Cajal–Retzius cell

Cajal–Retzius cells (also known as Horizontal cell of Cajal) are a heterogeneous population of morphologically and molecularly distinct reelin-producing cell types in the marginal zone/layer I of the developmental cerebral cortex and in the immature hippocampus of different species and at different times during embryogenesis and postnatal life.

These cells were discovered by two scientists, Cajal and Retzius, at two different times and in different species. They are originated in the developing brain in multiple sites within the neocortex and hippocampus. From there, Cajal–Retzius (CR) cells experience migration through the marginal zone, originating the layer I of the cortex.

As these cells are involved in the correct organization of the developing brain, there are several studies implicating CR cells in neurodevelopmental disorders, especially Alzheimer’s, schizophrenia, bipolar disorder, autism, lissencephaly and temporal lobe epilepsy.

History

In 1891 Santiago Ramón y Cajal described slender horizontal bipolar cells he had found in an histological preparation of the developing marginal zone of lagomorphs. These cells were then considered by Gustaf Retzius as homologous to the ones he had found in the marginal zone of human fetuses around mid-gestation in 1893 and 1894. He described those cells as having large, horizontal, sometimes vertically orientated somata located at some distance from the pia.