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Cell biology – technical details cont.

In yesterday’s post, we posed the technical question – when visualizing a population of cells, how can one discriminate between cells that are about to undergo cell division and single cells that happen to be so close together that they give the impression of being a cell in the process of cell division?

One of the answers is to include an indicator that can discriminate between these two categories, i.e. measure another experimental parameter in addition to shape. One such indicator would be a nuclear marker. In our example, a nuclear marker gives the following image:

cells nuclear marker

The nuclear marker in this image is a nuclear protein that is tagged with an endogenous fluorescent reporter, red fluorescent protein. Of course, for this experiment a simple compound microscope won’t do, this image was taken with a fluorescent microscope. However it does allow us to identify the top image as a cell en route to cell division, and the bottom cell is two independent cells lying next to each other on the microscope slide. Here’s the fluorescent image superimposed on the cell shape image  with a schematic on the right for clearer visualization:

cells overlay schematic

In the top picture, the single nucleus lies in between between the mother and the daughter cells in preparation for cell division. The bottom picture shows the two individual nuclei of two separate cells.

Examining a biological specimen with a compound microscope is one of the classic experiments of cell biology, first performed by Leeuwenhoek in the 17th century. Some readers may be wondering how relevant this kind of experiment could be in the 21st century. Check out this figure from the journal Nature in 2002.

FIGURE 5. The seven phenotypic categories of deletion mutant morphologies

From the following article:


Functional profiling of the Saccharomyces cerevisiae genome (2002) Giaever et al. Nature 418: 387-391


Figure 5 Nature

The advent of genomic information and high-throughput technologies is leading to many efforts to categorize gene function, in this particular instance, the genes involved in specifying cell shape and size have been identified by a straightforward microscopic examination of cell cultures, each one containing a deletion of a specific gene. Leeuwenhoek would be proud.

    

      

        

          February 19, 2010          | category:
          cell biology        

      

      

        
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