Both spore and sperm are created from other cells only after undergoing a complex process known as meiosis, in which a cell's DNA replicates and then undergoes two steps of division. Spore and sperm also have unique shapes relative to the cells that created them. In addition, two matured yeast spores can fuse to produce progeny just as sperm and egg fuse to produce offspring.

Spore and sperm are also both susceptible to being blocked in mid development, just before the cells from which they are produced undergo the first of the two divisions of their DNA. This interruption occurs at a stage of meiosis called pachytene and, in most cases, is temporary and beneficial, serving as a period during which the cell can repair any damage that may have occurred up to that point in development.

At least in human sperm, however, interruption can be permanent, preventing the further development of the cell--and thereby causing sterility, as in testicular maturation arrest.

In the UCSF study, the researchers determined that a gene, known as NDT80, plays a critical role in this pachytene stage of meiosis in yeast. They found that the NDT80 gene encodes the critical protein that acts to stimulate the synthesis of a set of proteins known as cyclins, which spark entry into DNA division. They also determined that the Ndt80 protein is responsible for the synthesis of another set of proteins, which contribute to the unique shape of the spore.

Finally, the authors showed that Ndt80 is itself controlled by a so-called "check point" protein called Rad17. Normally, check point proteins play the invaluable role of stalling further cell development when there are indications of damage, until repair has taken place. If a precursor cell's DNA has somehow accum
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Contact: Jennifer O'Brien
jobrien@itsa.ucsf.edu
(415) 476-2557
University of California - San Francisco
23-Apr-1998