Brain degeneration in Huntington's disease caused by amino acid deficiency

Working with genetically engineered mice, Johns Hopkins neuroscientists
report they have identified what they believe is the cause of the vast
disintegration of a part of the brain called the corpus striatum in
rodents and people with Huntington's disease: loss of the ability to
make the amino acid cysteine. They also found that disease progression
slowed in mice that were fed a diet rich in cysteine, which is found in
foods such as wheat germ and whey protein.

Cystathionine gamma lyase (CSE) synthesizes cysteine in mouse and human brain tissues
and this group found found considerably less CSE in Huntington's diseased tissues. All people
carry some normal huntingtin protein made by the Huntington's disease
gene, although the protein's function remains elusive. But people with
Huntington's disease also carry mutant huntingtin proteins. Snyder and
his team saw that the mutant proteins were attaching themselves to a
crucial protein responsible for turning the CSE gene on or off, which
ultimately led the diseased rodent and human brain tissues to be
deprived of cysteine.