A mouse model with a mutation in the serotonin transporter (SERT) exhibits a 'super SERT' phenotype leading to serotonin deficiency and autism-like behaviors.

“my collaborators and i have produced a mouse called g56a this mouse has a mutation in the serotonin transporter the serotonin transporter is the protein that you spoke of before that is the target of ssris and which removes serotonin from the circulation or from the synaptic cleft when it's a neurotransmitter what this mutation does though is not inhibit cert but make it more active so cert becomes what i like to call the super cert mouse this animal has essentially a deficiency of serotonin it is so effective at inactivating serotonin after it's released that it doesn't have a chance to act so that animal has a smaller nervous system in the gut too few neurons and it has slow transit and it has a problem in the gut in the brain it doesn't socially interact with other mice if you put them in a tube two mice convene one with the mutation backs out and lets the other mouse through all the time and it has repetitive behaviors it keeps tapping its foot hitting its head against the side of the cage so it has central features that look like autism and it has a gi tract which is abnormal”