Jackson's Bob Braun and collaborators report new insights in sperm formation

Date: April 2, 2010
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Bar Harbor, Maine -- In research that could have important implications for understanding male infertility as well as novel approaches to a male contraceptive, Jackson Laboratory Professor Bob Braun, Ph.D., with colleagues in Japan, showed that there's more than one way a man's body can make a sperm.

"In a single heartbeat, a man produces 1,500 sperm cells," says Braun, noting that this is a feat that requires a very robust stem cell system. "We formerly believed that sperm formation followed a one-way path of specialization from stem cells to mature sperm. Instead, we've found that there are multiple, and reversible, paths from stem cell to differentiation."

Braun and colleagues utilized live imaging and lineage analysis techniques to find that, instead of a homogenous stem cell population, it is a smaller subpopulation of single spermatogonia that exist as the normal stem cell pool. However, that is not the only store of stem cells. Intermediate germ cells--somewhere between stem cell and sperm--can serve as another stem cell pool, for example, in conditions of tissue damage and regeneration. Hence, the fate of differentiating spermatagonial populations is not set in stone and can be reversible.

According to Braun, the results were unexpected. "These findings improve our understanding of how sperm cells are generated from stem cells, but also lend more mystery to the question of what a stem cell really is."

Braun, a reproductive biologist who is also associate director of The Jackson Laboratory for research, collaborated with researchers at Kyoto University, the Graduate University for Advanced Studies in Okazaki, and the National Institutes for Natural Sciences in Okazaki. Their research was published in the April 2 edition of the journal Science, and on the Science Express website on March 18.

The Jackson Laboratory is an independent, nonprofit biomedical research institution based in Bar Harbor, Maine, with a facility in Sacramento, Calif. Its mission is to discover the genetic basis for preventing, treating and curing human diseases, and to enable research and education for the global biomedical community.

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Nakagawa et al.: Functional hierarchy and reversibility within the murine spermatogenic stem cell compartment. Science, Vol. 328.  no. 5974,  pp. 62-67, DOI: 10.1126/science.1182868

Read a National Geographic News article on this research

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