St. Jude identifies the specific cell that causes eye cancer, disproving long-h...( Investigators at St. Jude Children's...)

Investigators at St. Jude Children's Research Hospital have identified the cell that gives rise to the eye cancer retinoblastoma, disproving a long-standing principle of nerve growth and development. The finding suggests for the first time that it may one day be possible for scientists to induce fully developed neurons to multiply and coax the injured brain to repair itself.

A report of this work appears in the Oct. 19 issue of the journal Cell. Michael Dyer, Ph.D., an associate member in the St. Jude Department of Developmental Neurobiology, is the reports senior author.

Retinoblastoma arises in the retinathe multi-layered, membrane lining the back of the eye that responds to light by generating nerve impulses that are carried into the brain by the optic nerve.

The immediate importance of the St. Jude finding is that it unexpectedly showed that retinoblastoma can arise from fully matured nerves in the retina called horizontal interneurons. This disproves the scientific principle that fully formed, mature nerves cannot multiply like young, immature cells, Dyer said. Human neurodegenerative disorders such as Alzheimers disease can occur when differentiated nerves in the brain try to multiply, and in the process, trigger a self-destruct program called apoptosis. Differentiation is the process by which cells lose their primitive, stem-cell-like properties that include the ability to grow and multiply, and instead develop specialized shapes and functions.

For the past 100 years, its been ingrained among scientists that differentiated mature nerves are so elaborate that they cant divide, and if they try to divide, they undergo apoptosis, Dyer said. There was no exception to this rule until now. This is the first time that anyone has shown that under certain conditions, a fully mature and differentiated nerve can undergo cell division and multiply.

The discovery that fully differentiated horizontal interneurons can mu
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