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Weekly Seminar Highlights: “Livin’ and Dyin’ in the Ocular Lens”

Published September 24, 2013

Last Tuesday, the Burke Medical Research Institute welcomed Dr. Steven Bassnett, Professor of Opthalmology and Visual Sciences at Washington University in St. Louis, to deliver BMRI’s Weekly Seminar.  Bassnett discussed the peculiar cellular behaviors that give the ocular lens its characteristic transparency.

The lens—a clear, malleable sphere that sits behind the iris—is responsible for one-third of the eye’s focusing power.  A cross section of the lens reveals onion-like layers of cells, with the newest cells at the surface and the oldest in the center.  As cells mature, they migrate inward and lose their organelles, aggregating into a transparent core that allows light to pass through to the retina.  Bassnett’s lab has found that the generation of new cells at special germinative zones on the lens surface pushes older cells towards the center, a process Bassnett compared to “penny-pusher games” found in arcades.  Using fluorescent tags, Bassnett’s lab found that “penny-pushing” packs cells into tight hexagonal arrays that aid transparency.  Moreover, clonal cells are channeled into distinctive wedge-shaped streaks.  These streaks resemble the patterns of opacities seen in cortical cataracts (a leading cause of blindness), hinting at a possible mechanism for cataract formation.

Despite continuous cell proliferation, older lens cells rarely die—and as a result, lenses grow in size throughout a person’s life.  Bassnett’s team has found a clue to the death-defying abilities of lens cells in the anti-apoptotic gene Birc7, also known as livin.  Expressed nowhere else in the body except the lens and certain aggressive melanomas, livin helps lens cells persist through organelle loss and beyond.

In addition to his seminar, Bassnett also met one-on-one with BMRI faculty members.  “My impression was that the interests of the individual faculty members were very complementary, which should provide a good working environment with many opportunities for discussion and collaboration,” he said.  “While our work on the lens, an epithelial tissue, might seem to be somewhat removed from the scientific mission at Burke, there are in fact many points of confluence,” Bassnett added.  For example, his lab is investigating whether stem cells are present in the lens epithelium and involved in cell proliferation there.  “This relates very nicely to studies at Burke on neural stem cells and their potential role in treating degenerative conditions.”

Since 2003, the BMRI Weekly Seminar has invited renowned scientists from across the country to share their research with the Burke community.  Seminar speakers also have the opportunity to meet one-on-one with the BMRI investigators.  Check out upcoming speakers here

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