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extends those earlier results.
“This paper picks up the consequences
of the genetic variants that we and
others have shown are clearly clustering on certain [biochemical] pathways,”
Hakonarson says.
Changes in the activity of one particular gene, A2BP1, appeared to profoundly
affect the autistic brains. The A2BP1
protein is produced in nerve cells and helps
cut and stitch pieces of RNA together to
create the messenger RNA molecules
that guide the production of proteins.
In the autistic brains, over 200 distinct
RNA molecules were stitched together
incorrectly, the team found. While the
researchers don’t yet know the functional outcome of these errors, each of
the 200-plus RNA molecules has the
potential to be made into a dysfunctional
protein in the brain.
“We didn’t expect to see how gen-
erally important this gene looks,”
Geschwind says. “It looks to be one of
the things that has major dysregulation
in the brains of autistic kids.”
A second cluster of genes that boost
immune responses and inflammation
was much more active in the autis-
tic samples than in normal brains.
Previous studies have shown that inap-
propriate immune responses may play a
role in autism.
Back Story | A GENE TIC PUZZLE
autism spectrum disorders are highly heritable, but like many complex disorders they can’t be pinned to a
single genetic flaw. though many genetic changes have been associated with the disorder (the locations of
some are shown here on the human chromosomes), each one accounts for only a small fraction of cases.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 X Y
Chromosome 5
Chromosome 7
Chromosome 15
Several single-letter DNa
changes at one end of chromosome 5 (orange line) have been
associated with autism, but
each of these variations appears
to contribute only a very small
amount to a person’s risk of
developing autism.
By studying inheritance patterns
in families with autistic members,
scientists have found a region of
chromosome 7 (orange line) that
appears to be relevant to the condition. genes that tell nerve cells
how to hook up with each other as
the brain grows are located here.
about 1 percent of people
with autism have duplications
of a stretch of chromosome
15 (orange line). Large-scale
duplications, deletions and
rearrangements in other parts
of the genome have also been
linked to autism.
Chromosome 22
mutations in a gene at one end
of chromosome 22 (orange line)
that is involved in nerve cell communication, SHANK3, are linked
to some cases of one nonverbal
form of autism. these mutations
seem to arise spontaneously
rather than being inherited.
