(July 15, 2015) As early as 1943, when autism was first
described by psychiatrist Leo Kanner, reports were made that some, but not all,
children with autism spectrum disorder have relatively enlarged heads. But even
today, more than half a century later, the exact cause of this early abnormal
growth of the head and brain has remained unclear.
Now, scientists from the Florida campus of The Scripps
Research Institute (TSRI) have uncovered how mutations in a specific autism
risk gene alter the basic trajectory of early brain development in animal
models.
The study, published in the July 15 issue of The Journal of
Neuroscience, focused on the gene PTEN (Phosphatase and tensin homolog), which
is mutated in around 20 percent of individuals with autism spectrum disorder
and enlarged heads (macrocephaly).
In new research, the team led by Scripps Florida biologist
Damon Page found that mutations in the mouse version of PTEN, which approximate
those found in a subgroup of individuals with autism spectrum disorder, lead to
dynamic changes in the number of two key cell types that make up the
brain—neurons and glia. At birth, neurons are more abundant than normal.
Surprisingly, in adulthood the number of neurons in the brains of mutant
animals is virtually the same as normal, and glia (which provide support for
neurons) are overrepresented.