A new study of genetic factors involved causing autism
spectrum disorders (ASD) draws fresh attention to the impact these illnesses
have on motor skills, and more broadly on cognitive function.

“Diminished motor skills appear to be an almost
universal property of children with autism,” says Professor Michael
Wigler, one of three researchers including Ivan Iossifov from Cold
Spring Harbor Laboratory (CSHL) and the New York Genome Center, and Andreas
Buja, a statistician from The University of Pennsylvania, who led the
team.

Wigler adds that careful inference from the data suggests to
him that the genetic factors causing ASD broadly diminish the brain’s cognitive
functions.  

These genetic factors are increasingly becoming known, are
of two types: inherited mutations, and what scientists call de novo mutations.
The latter are changes to DNA that don’t appear in the genetic makeup of either
parent and are new in the child. Damaging de novo mutations correlate with
lower non-verbal IQ.  The new study finds that diminished motor skills
also correlate significantly with de novo mutations in ASD.

The researchers find that the defining core behavioral
components of ASD — impaired social skills and communication — do not
correlate with the presence or severity of de novo mutations. A child with
autism who has a severe de novo mutation is no more likely to have severely
impaired social skills than is a child with autism for whom no such mutation
was found, and who presumably has inherited causal factors. 

Restating: the researchers now think that children who have
autism as a consequence of inherited factors have less general cognitive damage
than those with severe de novo mutations.

This follows from Wigler’s hypothesis that mutations with
very damaging impact on human function will tend to be eliminated rapidly from
the gene pool, since those affected are much less likely to have
children.  In contrast, inherited factors involved in ASD that have
“survived” in the genome for several generations are assumed to have
a more restricted range of cognitive impact.

The near universality of diminished motor skills in ASD is
an indicator that the factors that cause the core behavioral defects also cause
general cognitive dysfunction, Professor Wigler explains. “As such,
objective assessment of cognitive function should be a facet of any clinical
evaluation of the patient,” he says, “and included when monitoring
therapeutic response.”

This study was based on DNA sequence and deep phenotypic
data from the Simons Simplex Collection, a set of 2,760 families that have a
single child affected by ASD.

Source: https://www.prnewswire.com/news-releases/autism-genetics-study-calls-attention-to-impaired-motor-skills-general-cognitive-impairment-300595412.html