Using long-term time-lapse imaging of mammalian cell cycle progression for laboratory instruction and analysis.

Video Microscopy Movies as a Teaching Tool for Cell Biology Laboratories Cinemicrography — the capture of moving cellular sequences through the microscope — has been influential in revealing the dynamic nature of cellular behavior (reviewed in Rose, 1963 ). Initially, cinemicrographic imaging was done using silver halide–based film, and these movies were instrumental in demonstrating the dramatic behavior of cell motility (Bajer and Bajer, 1972 ). Over the last 25 years, cell biology has benefited from improvements in electronic imaging technologies that have largely replaced silver-based film recordings. During the 1980s the use of analog video technology greatly expanded the use of light microscopy as an analytic tool (Inoue, 1986 ; Salmon, 1995 ). Over the last several years, the use of analog video-capture systems has been largely replaced by computer-based digital image-capture systems (Inoue and Spring, 1997 ; Sluder and Wolf, 2003 ). With their high quantum efficiency, low-noise characteristics, and ease of use, imaging systems for digital micrography have revolutionized the study of the dynamic events of cell biology. The recent advances in imaging technology have been coupled to improvements in photochemistry/photobiology, with the development of sophisticated molecular probes that have allowed the visualization of discrete molecules within living cells (Lippincott-Schwartz et al., 2001 ; Rieder and Khodjakov, 2003 ). The technological advances in these probes have allowed sophisticated molecular interactions to be studied at the level of the individual cell (Cardullo and Parpura, 2003 ). A major advance in the bioimaging field has been the discovery of green fluorescent protein (GFP; reviewed in Lippincott-Schwartz and Patterson, 2003 ), which allows individual proteins to be visualized and imaged. Chimeras made from any gene of interest coupled to GFP — and to genetically engineered chromatic variations of GFP — can be easily introduced into cultured cells as well as genetically tractable organisms such as yeast, flies, worms, and fish (Zhang et al., 2002 ; Haraguchi, 2002 ). More often than not, these GFP fusions retain their native biological activity while becoming fluorescently tagged. This technique has become a powerful tool for the investigation of the dynamics of individual proteins at the level of the single cell. In general, time-lapse digital microscopy provides an important tool for the instruction of students in a cell biology laboratory. The resultant image sequences portray the true nature of cellular processes and make it much easier for students to grasp the dynamics of these events. This is particularly true for movies of GFP-tagged proteins: they provide a direct way to assay for molecular interactions within the cell (Straight et al., 1996 ). But cinemicrographic sequences are not just pretty pictures; digital micrography sequences provide a wealth of analytical information that can be readily used by students in a laboratory course, even if equipped with only basic computer tools. Each student or group of students can be given the image file(s) and use inexpensive/free software to conduct very informative image analysis experiments (see analytical software tools developed by the Laboratory for Optical and Computational Instrumentation, LOCI, at the University of Wisconsin: http://www.loci.wisc.edu/ and the freeware program Image-J, developed by the NIH: http://rsb.info.nih.gov/ij/). Thus, a library of time-lapse image data is essential not only for demonstrating cellular processes but also to provide the basis for data interpretation and analysis by students in a laboratory course. It is ultimately these analytical skills that students need to acquire as they prepare for careers in research. Although some undergraduate laboratories are equipped to conduct cutting-edge, live-cell, time-lapse imaging, many are not. Setting up an imaging system to conduct these experiments can be problematic. The sophisticated equipment needed, although readily available, also comes with a substantial price tag. In addition, there is a certain amount of expertise necessary to conduct live-cell biology and maintain the imaging equipment. The use of simple laboratory organisms, such as the early embryos of marine invertebrates, fruit flies, or nematodes, can often circumvent these difficulties. A wealth of information can be obtained using invertebrate cells, and their culture and maintenance under the microscope are greatly simplified (Morris et al., 2004 ). These organisms are not only suited for teaching labs but also provide ideal experimental systems to be used with undergraduate research students as well as serving as the experimental organisms for big research labs in medical schools. However, if the laboratory is to use cultured mammalian cells for live-cell experiments, then the experimental needs and technical expertise increase (see Goldman and Spector, 2005 , for detailed methods on the imaging of living cells). An innovative solution to this problem is for the cell biology research field to provide digital image sequences as part of an increasingly available archive that can be utilized as part of a laboratory course. Cell Biology Education (CBE) has already begun this endeavor with the publication of the Video Views and Reviews series (see Watters, 2003 , and in this issue), which reviews annotated video files that exist in the Journal of Cell Biology collection and elsewhere. The use of movies published as part of research articles can be very beneficial to students, but not all great movies end up as part of peer-reviewed publications. In addition, movies submitted and archived by research journals are not always designed with the laboratory student in mind. The scope of the present article is to begin to provide novel, unpublished movies — along with a description of materials/methods, results, and discussion of the work — specifically for the CBE audience. If these movies become available to the cell biology community, even modest cell biology laboratory programs can begin to utilize this ever-increasing library of data to both demonstrate the movement of the cell and provide live-cell data to analyze in the laboratory.