DERMATOLOGY: Study Rewrites Biology of Tanning
When the sunlight hits human skin, melanocytes in the lower layers churn out packages of melanin and deliver them to the surface cells. The result is a darkened skin tone—for some people. Those with fair skin, particularly redheads, tend to burn rather than tan, and they also have a far higher risk of getting skin cancer. In the Sept. 21 Nature, David Fisher (front), John D’Orazio, and colleagues use a mouse model of fair-skinned people to identify a pathway that could be manipulated to provide the cancer protection of tanning without the sun.

LEADERSHIP: Martin Will Step Down After 10 Years as HMS Dean
HMS dean Joseph Martin announced that he will step down from that position in July 2007. His tenure as dean has been marked by increased collaboration, interdisciplinary research, and diversity. For the next nine months, his priorities will include advancing education, recruitments, and science planning.

NEUROSCIENCE: Receptor Linked to Brain Development, May Play Role in Alzheimer’s
Brain development follows a well-defined course, with neurons appearing first and then astrocytes. Are astrocyte precursors receiving their fate-determining signal after the early neurons do? Or does the message arrive promptly but get repressed, perhaps by another signal? The latter may be the case. Gabriel Corfas and colleagues report that a well-known messenger, neuregulin, triggers a pathway that results in the repression of astrocyte formation. What makes the scenario especially intriguing is that presenilin, a protein implicated in Alzheimer’s disease, is part of the pathway. The findings appear in the Oct. 6 Cell.

MILESTONES: Quad Centennial Celebrates 100 Years of Science
The frontiers of sensory perception and cognition, the molecular conversations between microorganisms and host cells, and genomic strategies to understand cancer and develop new drugs were the subjects of the recent HMS centennial, celebrating the 1906 dedication of the newly built Quadrangle. Three scientific symposia featured HMS faculty and alumni discussing their latest work and future directions. Among the speakers was HMS neurobiology chair Carla Shatz.