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Science Daily —
Uncontrolled neuronal death in the brain often gives rise to
neurodegenerative illnesses like Parkinson or Alzheimer disease.
Whether or not neurons have a long and healthy life is, apart from
other factors, determined by the presence of neurotrophic factors.
 To the left several cross sections of a mouse brain are shown. In the dark labeled areas the scientists of the Max Planck Institute were able to selectively eliminate the receptor for a specific neurotrophic factor. In the background neurons that would also die due to Parkinson's disease, but have been positively affected by GDNF and its receptor, are shown. (Credit: Max Planck Institute of Neurobiology)
Parkinson
patients suffer from loss of dopaminergic neurons in a certain region
of the brain, the substantia nigra. Several experiments seem to
indicate that the neurotrophic factor GDNF and its receptor might
prevent an early, uncontrolled death of these neurons. The
international team consisting of Edgar Kramer, Liviu Aron, Sabine Seitz
und Rüdiger Klein of the Max Planck Institute of Neurobiology has now
shown that neurons of the substantia nigra lacking the Ret-receptor
indeed suffer an earlier death compared to normal control neurons. Loss
of nerve cells and axons in this brain region is typical for Parkinson
disease.
The disappearance of neurons lacking the Ret-receptor
in this brain area has now for the first time been observed in mice,
since the scientists were able to eliminate the receptor specifically
in neurons of this brain region. The mice thus altered are viable and
live as long as their normal relatives. "For the first time it was now
possible to study the effects of missing GDNF signals on the
establishment and maintenance of the nigrostriatal pathway (a neural
pathway connecting the substantia nigra with the striatum)", stated
Rüdiger Klein, Director at the Max Planck Institute of Neurobiology and
head of the research team. Animals that lack GDNF and its receptor in
all neurons are not viable and therefore it was not possible to
investigate the precise role of GDNF and its receptor in the adult and
aging brain.
"Surprisingly even without the Ret- receptor the
nigrostriatal system developed normally", remarked Edgar Kramer, one of
the leading scientists of the study. Only in adulthood the inability of
these neurons to receive GDNF due to the missing receptor became
evident and the older the animals grew, the more nerve cells died.
Worldwide
more than 100 million especially older people suffer from diseases of
the brain that are characterized by a gradual loss of neurons.
Depending on which region of the brain is affected the symptoms vary,
e.g. Alzheimer patients suffer from a progressive loss of memory
whereas in Parkinson disease failures of the motor system are most
evident. However, the characteristic muscle shaking and the inability
to initiate movement of Parkinson’s disease, from which also prominent
people like Muhammed Ali and Michael J. Fox suffer, only become
apparent after more than 50 percent of the neurons have died.
"Our
results will help us to understand which factors nerve cells fated to
die in Parkinson’s patients need to survive" Rüdiger Klein stated. The
published results are therefore of importance for promoting therapeutic
approaches against Parkinson’s disease.
Note: This story has been adapted from a news release issued by Max Planck Society.
Source Science Daily
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