Cajal–Retzius cells (CR cells) (also known as Horizontal cells of Cajal) are a heterogeneous population of morphologically and molecularly distinct
reelin
Reelin, encoded by the ''RELN'' gene, is a large secreted extracellular matrix glycoprotein that helps regulate processes of neuronal migration and positioning in the developing brain by controlling cell–cell interactions. Besides this impor ...
-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,
Santiago Ramón y Cajal
Santiago Ramón y Cajal (; 1 May 1852 – 17 October 1934) was a Spanish neuroscientist, pathologist, and histologist specializing in neuroanatomy and the central nervous system. He and Camillo Golgi received the Nobel Prize in Physiology or Me ...
and
Gustaf Retzius
Prof Magnus Gustaf (or Gustav) Retzius FRSFor HFRSE MSA (17 October 1842 – 21 July 1919) was a Swedish physician and anatomist who dedicated a large part of his life to researching the histology of the sense organs and nervous system.
Lif ...
, at two different times and in different species. They are originated in the developing brain in multiple sites within the
neocortex
The neocortex, also called the neopallium, isocortex, or the six-layered cortex, is a set of layers of the mammalian cerebral cortex involved in higher-order brain functions such as sensory perception, cognition, generation of motor commands, ...
and
hippocampus
The hippocampus (via Latin from Greek , ' seahorse') is a major component of the brain of humans and other vertebrates. Humans and other mammals have two hippocampi, one in each side of the brain. The hippocampus is part of the limbic system, ...
. From there, Cajal–Retzius (CR) cells migrate 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
schizophrenia
Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social wi ...
,
bipolar disorder
Bipolar disorder, previously known as manic depression, is a mental disorder characterized by periods of depression and periods of abnormally elevated mood that last f