Fish receive genetic alteration associated with autism – 12/11/2023 – Suzana Herculano-Houzel

I find it astonishing that most people are neurologically “normal”, statistically speaking: 95% of people focus their existence on a somewhat limited range of diversity in various aspects of behavior. There is a lot to go wrong, and note that we are only talking about those pregnancies that were in fact full-term and gave rise to a new person, when a significant number of pregnancies are not even detected as they self-terminate due to variations here , there and there that make the embryo unviable.

I better not speak too loudly, or life-at-any-cost advocates will want to get involved in hospitalizing post-coital women to perhaps save embryos from their automatic developmental quality control process. Between this self-extinction of what doesn’t work and the self-organization of the brain that survived such intrinsic “quality control”, what emerges is a majority of passably “normal” individuals – plus a minority of neurodivergent ones.

And as there is a lot to go wrong, divergences also differ on the reason for their divergence. Therefore, it is rare for a “type” of neurodivergence to be univocally associated with a genetic variation. Consider the Shank genes, for example, which encode proteins that assemble synapses, connections between neurons. Less than one percent of neurodivergent people on the autism spectrum — which are already a tiny minority of the population — have pieces missing from this specific part of the genome, which is exactly the same in all normal people. There are several ways to be autistic, in fact.

But cut out a piece of one of these Shank genes, and 100% of the time the result is an animal – mouse, rat, monkey or human – that suffers from anxiety and has its social behavior altered in several aspects.

And my colleagues in Portugal have just added the paltry paulistinha fish to the list (sorry, fish lovers). That’s it: reproducing the genetic alteration associated with autism in a fish, even in a minority of autistic people, creates a fish that we just don’t call autistic because everyone would roll their eyes, so we just call it Mutant Fish -To-Shank3a.

This is the work of Rui Oliveira’s team, from the Instituto Gulbenkian de Ciências and the Instituto Universitário de Portugal. When watching videos of other fish from a corridor (yes, fish also pay attention to screens), “normal” fish turn their bodies towards the video of the fish that shows erratic and disorganized swimming in response to an alarm, away from the another fish swimming calmly in the other video — but the mutants don’t care and continue on their own, ignoring the others. Once the other person’s stress has passed, the normal fish continue to prefer to face where the stressed fish was — and the mutants continue to not give a damn: they continue facing forward in the corridor.

Conclusion: genetically autistic fish are the only ones who follow the British recommendation to Stay Calm and Carry On.

I ask Rui if they have any evidence that immunity to other people’s stress is harmful to someone, the requirement for something to be qualified as a “disorder”. Rui would love to be able to answer, but he can’t: the necessary experiment would involve exposing his fish to predation, which the ethics committee did not allow. But I imagine that right after that they went for a good cod lunch…

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