An amino acid, found in foods such as meat, eggs and dairy products, is essential for normal brain development, scientists have found.
Asparagine was until now considered non-essential because it is produced naturally by the body.
Researchers at the University of Montreal and its affiliated CHU Sainte-Justine Hospital found that brain cells depend on the local synthesis of asparagine to function properly.
"The cells of the body can do without it because they use asparagine provided through diet. Asparagine, however, is not well transported to the brain via the blood-brain barrier," said senior co-author of the study Dr Jacques Michaud.
In April 2009, a Quebec family lost their son, before the age of one, to a rare genetic disease causing congenital microcephaly, intellectual disability, cerebral atrophy, and refractory seizures. It was the third infant to die in this family from the disease.
This led Michaud to discover the genetic abnormality responsible for this developmental disorder.
The team identified the gene affected by the mutation code for asparagine synthetase, the enzyme responsible for synthesising the amino acid asparagine.
The study is the first to associate a specific genetic variant with a deficiency of this enzyme.
"In healthy subjects, it seems that the level of asparagine synthetase in the brain is sufficient to supply neurons," Michaud said.
"In individuals with the disability, the enzyme is not produced in sufficient quantity, and the resulting asparagine depletion affects the proliferation and survival of cells during brain development," Michaud said.
