Blindness Linked To The Cyt...( A research group at the Max Planck In...)

A research group at the Max Planck Institute for Molecular Genetics in Berlin identified the gene defect underlying a specific form of hereditary blindness, known as retinitis pigmentosa (nature genetics, Vol. 19, No. 4, August 1998).

Retinitis pigmentosa (RD) is characterized by premature cell death in the retina leading to a progressive contraction of the visual field in affected patients. The retina lines the back of the eye and contains different types of cells, including the photoreceptors and neurons. There are two main classes of photoreceptor cells: rods and cones. Rods are responsible for vision under dim light conditions while cones participate in fine and color vision. RP leads to a preferential loss of the rod photoreceptor cells and night blindness is one of the first clinical symptoms. During disease progression, cones are affected as well and patients become legally blind between the ages of 20 and 40.

The name ‘retinitis pigmentosa’ reflects observations with patients in whom ophthalmologists frequently recognize an abnormal pigmentation in the back of the eye as a consequence of the dying photoreceptor cells. So far, 14 genes were identified which, when defective, lead to the disease. Additional 14 loci were defined by genetic linkage analysis in families affected by the disease. In these cases, the genetic defect still has to be identified. Most of the genes involved in retinitis pigmentosa encode proteins from the so called ‘phototransduction cascade’, a complex biochemical mechanism which transforms the initial light stimulus to a chemical signal. The latter accomplishes the communication of the photoreceptor cells with the neurons of the retina.

Retinitis pigmentosa, due to a genetic defect, occurs with a frequency of 1 in 4,000 individuals and about 15-25%
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Contact: Wolfgang Berger
berger@mpimg-berlin-dahlem.mpg.de
49-30-8413-1253
Max-Planck-Gesellschaft
4-Aug-1998