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