The beauty of nerve cells

Albert Becker, Professor for Molecular Neuropathology, Bonn University

For many years, I have been fascinated by Neuroscience and the beauty of nerve cells. Their processes have a fractal architecture such as trees, rivers, the respiratory and vascular system of mammals have. In neurological disorder such as so-called developmental malformations manifesting with seizures, this organoid structure of processes is impaired.

We found that a molecule, termed SLK is important for the development of nerve cell processes in the brain. If it is missing, the neurons' branches are less abundant. In addition, it is then more difficult to inhibit the activity of the cells. This is consistent with the fact that there is less SLK in diseased brain tissue from epilepsy patients. Epileptic seizures are characterized by overexcitation of neuron clusters. The findings may help to improve treatment of the disease.

Nerve cells from mice - with normal (top) and reduced SLK expression (bottom). Without SLK, dendrites branch less; moreover, the number of inhibitory synapses (green) decreases. © Image: Institute of Neuropathology/University of Bonn

SLK belongs to the large group of kinases. These enzymes are extremely important: They attach phosphate groups (which are small molecular residues with a phosphorus atom in the center) to proteins and thus alter their activity. Kinases are involved in the regulation of almost all life processes in animals.

The kinase SLK was already known to play an important role in embryonic development: One of its effects is on the growth of cells and their migration in the body; these processes are also essential for the maturation of neurons. We have inhibited the production of the SLK protein in neurons of mice. The dendrites, which are the extensions that receive signals from other neurons and conduct them to the cell body, branched less. The dendrites resemble a kind of tree dotted with tiny contact points, the synapses.

This is where extensions of other nerve cells dock and transmit electrical impulses to the tree. The observed "thinning" did not affect the thick main branches, but exclusively the smallest shoots. The synapses on these small branches are called excitatory: Signals received there have an arousing effect. This means that they increase the probability that the neuron will in turn generate an electrical signal, in other words, that it will "fire".

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