We thank Bryne Ulmschneider for contributions to the protocol and Diane Barber for suggestions on the manuscript. This work was funded by a National Institute of Health grant GM116384 to T.G. Nystul and D.L. Barber.

NOTE: To measure pHi in the FSC lineage, we calculate the ratio of fluorescence intensities of pHluorin to mCherry in FSCs, pFCs, and follicle cells in physiological conditions, and convert the ratios into pHi values with standard calibration curves for each cell type7. First, live imaging experiments are performed to measure fluorescence intensities of pHluorin and mCherry in germaria dissected into a buffer containing NaHCO3, which mimics physiological conditions1</s...

<ol>
	<li>Grillo-Hill, B. K., Choi, C., Jimenez-Vidal, M., Barber, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+H++efflux+is+sufficient+to+induce+dysplasia+and+necessary+for+viability+with+oncogene+expression.">Increased H+ efflux is sufficient to induce dysplasia and necessary for viability with oncogene expression.</a> eLife. 03270, (2015).</li><li>Ulmschneider, B., Grillo-Hill, B. K., Benitez, M., Azimova, D. R., Barber, D. L., Nystul, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increased+intracellular+pH+is+necessary+for+adult+epithelial+and+embryonic+stem+cell+differentiation.">Increased intracellular pH is necessary for adult epithelial and embryonic stem cell differentiation.</a> J. Cell Biol. 215 (3), 345-355 (2016).</li><li>Han, J., Burgess, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+Indicators+for+Intracellular+pH.">Fluorescent Indicators for Intracellular pH.</a> Chemical reviews. 110 (5), 2709-2728 (2010).</li><li>Koivusalo, M., Welch, C., 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=Amiloride+inhibits+macropinocytosis+by+lowering+submembranous+pH+and+preventing+Rac1+and+Cdc42+signaling.">Amiloride inhibits macropinocytosis by lowering submembranous pH and preventing Rac1 and Cdc42 signaling.</a> J. Cell Biol. 188 (4), 547-563 (2010).</li><li>Choi, C. -. H., Webb, B. A., Chimenti, M. S., Jacobson, M. P., Barber, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=pH+sensing+by+FAK-His58+regulates+focal+adhesion+remodeling.">pH sensing by FAK-His58 regulates focal adhesion remodeling.</a> J. Cell Biology. 202 (6), 849-859 (2013).</li><li>Rossano, A. J., Chouhan, A. K., Macleod, G. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Genetically+encoded+pH-indicators+reveal+activity-dependent+cytosolic+acidification+of+Drosophila+motor+nerve+termini+in+vivo.">Genetically encoded pH-indicators reveal activity-dependent cytosolic acidification of Drosophila motor nerve termini in vivo.</a> J. Phys. 591 (7), 1691-1706 (2013).</li><li>Grillo-Hill, B. K., Webb, B. A., Barber, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ratiometric+imaging+of+pH+probes.">Ratiometric imaging of pH probes.</a> Methods in Cell Biol. 123, 429-448 (2014).</li><li>Miesenb&#246;ck, G., De Angelis, D. A., Rothman, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visualizing+secretion+and+synaptic+transmission+with+pH-sensitive+green+fluorescent+proteins.">Visualizing secretion and synaptic transmission with pH-sensitive green fluorescent proteins.</a> Nature. 394 (6689), 192-195 (1998).</li><li>Kirilly, D., Xie, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Drosophila+ovary:+an+active+stem+cell+community.">The Drosophila ovary: an active stem cell community.</a> Cell research. 17 (1), 15-25 (2007).</li><li>Sahai-Hernandez, P., Castanieto, A., Nystul, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+models+of+epithelial+stem+cells+and+their+niches.">Drosophila models of epithelial stem cells and their niches.</a> Wiley interdisciplinary reviews. Dev. Biol. 1 (3), 447-457 (2012).</li><li>Losick, V. P., Morris, L. X., Fox, D. T., Spradling, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Drosophila+stem+cell+niches:+a+decade+of+discovery+suggests+a+unified+view+of+stem+cell+regulation.">Drosophila stem cell niches: a decade of discovery suggests a unified view of stem cell regulation.</a> Dev. Cell. 21 (1), 159-171 (2011).</li><li>Pocha, S. M., Montell, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cellular+and+molecular+mechanisms+of+single+and+collective+cell+migrations+in+Drosophila:+themes+and+variations.">Cellular and molecular mechanisms of single and collective cell migrations in Drosophila: themes and variations.</a> Ann Rev. of Gen. 48, 295-318 (2014).</li><li>St Johnston, D., Ahringer, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+polarity+in+eggs+and+epithelia:+parallels+and+diversity.">Cell polarity in eggs and epithelia: parallels and diversity.</a> Cell. 141 (5), 757-774 (2010).</li><li>Castanieto, A., Johnston, M. J., Nystul, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=EGFR+signaling+promotes+self-renewal+through+the+establishment+of+cell+polarity+in+Drosophila+follicle+stem+cells.">EGFR signaling promotes self-renewal through the establishment of cell polarity in Drosophila follicle stem cells.</a> eLife. 3, (2014).</li><li>Margolis, J., Spradling, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+behavior+of+epithelial+stem+cells+in+the+Drosophila+ovary.">Identification and behavior of epithelial stem cells in the Drosophila ovary.</a> Development. 121 (11), 3797-3807 (1995).</li><li>Nystul, T. G., Spradling, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+epithelial+niche+in+the+Drosophila+ovary+undergoes+long-range+stem+cell+replacement.">An epithelial niche in the Drosophila ovary undergoes long-range stem cell replacement.</a> Cell stem cell. 1 (3), 277-285 (2007).</li><li>Morris, L. X., Spradling, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+live+imaging+provides+new+insight+into+stem+cell+regulation+and+germline-soma+coordination+in+the+Drosophila+ovary.">Long-term live imaging provides new insight into stem cell regulation and germline-soma coordination in the Drosophila ovary.</a> Development. 138 (11), 2207-2215 (2011).</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+(MARCM)+for+Drosophila+neural+development.">Mosaic analysis with a repressible cell marker (MARCM) for Drosophila neural development.</a> Trends in neuro. 24 (5), 251-254 (2001).</li></ol>

The authors have nothing to disclose.

Here, we describe a method for measuring the pHi of cells in the FSC lineage within wildtype tissue. This protocol has been developed and refined over the past five years, since we first began to study pHi in Drosophila ovarian tissue. During that time, the protocol has been used successfully by multiple investigators in our lab and on at least four different spinning disc and laser scanning microscopes. The reproducibility of our original observation, that pHi increases as cells in the FSC lineage differentiate...

Recent studies revealed a role for changes in pHi during cellular differentiation and dysplasia in vivo1,2. These studies found that pHi is remarkably consistent in cells of the same type at the same stage of differentiation, but that it changes as cells transition from one stage to another. In some cases, blocking the changes in pHi partially disrupts differentiation, suggesting that the change in pHi is not just a consequence of changes in cell fate but instead helps to promote the change in cell fate, perhaps through effects on pH-sensitive regulatory proteins or chemical reactions required for differentiation. Future studies have the potential to reveal more insight into the many different roles of pHi dynamics in vivo. However, one of the challenges of studying pHi during differentiation in vivo is obtaining accurate measurements of pHi. Unlike other features of differentiation, such as changes in cellular morphology and gene expression, pHi is a labile chemical property of the cell that is not preserved in cells that have been fixed and permeabilized with standard methods. In addition, pHi may not be stable in cells that are stressed or dying as a result of experimental manipulation. Thus, it is important to keep cells alive and as healthy as possible when measuring pHi. Several vital dyes are available that work well for measuring the pHi of cells in culture3, but in many cases they are not suitable for in vivo studies because they do not penetrate the tissue deeply or evenly enough to provide accurate measurements.
To circumvent the problem of poor dye penetration, we and others have used a genetically encoded probe, mCherry::pHluorin4,5,6,7, that can be expressed specifically in the cell types of interest and imaged in live tissue. pHluorin is a variant of GFP with a higher pKa (~ 7.0 vs. ~ 4.0) that folds more readily at higher pH; so the total fluorescence intensity emitted from a population of pHluorin molecules in the cell increases with increasing pHi8. Importantly, fluorescence is linear within the normal cytosolic range of pHi values. In contrast, the fluorescence of mCherry (pKa ~ 4.5) is insensitive to pH changes within the cytosolic range. These two reporters are covalently linked together as a single chimeric protein, encoded by a single open reading frame, so they are always present in equal amounts. Therefore, the ratio of pHluorin to mCherry fluorescence intensity provides a measurement of pHi that is normalized to the probe concentration in each cell. The ratios can then be converted to estimates of pHi values using a standard curve that is generated by obtaining the pHluorin to mCherry ratios from tissues that have been equilibrated to known pH values.
Here, we describe the methods for using mCherry::pHluorin to measure the pHi of the epithelial FSC lineage in the Drosophila ovary. This well-characterized tissue has been used to model many different aspects of epithelial biology, such as stem cell self-renewal and differentiation9,10,11, collective cell migration12, and the development and maintenance of cell polarity13,14. The follicle epithelium is produced by two FSCs that reside at the anterior edge of the tissue in a structure called the germarium15,16. These cells divide regularly during adulthood to self-renew and produce progeny, called prefollicle cells (pFCs), that can either re-enter the niche and become an FSC or differentiate into one of three different follicle cell types: polar cells, stalk cells, or main body follicle cells. We showed previously that in wildtype tissue, the pHi increases steadily during the early stages of differentiation, from a pHi of approximately 6.8 in FSCs to 7.0 in pFCs, to 7.3 in follicle cells2. Blocking this increase by RNAi knockdown of a ubiquitously expressed sodium/proton exchanger, DNhe2, severely impairs pFC differentiation, whereas increasing pHi by overexpression of DNhe2 causes a mild excess differentiation phenotype. These findings demonstrate that pHi is stably maintained in the early FSC lineage and that it can be experimentally increased or decreased in vivo. The methods described here can be used to measure pHi in either wildtype tissue or various forms of mutant tissues, including RNAi knockdown or overexpression using a Gal4 of interest, and mitotic clones.

<table>
	<tbody>
		<tr>
			<td>Fly Stocks</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>UAS-mCherry::pHluorin[1]</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>y1 w*;P{GawB}10930/CyO</td>
			<td>Bloomington Stock Center</td>
			<td>7023</td>
			<td></td>
		</tr>
		<tr>
			<td>Act-Gal4 flipout stock</td>
			<td>Bloomington Stock Center</td>
			<td>4409</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Chemicals for Buffer preparation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma Aldrich</td>
			<td>S5886</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma Aldrich</td>
			<td>P-3911</td>
			<td></td>
		</tr>
		<tr>
			<td>glucose</td>
			<td>Mallinckrodt</td>
			<td>4912</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Thermo Fisher Scientific</td>
			<td>BP310</td>
			<td></td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Thermo Fisher Scientific</td>
			<td>M63</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Sigma Aldrich</td>
			<td>C-5080</td>
			<td></td>
		</tr>
		<tr>
			<td>HCO3</td>
			<td>Sigma Aldrich</td>
			<td>S-5761</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2</td>
			<td>Sigma Aldrich</td>
			<td>M-9272</td>
			<td></td>
		</tr>
		<tr>
			<td>NMDG+</td>
			<td>Sigma Aldrich</td>
			<td>M-2004</td>
			<td></td>
		</tr>
		<tr>
			<td>K2HPO4</td>
			<td>Mallinckrodt</td>
			<td>7088</td>
			<td>Use to Make KHPO4 pH 7.4</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Thermo Fisher Scientific</td>
			<td>BP362</td>
			<td>Use to Make KHPO4 pH 7.4</td>
		</tr>
		<tr>
			<td>Concanavalin A, Alexa Fluor 647 Conjugate</td>
			<td>Thermo Fisher Scientific</td>
			<td>C21421</td>
			<td>0.25 mg/ml dilution</td>
		</tr>
		<tr>
			<td>Nigericin</td>
			<td>Thermo Fisher Scientific</td>
			<td>N1495</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Dissection and mounting tools</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2 Dumont Inox forceps (Size 5)</td>
			<td>Thermo Fisher Scientific</td>
			<td>NC9473431</td>
			<td></td>
		</tr>
		<tr>
			<td>2 23-gauge syringe needles</td>
			<td>Sigma Aldrich</td>
			<td>Z192457</td>
			<td></td>
		</tr>
		<tr>
			<td>9-well glass dissecting dish</td>
			<td>Thermo Fisher Scientific</td>
			<td>13-748B</td>
			<td></td>
		</tr>
		<tr>
			<td>Vacuum Grease</td>
			<td>Dow Corning</td>
			<td>1018817</td>
			<td></td>
		</tr>
		<tr>
			<td>22 X 40 mM glass coverslips</td>
			<td>Thermo Fisher Scientific</td>
			<td>12545C</td>
			<td></td>
		</tr>
		<tr>
			<td>Round Glass Coverslips, 12mm diameter, 0.13-0.16mm thickness</td>
			<td>Ted Pella, Inc.</td>
			<td>26023</td>
			<td></td>
		</tr>
		<tr>
			<td>3-D mounting chamber</td>
			<td>custom manufactured</td>
			<td></td>
			<td>.stl and .ipt files for 3-D printer included as supplemental files</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Other equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>pH meter</td>
			<td>Thermo Fisher Scientific</td>
			<td>13-620-183A</td>
			<td>Model: Accumet AB15</td>
		</tr>
		<tr>
			<td>Dissection microscope</td>
			<td>Olympus Corporation</td>
			<td>0H11436</td>
			<td>Model: SZ2-ST</td>
		</tr>
		<tr>
			<td>Confocal Microscope</td>
			<td>Leica Biosystems</td>
			<td></td>
			<td>SP5 or SP8 laser-scanning confocal microscope with a 40&#215; objective with a numerical aperture of 1.3</td>
		</tr>
	</tbody>
</table>

methods for imaging intracellular ph of the follicle stem cell lineage in live drosophila ovarian tissue

Changes in intracellular pH (pHi) play important roles in the regulation of many cellular functions, including metabolism, proliferation, and differentiation. Typically, pHi dynamics are determined in cultured cells, which are amenable to measuring and experimentally manipulating pHi. However, the recent development of new tools and methodologies has made it possible to study pHi dynamics within intact, live tissue. For Drosophila research, one important development was the generation of a transgenic line carrying a pHi biosensor, mCherry::pHluorin. Here, we describe a protocol that we routinely use for imaging live Drosophila ovarioles to measure pHi in the epithelial follicle stem cell (FSC) lineage in mCherry::pHluorin transgenic wild type lines; however, the methods described here can be easily adapted for other tissues, including the wing discs and eye epithelium. We describe techniques for expressing mCherry::pHluorin in the FSC lineage, maintaining ovarian tissue during live imaging, and acquiring and analyzing images to obtain pHi values.

Here we have described the process of measuring pHi in the follicle epithelium, which involves several steps. First, the ovaries are dissected from flies of the appropriate genotype using tools for dissecting and mounting (Figure 1). The ovarioles are then imaged using quantitative fluorescence microscopy and the images are analyzed to obtain measurements of pHi. For each image, the cell types of interest are identified as described in Section 3.1 (<strong cl...

Watch this Scientific Journal Video about Methods for Imaging Intracellular pH of the Follicle Stem Cell Lineage in Live Drosophila Ovarian Tissue at JoVE.com

Methods for Imaging Intracellular pH of the Follicle Stem Cell Lineage in Live Drosophila Ovarian Tissue

We provide a protocol for imaging intracellular pH of an epithelial stem cell lineage in live Drosophila ovarian tissue. We describe methods to generate transgenic flies expressing a pH biosensor, mCherry::pHluorin, image the biosensor using quantitative fluorescence imaging, generate standard curves, and convert fluorescence intensity values to pH values.

Methods for Imaging Intracellular pH of the Follicle Stem Cell Lineage in Live Drosophila Ovarian Tissue

Changes in intracellular pH (pHi) play important roles in the regulation of many cellular functions, including metabolism, proliferation, and ...

The overall goal of this procedure is to measure the intracellular pH of follicle cells within live explanted Drosophila ovarian tissue. This method can help us answer key questions in stem cell and developmental biology such as, how changes to intracellular pH contribute to sulfate decisions. The main advantage of this technique is that it makes it possible to accurately quantify pH within living intact tissue.To begin the experiment, prepare mounting chambers by applying a thin coating of vacuum grease to the flatter side of a 3D printed mounting chamber. Place the flatter side on a 22 x 40 millimeter cover slip to seal the cover slip to the mounting chamber. Next, dissect the ovaries from female adult flies in 500 microliters of dissection buffer.Anesthetize three to four flies using CO2 gas and transfer the flies onto a fly pad. Use forceps to select a fly and place it into the dissection media. Pinch the thorax of the fly with one pair of forceps while tugging on the tip of its abdomen until its ovaries are exposed.Set a timer for exactly 10 minutes. After detaching the ovaries from the other organs, tease apart the ovarioles using 22 and a half gauge syringe needles. Use one syringe needle to hold the cluster of ovarioles in place at its anterior end and stroke downwards along the length of single ovarioles to carefully separate the muscle sheath from the ovaries.Incubate the dissected ovaries in dissection media for the remainder of the time on the timer. It is important the ovaries remain in the dissection media for exactly 10 minutes to provide enough time for the cells. Place a small drop of dissection media onto the glass cover slip inside the mounting chamber.Transfer the separated ovarioles using forceps. Separate later stage egg chambers from germaria associated with earlier stage egg chambers and ensure that the dissected germaria are placed at the center of the dissection media drop. Add two small drops of nail polish to opposite sides of around 12 millimeter cover slip and let it air dry for about 10 seconds.Place the round cover slip on the drop of dissection media containing separated germaria, so that the side with nail polish faces down and contacts the dissection media. Press down on the edges to flatten and secure the germaria in position. Fill mounting chamber with additional dissection media and move on to live imaging.Image ovarioles in ny dissection buffer at pH 6.5. Adjust settings such that pixel intensities of the pHluorin and mCherry images are low, but not below the limits of detection of the camera. Next, image another set of ovarioles in nygerion dissection buffer at pH 7.5 and adjust the settings such that the pixel intensities of the pHluorin and mCherry images are high but not saturated.Image ovaries and bi-carbonate dissection buffer and ensure that the pixel intensities of the pHluorin and mCherry images are not saturated with the chosen settings. If pixels are saturated, adjust the settings. After selecting appropriate live imaging settings, proceed to collecting images of at least five germaria in each of the conditions.Subtract the background by opening unprocessed images in Fiji with each channel in a separate window. Use the rectangle tool to draw a region of interest or ROI in the pHluorin channel window and a part of the image without signal. Set the lower limit of the threshold so that pixels with intensity values below the background are excluded and set the upper limit of the threshold to maximum.When the threshold is set in this way, the areas of the image without signal are mostly blue and the signal is clearly visible. If the threshold was set, navigate to the set measurements dialog box and make sure to check the limit to threshold box. Measure the mean fluorescence intensity in the ROI, go to process, then, math menu to subtract the measured background intensity from each channel and slice of the image using the subtract function.Repeat the steps for the mCherry channel window but, use the restore selection function instead of drawing a new rectangle with the rectangle tool found in the edit selection menu, to add a rectangle with the same dimensions and position on the image. Choose one or more slices in which the cell of interest has highest fluorescence intensity in the mCherry channel and make sure that the concanavalin A staining in the far red channel, is in focus within the selected slice. Next, draw an ROI around each follicle stem cell or FSC and measure the mean fluorescence intensity of pHluorin and mCherry and all of the slices chosen for measurements.Finally, divide the mean fluorescence intensity of the pHluorin channel by the mean fluorescence intensity of the mCherry channel, to calculate a ratio of pHluorin to mCherry fluorescence. Two germaria were imaged using quantitative fluorescence microscopy with UAS mCherry pHluorin and 10930 gal 4, stained with concanavalin A and ROI outlining of follicle stem cell or FSC or PFC and a follicle cell is shown in each image. The ratio of the fluorescence intensities in the GFP and mCherry channels is converted to pH I values, using a standard curve.The pH I increases with differentiation in the early FSC lineage, from 6.8 in FSCs to 7.0 in prefollicle cells to 7.3 in follicle cells. The pH I values of each cell type can be represented as a pseudocolored micrograph that shows the differences in pHluorin to mCherry ratios, display these differences in color as defined by an LUT. When attempting this procedure, it is important to remember to have all the reagents ready before hand because many steps in this protocol are time sensitive.After its development, this technique paved the way for researchers in the field of developmental biology, to explore the role of pH in sulfate decisions intracellular malano gaster.

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6.7K Views.  University of California, San Francisco. The overall goal of this procedure is to measure the intracellular pH of follicle cells within live explanted Drosophila ovarian tissue. This method can help us answer key questions in stem cell and developmental biology such as, how changes to intracellular pH contribute to sulfate decisions. The main advantage of this technique is that it makes it possible to accurately quantify pH within living intact tissue.To begin the experiment, prepare mounting chambers by applying a thin coati...