Brain’s lost neurons
The slice on the right is from a mouse that lacks a gene called Arl13b - the same gene whose mutation causes Joubert syndrome in humans. This is a rare neurological condition that is linked with autism-spectrum disorders and brain structure malformations.
Without Arl13b, the nerve cells known as interneurons can’t find the right destination in the cerebral cortex during the brain’s development. Since the interneurons don’t end up in the right places, they can’t be wired up properly later on. This causes the disrupted brain development, typical of Joubert syndrome, visible in the image on the right.