Overview

Repeat expansion diseases refer to a group of genetic diseases caused by an abnormal increase in the number of repeats of a gene in a specific genomic region. In these diseases, certain sequences in the genes are repeated more than normal, and this causes the pathogenesis of the disease.
Major repeat expansion diseases include Huntington's disease, myotonic dystrophy, fragile X-associated tremor/ataxia syndrome, and some forms of spinocerebellar ataxia.

The number of repeats varies with the disease, but can be in the thousands.　
At present, more than 50 diseases have been discovered, many of which are brain nerve diseases or muscular diseases.

Characteristics

It is considered that abnormal repeats interfere with the normal functioning of genetic molecules, which leads to cellular dysfunction and tissue abnormalities. It is also known that the clinical symptoms of some of these diseases may depend on the number of repeats and that the number of repeats may increase with successive generations.

Research status

Possible mechanisms of disease include toxicity induced by repeat RNA, toxicity of peptides produced by non-ATG-dependent translations associated with repeats, and changes in gene expression, or abnormal splicing due to epigenetic influences.

Disease models using iPS cells can directly reflect information about the human genome, such as the length of repeat expansions and the position of insertion.

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