The authors would like to thank Natalia La Fourcade and Mon LaFerte for making the preparation of this manuscript a more enjoyable endeavor. Thanks to members of the Forsburg Lab who contributed to the completion of this work with their insight, experiment ideas, and moral support. This project was supported by NIGMS R35 GM118109 to SLF.

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The authors have nothing to disclose.

Live-cell imaging during mitosis and meiosis offers the opportunity to examine nuclear dynamics without substantially disrupting fission yeast physiology during data acquisition. However, caution must be exercised to ensure cells grow to the desired densities free of environmental stresses; and for meiosis, that the cells are imaged during the time of terminal differentiation and not too early or late. Excess cellular crowding, starvation, and inappropriate growth temperatures are common factors that contribute to irreproducible observations. In addition, during strain construction, it is crucial to test that fluorescent tags do not interfere with the functions of target genes nor impact overall cell fitness. Failure to closely inspect the phenotypes of strains carrying fluorescent markers may result in inconsistent and incomparable results across similar genotypes.
Though microscope agarose pads are simple to assemble, they can also pose a hurdle in obtaining valuable imaging data. Creating agarose pads is as simple as placing three microscope slides parallel to each other, dispensing molten agarose on the middle slide, and putting a slide that transverses the top of the other slides. It is useful, however, to assemble a slide-maker apparatus that allows for width modifications to manufacture resistant, situation-specific agarose pads. A simple slide-maker that gives pad width flexibility consists of a platform (pipette tips holder or the bench), two microscope slides, and lab tape acting as the pad-width adjusting mechanism (Figure 1A). Exact pad thickness will depend on imaging time requirements, agarose brand, temperature, coverslip sealant, evaporation rate, etc. Thus, it is important to calibrate the imaging system before data acquisition to increase technical reproducibility and to enhance the quality of live-cell imaging1,2,3. Pad surface, rigidity, and composition are essential during prolonged image acquisition. Agarose has low background fluorescence, can be easily molded, and at the appropriate concentration, withstands structural deformation due to evaporation. Moreover, combining fission yeast media with agarose does not compromise image quality and allows for extended observation of multiple mitoses and meiosis cycles. Also, it is important to avoid any air bubbles for time-lapse microscopy. Inside agarose pads and within the sample, air pockets expand over time, causing cell-shifting and disrupting focal planes. Provided cells are efficiently spread apart by coverslip rotation, researchers can follow mitotic processes across several generations and meiotic events from nuclear fusion to sporulation. Making and choosing the right pad for imaging experiments takes time to master, but once achieved, can contribute to highly informative microscope observations.
As is the case with other methods, live-cell microscopy is not free of technical limitations. The use of fluorescently-tagged proteins introduces boundaries to experiments that limit the scope of what can be studied. Photo-bleaching and photo-toxicity are problems typical of prolonged image acquisition. They can be counteracted by not exposing cells to short wavelengths for too long or too frequently. For experiments involving GFP, CFP, YFP, mRFP, and DsRed, typical fluorescent proteins used in fission yeast live-cell imaging, it is common to employ 5-15% excitation light and 100-500 ms exposure time for routine experiments. These parameters change, however, according to the specific experiment requirements of the researcher. In addition, z-stacks comprised of 9-13 sections with 0.5 &#181;m spacing using a 60x objective is enough to resolve the thickness of a fission yeast cell. Moreover, it is important to confirm that fluorescent markers do not disrupt proper regulation or function of target proteins or generate spurious phenotypes. Thus, it is advisable to construct strains containing different fluorescent and affinity tags for the same target gene to corroborate observations by different means. Furthermore, it is the responsibility of researchers to ensure that experimental parameters can be reproduced across experiments and that the collected data is fit for downstream analysis1,3. No technology can replace the time-tested practice of meticulously validating experimental systems by careful observation and rigorous examination of linearity in detecting fluorescent signals.
Finally, it is crucial to analyze microscopy data in formats that do not modify raw images. Fiji provides excellent documentation tools to keep track of raw data measurements and allows researchers to examine different cell parameters in a single session. These features, as well as its wealth of online tutorials and extensive literature coverage, make Fiji an important tool for measuring, analyzing, and presenting live cell imaging data that describe the nuclear dynamics of fission yeast in mitosis and meiosis.

Live-cell microscopy allows researchers to examine nuclear dynamics without killing fission yeast cells and eliminates the need for lethal fixatives and stains. It is possible to observe the stability, movement, localization, and timing of fluorescently tagged proteins that are involved in important events such as chromosome replication, recombination, and segregation, in addition to the membrane and cytoskeletal movements. By maintaining cell viability and non-toxic signal detection, there is minimal physiological intrusion. When performed properly, this microscopy method can reduce confounding effects that arise from the extended technical handling or from spurious chemical reactivity. Furthermore, during an experiment, researchers can make pertinent observations of fission yeast nutritional and stress states, proliferative efficiency, and apoptotic status that indicate inappropriate imaging parameters or abnormal cell physiology1,2,3.
Mitosis and meiosis are characterized by nuclear and cellular division. In meiosis, contrary to mitosis, genetic content is halved as parent cells give rise to daughter cells4. Because live-cell imaging provides a temporal dimension in addition to the spatial relationship, large numbers of cells can be examined in real-time. Live-cell microscopy has enabled researchers to examine the dynamics of nuclear division using fluorescent tags for histones5, cohesin subunits6, microtubules7, centromeres8, kinetochores9, components of the spindle pole body (SPB)10, and those of the chromosome passenger complex (CPC)11. Outside of the chromosome segregation apparatus, live-cell imaging has also captured the behavior of proteins necessary, but not directly involved in chromosome segregation. The function of these proteins has been shown to influence replication, chromosome recombination, nuclear movement, and chromosome attachment to microtubules12,13,14. These observations have contributed to a better understanding of cellular events whose functional components were not amenable to biochemical or genetic examination. With new advances in microscopy technology, limitations such as poor resolution, photobleaching, phototoxicity, and focus stability will lessen, thereby facilitating better real-time observations of mitotic and meiotic nuclear dynamics1,2,3. Meiosis is particularly challenging as it is a terminal differentiation pathway that requires close attention to timing.
The goal of this protocol is to present a relatively simple method for examining real-time fission yeast nuclear dynamics in mitosis and meiosis. To accomplish this, it is necessary to use cells that have not been exposed to environmental stress, prepare agarose pads that can withstand prolonged imaging, and mount cells at densities that facilitate visualization of single-cell dynamics. Moreover, this protocol makes use of cells carrying fluorescently tagged proteins that serve as useful markers for nuclear kinetics (Hht1-mRFP or Hht1-GFP), chromosome segregation (Sad1-DsRed), cytoskeleton dynamics (Atb2-mRFP), transcriptional activation in G1/S (Tos4-GFP), and cohesion stability in meiosis (Rec8-GFP). This method also introduces additional nuclear and cytosolic markers (Table I) that can be used in different combinations to address questions about specific cellular processes. Furthermore, basic Fiji tools are featured to help researchers process live-cell images and analyze different types of data. The strength of this approach stems from the use of real-time observations of protein dynamics, timing, and stability to describe processes that are integral for the proper execution of mitosis and meiosis.

<table>
	<tbody>
		<tr>
			<td>60x Plan Apochromat objective lens</td>
			<td>Olympus</td>
			<td>AMEP4694</td>
			<td></td>
		</tr>
		<tr>
			<td>Adenine</td>
			<td>Sigma</td>
			<td>A-8751</td>
			<td></td>
		</tr>
		<tr>
			<td>Agar</td>
			<td>7558B</td>
			<td>IB4917-10 kg</td>
			<td></td>
		</tr>
		<tr>
			<td>Agarose</td>
			<td>Sigma</td>
			<td>A9539-500g</td>
			<td></td>
		</tr>
		<tr>
			<td>Belly Dancer rotator</td>
			<td>Stovall</td>
			<td>US Patent #4.702.610</td>
			<td></td>
		</tr>
		<tr>
			<td>Biotin</td>
			<td>Sigma</td>
			<td>B-4501</td>
			<td></td>
		</tr>
		<tr>
			<td>Boric acid</td>
			<td>Sigma</td>
			<td>B-6768-5kg</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2&#183;2H20,</td>
			<td>Sigma</td>
			<td>C3306-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>Citric acid</td>
			<td>Sigma</td>
			<td>C-0759</td>
			<td></td>
		</tr>
		<tr>
			<td>Convolve 3D software plug-in</td>
			<td>OptiNav, Inc.</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>CoolSnap HQ CCD camera</td>
			<td>Roper</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>Cover slip</td>
			<td>VWR</td>
			<td>16004-302</td>
			<td></td>
		</tr>
		<tr>
			<td>CuSO4&#183;5H20,</td>
			<td>END</td>
			<td>CX-2185-1</td>
			<td></td>
		</tr>
		<tr>
			<td>DeltaVision deconvolution fluorescence microscope</td>
			<td>GE Healthcare/Applied Precision</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>Diffraction PSF 3D software plug-in</td>
			<td>OptiNav, Inc.</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>Edinburgh minimal medium (EMM) Notrogen</td>
			<td>Sunrise</td>
			<td>2023;1kg</td>
			<td></td>
		</tr>
		<tr>
			<td>FeCl2&#183;6H2O</td>
			<td>END</td>
			<td>FX9259-04</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose</td>
			<td>Sigma</td>
			<td>G-7021</td>
			<td></td>
		</tr>
		<tr>
			<td>Heat plate</td>
			<td>Barnstead</td>
			<td>Thermo Lyne</td>
			<td></td>
		</tr>
		<tr>
			<td>Histidine</td>
			<td>Sigma</td>
			<td>H8125-100g</td>
			<td></td>
		</tr>
		<tr>
			<td>Huygens deconvolution software</td>
			<td>SVI</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>Imaris deconvolution software</td>
			<td>Bitplane</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator</td>
			<td>Shell lab</td>
			<td>#3015</td>
			<td></td>
		</tr>
		<tr>
			<td>Inositol</td>
			<td>Sigma</td>
			<td>I-5125</td>
			<td></td>
		</tr>
		<tr>
			<td>Iterative Deconvolve 3D software plug-in</td>
			<td>OptiNav, Inc.</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Mallinckvadt</td>
			<td>6858-04</td>
			<td></td>
		</tr>
		<tr>
			<td>Lanolin</td>
			<td>Sigma</td>
			<td>L7387-1kg</td>
			<td></td>
		</tr>
		<tr>
			<td>Leucine</td>
			<td>Sigma</td>
			<td>L8912-100g</td>
			<td></td>
		</tr>
		<tr>
			<td>Lysine</td>
			<td>Sigma</td>
			<td>L5626-500g</td>
			<td></td>
		</tr>
		<tr>
			<td>Malt extract (ME)</td>
			<td>MP</td>
			<td>4103-032</td>
			<td></td>
		</tr>
		<tr>
			<td>MgCl2&#183;6H20</td>
			<td>AMRESCO</td>
			<td>0288-500G</td>
			<td></td>
		</tr>
		<tr>
			<td>MetaMorph</td>
			<td>Molecular Devices</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>Microscope slides</td>
			<td>VWR</td>
			<td>16004-422</td>
			<td></td>
		</tr>
		<tr>
			<td>MnSO4,</td>
			<td>Mallinckvadt</td>
			<td>6192-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Molybdic acid</td>
			<td>Sigma</td>
			<td>M-0878</td>
			<td></td>
		</tr>
		<tr>
			<td>Na2S04</td>
			<td>Mallinckvadt</td>
			<td>8024-03</td>
			<td></td>
		</tr>
		<tr>
			<td>Nicotinic acid,</td>
			<td>Sigma</td>
			<td>N-4126</td>
			<td></td>
		</tr>
		<tr>
			<td>Pantothenic acid</td>
			<td>Sigma</td>
			<td>P-5161</td>
			<td></td>
		</tr>
		<tr>
			<td>Paraffin wax</td>
			<td>Fisher</td>
			<td>s80119WX</td>
			<td></td>
		</tr>
		<tr>
			<td>Pombe glutamate medium (PMG)</td>
			<td>Sunrise</td>
			<td>2060-250</td>
			<td></td>
		</tr>
		<tr>
			<td>softWorx v3.3 image processing software</td>
			<td>GE Healthcare</td>
			<td>n/a</td>
			<td></td>
		</tr>
		<tr>
			<td>Sporulation Medium powder</td>
			<td>Sunrise</td>
			<td>1821-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Temperature controlled centrifuge</td>
			<td>Beckman</td>
			<td>Allwgra 6KR xentrifuge</td>
			<td></td>
		</tr>
		<tr>
			<td>Uracil</td>
			<td>AMRESCO</td>
			<td>0847-500g</td>
			<td></td>
		</tr>
		<tr>
			<td>Vaseline</td>
			<td>Equaline</td>
			<td>F79658</td>
			<td></td>
		</tr>
		<tr>
			<td>yeast extract</td>
			<td>EMD</td>
			<td>1.03753.0500</td>
			<td></td>
		</tr>
		<tr>
			<td>Yeast extract plus supplements (YES)</td>
			<td>Sunrise</td>
			<td>2011-1kg</td>
			<td></td>
		</tr>
		<tr>
			<td>ZnSO4&#183;7H2O</td>
			<td>J.T.Baker</td>
			<td>4382-04</td>
			<td></td>
		</tr>
	</tbody>
</table>

examination of mitotic and meiotic fission yeast nuclear dynamics by fluorescence live-cell microscopy

Live-cell imaging is a microscopy technique used to examine cell and protein dynamics in living cells. This imaging method is not toxic, generally does not interfere with cell physiology, and requires minimal experimental handling. The low levels of technical interference enable researchers to study cells across multiple cycles of mitosis and to observe meiosis from beginning to end. Using fluorescent tags such as Green Fluorescent Protein (GFP) and Red Fluorescent Protein (RFP), researchers can analyze different factors whose functions are important for processes like transcription, DNA replication, cohesion, and segregation. Coupled with data analysis using Fiji (a free, optimized ImageJ version), live-cell imaging offers various ways of assessing protein movement, localization, stability, and timing, as well as nuclear dynamics and chromosome segregation. However, as is the case with other microscopy methods, live-cell imaging is limited by the intrinsic properties of light, which put a limit to the resolution power at high magnifications, and is also sensitive to photobleaching or phototoxicity at high wavelength frequencies. However, with some care, investigators can bypass these physical limitations by carefully choosing the right conditions, strains, and fluorescent markers to allow for the appropriate visualization of mitotic and meiotic events.

Watch this Scientific Journal Video about Examination of Mitotic and Meiotic Fission Yeast Nuclear Dynamics by Fluorescence Live-cell Microscopy at JoVE.com

Examination of Mitotic and Meiotic Fission Yeast Nuclear Dynamics by Fluorescence Live-cell Microscopy

Here, we present live-cell imaging which is a non-toxic microscopy method that allows researchers to study protein behavior and nuclear dynamics in living fission yeast cells during mitosis and meiosis.

Live-cell imaging is a microscopy technique used to examine cell and protein dynamics in living cells. This imaging method is not toxic, generally does ...

examination-mitotic-meiotic-fission-yeast-nuclear-dynamics

Research

JoVE Journal

Biology

9.4K Views.  University of Southern California. Here, we present live-cell imaging which is a non-toxic microscopy method that allows researchers to study protein behavior and nuclear dynamics in living fission yeast cells during mitosis and meiosis.

Video: Examination of Mitotic and Meiotic Fission Yeast Nuclear Dynamics by Fluorescence Live-cell Microscopy

Live Cell Imaging of F-actin Dynamics via Fluorescent Speckle Microscopy (FSM)

In this protocol we describe the use of Fluorescent Speckle Microscopy (FSM) to capture high-resolution images of actin dynamics in PtK1 cells. A unique advantage of FSM is its ability to capture the movement and turnover kinetics (assembly/disassembly) of the F-actin network within living cells. This technique is particularly useful in deriving quantitative measurements of F-actin dynamics when paired with computer vision software (qFSM).  We describe  the selection, microinjection and visualization of fluorescent actin probes in living cells. Importantly, similar procedures are applicable to visualizing other macomolecular assemblies. FSM has been demonstrated for microtubules, intermediate filaments, and adhesion complexes.  

Live Cell Imaging of F-actin Dynamics via Fluorescent Speckle Microscopy FSM

Selection, microinjection, and imaging of fluorescently-labeled F-actin via fluorescent speckle microscopy (FSM).

In this protocol we describe the use of Fluorescent Speckle Microscopy (FSM) to capture high-resolution images of actin dynamics in PtK1 cells. A unique ...

Time-lapse Imaging of Mitosis After siRNA Transfection

Changes in cellular organization and chromosome dynamics that occur during mitosis are tightly coordinated to ensure accurate inheritance of genomic and cellular content. Hallmark events of mitosis, such as chromosome movement, can be readily tracked on an individual cell basis using time-lapse fluorescence microscopy of mammalian cell lines expressing specific GFP-tagged proteins. In combination with RNAi-based depletion, this can be a powerful method for pinpointing the stage(s) of mitosis where defects occur after levels of a particular protein have been lowered. In this protocol, we present a basic method for assessing the effect of depleting a potential mitotic regulatory protein on the timing of mitosis. Cells are transfected with siRNA, placed in a stage-top incubation chamber, and imaged using an automated fluorescence microscope. We describe how to use software to set up a time-lapse experiment, how to process the image sequences to make either still-image montages or movies, and how to quantify and analyze the timing of mitotic stages using a cell-line expressing mCherry-tagged histone H2B. Finally, we discuss important considerations for designing a time-lapse experiment. This strategy is complementary to other approaches and offers the advantages of 1) sensitivity to changes in kinetics that might not be observed when looking at cells as a population and 2) analysis of mitosis without the need to synchronize the cell cycle using drug treatments. The visual information from such imaging experiments not only allows the sub-stages of mitosis to be assessed, but can also provide unexpected insight that would not be apparent from cell cycle analysis by FACS.

Here we describe a basic protocol to image and quantify the mitotic timing of live mammalian tissue culture cells after siRNA transfection.

Changes in cellular organization and chromosome dynamics that occur during mitosis are tightly coordinated to ensure accurate inheritance of genomic and ...

A Fluorescence Microscopy Assay for Monitoring Mitophagy in the Yeast Saccharomyces cerevisiae

Autophagy is important for turnover of cellular components under a range of different conditions. It serves an essential homeostatic function as well as a quality control mechanism that can target and selectively degrade cellular material including organelles1-4. For example, damaged or redundant mitochondria (Fig. 1), not disposed of by autophagy, can represent a threat to cellular homeostasis and cell survival. In the yeast, Saccharomyces cerevisiae, nutrient deprivation (e.g., nitrogen starvation) or damage can promote selective turnover of mitochondria by autophagy in a process termed mitophagy 5-9.
We describe a simple fluorescence microscopy approach to assess autophagy. For clarity we restrict our description here to show how the approach can be used to monitor mitophagy in yeast cells. The assay makes use of a fluorescent reporter, Rosella, which is a dual-emission biosensor comprising a relatively pH-stable red fluorescent protein linked to a pH-sensitive green fluorescent protein. The operation of this reporter relies on differences in pH between the vacuole (pH ~ 5.0-5.5) and mitochondria (pH ~ 8.2) in living cells. Under growing conditions, wild type cells exhibit both red and green fluorescence distributed in a manner characteristic of the mitochondria. Fluorescence emission is not associated with the vacuole. When subjected to nitrogen starvation, a condition which induces mitophagy, in addition to red and green fluorescence labeling the mitochondria, cells exhibit the accumulation of red, but not green fluorescence, in the acidic vacuolar lumen representing the delivery of mitochondria to the vacuole. Scoring cells with red, but not green fluorescent vacuoles can be used as a measure of mitophagic activity in cells5,10-12.

A Fluorescence Microscopy Assay for Monitoring Mitophagy in the Yeast Saccharomyces cerevisiae

A robust approach to monitor the delivery of organelles to the acidic lumen of the yeast vacuole for degradation and recycling is described. The method relies on the specific labeling of target organelles with a genetically encoded dual-emission fluorescence pH-biosensor, and visualization of individual cells using fluorescence microscopy.

Autophagy is important for turnover of cellular components under a range of different conditions. It serves an essential homeostatic function as well as a ...

Quantitative Live Cell Fluorescence-microscopy Analysis of Fission Yeast

Several microscopy techniques are available today that can detect a specific protein within the cell. During the last decade live cell imaging using fluorochromes like Green Fluorescent Protein (GFP) directly attached to the protein of interest has become increasingly popular 1. Using GFP and similar fluorochromes the subcellular localisations and movements of proteins can be detected in a fluorescent microscope. Moreover, also the subnuclear localisation of a certain region of a chromosome can be studied using this technique. GFP is fused to the Lac Repressor protein (LacR) and ectopically expressed in the cell where tandem repeats of the lacO sequence has been inserted into the region of interest on the chromosome2. The LacR-GFP will bind to the lacO repeats and that area of the genome will be visible as a green dot in the fluorescence microscope. Yeast is especially suited for this type of manipulation since homologous recombination is very efficient and thereby enables targeted integration of the lacO repeats and engineered fusion proteins with GFP 3. Here we describe a quantitative method for live cell analysis of fission yeast. Additional protocols for live cell analysis of fission yeast can be found, for example on how to make a movie of the meiotic chromosomal behaviour 4. In this particular experiment we focus on subnuclear organisation and how it is affected during gene induction. We have labelled a gene cluster, named Chr1, by the introduction of lacO binding sites in the vicinity of the genes. The gene cluster is enriched for genes that are induced early during nitrogen starvation of fission yeast 5. In the strain the nuclear membrane (NM) is labelled by the attachment of mCherry to the NM protein Cut11 giving rise to a red fluorescent signal. The Spindle Pole body (SPB) compound Sid4 is fused to Red Fluorescent Protein (Sid4-mRFP) 6. In vegetatively growing yeast cells the centromeres are always attached to the SPB that is embedded in the NM 7. The SPB is identified as a large round structure in the NM. By imaging before and 20 minutes after depletion of the nitrogen source we can determine the distance between the gene cluster (GFP) and the NM/SPB. The mean or median distances before and after nitrogen depletion are compared and we can thus quantify whether or not there is a shift in subcellular localisation of the gene cluster after nitrogen depletion.

The fission yeast, Schizosaccharomyces pombe, is a good model system to study basic cellular processes. Here we describe a method to perform quantitative live cell analysis of fission yeast. In this particular experiment we focus on organisation of the genome within the cell nucleus, but the method can also be used to study cytosolic factors.

Several microscopy techniques are available today that can detect a specific protein within the cell. During the last decade live cell imaging using ...

Acquiring Fluorescence Time-lapse Movies of Budding Yeast and Analyzing Single-cell Dynamics using GRAFTS

Fluorescence time-lapse microscopy has become a powerful tool in the study of many biological processes at the single-cell level. In particular, movies depicting the temporal dependence of gene expression provide insight into the dynamics of its regulation; however, there are many technical challenges to obtaining and analyzing fluorescence movies of single cells. We describe here a simple protocol using a commercially available microfluidic culture device to generate such data, and a MATLAB-based, graphical user interface (GUI) -based software package to quantify the fluorescence images. The software segments and tracks cells, enables the user to visually curate errors in the data, and automatically assigns lineage and division times. The GUI further analyzes the time series to produce whole cell traces as well as their first and second time derivatives. While the software was designed for S. cerevisiae, its modularity and versatility should allow it to serve as a platform for studying other cell types with few modifications.

We present a simple protocol to obtain fluorescence microscopy movies of growing yeast cells, and a GUI-based software package to extract single-cell time series data. The analysis includes automated lineage and division time assignment integrated with visual inspection and manual curation of tracked data.

Fluorescence time-lapse microscopy has become a powerful tool in the study of many biological processes at the single-cell level. In particular, movies ...

Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy

Cell shape is critical for cell function. However, despite the importance of cell morphology, little is known about how individual cells generate specific shapes. Drosophila tracheal terminal cells have become a powerful genetic model to identify and elucidate the roles of genes required for generating cellular morphologies. Terminal cells are a component of a branched tubular network, the tracheal system that functions to supply oxygen to internal tissues. Terminal cells are an excellent model for investigating questions of cell shape as they possess two distinct cellular architectures. First, terminal cells have an elaborate branched morphology, similar to complex neurons; second, terminal cell branches are formed as thin tubes and contain a membrane-bound intracellular lumen. Quantitative analysis of terminal cell branch number, branch organization and individual branch shape, can be used to provide information about the role of specific genetic mechanisms in the making of a branched cell. Analysis of tube formation in these cells can reveal conserved mechanisms of tubulogenesis common to other tubular networks, such as the vertebrate vasculature. Here we describe techniques that can be used to rapidly fix, image, and analyze both branching patterns and tube formation in terminal cells within Drosophila larvae. These techniques can be used to analyze terminal cells in wild-type and mutant animals, or genetic mosaics. Because of the high efficiency of this protocol, it is also well suited for genetic, RNAi-based, or drug screens in the Drosophila tracheal system.

Examination of Drosophila Larval Tracheal Terminal Cells by Light Microscopy

Here, we present a method for light microscopy analysis of tracheal terminal cells in Drosophila larvae. This method allows for quick examination of branch and lumen morphology in whole animals and would be useful for analysis of individual mutants or screens for mutations affecting terminal cell development.

Cell shape is critical for cell function. However, despite the importance of cell morphology, little is known about how individual cells generate specific ...

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) maintain the turnover of all mature blood cell lineages. The coordination of the complex signals leading to specific HSC fates relies upon the interaction between HSCs and the intricate bone marrow microenvironment, which is still poorly understood[1-2].
We describe how by combining a newly developed specimen holder for stable animal positioning with multi-step confocal and two-photon in vivo imaging techniques, it is possible to obtain high-resolution 3D stacks containing HSPCs and their surrounding niches and to monitor them over time through multi-point time-lapse imaging. High definition imaging allows detecting ex vivo labeled hematopoietic stem and progenitor cells (HSPCs) residing within the bone marrow. Moreover, multi-point time-lapse 3D imaging, obtained with faster acquisition settings, provides accurate information about HSPC movement and the reciprocal interactions between HSPCs and stroma cells.
Tracking of HSPCs in relation to GFP positive osteoblastic cells is shown as an exemplary application of this method. This technique can be utilized to track any appropriately labeled hematopoietic or stromal cell of interest within the mouse calvarium bone marrow space.

In Vivo 4-Dimensional Tracking of Hematopoietic Stem and Progenitor Cells in Adult Mouse Calvarial Bone Marrow

The nature of the interactions between hematopoietic stem and progenitor cells (HSPCs) and bone marrow niches is poorly understood. Custom hardware modifications and a multi-step acquisition protocol allow the use of two-photon and confocal microscopy to image ex vivo labeled HSPCs homed within bone marrow areas, tracking interactions and movement.

Through a delicate balance between quiescence and proliferation, self renewal and production of differentiated progeny, hematopoietic stem cells (HSCs) ...

Microscopy of Fission Yeast Sexual Lifecycle

The fission yeast Schizosaccharomyces pombe has been an invaluable model system in studying the regulation of the mitotic cell cycle progression, the mechanics of cell division and cell polarity. Furthermore, classical experiments on its sexual reproduction have yielded results pivotal to current understanding of DNA recombination and meiosis. More recent analysis of fission yeast mating has raised interesting questions on extrinsic stimuli response mechanisms, polarized cell growth and cell-cell fusion. To study these topics in detail we have developed a simple protocol for microscopy of the entire sexual lifecycle. The method described here is easily adjusted to study specific mating stages. Briefly, after being grown to exponential phase in a nitrogen-rich medium, cell cultures are shifted to a nitrogen-deprived medium for periods of time suited to the stage of the sexual lifecycle that will be explored. Cells are then mounted on custom, easily built agarose pad chambers for imaging. This approach allows cells to be monitored from the onset of mating to the final formation of spores.

We provide a reproducible basic method for the long-term microscopy of the fission yeast sexual lifecycle. With minor adjustments described, the presented protocol allows research focus on different steps of the reproductive process.

The fission yeast Schizosaccharomyces pombe has been an invaluable model system in studying the regulation of the mitotic cell cycle progression, the ...

Spatiotemporal Analysis of Cytokinetic Events in Fission Yeast

Cytokinesis, the final step in cell division is critical for maintaining genome integrity. Proper cytokinesis is important for cell differentiation and development. Cytokinesis involves a series of events that are well coordinated in time and space. Cytokinesis involves the formation of an actomyosin ring at the division site, followed by ring constriction, membrane furrow formation and extra cellular matrix remodeling. The fission yeast, Schizosaccharomyces pombe (S.&#160;pombe)&#160;is a well-studied model system that has revealed with substantial clarity the initial events in cytokinesis. However, we do not understand clearly how different cytokinetic events are coordinated spatiotemporally. To determine this, one needs to analyze the different cytokinetic events in great details in both time and in space. Here we describe a microscopy approach to examine different cytokinetic events in live cells. With this approach it is possible to time different cytokinetic events and determine the time of recruitment of different proteins during cytokinesis. In addition, we describe protocols to compare protein localization, and distribution at the site of cell division. This is a basic protocol to study cytokinesis in fission yeast and can also be used for other yeasts and fungal systems.

The fission yeast, Schizosaccharomyces pombe&#160;is an excellent model system to study cytokinesis, the final stage in cell division. Here we describe a microscopy approach to analyze different cytokinetic events in live fission yeast cells.

Cytokinesis, the final step in cell division is critical for maintaining genome integrity. Proper cytokinesis is important for cell differentiation and ...

Live Cell Fluorescence Microscopy to Observe Essential Processes During Microbial Cell Growth

Core cellular processes such as DNA replication and segregation, protein synthesis, cell wall biosynthesis, and cell division rely on the function of proteins which are essential for bacterial survival. A series of target-specific dyes can be used as probes to better understand these processes. Staining with lipophilic dyes enables the observation of membrane structure, visualization of lipid microdomains, and detection of membrane blebs. Use of fluorescent-d-amino acids (FDAAs) to probe the sites of peptidoglycan biosynthesis can indicate potential defects in cell wall biogenesis or cell growth patterning. Finally, nucleic acid stains can indicate possible defects in DNA replication or chromosome segregation. Cyanine DNA stains label living cells and are suitable for time-lapse microscopy enabling real-time observations of nucleoid morphology during cell growth. Protocols for cell labeling can be applied to protein depletion mutants to identify defects in membrane structure, cell wall biogenesis, or chromosome segregation. Furthermore, time-lapse microscopy can be used to monitor morphological changes as an essential protein is removed and can provide additional insights into protein function. For example, the depletion of essential cell division proteins results in filamentation or branching, whereas the depletion of cell growth proteins may cause cells to become shorter or rounder. Here, protocols for cell growth, target-specific labeling, and time-lapse microscopy are provided for the bacterial plant pathogen Agrobacterium tumefaciens. Together, target-specific dyes and time-lapse microscopy enable characterization of essential processes in A. tumefaciens. Finally, the protocols provided can be readily modified to probe essential processes in other bacteria.

Understanding the function of essential processes in bacteria is challenging. Fluorescence microscopy with target-specific dyes can provide key insights into microbial cell growth and cell cycle progression. Here, Agrobacterium tumefaciens is used as a model bacterium to highlight methods for live cell imaging for characterization of essential processes.

Core cellular processes such as DNA replication and segregation, protein synthesis, cell wall biosynthesis, and cell division rely on the function of ...