“The main thing we want to emphasize is the usefulness of this model. We can very quickly look at genetic and environmental factors associated with autism that are very difficult to understand in humans. The ease and speed of the genetic analysis in this model make it very attractive compared to a rodent model,” said co-author Courtney Roper, a postdoctoral fellow in OSU's College of Agricultural Sciences.
ASD consists of five related neurodevelopmental diseases that are defined by extreme impairments in social interactions, inability to have proper modes of verbal and nonverbal communications, repetitive behavioral patterns, and weird sensitivity to sensory stimulation.
The causes of autism are not known, but it has been linked with both genetic and environmental components, including prenatal exposure to two drugs: thalidomide, a sedative linked to severe birth defects, and valproic acid, which is used to prevent migraine headaches. (Related: Autism, mercury, aluminum and vaccine-induced encephalopathy)
Autism diagnoses have been rising since the 1990s. About one child in 68, will be classified as having autism spectrum disorder, according to the Centers for Disease Control and Prevention (CDC).
ASD affects all ethnic, socioeconomic, and racial groups but is around 4.5 times more common among boys (one in 42) than girls (one in 189).
Zebrafish are small freshwater species that go from a tiny cell to a swimming fish in just five days. They reproduce at a fast rate and are essential for studying the genetic components of vertebrates, including the effects of environmental contaminants and pharmaceuticals on early embryonic development.
Zebrafish have an uncanny likeness to humans at the genetic, cellular, and molecular levels; this means that the implications of findings associated with zebrafish are extremely relevant to humans.
Studies on embryonic zebrafish are particularly important, for embryonic zebrafish develop quickly, are transparent, and can easily thrive even in small amounts of water.
The research's findings concluded that treating zebrafish embryos with valproic acid starting eight hours after fertilization results in a significant rise in the ASD macrocephalic phenotype, that is, an enlarged head.
It also caused hyperactivity in embryos and larvae.
“In addition to the ASD-like characteristics, we observed an overgrowth of mature newborn neurons and neural stem cells in the developing brain after VPA exposure. Next, now that we have models for behavior established, is to start looking at the genetic and environmental interactions, examining some of the potential factors that might be driving autism in humans,” Roper said.
The findings were published in the journal Neurotoxicology and Teratology. The National Natural Science Foundation of China supported the conduct of this research.
More on autism spectrum disorder
Some of the behavioral and medical conditions that are associated with autism spectrum disorder include anxiety, attention deficit hyperactivity disorder, gastrointestinal problems, depression, epilepsy, and sleep disturbances.
According to the CDC, children with autism are:
- 1.8 times more likely than children without developmental illnesses to have asthma
- 1.8 times more likely to have eczema
- 1.8 times more likely to have food allergies
- 2.2 times more likely to have chronic headaches
- 3.5 times more likely to have chronic diarrhea
For more stories on disorders of the mind and behavior, visit Mind.news.
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