Over the past century, scientists have used a variety of animal models to advance their understanding of the developing brain and autism. Here’s a chronology of some of the landmark discoveries involving uncommon autism models.
Biologist Thomas Hunt Morgan identifies a fruit fly gene called NOTCH that affects wing maturation and is part of a pathway later linked to nervous system development in people.
Heart to heart:
Austrian scientist Otto Loewi observes parallel activity in two frog hearts suspended in saline, theorizing that a chemical messenger he dubs ‘vagusstoff’ traveled through the solution — the first identified neurotransmitter.
English zoologist John Gurdon replaces the nucleus of a frog egg with a nucleus from an intestinal cell. The resulting embryo successfully develops into a tadpole, demonstrating that mature cells contain all the information needed to create any cell type and kicking off research in induced pluripotent stem cells.
Biologist Seymour Benzer and a colleague demonstrate that mutations in a fruit fly gene dubbed PER disrupt the fly’s circadian rhythm, launching Drosophila melanogaster as a model for the study of how genes control behavior.
Scientists publish the complete wiring diagram of the Caenorhabditis elegans nervous system, paving the way for the extensive use of roundworms in studies of nervous system development.
Studies show that C. elegans is capable of habituation, a simple form of learning that may be disrupted in autism.
Researchers debut a single-gene mouse model of autism: mice with a mutation in the gene NLGN3.
Scientists create one of the first invertebrate models of autism: a strain of C. elegans with a faulty version of the roundworm’s neuroligin gene NLG1.
A zebrafish study shows that multiple genes in the 16p11.2 chromosomal region, which may be deleted or duplicated in autism, play roles in brain development.
Researchers report that fruit flies in an enclosure tend to keep a reliable amount of space between them, an observation that can be used to investigate how mutations in autism-linked genes affect social behavior.
Eight is enough:
The complete genome sequence of the California two-spot octopus (Octopus bimaculoides) is published, revealing striking similarities to people in genes involved in nervous system development and function.
Zebrafish larvae lacking the autism-linked gene CNTNAP2 are hyperactive at night, but adding estrogen-like compounds to their tank calms the fish — demonstrating a use for the animals in screening potential autism treatments.
Two to tango:
A study of gene expression in the developing fly eye reveals the importance of interactions between genes in the 16p11.2 region during neurodevelopment.
Researchers identify neurons in the forebrain of zebrafish that support their social interactions, suggesting that zebrafish can be used to probe social brain circuitry.
An analysis of 20 autism-linked mutations in roundworms flags 10 autism candidate genes as worthy of further study, because of their impact on the worm.
Scientists find that food moves through the gut slowly in zebrafish larvae with SHANK3 mutations, providing a clue to the roots of digestive problems associated with autism.
The behavior of fruit flies with mutations in autism-linked genes suggests that dozens of these mutations lead to impairments in habituation.
Like their mouse counterparts, zebrafish lacking the autism-linked gene RELN show little interest in socializing with unfamiliar fish, supporting use of the fish as a model for social difficulties in autism.
A study of more than 27,000 roundworms with mutations in the worm versions of 98 autism-linked genes hints at the function of these genes; many of them affect habituation.
Zebrafish larvae lacking FMR1, the gene altered in fragile X syndrome, are hypersensitive to sound, suggesting that zebrafish can be used to study sensory processing differences in autism.
Reducing the expression of the autism-linked gene FOXP1 in a particular brain region in songbirds impairs the birds’ ability to memorize songs they hear from their fathers, suggesting a specific role for this gene in language learning.
Fly by night:
Fruit flies lacking a gene akin to the autism-linked genes CHD7 and CHD8 have fragmented sleep, a problem researchers corrected using an adapted form of ‘sleep restriction,’ an insomnia treatment.
Cite this article: https://doi.org/10.53053/TIYT8223