Brain Circuits Disrupted in Mice Missing an Autism Gene
Alterations to brain circuits underpinning intellectual disability, autism and other neuropsychiatric disorders appear to be related to subtle cellular changes that occur when a gene is disrupted in the hippocampus–a major part of the brain needed for learning and memory, new research with mice has shown. Variations in the Kirrel3 gene are associated with autism spectrum disorder, intellectual disability and Jacobsen syndrome, a rare developmental disorder.
In light of this association, Utah researchers studied how changes in Kirrel3 damage brain circuits that people need for learning and memorization. Their study found that the gene helps form part of the mossy fiber synapse, a large synapse in the hippocampus. Synapses are connectors that help brain cells, or neurons, to communicate through electrical and chemical signals. Any cognitive task a person undertakes–from tying shoelaces, to memorizing the alphabet, to solving complex problems–requires neurons to communicate with each other.
The researchers found that in developing mice lacking the Kirrel3 gene part of the mossy fiber synapse was malformed, causing the hippocampus to become overactive. It has long been thought that intellectual disabilities arise from altered brain functions following even tiny changes to synapses. But what we do still do not understand, is exactly where these tiny changes occur. according to Megan Williams, Ph.D., assistant professor of neurobiology and anatomy and lead author on the study. In addition to the hippocampus, Kirrel3 is expressed in other areas of the brain that may also have impaired synapses that could contribute to neurodevelopmental disorders. Autism spectrum disorder, which affects the social and intellectual development of an estimated one in 68 U.S. children, according to recent studies.