Cerebellar Ataxias

Cerebellar dysfunction causes a specific alteration of movement 

Muscle strength and sensibility are normal, but voluntary movements are irregular and miss their target. It is this specific disturbance of movement that is described by the word ataxia (a- without, -taxis order).

Cerebellar ataxias are caused by multiple disorders

Samples that have been collected in the Brain Bank are principally related to ataxias caused by mutations.

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Inherited cerebellar ataxias may be autosomal dominant

The mutation of one single gene causes the disease. The mutated gene may come from the father, the mother or the mutation may be new (de novo mutation). The mutations causing cerebellar ataxias are often of a special type: the size of the gene is increased by the repeat of a codon that codes for the amino-acid glutamine. As a consequence, the coded protein contains an abnormally long sequence of repeated glutamine.

This particular type of mutation is commonly associated with an abnormal structure (an "inclusion") that is located in the nucleus of some neurons and that contains all the abnormal protein or only part of it. The role of these inclusions in the mechanism of the disease is discussed: they could be toxic or protective. Their study in humans and animal models is very active. 

They may be recessive

The two genes (one from the mother, the other from the father) must be mutated. Friedreich ataxia, due to the mutation of the frataxin gene, is the most frequent recessive ataxia. Frataxin is a protein involved in iron metabolism. The neuropathology of Friedreich ataxia is still badly known to-day.