Decreasing levels of that protein, an adhesion molecule called MDGA1, prevents neurons that normally make this protein from assuming their proper position, resulting in brain malformation, researchers report in the April 26th issue of the Journal of Neuroscience.
As Dennis D. M. O'Leary, Ph.D., senior author of the study and a Professor in the Molecular Neurobiology Laboratory put it, "proper neuronal positioning is essential for development of appropriate wiring, which is in turn critical for establishing a normal, functioning nervous system."
Neurons migrate throughout the brain, but migration is particularly important for development of part of the brain known as the cerebral cortex. The cortex sits like a skullcap over the rest of the brain and is responsible for sensory perception, higher-level reasoning, and, in humans, language. In mammals, the largest and evolutionarily newest part of the cortex, the neocortex, is recognized anatomically by its six horizontal layers.
The neocortex develops outward from an underlying zone of cells. From that zone, crawling neurons migrate radially out toward the surface or "superficial" part of the developing cortex, giving rise to a laminar structure. Neurons forming layers 2 and 3, the focus of the current study, are born last and so must elbow their way through cells lying in earlier formed layers to reach what will become the outermost layers. Without MDGA1, these neurons begin to migrate but get stuck before they reach their normal destina