Cajal–Retzius cell

Cajal-Retzius cell drawing by Cajal 1891

Cajal–Retzius cells are a type of neuron found in the mammalian cerebral cortex. They are named after the Spanish neuroscientist Santiago Ramón y Cajal and the German anatomist Heinrich Retzius who independently described these cells in the late 19th century. Cajal–Retzius cells play a crucial role during the development of the nervous system, particularly in the formation of the cerebral cortex's layered structure.

Function

Cajal–Retzius cells are primarily known for their role in the development of the cerebral cortex. They secrete a protein called Reelin, which is crucial for the proper layering of neurons in the cortex. Reelin signals to migrating neurons, helping them to position themselves in the correct layer of the cortex, a process essential for the establishment of cortical circuits and, consequently, for the functioning of the brain.

Location

These cells are found in the marginal zone of the developing cerebral cortex, which later becomes layer I in the mature cortex. They are among the first neurons to be generated during cortical development and are characterized by their widespread axonal projections and distinctive morphology.

Morphology

Cajal–Retzius cells have a unique and easily recognizable morphology. They possess a large, horizontally oriented cell body with a single axon and several dendrites extending from it. Their extensive axonal and dendritic trees allow them to interact with a large number of other neurons in the cortex.

Developmental Dynamics

The population of Cajal–Retzius cells decreases significantly after the completion of cortical development. Their numbers diminish as the brain matures, suggesting that their primary function is related to the early stages of brain development. The mechanisms behind their reduction are not fully understood but are thought to involve programmed cell death or apoptosis.

Clinical Significance

Alterations in the function or number of Cajal–Retzius cells have been implicated in several neurodevelopmental disorders, including schizophrenia, autism, and epilepsy. Given their role in cortical layering and circuit formation, abnormalities in these cells can lead to significant disruptions in brain function.

Research

Research on Cajal–Retzius cells continues to be an active area of study, with scientists exploring their roles in brain development, their interactions with other types of neurons, and their potential involvement in various neurological disorders. Understanding the functions and mechanisms of Cajal–Retzius cells offers insights into the fundamental processes of brain development and the pathogenesis of neurodevelopmental diseases.