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Davis, California

Tuesday, April 23, 2024

Column: Marbles

Of the myriad childhood illnesses and disorders that cause anxiety to pregnant women everywhere, few are as common yet mysterious as autism. According to the Centers for Disease Control and Prevention (CDC), about one in every 150 children are born with autism; however, despite decades of research, scientists are left with scant clues on the possible cause or causes of this disorder.

A UC Davis study called Markers of Autism Risk in Babies: Learning Early Signs (MARBLES) is a unique attempt to find and test many possible causes and how they may interact to cause autism.

Despite its common, singular name, autism is more accurately described as being part of a spectrum, called Autism Spectrum Disorders (ASD) that vary in severity. The most severe is Autistic Disorder, what most people think of as “classic” autism. People with Autistic Disorder have problems communicating in social situations, overreact to minor changes in routine and may develop obsessive interests or other unusual behaviors.

The most common way to study the possible causes of autism (and many other conditions) is through twin studies. The idea here is that the twins will have the same environment and same age; the only thing that is different between identical and fraternal twins is that identical twins share all of their DNA. If the identical twins are more likely to both have autism than the fraternal twins, then it makes it more likely the cause of autism is genetic.

However, twin studies have a major weakness. If the answer isn’t primarily in the genes, the twin studies don’t have much more to say.

“Twin studies are concerned with heritability, while MARBLES is looking for the non-heritable factors, which is everything except DNA,” said Irva Hertz-Picciotto, an epidemiologist, environmental chemicals expert and the MARBLES study principal investigator.

The process of looking for these non-heritable factors the MARBLES way means first finding mothers of autistic children who plan to become pregnant again. When the mother does become pregnant, the team gets to work collecting samples of pretty much everything a child is exposed to in its first few years: blood, urine, breast milk, stool, even things like dust and cleaning products.

“We do a walk through which details how many TVs are in the house, and we do a dust collection for the dust in the house,” said McKenzie Oliver, the project manager of MARBLES. “We have nutrition questionnaires, environmental history questionnaires, exposure questionnaires, so we get actual samples to analyze any self-reported data.”

The work isn’t just on the researchers’ end, though. The mother has to fill out a weekly symptom diary while she is pregnant, a monthly diary for the first year of the baby’s life and a quarterly diary for the two years after that.

The work can be taxing.

“We have some families that are really excited to be part of the research and will do anything to help us and don’t think of us as a burden in their life,” Oliver said. “With other [families], we struggle to get them to complete the questionnaires and forms and complete a visit.”

When the families live far away, there are other challenges. Most of the study involves home visits, but they do have to visit a MIND Institute clinic, which can be problematic.

“Some families already have two or three kids that may be in school, and have to drive all the way to Sacramento,” Oliver said. “It can be their whole day to drive from San Jose to Sacramento, and going to the MIND Institute and having to go back. It’s a real challenge that we’re facing now.”

Hertz-Picciotto, the principal investigator, thinks looking at the big picture of environmental factors is the way to find clues.

“Environmental factors have to be taken broadly, including nutrition, maternal medical and obstetric [women’s reproduction] conditions (which create the environment for the fetus) and some chemicals in household products, particularly those that disrupt systems crucial for fetal development,” Hertz-Picciotto said .

Funding for the project comes partially from the UC Davis Medical Investigation of Neurodevelopmental Disorders (MIND) Institute, but they also received a five-year, $10 million grant from the National Institutes of Environmental Health Sciences (NIEHS).

“We’re at the first five years of the grant, so things are just getting started,” Oliver said.

AMY STEWART can be reached at science@theaggie.org.


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