Spatiotemporal Analysis of Cytokinetic Events in Fission Yeast

Summary

The fission yeast, Schizosaccharomyces pombe 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.

Abstract

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. pombe) 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.

Introduction

Cytokinesis, the final step in cell division, is a complex process essential for proper differentiation, development, and survival of an organism. Cytokinesis involves multiple events that are organized to ensure successful cell separation while maintaining genomic integrity¹. Cytokinesis involves events where an actomyosin ring once assembled undergoes constriction, which is concurrent with membrane expansion and furrowing, and extracellular cellular matrix remodeling, finally followed by cell abscission^1,2,3. Improper organization of cytokinetic even....

Protocol

1. Preparation of Sample

1. Grow fission yeast cells expressing the spindle pole body marker Sad1-mCherry²³ and type II myosin regulatory light chain Rlc1-Tomato²⁴ in YE liquid media at 32 °C for 8 generations.
   NOTE: For temperature sensitive mutants, grow cells at 25 °C. Grow cells to mid-log phase to an O.D.₆₀₀ of 0.5 in YE. For more on fission yeast growth conditions refer to the Fission yeast lab manual²⁵.
2. Prepare YE (or minimal) media with 0.6% agarose (Agarose based media show less fluorescent background in comparison to agar). To the melted med....

Results

Fission yeast cells expressing the ring marker, Rlc1-GFP (green, Figure 2) and spindle pole body marker Sad1-mCherry (red, Figure 2) were imaged during cytokinesis. Onset of spindle pole body marker (white arrow, Figures 2A, B) is considered as time 0. Rlc1-GFP signal appears at time -4 min with reference to spindle pole body separation (red arrow, Figures 2A, 2B). Rlc1-GFP signal forms a continuous ring 10 min post spindle pole body sepa.......

Discussion

Here we have described a protocol to study cytokinetic events in fission yeast in a temporal manner. The protocol described here provides temporal resolution of different cytokinetic events with reference to each other; timing of protein recruitment or loss with reference to cytokinetic phase; structure of the ring throughout the different phases of cytokinesis; and the progression of cytokinesis with reference to mitosis. With this protocol it is possible to precisely define the cytokinetic phase that may be altered in .......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Yeast extract media	Sunrise Science Products	YES 225	0.5% w/v yeast extract, 3% w/v glucose, 225mg/L adenine, histidine, leucine, uracil, and lysine
Agarose	SeaKem LE agarose, Lonza	50001
Ascorbic acid	Sigma-Aldrich	A4544
Glass Bottomed culture dish	MatTek Corporation	P35G-1.5-14-C	Coverslip No. 1.5 was used. This will vary as per the microscope specifications used.
VT-Hawk 2D array laser scanning confocal microscopy system	Visitech International, UK		with an Olympus IX-83 inverted microscope with a 100X / numerical aperture 1.49 UAPO lens (Olympus) and EM-CCD digital camera (Hamamatsu).
ImageJ	NIH		Image analysis software