The question interesting the UCSF researchers is whether there is a molecular pathway in the creation of human sperm that is similar to the one they have observed in yeast. And, if so, whether a human equivalent to Ndt80 or Rad17 might be involved in progression through the pachytene stage of sperm development.
Other research groups have reported a burst in cyclin synthesis at the pachytene stage of meiosis in both fly and mouse that resembles the actions of Ndt80. This suggests, say the UCSF researchers, that an equivalent gene may have been conserved throughout evolution.
Moreover, there is some question as to whether NDT80 may parallel, in some aspects, a set of genes known as DAZ, which are found on the human Y, or male, chromosome. Both the NDT80 gene in yeast, and DAZ genes in men, are required for development beyond the pachytene stage in spore and sperm, respectively.
Previous research conducted by UCSF's human male infertility researcher Reijo and co-workers showed that the DAZ genes are deleted in 13 percent of infertile men, and in many of these men sperm development is permanently arrested--again, at the pachytene stage of meiosis.
"There are probably hundreds of yet to be discovered genes involved in
the creation of human sperm," says Reijo, "and we're not saying DAZ and NDT80
are the same genes or that DAZ is regulated by the equivalent of Rad17, but
since there's pachytene arrest in both, we may be on to something."
"Their work makes me even more curious about what is regulating DAZ," says
Reijo. "I think now we can put together the spermatogenesis
Contact: Jennifer O'Brien
University of California - San Francisco