Huntingtin

The name of the gene responsible for Huntington disease (HD) and of the protein encoded by that gene. The molecular basis of HD is an increase in the length of a CAG triplet repeat (or 'polyglutamine') within the huntingtin gene. The gene is on chromosome 4p16.3. The huntingtin mutation (gene change) is fully dominant; homozygotes (who have two copies of the huntingtin gene) are no more severely affected than heterozygotes (who have only one copy of the gene). It has long been recognized that paternal transmission results in increased severity (the 'rigid' form), earlier onset (anticipation), and more rapid progress than does maternal transmission of the gene. HD gives rise to progressive, selective (localized) death of neuronal cells (neural cells) associated with choreic (involuntary) movements, gradually decreasing psychomotor skills and dementia (mental deterioration). It is the terrible disease that caused the decline and death of the American folksinger Woody Guthrie (1912-1967) who wrote "Your Land is My Land", "So Long it's Been Good to Know You" and many other memorable songs.

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hun·ting·tin (hunґting-tin) a protein encoded by a gene located on 4p16.3 and altered in structure and function in Huntington disease. Mutation causes increased and unstable numbers of CAG triplet repeats in the gene and thus increased numbers of glutamine residues in the protein; above a threshold of 40 glutamine repeats, clinical disease is apparent, with age of onset inversely correlated with the number of repeats. The altered proteins tend to form tangled aggregates.