The authors would like thank the Bloomington stock center, Liqun Luo, Charles Zuker, and Lily and Yuh Nung Jan for the generous sharing of fly stocks and the following for funding: SOMAS-URM (to JD and SW), Bachelor Ford Faculty Summer Fellowship (to SW), BD Corporation Summer Research Fellowship (to CL and DL), The Renee and Anthony M. Marlon, M.D. &#39;63 Summer Research Fellowship (to DL)James C. &#39;75 and Jane Colihan Summer Research Fellowship (TO) through the Alumni/Parent Summer Research Fund of the College of the Holy Cross and the Stransky Foundation Summer Research Fellowship (to TO). Special thanks to the Department of Biology and the Dean&#39;s Office at College of the Holy Cross for the support of all the work in the lab.

1. Crosses to Generate MARCM Flies
<ol>
	<li>Maintain flies on cornmeal molasses media (6.5 g/L agar; 23.5 g/L yeast; 60 g/L cornmeal; 60 ml/L molasses; 4 ml/L acid mix; 0.13% Tegosept) or standard Drosophila media at 22 degrees Celsius in a 12-hr light/dark cycle. 
	Note: A Lower than standard temperature is used to keep MARCM-stocks healthy. This extends the developmental time between egg and adulthood to 14 days.</li>
	<li>Use virgin females (approximately 1 - 8 days old) from a MARCM-ready stock conta...

<ol>
	<li>Gr&#252;nert, U., Gnatzy, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=K++and+Ca+++in+the+receptor+lymph+of+arthropod+cuticular+mechanoreceptors.">K+ and Ca++ in the receptor lymph of arthropod cuticular mechanoreceptors.</a> J Comp Physiol A. 161, 329-333 (1987).</li><li>Kernan, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanotransduction+and+auditory+transduction+in+Drosophila.">Mechanotransduction and auditory transduction in Drosophila.</a> Pflugers Arch. 454, 703-720 (2007).</li><li>Gillespie, P. G., Walker, 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=Molecular+basis+of+mechanosensory+transduction.">Molecular basis of mechanosensory transduction.</a> Nature. 413, 194-202 (2001).</li><li>Corfas, G., Dudai, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adaptation+and+fatigue+of+a+mechanosensory+neuron+in+wild-type+Drosophila+and+in+memory+mutants.">Adaptation and fatigue of a mechanosensory neuron in wild-type Drosophila and in memory mutants.</a> J Neurosci. 10, 491-499 (1990).</li><li>Kernan, M., Cowan, D., Zuker, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+dissection+of+mechanosensory+transduction:+mechanoreception-defective+mutations+of+Drosophila.">Genetic dissection of mechanosensory transduction: mechanoreception-defective mutations of Drosophila.</a> Neuron. 12, 1195-1206 (1994).</li><li>Vandervorst, P., Ghysen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetic+control+of+sensory+connections+in+Drosophila.">Genetic control of sensory connections in Drosophila.</a> Nature. 286, 65-67 (1980).</li><li>Corfas, G., Dudai, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Habituation+and+dishabituation+of+a+cleaning+reflex+in+normal+and+mutant+Drosophila.">Habituation and dishabituation of a cleaning reflex in normal and mutant Drosophila.</a> J Neurosci. 9, 56-62 (1989).</li><li>Chen, 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=Discovery-based+science+education:+functional+genomic+dissection+in+Drosophila+by+undergraduate+researchers.">Discovery-based science education: functional genomic dissection in Drosophila by undergraduate researchers.</a> PLoS Biol. 3, e59 (2005).</li><li>Lee, T., Luo, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosaic+analysis+with+a+repressible+cell+marker+for+studies+of+gene+function+in+neuronal+morphogenesis.">Mosaic analysis with a repressible cell marker for studies of gene function in neuronal morphogenesis.</a> Neuron. 22, 451-461 (1999).</li><li>Wu, J. S., Luo, 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+protocol+for+mosaic+analysis+with+a+repressible+cell+marker+(MARCM)+in+Drosophila.">A protocol for mosaic analysis with a repressible cell marker (MARCM) in Drosophila.</a> Nature Protocols. 1, 2583-2589 (2006).</li><li>Eberl, D. F., Hardy, R. W., Kernan, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+similar+transduction+mechanisms+for+touch+and+hearing+in+Drosophila.">Genetically similar transduction mechanisms for touch and hearing in Drosophila.</a> J Neurosci. 20, 5981-5988 (2000).</li><li>Walker, R. G., Willingham, A. T., Zuker, C. 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+Drosophila+mechanosensory+transduction+channel.">A Drosophila mechanosensory transduction channel.</a> Science. 287, 2229-2234 (2000).</li><li>Yan, Z., 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+NOMPC+is+a+mechanotransduction+channel+subunit+for+gentle-touch+sensation.">Drosophila NOMPC is a mechanotransduction channel subunit for gentle-touch sensation.</a> Nature. 493, 221-225 (2013).</li><li>Arnadottir, J., Chalfie, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eukaryotic+Mechanosensitive+Channels.">Eukaryotic Mechanosensitive Channels.</a> Annual Review of Biophysics. 39, 111-137 (2010).</li><li>Christensen, A. P., Corey, 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=TRP+channels+in+mechanosensation:+direct+or+indirect+activation?.">TRP channels in mechanosensation: direct or indirect activation?.</a> Nature Reviews Neuroscience. 8, 510-521 (2007).</li><li>Cheng, L. E., Song, W., Looger, L. L., Jan, L. Y., Jan, Y. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Role+of+the+TRP+Channel+NompC+in+Drosophila+Larval+and+Adult+Locomotion.">The Role of the TRP Channel NompC in Drosophila Larval and Adult Locomotion.</a> Neuron. 67, 373-380 (2010).</li><li>Lee, J., Moon, S., Cha, Y., Chung, Y. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+TRPN(=NOMPC)+channel+localizes+to+the+distal+end+of+mechanosensory+cilia.">Drosophila TRPN(=NOMPC) channel localizes to the distal end of mechanosensory cilia.</a> PLoS One. 5, e11012 (2010).</li><li>Liang, X., Madrid, J., Saleh, H. S., Howard, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NOMPC,+a+Member+of+the+TRP+Channel+Family,+Localizes+to+the+Tubular+Body+and+Distal+Cilium+of+Drosophila+Campaniform+and+Chordotonal+Receptor+Cells.">NOMPC, a Member of the TRP Channel Family, Localizes to the Tubular Body and Distal Cilium of Drosophila Campaniform and Chordotonal Receptor Cells.</a> Cytoskeleton. 68, 1-7 (2011).</li><li>de Vries, S. E., Clandinin, T. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loom-sensitive+neurons+link+computation+to+action+in+the+Drosophila+visual+system.">Loom-sensitive neurons link computation to action in the Drosophila visual system.</a> Curr Biol. 22, 353-362 (2012).</li><li>Jarman, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Studies+of+mechanosensation+using+the+fly.">Studies of mechanosensation using the fly.</a> Hum Mol Genet. 11, 1215-1218 (2002).</li></ol>

This protocol utilizes an adult behavioral assay to screen for mutations that affect mechanosensation in Drosophila. Because the collection of mutants contains lethal p-element mutations that would preclude screening as adults, this protocol makes use of a complex genetic technique first described by Lee and Luo, (1999) and detailed as a protocol by Wu and Luo, (2006) to circumvent adult lethality. MARCM induces mitotic recombination between homologous chromosomes to generate clonal regions of homozygous cells. ...

Humans rely on the ability to convert mechanical stimuli from their environment, such as touch, pressure, vibration, or sound waves, into sensory information that can be processed by the nervous system, in a process termed mechanotransduction. Many of the overall mechanistic features of mechanotransduction between humans and invertebrates are the same1, making Drosophila a useful model to study the molecular mechanisms of mechanotransduction. Drosophila melanogaster contain two sets of specialized sensory organs (Type I and II) that are capable of converting mechanical stimuli into action potentials. Type I mechanoreceptors have a neuron with a single dendrite or sensory process, surrounded by three support cells2. The Type I mechanoreceptors include bristle mechanoreceptors, hearing sensitive chordotonal organs (the Johnston's organ), and campaniform sensilla that convey information about wing beats3. The bristles that cover the dorsal side of the fly are the most abundant and easily accessible of the Type I organs. Similar to the extracellular environment of hair cells associated with hearing and balance in vertebrates, the support cells surrounding fly mechanosensitive neurons secrete a high potassium endolymph that creates an unusual concentration gradient for potassium1. Mechanosensitive neurons, of both the mammalian and fly systems, utilize this high extracellular potassium to depolarize the cell. In response to mechanical stimulation of the macrochaete bristles towards the body wall, the sensory neurons respond with a burst of action potentials driven by this potassium depolarization of the cell membrane4. The Drosophila sensory neurons that innervate bristles resemble the mechanosensitive cells of other organisms, including vertebrate hair cells, in both structure and function1,5. The accessibility of Drosophila external sense organs to experimental manipulation and the abundance of genetic techniques available to researchers make Drosophila an excellent model system to investigate the molecular underpinnings of mechanosensation. 
In the fly, stimulation of a single sensory neuron that innervates a bristle leads to an observable behavioral response. Stimulation of different bristles evokes specific, reproducible behavioral responses, depending on the bristle that is stimulated. Upon tactile stimulation, decapitated wild-type flies exhibit a complex grooming reflex wherein they clean the area near the stimulated bristle with a patterned set of leg movements5-7. When homozygous for known single-gene mutations that interfere with learning7 or coordination and locomotor activity5, flies respond abnormally to mechanical stimulation. This grooming reflex is therefore a useful tool to study the effects of single-gene mutations on a specific, replicable behavior.
The robust behavioral response to stimulation of a single macrochaete bristle holds the potential to assist in identifying new genes involved in mechanotransduction. This protocol being used to test a collection of mutant flies for the absence of a behavioral response to indicate that the mutation interferes with mechanosensation. In the mutant collection selected for screening, the mutations cause lethality before adulthood, and therefore would be impossible to test using traditional adult behavior screens. Originally, this collection of lethal p-elements was combined with FRT recombination sites to test cell growth defects in clones. The clones were made specifically in the eye because adult flies can survive in the lab setting without functional vision8. However, removal of all mechanosensation can cause adults to be severely uncoordinated or die before eclosion5. This protocol uses a mosaic approach to circumvent the lethality of the mutations and allow for adult stage testing. A genetic technique called Mosaic Analysis with a Repressible Cell Marker (MARCM)9 is used to generate homozygous mutant cells in a limited number of adult fly sensory organs, while the rest of the organism remains heterozygous. These MARCM flies readily survive until adulthood, yet the bristles are homozygous for the lethal genes of interest.
MARCM allows for regions of homozygous mutant cells to be generated and marked by the expression of green fluorescent protein (GFP), while the rest of the organism remains heterozygous at that particular locus and unmarked9. MARCM combines individual p-element mutations with five common genetic elements: GFP under the control of an upstream-activating sequence (UAS-GFP), Gal80 repressor protein under control of a general promoter (tub-Gal80), Gal4 transcription factor under control of a general promoter (tub-Gal4), the FRT recombinase enzyme expressed through a heat-shock controlled promoter, and a FRT recombination site10. By driving mitotic recombination through a heat-shock activated recombinase, a limited number of cells are made homozygous for the mutation and marked with GFP. GFP expression is repressed in heterozygous cells by the presence of Gal80 on the wild-type copy of the chromosome. 
A heat-shock protocol for MARCM was optimized to induce recombination in the fly bristle external sense organs, while much of the organism remains heterozygous, and thus unmarked with GFP. Mosaic flies generated using this protocol contained homozygous mutations most frequently in the post alar or dorsal central bristles on the surface of the notum. 
We have tested the utility of this combination of MARCM and the grooming behavior screen with a known mechanosensitive mutant, NOMPC. The ion channel, no mechanoreceptor potential C (NOMPC), is an essential component of the mechanotransduction pathway in Drosophila5,11-13. NOMPC belongs to the transient receptor potential (TRP) superfamily of cation channels5 and satisfies all of the criteria to qualify as a mechanosensitive channel in Drosophila14,15: 1) NOMPC is expressed in the ciliate tips of type 1 sensory neurons of Drosophila 13,16-18, 2) NOMPC null larvae do not have an electrical response to tactile stimulation13, 3) Ectopic expression of NOMPC in touch insensitive cells can induce sensitivity to mechanical stimulation13, 4) heterologous expression of NOMPC in Schneider 2 cells yields a mechanosensitive channel13, and 5) NOMPC adult mutants display defects in their response to mechanical stimulation5. Given this evidence, we predicted that NOMPC mutant clones would show an altered or inhibited grooming response in response to mechanical stimulation of bristles.
A MARCM-stock containing the NOMPC mutation was developed for use in a proof of principle experiment of the grooming assay. Mosaic flies were stimulated at macrochaete bristles containing homozygous NOMPC mutant cells. We expected an inhibition of the grooming response following stimulation of the macrochaete bristle. We found that only 2 of 14 mutant bristle flies tested gave a single response to repeated stimulation; most did not respond to stimulation of the homozygous mutant bristle. Having confirmed that this MARCM-based behavioral assay produces an abnormal grooming reflex in a known mechanosensitive mosaic mutant, this technique can be used in a screen for additional mechanosensitive mutations.

<table border="0" cellpadding="0" cellspacing="0" width="648">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Brewers Yeast (25 lb)</td>
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			<td style="width:163px;">ICN90331225&#160;</td>
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			<td height="21" style="height:21px;width:163px;">Tegosept (5kg)</td>
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			<td style="width:163px;">20-259</td>
			<td style="width:163px;">Fly Food</td>
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			<td height="39" style="height:39px;width:163px;">Molasses (1Gallon)</td>
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			<td height="40" style="height:40px;width:163px;">Drosophila Vials, Narrow (PS)</td>
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			<td style="width:163px;">32-109</td>
			<td style="width:163px;">Fly Cultures</td>
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			<td style="width:163px;">Fly Cultures</td>
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			<td height="21" style="height:21px;width:163px;">Droso-Filler, Narrow</td>
			<td style="width:163px;">Genesee</td>
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			<td style="width:163px;">Fly Food Preparation</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Droso-Filler, Bottles</td>
			<td style="width:163px;">Genesee</td>
			<td style="width:163px;">59-170</td>
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			<td height="63" style="height:63px;width:163px;">Diurnal Growth Chamber</td>
			<td style="width:163px;">Forma Scientific</td>
			<td style="width:163px;"></td>
			<td style="width:163px;">Temperature and light/dark cycle controlled</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:163px;">Water bath</td>
			<td style="width:163px;">VWR</td>
			<td style="width:163px;"></td>
			<td style="width:163px;">For heat shock</td>
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			<td height="21" style="height:21px;width:163px;">MicroScissors&#160;</td>
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			<td height="42" style="height:42px;width:163px;">Fluroscence Dissecting Microscope</td>
			<td style="width:163px;">Zeiss</td>
			<td style="width:163px;">SteREO Discovery V8&#160;</td>
			<td style="width:163px;">With GFP cube (KSC295-814D) band pass filter</td>
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			<td height="42" style="height:42px;width:163px;">Image acquistion software</td>
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			<td height="21" style="height:21px;width:163px;">Ice bucket</td>
			<td style="width:163px;"></td>
			<td style="width:163px;"></td>
			<td style="width:163px;">for cold anthesia</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:163px;">Homemade cold anthesia tray</td>
			<td style="width:163px;"></td>
			<td style="width:163px;"></td>
			<td style="width:163px;">for cold anthesia decapitation</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:163px;">Plastic boxes</td>
			<td style="width:163px;"></td>
			<td style="width:163px;"></td>
			<td style="width:163px;">for recovery of decaptitated flies in humid environment</td>
		</tr>
	</tbody>
</table>

a behavioral assay for mechanosensation of marcm-based clones in drosophila melanogaster

Because of the structural and functional homology to the hair cells of the mammalian inner ear, the neurons that innervate the Drosophila external sense organs provide an excellent model system for the study of mechanosensation. This protocol describes a simple touch behavior in fruit flies which can be used to identify mutations that interfere with mechanosensation. The tactile stimulation of a macrochaete bristle on the thorax of flies elicits a grooming reflex from either the first or third leg. Mutations that interfere with mechanotransduction (such as NOMPC), or with other aspects of the reflex arc, can inhibit the grooming response. A traditional screen of adult behaviors would have missed mutants that have essential roles during development. Instead, this protocol combines the touch screen with mosaic analysis with a repressible cell marker (MARCM) to allow for only limited regions of homozygous mutant cells to be generated and marked by the expression of green fluorescent protein (GFP). By testing MARCM clones for abnormal behavioral responses, it is possible to screen a collection of lethal p-element mutations to search for new genes involved in mechanosensation that would have been missed by more traditional methods.

The success of this protocol largely depends on the overall yield of testable flies, the effectiveness of the heat shock to induce mitotic recombination, and the ability to obtain a robust behavioral response in flies stimulated at 2 min intervals. Given that an estimated 12.5% of embryos contain the necessary MARCM elements and an estimated 16.67% of adults that eclose have the potential for GFP expression, it is critical to obtain a high number of eggs during timed lays. An example of a...

Watch this Scientific Journal Video about A Behavioral Assay for Mechanosensation of MARCM-based Clones in Drosophila melanogaster at JoVE.com

A Behavioral Assay for Mechanosensation of MARCM-based Clones in Drosophila melanogaster

In order to identify novel mutations affecting mechanosensation, we designed an assay that measures the behavioral response to tactile stimulation of fly bristles in mutant clones generated by the MARCM method. The combination of techniques allows for the identification of mechanosensitive mutations that would otherwise be lethal.

A Behavioral Assay for Mechanosensation of MARCM-based Clones in Drosophila melanogaster

Because of the structural and functional homology to the hair cells of the mammalian inner ear, the neurons that innervate the Drosophila external sense ...

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10.1K vistas.  College of the Holy Cross. In order to identify novel mutations affecting mechanosensation, we designed an assay that measures the behavioral response to tactile stimulation of fly bristles in mutant clones generated by the MARCM method. The combination of techniques allows for the identification of mechanosensitive mutations that would otherwise be lethal.