Houston Researchers Find Gene Clues to Why Autism Is More Common in Boys
A Baylor and Texas Children's team found small changes near the MECP2 gene, inherited from mothers without autism, that turned the gene down in their sons.
Autism is diagnosed about four times more often in boys than in girls, and no one fully knows why. Researchers at Baylor College of Medicine and the Duncan Neurological Research Institute at Texas Children's Hospital say they have found part of the answer in a single gene on the X chromosome, according to Baylor.
The study, published in the American Journal of Human Genetics, looked at MECP2, a gene where the right dose matters. Having too little, about 50% or less of normal levels, leads to Rett syndrome, and having twice the normal amount causes MECP2 duplication syndrome, Baylor said.
The idea
Girls have two X chromosomes and boys have one. The team tested whether mild changes in the regions that control how much MECP2 a cell makes could be cushioned in girls by their second X but cause trouble in boys.
"The regulatory regions are like dials that control whether a gene will be expressed and by how much," said first author Dr. Rebecca Meyer-Schuman, a postdoctoral associate in the lab of Dr. Huda Zoghbi.
What they found
Using a laboratory tool called a massively parallel reporter assay, the researchers screened the control regions of MECP2. "We identified two regulatory regions where male autistic individuals inherited a variant from their unaffected mother that altered regulatory activity," Meyer-Schuman said.
One reduced MECP2 levels by about 30% in human neurons. In mice, a cut that size causes social problems, hyperactivity and anxiety-like behavior. The boy with that variant was diagnosed with autism and ADHD but had none of the defining features of Rett syndrome, Meyer-Schuman said, according to the release also issued by Texas Children's.
"These findings ... reveal just the tip of the iceberg," Zoghbi said, adding that they provide "a framework for uncovering regulatory variants in other X chromosome neurodevelopmental genes that may contribute to autism's missing heritability."
What it does not mean
This is early research that points to two variants. It does not offer a test or treatment, and it explains only part of why boys are diagnosed more often. Parents should not read it as a cause for any one child's autism.
Families still need help now
Research like this is a gift from Texas scientists, and every child it may one day help is precious. Families living with autism today need therapy and support, which is why the state's proposal to end its children's autism program matters. Medical costs are a burden too; see our report on how Texas nonprofit hospitals handle financial aid.
Hero photo: WhisperToMe / Wikimedia Commons, CC0 (public domain dedication).
