We thank Stefanie Schirmeier and Takeshi Iwatsubo for providing Drosophila strains. We also thank Patricia Jansma for assisting with imaging in the Marley Imaging Core at the University of Arizona. This work was funded by National Institutes of Health NIH NS091299, NS115514 (to DCZ), HHMI Gilliam Fellowship (to EM) and the Undergraduate Biology Research Program (to HB).

The UAS FLII12Pglu-700&#181;&#948;6 transgenic flies were reported in Volkenhoff et al.10 and kindly provided by Dr. S. Schirmeier. The UAS TDP-43G298S transgenic lines were kindly provided by Dr. T. Iwatsubo13. Recombinant Drosophila lines harboring both UAS FLII12Pglu-700&#181;&#948;6 and UAS TDP-43 transgenes were generated in the Zarnescu laboratory using standard genetic approaches and reported in Manzo et al.9. D42 GAL4 was used to drive the expression of the glucose sensor alone or together with TDP-43G298S in motor neurons. All fly lines are maintained on molasses cornmeal media, at 25 &#176;C in 12 h dark:light cycle.
1. Drosophila Ventral Nerve Cord (VNC) dissections
<ol>
	<li>Make silicone elastomer dissection dishes.
	<ol>
		<li>Pour silicone elastomer components into a 50 mL tube as indicated in the manufacturer&#39;s protocol and stir well.</li>
		<li>Fill 35 mm tissue culture dishes with approximately 2 mL of the elastomer mixture. Use a syringe to remove any bubbles. Cover the dishes and place them on a level surface in a 60 &#176;C oven overnight to cure.</li>
	</ol>
	</li>
	<li>Dissect Drosophila larvae to expose the VNC while maintaining tissue viability.
	<ol>
		<li>Collect a wandering third instar larva, rinse with ddH2O, and then place it in a drop of HL3-buffer (70 mM NaCl, 5 mM KCl, 20 mM MgCl2, 10 mM NaHCO3, 115 mM sucrose, 5 mM trehalose, 5 mM HEPES; pH 7.1) on an elastomer lined dish.</li>
		<li>Using a pair of forceps (#5 or 55 forceps) under a dissecting microscope, pin the anterior and posterior ends of the larva dorsal side up, carefully stretching the larva lengthwise with insect pins (Minutein Pins).</li>
		<li>Make an incision just above the posterior pin using a pair of angled iris scissors. Make a vertical cut starting from the incision toward the anterior end of the larva.</li>
		<li>Add a few drops of HL-3 buffer if needed. Remove the trachea and the rest of the floating organs without disturbing the CNS. Pin the flaps stretching the body wall to expose the CNS while keeping the neuromuscular system (VNCs, axons, and neuromuscular junctions) intact.</li>
	</ol>
	</li>
</ol>
2. Image acquisition
<ol>
	<li>Optimize the imaging parameters.
	<ol>
		<li>Turn on the microscope and lasers before starting dissections. Images must be acquired using an upright confocal microscope with a 40x water immersion lens. Use a 405 nm laser to excite CFP and acquire the images in both the CFP (465-499 nm) and the FRET (535-695 nm) detection channels.</li>
		<li>Optimize acquisition parameters such as scan speed (6), average (2), objective (40x), zoom (1x), pinhole size (1 AU), and spatial resolution (512 x 512). Adjust the gain such that the signal is in the optimal dynamic range. The same parameters must be used for all genotypes.</li>
	</ol>
	</li>
	<li>Image motor neurons within the VNC.
	<ol>
		<li>Place the silicone dish with the dissected sample under the lens. Lower the lens so that it comes in contact with trehalose-sucrose HL3 buffer (see 1.2.1). It is critical to ensure that the lens is completely submerged in the buffer. Add more buffer if required.</li>
		<li>Use the CFP and FRET channels to manually select an optical section that consists of at least 6 motor neurons in focus, located along the VNC midline. The motor neurons are identified based on the expression of the glucose sensor and position along the anterior-posterior axis.</li>
		<li>Acquire images every 10 s for 10 min. These images represent the baseline.</li>
	</ol>
	</li>
	<li>Stimulate with glucose supplemented HL-3.
	<ol>
		<li>Remove the trehalose-sucrose containing HL3-buffer using a Pasteur pipette and replace it with 5 mM glucose supplemented HL-3 (70 mM NaCl, 5 mM KCl, 20 mM MgCl2, 10 mM NaHCO3, 115 mM sucrose, 5 mM glucose, 5 mM HEPES, pH 7.1). This step needs to be performed with great care, to avoid the movement of the VNC as much as possible.</li>
		<li>Acquire images every 10 s for another 10 min. These images represent the stimulation phase.</li>
	</ol>
	</li>
	<li>Save the images as .czi files or any file type supported by the imaging software with a file name including date, genetic background, experimental condition (baseline or stimulation), and channels used.</li>
	<li>Reuse the parameters to image all the genotypes (Figure 2A).</li>
</ol>
3. Image processing and ROI selection
<ol>
	<li>Open the czi files in Fiji/ImageJ and set Color Mode: Grayscale, choose View Stack with: Hyperstack, and select Split Channels into Separate Windows.</li>
	<li>Process images using the drift correction plugins: turboreg and stackreg. Each channel is corrected separately by selecting Stackreg under Plugins, and then choose Transformation: Translation.</li>
	<li>Manually select the Regions of interest (ROIs) to extract the mean gray value of each channel.
	<ol>
		<li>Choose the ROIs by tracing all motor neurons that remain in focus over the entire time series. Use the ROI manager to save each motor neuron outline.</li>
		<li>Use the Multi-measure function to measure the mean gray value in each ROI at each time point. Copy the ROIs traced from the first channel to the second channel for the pre-stimulation image.</li>
		<li>Repeat this process for the post-stimulation images in each channel using the same cells/ROIs selected for the pre-stimulation image.</li>
	</ol>
	</li>
</ol>
4. Data analysis
<ol>
	<li>Calculate the FRET/CFP ratio, using the mean gray values for the FRET and CFP channels. Changes in the FRET/CFP ratios reflect alterations in the intracellular glucose concentration.
	<ol>
		<li>Plot FRET/CFP ratios for each ROI and time point versus time. Within every VNC some of the ROIs will exhibit a drop in FRET/CFP ratios following stimulation. 
		NOTE: This is interpreted as an inability of some neurons to uptake glucose, possibly due to stress caused by dissections and are therefore eliminated from the analysis. The remaining FRET/CFP ratios for each ROI and time point are averaged to generate a single FRET/CFP ratio per time point per genotype (glucose sensor alone and glucose sensor with TDP-43G298S). These single FRET/CFP ratios are used for all subsequent normalizations. 31 ROIs were analyzed for Glucose Sensor controls and 24 ROIs were analyzed for TDP-43G298S.</li>
	</ol>
	</li>
	<li>Baseline normalization: Calculate the average of FRET/CFP ratios for the first 10 min (baseline), and then normalize individual FRET/CFP ratios for each time point of the entire experiment to the 10 min baseline average (see Figure 2B).</li>
	<li>Timepoint normalization: Normalize TDP-43G298S FRET/CFP ratios to FRET/CFP ratios from glucose sensor alone at each time point (see Figure 3A).</li>
	<li>Bar graphs: For baseline versus stimulation comparisons in the form of bar graphs, use FRET/CFP ratios from 5-10 min (baseline) and 15-20 min (stimulation) for each genotype. Normalize stimulation ratio to the baseline ratio (see Figure 3B).</li>
</ol>
5. Statistical analyses
<ol>
	<li>Evaluate the normalized data sets using Mann-Whitney correction (for baseline and timepoint normalizations) or Kruskall-Walis test (for bar graph representation of stimulation versus baseline FRET/CFP ratios).</li>
</ol>

<ol>
	<li>Ingre, C., Roos, P. M., Piehl, F., Kamel, F., Fang, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Risk+factors+for+amyotrophic+lateral+sclerosis.">Risk factors for amyotrophic lateral sclerosis.</a> Clinical Epidemiology. 7, 181-193 (2015).</li><li>Dupuis, L., Pradat, P. F., Ludolph, A. C., Loeffler, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Energy+metabolism+in+amyotrophic+lateral+sclerosis.">Energy metabolism in amyotrophic lateral sclerosis.</a> The Lancet Neurology. 10 (1), 75-82 (2011).</li><li>Buratti, E., Baralle, F. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+and+functional+implications+of+the+RNA+binding+properties+of+nuclear+factor+TDP-43,+a+novel+splicing+regulator+of+CFTR+exon+9.">Characterization and functional implications of the RNA binding properties of nuclear factor TDP-43, a novel splicing regulator of CFTR exon 9.</a> The Journal of Biological Chemistry. 276 (39), 36337-36343 (2001).</li><li>Polymenidou, 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=Long+pre-mRNA+depletion+and+RNA+missplicing+contribute+to+neuronal+vulnerability+from+loss+of+TDP-43.">Long pre-mRNA depletion and RNA missplicing contribute to neuronal vulnerability from loss of TDP-43.</a> Nature Neuroscience. 14 (4), 459-468 (2011).</li><li>Tollervey, J. R., 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=Characterizing+the+RNA+targets+and+position-dependent+splicing+regulation+by+TDP-43.">Characterizing the RNA targets and position-dependent splicing regulation by TDP-43.</a> Nature Neuroscience. 14 (4), 452-458 (2011).</li><li>Ling, S. C., Polymenidou, M., Cleveland, D. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Converging+mechanisms+in+ALS+and+FTD:+disrupted+RNA+and+protein+homeostasis.">Converging mechanisms in ALS and FTD: disrupted RNA and protein homeostasis.</a> Neuron. 79 (3), 416-438 (2013).</li><li>Estes, P. 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=Wild-type+and+A315T+mutant+TDP-43+exert+differential+neurotoxicity+in+a+Drosophila+model+of+ALS.">Wild-type and A315T mutant TDP-43 exert differential neurotoxicity in a Drosophila model of ALS.</a> Human Molecular Genetics. 20 (12), 2308-2321 (2011).</li><li>Estes, P. 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=Motor+neurons+and+glia+exhibit+specific+individualized+responses+to+TDP-43+expression+in+a+Drosophila+model+of+amyotrophic+lateral+sclerosis.">Motor neurons and glia exhibit specific individualized responses to TDP-43 expression in a Drosophila model of amyotrophic lateral sclerosis.</a> Disease Models &amp; Mechanisms. 6 (3), 721-733 (2013).</li><li>Manzo, 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=Glycolysis+upregulation+is+neuroprotective+as+a+compensatory+mechanism+in+ALS.">Glycolysis upregulation is neuroprotective as a compensatory mechanism in ALS.</a> eLife. 8, 45114 (2019).</li><li>Volkenhoff, A., Hirrlinger, J., Kappel, J. M., Klambt, C., Schirmeier, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+imaging+using+a+FRET+glucose+sensor+reveals+glucose+delivery+to+all+cell+types+in+the+Drosophila+brain.">Live imaging using a FRET glucose sensor reveals glucose delivery to all cell types in the Drosophila brain.</a> Journal of Insect Physiology. 106, 55-64 (2018).</li><li>Fehr, M., Lalonde, S., Lager, I., Wolff, M. W., Frommer, W. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+imaging+of+the+dynamics+of+glucose+uptake+in+the+cytosol+of+COS-7+cells+by+fluorescent+nanosensors.">In vivo imaging of the dynamics of glucose uptake in the cytosol of COS-7 cells by fluorescent nanosensors.</a> The Journal of Biological Chemistry. 278 (21), 19127-19133 (2003).</li><li>Takanaga, H., Chaudhuri, B., Frommer, W. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=GLUT1+and+GLUT9+as+major+contributors+to+glucose+influx+in+HepG2+cells+identified+by+a+high+sensitivity+intramolecular+FRET+glucose+sensor.">GLUT1 and GLUT9 as major contributors to glucose influx in HepG2 cells identified by a high sensitivity intramolecular FRET glucose sensor.</a> Biochimedica et Biophysica Acta. 1778 (4), 1091-1099 (2008).</li><li>Ihara, R., 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=RNA+binding+mediates+neurotoxicity+in+the+transgenic+Drosophila+model+of+TDP-43+proteinopathy.">RNA binding mediates neurotoxicity in the transgenic Drosophila model of TDP-43 proteinopathy.</a> Human Molecular Genetics. 22 (22), 4474-4484 (2013).</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>Diaz-Garcia, C. 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=Quantitative+in+vivo+imaging+of+neuronal+glucose+concentrations+with+a+genetically+encoded+fluorescence+lifetime+sensor.">Quantitative in vivo imaging of neuronal glucose concentrations with a genetically encoded fluorescence lifetime sensor.</a> Journal of Neuroscience Research. 97 (8), 946-960 (2019).</li><li>Mergenthaler, P., Lindauer, U., Dienel, G. 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The authors declare no conflicts of interest.

The technique described in detail here can be applied to measure glucose uptake in a specific cell type of interest in live Drosophila using FLII12Pglu-700&#181;&#948;6, a FRET based sensor which can detect changes in glucose levels to a millimolar range10,11,12. This sensor has been previously used in conjunction with the UAS-GAL4 system to target its expression to specific cell types, including neurons<sup class="xref...

Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disorder that is currently incurable. ALS affects upper and lower motor neurons leading to loss of motor coordination, irreversible paralysis, respiratory failure, and eventual death within 2-5 years of diagnosis1. ALS is associated with metabolic defects such as weight loss, dyslipidemia, and hypermetabolism (reviewed in2); however, it remains unclear how these alterations in metabolism relate to motor neuron degeneration. A common denominator in ALS and related neurodegenerative diseases is TDP-43, a nucleic acid binding protein involved in several steps of RNA processing3,4,5. Although mutations in TDP-43 only affect 3%-5% of patients, wild-type TDP-43 protein is found within cytoplasmic aggregates in &#62;97% of ALS cases (reviewed in6). This pathology was modeled in Drosophila by overexpression of human wildtype or mutant TDP-43 (G298S) in motor neurons, which recapitulates multiple aspects of ALS, including cytoplasmic inclusions, locomotor dysfunction and reduced lifespan7,8. Using these models, it was recently reported that TDP-43 proteinopathy causes a significant increase in pyruvate levels and phosphofructokinase (PFK) mRNA, the rate limiting enzyme of glycolysis9. Similar increases in PFK transcripts were found in patient-derived motor neurons and spinal cords, suggesting that glycolysis is upregulated in the context of TDP-43 proteinopathy. Interestingly, further increase in glycolysis using dietary and genetic manipulations mitigated several ALS phenotypes such as locomotor dysfunction and increased lifespan in fly models of TDP-43 proteinopathy, consistent with a compensatory, neuroprotective mechanism in degenerating motor neurons.
To further probe changes in glycolysis and measure glucose uptake in Drosophila models of TDP-43 proteinopathy, a previously reported genetically encoded FRET-based sensor FLII12Pglu-700&#181;&#948;610 was expressed in motor neurons specifically using the UAS-GAL4 expression system. The FLII12Pglu-700&#181;&#948;6 glucose sensor uses resonance energy transfer between two variants of green fluorescent protein, cyan and yellow fluorescent proteins (CFP and YFP) to detect glucose at the cellular level. It consists of a bacterial glucose binding domain from the E. coli MglB gene fused to CFP and YFP at opposite ends of the molecule. When bound to a glucose molecule, the sensor undergoes a conformational change bringing CFP and YFP closer together and allowing FRET to occur, which can then be used to quantify intracellular glucose levels10,11,12 (Figure 1). Here, we show how the FLII12Pglu-700&#181;&#948;6 sensor can be used to determine changes in glucose uptake caused by TDP-43 proteinopathy in motor neurons. The experiments described here show that overexpression of an ALS-associated mutant, TDP-43G298S, in motor neurons causes a significant increase in glucose uptake compared to controls. This approach can be used in other types of ALS (e.g., SOD1, C9orf72, etc.) and/or other cell types (e.g., glia, muscles) to determine changes in glucose uptake associated with neurodegeneration.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>35 mm tissue culture dishes</td>
			<td>Sigma Aldrich</td>
			<td>CLS430165</td>
			<td></td>
		</tr>
		<tr>
			<td>40X water immersion lens</td>
			<td>Zeiss</td>
			<td>440090</td>
			<td>dippable, N.A. 0.8</td>
		</tr>
		<tr>
			<td>dissection scissors</td>
			<td>Roboz</td>
			<td>RS-5618</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont #5 forceps</td>
			<td>VWR</td>
			<td>100189-236</td>
			<td></td>
		</tr>
		<tr>
			<td>Dumont #55 forceps</td>
			<td>VWR</td>
			<td>100189-244</td>
			<td></td>
		</tr>
		<tr>
			<td>Minutien pins</td>
			<td>Fine Science tools</td>
			<td>26002-10</td>
			<td>used for dissections</td>
		</tr>
		<tr>
			<td>SYLGARD 184 Silicone Elastomer Kit</td>
			<td>Dow</td>
			<td>1317318</td>
			<td></td>
		</tr>
		<tr>
			<td>Zeiss LSM880 NLO upright multiphoton/confocal microscope</td>
			<td>Zeiss</td>
			<td>N/A</td>
			<td></td>
		</tr>
	</tbody>
</table>

measuring glucose uptake in drosophila models of tdp-43 proteinopathy

Amyotrophic lateral sclerosis is a neurodegenerative disorder causing progressive muscle weakness and death within 2-5 years following diagnosis. Clinical manifestations include weight loss, dyslipidemia, and hypermetabolism; however, it remains unclear how these relate to motor neuron degeneration. Using a Drosophila model of TDP-43 proteinopathy that recapitulates several features of ALS including cytoplasmic inclusions, locomotor dysfunction, and reduced lifespan, we recently identified broad ranging metabolic deficits. Among these, glycolysis was found to be upregulated and genetic interaction experiments provided evidence for a compensatory neuroprotective mechanism. Indeed, despite upregulation of phosphofructokinase, the rate limiting enzyme in glycolysis, an increase in glycolysis using dietary and genetic manipulations was shown to mitigate locomotor dysfunction and increased lifespan in fly models of TDP-43 proteinopathy. To further investigate the effect on TDP-43 proteinopathy on glycolytic flux in motor neurons, a previously reported genetically encoded, FRET-based sensor, FLII12Pglu-700&#181;&#948;6, was used. This sensor is comprised of a bacterial glucose-sensing domain and cyan and yellow fluorescent proteins as the FRET pair. Upon glucose binding, the sensor undergoes a conformational change allowing FRET to occur. Using FLII12Pglu-700&#181;&#948;6, glucose uptake was found to be significantly increased in motor neurons expressing TDP-43G298S, an ALS causing variant. Here, we show how to measure glucose uptake, ex vivo, in larval ventral nerve cord preparations expressing the glucose sensor FLII12Pglu-700&#181;&#948;6 in the context of TDP-43 proteinopathy. This approach can be used to measure glucose uptake and assess glycolytic flux in different cell types or in the context of various mutations causing ALS and related neurodegenerative disorders.

Image acquisition of the glucose sensor in the ventral nerve cord (VNC), ex vivo 
To determine differences in glucose uptake in a Drosophila model of ALS based on TDP-43, a genetically encoded FRET-based glucose sensor was used. The sensor comprised CFP and YFP fused to the glucose binding domain from the E. coli MglB gene. Glucose binding elicits a conformational change, which can be detected by fluorescence resonance energy transfer (FRET) between the CF...

Watch this Scientific Journal Video about Measuring Glucose Uptake in Drosophila Models of TDP-43 Proteinopathy at JoVE.com

Measuring Glucose Uptake in Drosophila Models of TDP-43 Proteinopathy

Glucose uptake is increased in Drosophila motor neurons affected by TAR DNA binding protein (TDP-43) proteinopathy, as indicated by a FRET-based, genetically encoded glucose sensor.

Measuring Glucose Uptake in Drosophila Models of TDP-43 Proteinopathy

Amyotrophic lateral sclerosis is a neurodegenerative disorder causing progressive muscle weakness and death within 2-5 years following diagnosis. Clinical ...

measuring-glucose-uptake-in-drosophila-models-of-tdp-43-proteinopathy

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2.7K Views.  University of Arizona, Tucson. Glucose uptake is increased in Drosophila motor neurons affected by TAR DNA binding protein (TDP-43) proteinopathy, as indicated by a FRET-based, genetically encoded glucose sensor.

Video: Measuring Glucose Uptake in Drosophila Models of TDP-43 Proteinopathy

Assaying Locomotor, Learning, and Memory Deficits in Drosophila Models of Neurodegeneration

Advances in genetic methods have enabled the study of genes involved in human neurodegenerative diseases using Drosophila as a model system1. Most of these diseases, including Alzheimer's, Parkinson's and Huntington's disease are characterized by age-dependent deterioration in learning and memory functions and movement coordination2. Here we use behavioral assays, including the negative geotaxis assay3 and the aversive phototaxic suppression assay (APS assay)4,5, to show that some of the behavior characteristics associated with human neurodegeneration can be recapitulated in flies. In the negative geotaxis assay, the natural tendency of flies to move against gravity when agitated is utilized to study genes or conditions that may hinder locomotor capacities. In the APS assay, the learning and memory functions are tested in positively-phototactic flies trained to associate light with aversive bitter taste and hence avoid this otherwise natural tendency to move toward light. Testing these trained flies 6 hours post-training is used to assess memory functions. Using these assays, the contribution of any genetic or environmental factors toward developing neurodegeneration can be easily studied in flies.

Assaying Locomotor, Learning, and Memory Deficits in Drosophila Models of Neurodegeneration

Behavior assays for measuring locomotor functions, learning, and memory abilities in Drosophila.

Advances in genetic methods have enabled the study of genes involved in human neurodegenerative diseases using Drosophila as a model system1. Most of ...

Measuring Motor Coordination in Mice

Mice are increasingly being used in behavioral neuroscience, largely replacing rats as the behaviorist's animal of choice. Before aspects of behavior such as emotionality or cognition can be assessed, however, it is vital to determine whether the motor capabilities of e.g. a mutant or lesioned mouse allow such an assessment. Performance on a maze task requiring strength and coordination, such as the Morris water maze, might well be impaired in a mouse by motor, rather than cognitive, impairments, so it is essential to selectively dissect the latter from the former. For example, sensorimotor impairments caused by NMDA antagonists have been shown to impair water maze performance2. 
Motor coordination has traditionally been assessed in mice and rats by the rotarod test, in which the animal is placed on a horizontal rod that rotates about its long axis; the animal must walk forwards to remain upright and not fall off. Both set speed and accelerating versions of the rotarod are available.
The other three tests described in this article (horizontal bar, static rods and parallel bars) all measure coordination on static apparatus. The horizontal bar also requires strength for adequate performance, particularly of the forelimbs as the mouse initially grips the bar just with the front paws. 
Adult rats do not perform well on tests such as the static rods and parallel bars (personal observations); they appear less well coordinated than mice. I have only tested male rats, however, and male mice seem generally less well coordinated than females. Mice appear to have a higher strength:weight ratio than rats; the Latin name, Mus musculus, seems entirely appropriate. The rotarod, the variations of the foot fault test12 or the Catwalk (Noldus)15 apparatus are generally used to assess motor coordination in rats.

Protocols are presented for two established motor coordination tasks, the accelerating rotarod and horizontal bar, also two tests developed in Oxford recently, the static rods and parallel bars. These tests can detect motor impairments potentially of interest in their own right, as well as being possible variables in tests of other areas of behavior.

Mice are increasingly being used in behavioral neuroscience, largely replacing rats as the behaviorist's animal of choice. Before aspects of behavior such ...

Visualization of Proprioceptors in Drosophila Larvae and Pupae

Proprioception is the ability to sense the motion, or position, of body parts by responding to stimuli arising within the body. In fruitflies and other insects proprioception is provided by specialized sensory organs termed chordotonal organs (ChOs) 2. Like many other organs in Drosophila, ChOs develop twice during the life cycle of the fly. First, the larval ChOs develop during embryogenesis. Then, the adult ChOs start to develop in the larval imaginal discs and continue to differentiate during metamorphosis.
The development of larval ChOs during embryogenesis has been studied extensively 10,11,13,15,16. The centerpiece of each ChO is a sensory unit composed of a neuron and a scolopale cell. The sensory unit is stretched between two types of accessory cells that attach to the cuticle via specialized epidermal attachment cells 1,9,14. When a fly larva moves, the relative displacement of the epidermal attachment cells leads to stretching of the sensory unit and consequent opening of specific transient receptor potential vanilloid (TRPV) channels at the outer segment of the dendrite 8,12. The elicited signal is then transferred to the locomotor central pattern generator circuit in the central nervous system.
Multiple ChOs have been described in the adult fly 7. These are located near the joints of the adult fly appendages (legs, wings and halters) and in the thorax and abdomen. In addition, several hundreds of ChOs collectively form the Johnston's organ in the adult antenna that transduce acoustic to mechanical energy 3,5,17,4.
In contrast to the extensive knowledge about the development of ChOs in embryonic stages, very little is known about the morphology of these organs during larval stages. Moreover, with the exception of femoral ChOs 18 and Johnston's organ, our knowledge about the development and structure of ChOs in the adult fly is very fragmentary.
Here we describe a method for staining and visualizing ChOs in third instar larvae and pupae. This method can be applied together with genetic tools to better characterize the morphology and understand the development of the various ChOs in the fly.

Visualization of Proprioceptors in Drosophila Larvae and Pupae

A method to immunostain and visualize chordotonal organs in larvae and pupae of Drosophila melanogaster is described.

Proprioception is the ability to sense the motion, or position, of body parts by responding to stimuli arising within the body. In fruitflies and other ...

An Inexpensive, Scalable Behavioral Assay for Measuring Ethanol Sedation Sensitivity and Rapid Tolerance in Drosophila

Alcohol use disorder (AUD) is a serious health challenge. Despite a large hereditary component to AUD, few genes have been unambiguously implicated in their etiology. The fruit fly, Drosophila melanogaster, is a powerful model for exploring molecular-genetic mechanisms underlying alcohol-related behaviors and therefore holds great promise for identifying and understanding the function of genes that influence AUD. The use of the Drosophila model for these types of studies depends on the availability of assays that reliably measure behavioral responses to ethanol. This report describes an assay suitable for assessing ethanol sensitivity and rapid tolerance in flies. Ethanol sensitivity measured in this assay is influenced by the volume and concentration of ethanol used, a variety of previously reported genetic manipulations, and also the length of time the flies are housed without food immediately prior to testing. In contrast, ethanol sensitivity measured in this assay is not affected by the vigor of fly handling, sex of the flies, and supplementation of growth medium with antibiotics or live yeast. Three different methods for quantitating ethanol sensitivity are described, all leading to essentially indistinguishable ethanol sensitivity results. The scalable nature of this assay, combined with its overall simplicity to set-up and relatively low expense, make it suitable for small and large scale genetic analysis of ethanol sensitivity and rapid tolerance in Drosophila.

An Inexpensive, Scalable Behavioral Assay for Measuring Ethanol Sedation Sensitivity and Rapid Tolerance in Drosophila

Straightforward assays for measuring ethanol sensitivity and rapid tolerance in Drosophila facilitate the use of this model organism for investigating these important ethanol-related behaviors. Here, a relatively simple, scalable assay for measuring ethanol sensitivity and rapid tolerance in flies is described.

Alcohol use disorder (AUD) is a serious health challenge. Despite a large hereditary component to AUD, few genes have been unambiguously implicated in ...

Measuring and Altering Mating Drive in Male Drosophila melanogaster

Despite decades of investigation, the neuronal and molecular bases of motivational states remain mysterious. We have recently developed a novel, reductionist, and scalable system for in-depth investigation of motivation using the mating drive of male Drosophila&#160;melanogaster (Drosophila), the methods for which we detail here. The behavioral paradigm centers on the finding that male mating drive decreases alongside fertility over the course of repeated copulations and recovers over ~3 d. In this system, the powerful neurogenetic tools available in the fly converge with the genetic accessibility and putative wiring diagram available for sexual behavior. This convergence allows rapid isolation and interrogation of small neuronal populations with specific motivational functions. Here we detail the design and execution of the satiety assay that is used to measure and alter courtship motivation in the male fly. Using this assay, we also demonstrate that low male mating drive can be overcome by stimulating dopaminergic neurons. The satiety assay is simple, affordable, and robust to influences of genetic background. We expect the satiety assay to generate many new insights into the neurobiology of motivational states.

Measuring and Altering Mating Drive in Male Drosophila melanogaster

This article describes a behavioral assay that uses male mating drive in Drosophila melanogaster to study motivation. Using this method, researchers can utilize advanced fly neurogenetic techniques to uncover the genetic, molecular, and cellular mechanisms that underlie this motivation.

Despite decades of investigation, the neuronal and molecular bases of motivational states remain mysterious. We have recently developed a novel, ...

Assessment of Dopaminergic Homeostasis in Mice by Use of High-performance Liquid Chromatography Analysis and Synaptosomal Dopamine Uptake

Dopamine (DA) is a modulatory neurotransmitter controlling motor activity, reward processes and cognitive function. Impairment of dopaminergic (DAergic) neurotransmission is strongly associated with several central nervous system-associated diseases such as Parkinson&#39;s disease, attention-deficit-hyperactivity disorder and drug addiction1,2,3,4. Delineating disease mechanisms involving DA imbalance is critically dependent on animal models to mimic aspects of the diseases, and thus protocols that assess specific parts of the DA homeostasis are important to provide novel insights and possible therapeutic targets for these diseases.
Here, we present two useful experimental protocols that when combined provide a functional read-out of the DAergic system in mice. Biochemical and functional parameters on DA homeostasis are obtained through assessment of DA levels and dopamine transporter (DAT) functionality5. When investigating the DA system, the ability to reliably measure endogenous levels of DA from adult brain is essential. Therefore, we present how to perform high-performance liquid chromatography (HPLC) on brain tissue from mice to determine levels of DA. We perform the experiment on tissue from dorsal striatum (dStr) and nucleus accumbens (NAc), but the method is also suitable for other DA-innervated brain areas.
DAT is essential for reuptake of DA into the presynaptic terminal, thereby controlling the temporal and spatial activity of released DA. Knowing the levels and functionality of DAT in the striatum is of major importance when assessing DA homeostasis. Here, we provide a protocol that allows to simultaneously deduce information on surface levels and function using a synaptosomal6 DA uptake assay.
Current methods combined with standard immunoblotting protocols provide the researcher with relevant tools to characterize the DAergic system.

Synaptosomal dopamine uptake and high-performance liquid chromatography analysis represent experimental tools to investigate dopamine homeostasis in mice by assessing the function of the dopamine transporter and levels of dopamine in striatal tissue, respectively. Here we present protocols to measure dopamine tissue content and assess the functionality of the dopamine transporter.

Dopamine (DA) is a modulatory neurotransmitter controlling motor activity, reward processes and cognitive function. Impairment of dopaminergic (DAergic) ...

Alternate Immersion in Glucose to Produce Prolonged Hyperglycemia in Zebrafish

Zebrafish (Danio rerio) are an excellent model to investigate the effects of chronic hyperglycemia, a hallmark of Type II Diabetes Mellitus (T2DM). This alternate immersion protocol is a noninvasive, step-wise method of inducing hyperglycemia for up to eight weeks. Adult zebrafish are alternately exposed to sugar (glucose) and water for 24 hours each. The zebrafish begin treatment in a 1% glucose solution for 2 weeks, then a 2% solution for 2 weeks, and finally a 3% solution for the remaining 4 weeks. Compared to water-treated (stress) and mannitol-treated (osmotic) controls, glucose-treated zebrafish have significantly higher blood sugar levels. The glucose-treated zebrafish show blood sugar levels of 3-times that of controls, suggesting that after both four and eight weeks hyperglycemia can be achieved. Sustained hyperglycemia was associated with increased Glial Fibrillary Acidic Protein (GFAP) and increased nuclear factor Kappa B (NF-kB)&#160;levels in retina and decreased physiological responses, as well as cognitive deficits suggesting this protocol can be used to model disease complications.

This protocol noninvasively induces hyperglycemia in zebrafish for up to 8 weeks. Using this protocol, an in-depth study of the adverse effects of hyperglycemia can be made.

Zebrafish (Danio rerio) are an excellent model to investigate the effects of chronic hyperglycemia, a hallmark of Type II Diabetes Mellitus (T2DM). This ...

Semi-Quantitative Determination of Dopaminergic Neuron Density in the Substantia Nigra of Rodent Models using Automated Image Analysis

Estimation of the number of dopaminergic neurons in the substantia nigra is a key method in pre-clinical Parkinson's disease research. Currently, unbiased stereological counting is the standard for quantification of these cells, but it remains a laborious and time-consuming process, which may not be feasible for all projects. Here, we describe the use of an image analysis platform, which can accurately estimate the quantity of labeled cells in a pre-defined region of interest. We describe a step-by-step protocol for this method of analysis in rat brain and demonstrate it can identify a significant reduction in tyrosine hydroxylase positive neurons due to expression of mutant &#945;-synuclein in the substantia nigra. We validated this methodology by comparing with results obtained by unbiased stereology. Taken together, this method provides a time-efficient and accurate process for detecting changes in dopaminergic neuron number, and thus is suitable for efficient determination of the effect of interventions on cell survival.

Here we present an automated method for semi-quantitative determination of dopaminergic neuron number in the rat substantia nigra pars compacta.

Estimation of the number of dopaminergic neurons in the substantia nigra is a key method in pre-clinical Parkinson's disease research. Currently, unbiased ...

Uptake of Fluorescent Labeled Small Extracellular Vesicles In Vitro and in Spinal Cord

Small extracellular vesicles (sEVs) are 50-150 nm vesicles secreted by all cells and present in bodily fluids. sEVs transfer biomolecules such as RNA, proteins, and lipids from donor to acceptor cells, making them key signaling mediators between cells. In the central nervous system (CNS), sEVs can mediate intercellular signaling, including neuroimmune interactions. sEV functions can be studied by tracking the uptake of labeled sEVs in recipient cells both in vitro and in vivo. This paper describes the labeling of sEVs from the conditioned media of RAW 264.7 macrophage cells using a PKH membrane dye. It shows the uptake of different concentrations of labeled sEVs at multiple time points by Neuro-2a cells and primary astrocytes in vitro. Also shown is the uptake of sEVs delivered intrathecally in mouse spinal cord neurons, astrocytes, and microglia visualized by confocal microscopy. The representative results demonstrate time-dependent variation in the uptake of sEVs by different cells, which can help confirm successful sEVs delivery into the spinal cord.

Uptake of Fluorescent Labeled Small Extracellular Vesicles In Vitro and in Spinal Cord

We describe a protocol to label macrophage-derived small extracellular vesicles with PKH dyes and observe their uptake in vitro and in the spinal cord after intrathecal delivery.

Small extracellular vesicles (sEVs) are 50-150 nm vesicles secreted by all cells and present in bodily fluids. sEVs transfer biomolecules such as RNA, ...

Optogenetic Phase Transition of TDP-43 in Spinal Motor Neurons of Zebrafish Larvae

Abnormal protein aggregation and selective neuronal vulnerability are two major hallmarks of neurodegenerative diseases. Causal relationships between these features may be interrogated by controlling the phase transition of a disease-associated protein in a vulnerable cell type, although this experimental approach has been limited so far. Here, we describe a protocol to induce phase transition of the RNA/DNA-binding protein TDP-43 in spinal motor neurons of zebrafish larvae for modeling cytoplasmic aggregation of TDP-43 occurring in degenerating motor neurons in amyotrophic lateral sclerosis (ALS). We describe a bacterial artificial chromosome (BAC)-based genetic method to deliver an optogenetic TDP-43 variant selectively to spinal motor neurons of zebrafish. The high translucency of zebrafish larvae allows for the phase transition of the optogenetic TDP-43 in the spinal motor neurons by a simple external illumination using a light-emitting diode (LED) against unrestrained fish. We also present a basic workflow of live imaging of the zebrafish spinal motor neurons and image analysis with freely available Fiji/ImageJ software to characterize responses of the optogenetic TDP-43 to the light illumination. This protocol enables the characterization of TDP-43 phase transition and aggregate formation in an ALS-vulnerable cellular environment, which should facilitate an investigation of its cellular and behavioral consequences.

We describe a protocol to induce phase transition of TAR DNA-binding protein 43 (TDP-43) by light in the spinal motor neurons using zebrafish as a model.

Abnormal protein aggregation and selective neuronal vulnerability are two major hallmarks of neurodegenerative diseases. Causal relationships between ...