<tr height="21">
			<td colspan="4" height="21" style="height:21px;width:743px;">Gene mapping</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">CantonS</td>
			<td style="width:195px;">Bloomington Drosophila Stock Center</td>
			<td>9517</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">w1118</td>
			<td style="width:195px;">Bloomington Drosophila Stock Center</td>
			<td>5905</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">yw&#160;</td>
			<td style="width:195px;">Bloomington Drosophila Stock Center</td>
			<td align="right">6599</td>
			<td></td>
		</tr>
		<tr height="62">
			<td height="62" style="height:62px;width:255px;">Drosophila line used for recombination mapping</td>
			<td style="width:195px;">Bloomington Drosophila Stock Center</td>
			<td style="width:123px;">3227</td>
			<td style="width:171px;">Genotype: wg[Sp-1] J[1] L[2] Pin[1]/CyO, P{ry[+t7.2]=ftz/lacB}E3</td>
		</tr>
		<tr height="62">
			<td height="62" style="height:62px;width:255px;">CyO/sno[Sco]&#160;</td>
			<td style="width:195px;">Bloomington Drosophila Stock Center</td>
			<td style="width:123px;">2555</td>
			<td style="width:171px;">Drosophila balancer line used for recombination mapping</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Deficiency Kit for chromosome 2L</td>
			<td style="width:195px;">Bloomington Drosophila Stock Center</td>
			<td style="width:123px;">DK2L</td>
			<td>Cook et al., 2012</td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:255px;">Histology analysis</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Ethanol, (100%)</td>
			<td style="width:195px;">Thermo Fischer Scientific</td>
			<td style="width:123px;">A4094</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Chloroform</td>
			<td style="width:195px;">Thermo Fischer Scientific</td>
			<td style="width:123px;">C298-500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Glacial Acetic Acid</td>
			<td style="width:195px;">Thermo Fischer Scientific</td>
			<td style="width:123px;">A38-500</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Fisherbrand&#8482;&#160;Premium Microcentrifuge Tubes: 1.5mL</td>
			<td style="width:195px;">Thermo Fischer Scientific</td>
			<td style="width:123px;">05-408-129</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Histochoice clearing agent 1X</td>
			<td style="width:195px;">VWR Life Sciences</td>
			<td style="width:123px;">97060-934</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Harris Hematoxylin</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;">95057-858</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Eosin</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;">95057-848</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Thermo Scientific&#8482;&#160;Richard-Allan Scientific&#8482; Mounting Medium</td>
			<td style="width:195px;">Thermo Scientific&#8482; 4112</td>
			<td style="width:123px;">22-110-610</td>
			<td>CyO/sna[Sco]</td>
		</tr>
		<tr height="62">
			<td height="62" style="height:62px;width:255px;">Unifrost Poly-L-Lysine microscope slides, 75x25x1mm, EverMark Select Plus</td>
			<td style="width:195px;">Azer Scientific</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Fisherbrand&#8482;&#160;Cover Glasses: Rectangles</td>
			<td style="width:195px;">Fisherbrand</td>
			<td style="width:123px;">12-545M</td>
			<td>Dimensions: 24x60 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Traceable timer</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Slide Warmer</td>
			<td style="width:195px;">Barnstead International</td>
			<td style="width:123px;"></td>
			<td>model no. 26025</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Slide tray and racks</td>
			<td style="width:195px;">DWK Life Sciences</td>
			<td style="width:123px;"></td>
			<td>Rack to hold 20 slides</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Fisherbrand&#8482;&#160;General-Purpose Extra-Long Forceps</td>
			<td style="width:195px;">Fisherbrand</td>
			<td style="width:123px;">10-316A</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Kimwipes&#8482;</td>
			<td style="width:195px;">Kimberly-Clark&#8482; Professional&#160;</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">6 inch Puritan applicators</td>
			<td style="width:195px;">Hardwood Products Company, Guilford, Maine</td>
			<td style="width:123px;">807-12</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">VWR&#174; Razor Blades</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;">55411-050</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Tupperware or glass containers for histology liquids</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td>16 + 1 for running water</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">High Profile Coated Microtome Blades</td>
			<td style="width:195px;">VWR</td>
			<td style="width:123px;">95057-834</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Corning&#8482;&#160;Round Ice Bucket with Lid, 4L</td>
			<td style="width:195px;">Corning&#8482;</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Beaker</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td>Or other container for ice water and cassettes</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Tissue Bath</td>
			<td style="width:195px;">Precision Scientific Company</td>
			<td style="width:123px;">66630</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Microtome</td>
			<td style="width:195px;">Leica Biosystems</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:255px;">Molecular analysis</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Wizard&#174; SV Gel and PCR Clean-Up System</td>
			<td style="width:195px;">Promega</td>
			<td style="width:123px;">A9282</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">Ex Taq DNA polymerase</td>
			<td style="width:195px;">TaKaRa</td>
			<td style="width:123px;"></td>
			<td>5 U/&#956;l</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">Invitrogen&#8482;&#160;SYBR&#8482; Safe&#8482; DNA Gel Stain&#160;</td>
			<td style="width:195px;">&#160;Invitrogen&#8482;</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">UltraPure&#8482; Agarose</td>
			<td style="width:195px;">&#160;Invitrogen&#8482;</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">1 Kb Plus DNA Ladder</td>
			<td style="width:195px;">&#160;Invitrogen&#8482;</td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:255px;">ApE-A plasmid Editor software</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td style="width:171px;">Available for free download</td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:255px;">Statistical analysis</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:255px;">R software package</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="28">
			<td height="28" style="height:28px;width:255px;">Further analysis</td>
			<td style="width:195px;"></td>
			<td style="width:123px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">y[1] w[*]; wg[Sp-1]/CyO; Dr[1]/TM3, Sb[1]</td>
			<td style="width:195px;">Bloomington Drosophila Stock Center</td>
			<td style="width:123px;">59967</td>
			<td></td>
		</tr>
	</tbody>
</table>

in vivo forward genetic screen to identify novel neuroprotective genes in drosophila melanogaster

There is much to understand about the onset and progression of neurodegenerative diseases, including the underlying genes responsible. Forward genetic screening using chemical mutagens is a useful strategy for mapping mutant phenotypes to genes among Drosophila and other model organisms that share conserved cellular pathways with humans. If the mutated gene of interest is not lethal in early developmental stages of flies, a climbing assay can be conducted to screen for phenotypic indicators of decreased brain functioning, such as low climbing rates. Subsequently, secondary histological analysis of brain tissue can be performed in order to verify the neuroprotective function of the gene by scoring neurodegeneration phenotypes. Gene mapping strategies include meiotic and deficiency mapping that rely on these same assays can be followed by DNA sequencing to identify possible nucleotide changes in the gene of interest.

In this aerticle, we present the steps used to identify the gene brain tumor (brat) as playing a role in maintenance of neuronal integrity (e.g., neuroprotection) in adult flies17; a methodology that can be used to identify genes involved in neuroprotection. We used a forward genetic approach (the strategy is outlined in Figure 1A) to screen through a collection of chemically mutagenized flies using a climbing assay (...

Watch this Scientific Journal Video about In Vivo Forward Genetic Screen to Identify Novel Neuroprotective Genes in Drosophila melanogaster at JoVE.com

In Vivo Forward Genetic Screen to Identify Novel Neuroprotective Genes in Drosophila melanogaster

We present a protocol using a forward genetic approach to screen for mutants exhibiting neurodegeneration in Drosophila melanogaster. It incorporates a climbing assay, histology analysis, gene mapping and DNA sequencing to ultimately identify novel genes related to the process of neuroprotection.

In Vivo Forward Genetic Screen to Identify Novel Neuroprotective Genes in Drosophila melanogaster

There is much to understand about the onset and progression of neurodegenerative diseases, including the underlying genes responsible. Forward genetic ...

The main goal of this protocol is to use the power of forward genetics to identify genes which when dysregulated lead to neurodegeneration. The main advantage of this technique is that it provides an unbiased and straightforward approach for the identification of neuroprotective genes which might be more difficult to perform in mammalian models. This technique can be used to identify novel genes implicated in the process of neurodegeneration which is associated with many disease conditions such as Alzheimer's and Parkinson's disease.In addition to identifying neuroprotective genes, the forward genetic approach can be used to discover genes involved in other biological processes such as neuronal function and transmission. To begin, collect homozygous flies from lines belonging to the ENU mutagenized collection of Drosophila mutants mapped to the second chromosome. Flip the flies aged 10 to 12 days into a testing chamber without anesthesia one line at a time and allow them to recover for five minutes.With the five centimeter line mark side down, forcibly tap the chamber three times on a mouse pad placed on a solid surface so that all flies begin the assay at the bottom. Observe fly locomotion over a period of 10 seconds. Record the number of flies that reach or pass the five centimeter line within this time as well as the total number of flies tested.Wait one minute before starting a second trial. Repeat a minimum of three trial replicates per line. After anesthetizing the flies on a carbon dioxide pad, sever fly heads with a surgical blade and use a paintbrush to gently place them in one milliliter of Carnoy's fixative in a 1.5 milliliter microcentrifuge tube.Then store the tube at four degrees Celsius overnight. The following day, make sure the heads are sunk in the fixative solution. Under a fume hood, use a P1000 pipette to replace the fixative solution with one milliliter of 70%ethanol and maintain the samples at four degrees Celsius for future analysis.Using a Pasteur pipette, transfer the fixed heads into microbiopsy cassettes and close the cassettes. Send the cassettes to a histology facility for processing or place them in an automated tissue processing machine if available on site. Run the program to dehydrate, clear and infiltrate the heads with paraffin.Then transfer the cassettes into a paraffin embedding station with paraffin heated at 60 degrees Celsius and place metal base molds that fit the cassettes on the heated station. Use fine forceps to orient the heads such that they face the top in the base mold. Proper head orientation is critical for the histology analysis.After hardening, trim each paraffin block to minimize the surface that will be sectioned. Cut five micrometer sections of each block on the microtome. Next, place the sectioned paraffin ribbons in a heated water bath at 35 degrees Celsius for a maximum of five minutes.Immerse a polylysine-coated slide in the heated water bath and use a wood applicator to place the sectioned ribbons on the slide. Let the slides air dry overnight at room temperature. The next day, use a slide warmer to heat the slides for 15 minutes at 63 degrees Celsius.Under a fume hood, place the slides on a slide staining rack and place the rack in HistoChoice for five minutes twice followed by several ethanol and distilled water bath treatments according to the manuscript. Transfer the rack into a container filled with Harris Hematoxylin for two to five minutes to stain. Then take the rack out of the Hematoxylin solution and place it under running tap water for 10 minutes before the following staining steps.After staining, using forceps, take the slides out of the HistoChoice or Xylene solution. Drip a thin layer of permanent mounting medium on the sample and gently place a coverslip on the top. Avoid formation of bubbles.After the mounting medium is hardened, place the slide under a light microscope to obtain images of representative brain sections at approximately midbrain. First, prepare a food containing vial for generating heterozygous female flies. After carbon dioxide anesthesia, use a paintbrush to transfer five males of the mutant line and 10 virgin females of the sternopleural jammed lobe and pin over Curly O line into the vial to make a cross.Place the vial at 25 degrees Celsius. After 10 to 12 days, collect at least 15 virgin female progeny carrying the mutated chromosome and the marker chromosome. Cross them to five males from a balanced line that carries another visible dominant marker Curly O over scutoid or equivalent.After 10 to 12 days, collect the heterozygous male progeny carrying either scutoid or Curly O and the potentially recombined chromosome from the cross. Individually mate them to virgin females from the stock carrying the mutated chromosome. Ten to 12 days later, collect the progeny from the last cross into new food containing vials and age the flies at 29 degrees Celsius to 10 to 14 days.Perform histology on fly heads and repeat for progeny of each individual cross. With this information, perform deficiency mapping on narrowed region of the chromosome to refine the location of the recessive mutation. Each deficiency line has a deletion of different region of the chromosomes allowing them to be used for complementation testing.Next, cross lines from the Drosophila deficiency kit for the second chromosome and look for non-complementation of the phenotype of the interest. To obtain reference for DNA sequence analysis, download a FASTA format file containing the genomic consensus sequence of the BRAT gene from FlyBase or use a file containing results for BRAT sequence of a genetic background control, for example the originally mutagenized Drosophila line. Open sequencing files in the A Plasmid Editor.Go to Edit and click Align Sequences. Using the computer's mouse, select all sequences to compare. In the drop menu, indicate the reference sequence for this alignment.Inspect the sequenced region for nucleotide changes in comparison with the reference sequence. If desired, save the alignment on a computer in RTF format by clicking on Text then Save. Perform the rescue experiment by collecting F1 progeny from each cross.Carefully select away marked balancers. Age the flies on Drosophila food medium at 29 degrees Celsius and perform histology analysis on brains to look for neurodegeneration as previously. To perform age-dependent analysis of neurodegeneration in 867 mutants, age the flies to five, 15 and 25 days and perform subsequent histology analysis.This protocol presents a forward genetic approach to screen through a collection of chemically mutagenized flies using a climbing assay. Among 235 homozygous lines, about 37%of the tested lines exhibited a climbing pass rate below 50%when tested at the age of 10 to 12 days. Subsequent histological screen on 51 of the lines exhibiting the lowest climbing pass rate revealed that 29 of these lines showed visible appearance of holes in the brain neuropil ranging from mild to severe indicative of neurodegeneration.The neurodegeneration phenotype in 867 flies is recessive because the brains of heterozygous 867 flies that have been out-crossed to a wild type strain were comparable to those of controls. The deficiency line Df24116 does not complement the 867 mutant phenotype based on the climbing assay. Histological verification shows the deficiency line Df24116 does not complement the 867 neurodegeneration phenotype whereas Df9296 does.Examining the brain phenotype of 867 mutants crossed to additional deficiency lines confirmed that the mutation is contained in the region of the genome that includes the gene BRAT. It's important to remember during this procedure to work as rigorously and precisely as possible as this protocol combines several steps which if executed improperly can affect the identification of mutants with neurodegeneration in candidate genes. Depending on the genes identified, subsequent analysis can include testing additional ovules of the gene of the interest or interactions with genes that play a role in known pathways of neurodegeneration.During the histology procedure, remember to handle the Carnoy's fixative solution with caution since it contains chloroform. Wear gloves and use with adequate ventilation ideally under the fume hood. Similarly, perform all histology staining under the fume hood.

in-vivo-forward-genetic-screen-to-identify-novel-neuroprotective

Research

JoVE Journal

Genetics

9.2K Görüntüleme.  University of Alabama. Bu protokolün temel amacı, disregulated nörodejenerasyona yol açan genleri tanımlamak için ileri genetiğin gücünü kullanmaktır. Bu tekniğin en büyük avantajı, memeli modellerinde daha zor olabilecek nöroprotektif genlerin belirlenmesi için tarafsız ve basit bir yaklaşım sağlamasıdır. Bu teknik, Alzheimer ve Parkinson hastalığı gibi birçok hastalık koşulları ile ilişkili nörodejenerasyon sürecinde karıştığı yeni genleri tanımlamak için kullanılabilir.