Lots of interesting reads in Scientific American & Nature these past few weeks.  Ewen Callaway of Nature magazine brings us this story:

A rare, hereditary form of autism has been found — and it may be treatable with protein supplements.

Genome sequencing of six children with autism has revealed mutations in a gene that stops several essential amino acids being depleted. Mice lacking this gene developed neurological problems related to autism that were reversed by dietary changes, a paper published today in Scienceshows¹.

“This might represent the first treatable form of autism,” says Joseph Gleeson, a child neurologist at the University of California, San Diego, who led the study. “That is both heartening to families with autism, and also I think revealing of the underlying mechanisms of autism.”

The children came from three families with Middle Eastern ancestry; in each case the parents were first cousins. Studying such families makes the hunt for the rare recessive mutations underlying some forms of autism simpler than it would be among the general population, Gleeson says, because the odds are higher that children will be born with two copies of the recessive mutation.

In each family, Gleeson’s team identified mutations that inactivate the enzyme BCKD-kinase, which normally prevents the body from breaking down branched-chain amino acids called leucine, isoleucine and valine after a meal. Humans cannot synthesize these amino acids and must obtain them from food.

“We predicted that patients would burn through these amino acids,” says Gleeson. The prediction was correct: after eating, the children had low blood levels of the branched-chain amino acids. Mice lacking the gene that codes for BCKD-kinase also had low levels of the amino acids in their blood and tissue.

The sample size of six is extremely limited due to the rarity of the disease, so we don’t know if the result are generalizable. But the results are interesting nonetheless.