By studying the membranes of cells in a patient’s eye cataract, Scheuring has discovered the molecular cause of this disease. This is the first time that high-resolution AFM imaging of a diseased tissue has yielded information on the single molecule level of the disease. AFM has emerged from the state-of-the-art laboratory to bring us medical nanoimaging. These results are now online in the Journal of Molecular Biology.
The eye’s lens focuses light and forms a sharp image on the retina thanks to the organization and specific properties of its constituent cells (see box overleaf). As in all tissues, cellular exchanges are essential for nutrition and removal of waste products, but in the eye they must nonetheless be adapted to the particular properties of the lens. The membranes of lens cells contain protein assemblies, the aquaporins and connexons (2): the former act as water channels and the latter as channels for metabolites and ions. Together these membrane proteins ensure cell adhesion.
Using atomic force microscopy (AFM), which images the surface of a sample at a precision of one nanometer (one billionth of a meter), Simon Scheuring’s team at the Institut Curie is studying how these protein assemblies function. An atomically sharp tip is scanned over the sample surface and its movements are tracked by a laser. The resulting data can be used to draw a topographical map of the sample. By comparing assemblies of aquaporins and connexons in membranes of healthy and diseased lens cells, Scheuring and colleagues have identified the biological changes that cause cataracts (see box overleaf).
This is the first time that high-resolution AFM imaging of diseased tissue has shed light on the molecular cause of a disease at the single membrane protein level. A step towards medical nanoimaging has been taken with atomic force microscopy.The lens
N. Buzhynskyy, R. Hite, T. Walz, S Scheuring. EMBO R. January 2007, vol. 8, p. 51-55.
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