Name: computational analysis of the caenorhabditis elegans germline to study the distribution of nuclei, proteins, and the cytoskeleton
Uploaded: 2018-04-19T12:30:00
Description: Watch this Scientific Journal Video about Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton at JoVE.com

We thank Monash Microimaging for their technical support. Some strains were provided by the Caenorhabditis Genetics Center, which is funded by NIH Office of Research Infrastructure Programs (P40 OD010440). This work was supported by a Monash University Biomedicine Discovery Fellowship, NHMRC Project Grant (GNT1105374), NHMRC Senior Research Fellowship (GNT1137645) and veski innovation fellowship: VIF 23 to Roger Pocock.

1. Preparation and Worm Husbandry
Note: Refer Table of Materials for all product information.
<ol>
	<li>OP50 Escherichia coli culture: culture OP50 bacteria in Lysogeny broth (LB) (1% tryptone, 0.5% yeast, 0.5% NaCl, pH 7.0) overnight at 37 &#176;C without antibiotics.</li>
	<li>Seed 400 &#181;L of OP50 bacteria to nematode growth media (NGM) plates (1.5 g of NaCl, 8.5 g of agar, 1.25 g of peptone, 1 mL of 1 M CaCl2, 1 mL of 5 mg/mL cholesterol in ethanol...

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The goal of this protocol is to improve the accuracy and reduce the time required for germline analysis. After standard preparation of dissected germlines, a three-dimensional model of germline nuclei is prepared by computational rendering. While allowing the observation of germline nuclei distribution in space, three-dimensional rendering calculates the number of nuclei at specific regions of the germline. The critical aspect of our method is accurate definition of size and shape parameters of nuclei. This depends on cl...

The conservation of signaling pathways with mammals makes C. elegans an excellent model to study multiple biological processes1,2. In our lab, we use the C. elegans germline to study stem cell development, apoptosis, and gene expression. While the germline is a three-dimensional structure, many studies are two dimensional due to the time-consuming and labor-intensive nature of three-dimensional analysis. It is highly likely that two-dimensional analysis may misrepresent in vivo events in the germline. The C. elegans adult hermaphrodite has two germline arms, each of which houses a somatic distal tip cell (DTC) that maintains distal germ cells in an undifferentiated state3,4. These germ cells begin to differentiate as they move away from the DTC, escaping its influence, and become oocytes and sperm as they reach the proximal end of the germline. During this process, germ cell nuclei undergo mitosis, before transitioning to meiosis5,6. Sperm production is completed by larval stage 4 (L4) of the development, after which oocytes are produced during the adulthood. The sperm are stored in the spermatheca where they fertilize oocytes to generate embryos.
There are multiple genetic and environmental factors that can influence germline development in C. elegans resulting in changes in the number of nuclei, number of apoptotic events, chromosome dynamics, and protein expression and/or localization7,8,9,10,11. The analysis of these events requires the identification of each stage of differentiation based on nuclear morphology and distribution. To accurately analyze these parameters manually with a large sample size is labor-intensive and time-consuming. To circumvent these drawbacks and to enable the consistency of analysis, we developed an automated method for three-dimensional examination of the C. elegans germline for nuclei counting, nuclei distribution, protein expression, and cytoskeletal structure. By combining confocal microscopy with three-dimensional rendering, we generated size and shape parameters for the identification of each stage of germ cell differentiation. Further, this method enables counting of germ cell nuclei and sperm plus scoring of chromosome number in each oocyte.
One crucial structure in the germline is the cytoskeleton, which provides stability to the germline compartment, aids cytoplasmic streaming and protection to germline nuclei12. Using computational rendering, we performed three-dimensional reconstruction of the germline cytoskeleton and identified distinct cytoskeletal features within the germline. Here, we describe a step-by-step protocol to illustrate how computational analysis combined with confocal imaging enables comprehensive analysis of the C. elegans germline.
We propose a rapid method for the three-dimensional analysis of C. elegans germline (Figure 1). Using three-dimensional analysis, it is possible to study the three-dimensional distribution of germline nuclei (Figure 2 and Figure 3), automated counting of cells (Figure 2), reconstruction of the germline cytoskeleton (Figure 3), distribution of proteins (Figure 4), and scoring the number of sperm in the spermatheca and chromosomes in oocytes (Figure 5). The method not only enables easy and accurate quantification of the germline but identifies physiologically relevant phenotypes.

<table border="0" cellpadding="0" cellspacing="0" style="width:933px;" width="934">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:335px;">C. elegans strains: wild type (N2, Bristol), rnp-8(tm2435) I/hT2[bli-4(e937) let-?(q782) qIs48] (I;III), cpb-3(bt17) I, glp-1 (e2141) III&#160;</td>
			<td style="width:264px;">Caenorhabditis Genetics Center (CGC)</td>
			<td style="width:168px;"></td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">OP50 Escherichia coli bacteria</td>
			<td style="width:264px;">Homemade</td>
			<td style="width:168px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Nematode Growth Media (NGM) plates</td>
			<td style="width:264px;">Homemade</td>
			<td style="width:168px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">polyclonal rabbit anti-REC-8&#160;</td>
			<td>SDIX</td>
			<td>29470002</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Alexa 488 conjugated antibody raised in goat</td>
			<td>Thermofisher Scientific</td>
			<td>A-21236</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cytoskeletal dye phalloidin&#160;</td>
			<td>Thermofisher Scientific</td>
			<td style="width:168px;">A-12380</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">DAPI&#160;</td>
			<td>Thermofisher Scientific&#160;</td>
			<td>62248</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Poly-L-lysine&#160;</td>
			<td>Sigma Aldrich</td>
			<td>P5899</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tetramisol&#160;</td>
			<td>Sigma Aldrich</td>
			<td>P5899</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">MgSO4</td>
			<td>Sigma Aldrich</td>
			<td style="width:168px;">M7506</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">1M HEPES buffer, pH 7.4&#160;</td>
			<td>Sigma Aldrich</td>
			<td style="width:168px;">G0887</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">10X PBS pH 7.4&#160;</td>
			<td>Thermofisher Scientific</td>
			<td>AM9625</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tween-20&#160;</td>
			<td>Sigma Aldrich</td>
			<td>P1389</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">EGTA</td>
			<td>Sigma Aldrich</td>
			<td>E3889</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">37% Paraformaldehyde solution</td>
			<td>Merck Millipore</td>
			<td>1040031000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Normal goat serum</td>
			<td>Sigma Aldrich</td>
			<td>G9023</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fluoroshield fixing reagent&#160;</td>
			<td>Sigma Aldrich</td>
			<td>F6182</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol&#160;</td>
			<td>Millipore&#160;</td>
			<td>1009832511</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Methanol</td>
			<td>Sigma Aldrich</td>
			<td>34860</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">20&#176;C &#38; 25&#176;CIncubator&#160;</td>
			<td>Any brand</td>
			<td style="width:168px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Light microscope</td>
			<td style="width:264px;">Any brand</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Confocal microscope&#160;&#160;</td>
			<td style="width:264px;">Any brand (Leica, Zeiss)</td>
			<td style="width:168px;"></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Computer equipped with Imaris suit 8.4.1 or later version, full licence to use the software and Matlab software.</td>
			<td style="width:264px;">Bitplane</td>
			<td style="width:168px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:335px;">Phospho buffered saline, pH 7.4</td>
			<td style="width:264px;">Homemade</td>
			<td style="width:168px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Teflon microscope slides&#160;</td>
			<td style="width:264px;">Tekdon&#160;</td>
			<td style="width:168px;">&#160;941-322-8288</td>
			<td></td>
		</tr>
	</tbody>
</table>

computational analysis of the caenorhabditis elegans germline to study the distribution of nuclei, proteins, and the cytoskeleton

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and chromosome dynamics. While the germline is an excellent model, the analysis is often two dimensional due to the time and labor required for three-dimensional analysis. Major readouts in such studies are the number/position of nuclei and protein distribution within the germline. Here, we present a method to perform automated analysis of the germline using confocal microscopy and computational approaches to determine the number and position of nuclei in each region of the germline. Our method also analyzes germline protein distribution that enables the three-dimensional examination of protein expression in different genetic backgrounds. Further, our study shows variations in cytoskeletal architecture in distinct regions of the germline that may accommodate specific spatial developmental requirements. Finally, our method enables automated counting of the sperm in the spermatheca of each germline. Taken together, our method enables rapid and reproducible phenotypic analysis of the C. elegans germline.

Figure 1 indicates the time required for three-dimensional germline analysis. L4 hermaphrodites incubated at 20 &#176;C were dissected to isolate germlines and stained with DAPI, phalloidin, and antibodies against germline proteins. Germlines are imaged using confocal microscopy. Staining and confocal microscopy requires approximately 24 h. Computational analysis for the complete germline requires 10 - 15 min to count the number and position of nuclei, identi...

Watch this Scientific Journal Video about Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton at JoVE.com

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

We present an automated method for three-dimensional reconstruction of the Caenorhabditis elegans germline. Our method determines the number and position of each nucleus within the germline and analyses germline protein distribution and cytoskeletal structure.

Computational Analysis of the Caenorhabditis elegans Germline to Study the Distribution of Nuclei, Proteins, and the Cytoskeleton

The Caenorhabditis elegans (C. elegans) germline is used to study several biologically important processes including stem cell development, apoptosis, and ...

The overall goal of this method is to automate the analysis of a Caenorhabditis elegans germline to study its nuclei, protein, and cytoskeletal distribution. This method can help answer the key questions in the C.Elegans field about the number of nuclei and sperm, nuclear distribution, and cytoskeletal structure of the germline. The main advantages of this technique are it reduces the analysis time, increases the sample size, and eliminate the human error associated with the manual analysis.To image the samples, place slides with stained germlines into the slide holder above the 63X objective of a confocal microscope, and locate a germline. Focus on the top of the germline, and mark it with the confocal microscope software. When the total germline thickness has been established, define the thickness of each slice up to 0.5 micrometers, and mark the complete germline.Then, start the acquisition, scanning each slice eight times and averaging the values to improve the image quality. When all of the images have been obtained, import the images to an appropriate image analysis software program, and use the surface function tool to select the mitotic region. An image of the distal end of the germline will appear.Cancel the automatic surface creation wizard, and manually draw a region of interest around the mitotic region at the first and last slices of the image from the three-dimensional stack. Click Create Surface, followed by Mask Channel, to mask all of the channels except the DAPI channel. Using the spot function tool, define the size parameters of the mitotic region with an XY diameter of two micrometers and with the Z diameter undefined.Click subtract background to subtract the background. To define the minimum threshold, increase the minimum 3D rendering threshold on a DAPI-stained wild-type germline until the first spot appears outside of the germline, and generate a 3D model for each region. After saving the images, click table to view the number of nuclei, as generated automatically by the software, and export the images as TIFF files.For the transition zone, create surface as explained before. Then, click Mask Channel to mask all the channels except the DAPI channel. Using spot function, define an XY diameter of two micrometers and Z diameter of 1.5 micrometers, and click subtract background to subtract the background.To define the minimum threshold, increase the minimum 3D rendering threshold on a DAPI-stained wild-type germline until the first spot appears outside of the germline, and generate a 3D model for each region. After saving the images, click table to view the number of nuclei, as generated automatically by the software, and export the images as TIFF files. For scoring the sperm number, select the spermatheca as the region of interest, as demonstrated for the nuclei regions, and use the spot function tool to define the XY diameter between 0.75 and one micrometers with an undefined Z diameter to detect each sperm.Select the Background Subtract box, and use the background correction values calculated by the software to subtract the background. Then, adjust the 3D rendering threshold to detect all of the DAPI-stained sperm in the spermatheca. For chromosome counting in the oocytes, select the oocytes and define the XY diameter as less than 0.75 micrometers, and define the threshold before developing the 3D models.Then, save the images for export as TIFF files. For cytoskeletal germline reconstruction, identify the mitotic region of interest in the germline and create a surface mask as previously demonstrated. Click Mask Channels to mask all of the channels except the phalloidin channel, and use the surface function tool to define a surface detail of 0.25 micrometers.After subtracting the background, adjust the 3D rendering threshold to save the developed 3D image for export as a TIFF file. The nuclei distribution is dependent on the stage of differentiation. For example, at the mitotic region, the inner actin appears as a solid mass upon which the nuclei are organized.In a wild-type germline, the mitotic region contains approximately 250 nuclei and is tightly packed with nuclei compared to the rest of the germline. As the nuclei move away from the distal end, however, they appear closer to the circumference of the germline, with the change in distribution starting at the transition zone and finishing as the nuclei enter the third stage of prophase in meiosis. At the transition zone, the germline inner actin assumes a more cylindrical structure, becoming a hollow cylinder as it reaches the pachytene.The second layer of actin covers the inner layer, giving shape to the germline. This cylinder within a cylinder actin structure disappears toward the oocyte region, at which point the actin appears as thick fibers covering the oocytes. In the spermatheca, the actin also forms into thick bundles of fiber, although these fibers appear to be packed more closely together than in the oocyte region.Three-dimensional rendering of the proximal end of the germline, as demonstrated, reveals an average of 151 sperm in each spermatheca. Once mastered, this analysis can be completed in 10 minutes per germline. While attempting this procedure, it is important to remember to define the analysis parameters according to the magnification of the objective used to visualize the germline in your experiment.After watching this video, you should have a good understanding of how to perform an automatic analysis of a germline and to study cytoskeletal structure and to score the number of the nuclei within the germline.

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JoVE Journal

Developmental Biology

Comprehensive Assessment of Germline Chemical Toxicity Using the Nematode Caenorhabditis elegans

Comprehensive Assessment of Germline Chemical Toxicity Using the Nematode Caenorhabditis elegans

Identifying the reproductive toxicity of the thousands of chemicals present in our environment has been one of the most tantalizing challenges in the ...

Using Confocal Analysis of Xenopus laevis to Investigate Modulators of Wnt and Shh Morphogen Gradients

Using Confocal Analysis of Xenopus laevis to Investigate Modulators of Wnt and Shh Morphogen Gradients

This protocol describes a method to visualise ligands distributed across a field of cells. The ease of expressing exogenous proteins, together with the ...

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

Spatial and Temporal Analysis of Active ERK in the C. elegans Germline

The evolutionarily conserved&#160;extracellular signal transducing RTK-RAS-ERK pathway is an important kinase-signaling cascade that controls multiple ...

Isolation and Characterization of Primary Rat Valve Interstitial Cells: A New Model to Study Aortic Valve Calcification

Calcific aortic valve disease (CAVD) is characterized by the progressive thickening of the aortic valve leaflets. It is a condition frequently found in ...

Immobilization of Caenorhabditis elegans to Analyze Intracellular Transport in Neurons

Immobilization of Caenorhabditis elegans to Analyze Intracellular Transport in Neurons

Axonal transport and intraflagellar transport (IFT) are essential for axon and cilia morphogenesis and function. Kinesin superfamily proteins and dynein ...

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

Application of RNAi and Heat-shock-induced Transcription Factor Expression to Reprogram Germ Cells to Neurons in C. elegans

Studying the cell biological processes during converting the identities of specific cell types provides important insights into mechanism that maintain ...

Assessing Lysosomal Alkalinization in the Intestine of Live Caenorhabditis elegans

Assessing Lysosomal Alkalinization in the Intestine of Live Caenorhabditis elegans

The nematode Caenorhabditis elegans (C. elegans) is a model system that is widely used to study longevity and developmental pathways. Such studies are ...

Cell Cycle Analysis in the C. elegans Germline with the Thymidine Analog EdU

Cell Cycle Analysis in the C. elegans Germline with the Thymidine Analog EdU

Cell cycle analysis in eukaryotes frequently utilizes chromosome morphology, expression and/or localization of gene products required for various phases ...

Studying Oxidative Stress Caused by the Mitis Group Streptococci in Caenorhabditis elegans

Studying Oxidative Stress Caused by the Mitis Group Streptococci in Caenorhabditis elegans

Caenorhabditis elegans (C. elegans), a free-living nematode, has emerged as an attractive model to study host-pathogen interactions. The presented ...

Isotropic Light-Sheet Microscopy and Automated Cell Lineage Analyses to Catalogue Caenorhabditis elegans Embryogenesis with Subcellular Resolution

Caenorhabditis elegans (C. elegans) stands out as the only organism in which the challenge of understanding the cellular origins of an entire nervous ...