Huntingtin Protein and Protein Aggregation
Part 1

What Causes the Onset of HD?

An Explanation of Terms:
Please note that although "Huntington's disease" is spelled with an "o," the correct spelling of the protein involved is "huntingtin" with an "i." The scientific literature on HD refers to the gene as both the "Huntington gene" and the "huntingtin gene." For the purposes of this site, we will refer to the gene as the "Huntington gene" or the "HD gene."

The Huntington Gene

Recall that a gene is a section of DNA made up of four different nucleotide bases, abbreviated by the letters A, T, C, and G. The order of these bases determines the protein “product” of the gene. (To read more about DNA, click here.) Everyone has a gene that codes for huntingtin protein, a protein found in the cells of the body, which we will discuss later. Towards the beginning of this gene, the three-letter codon sequence C-A-G is repeated a few times. Each C-A-G sequence codes for the amino acid glutamine, a protein building block. People with HD simply have an increased number of these C-A-G repeats toward the beginning of their Huntington gene, coding for an excess number of glutamines in their huntingtin protein. This glutamine extension in altered huntingtin leads to further problems, as we will see.

Last Modified: 12-23-02

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