A pioneer neuron is a cell that is a derivative of the

preplate The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...

in the early stages of

corticogenesis Corticogenesis is the process during which the cerebral cortex of the brain is formed as part of the development of the nervous system of mammals including its development in humans. The cortex is the outer layer of the brain and is composed of u ...

of the brain. Pioneer neurons settle in the marginal zone of the cortex and project to sub-cortical levels. In the rat, pioneer neurons are only present in prenatal brains. Unlike Cajal-Retzius cells, these neurons are

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 ...

-negative. Pioneer neurons are born in the ventricular

neuroepithelium Neuroepithelial cells, or neuroectodermal cells, form the wall of the closed neural tube in early embryonic development. The neuroepithelial cells span the thickness of the tube's wall, connecting with the pial surface and with the ventricular or ...

all over the cortical

primordium A primordium (; plural: primordia; synonym: anlage) in embryology, is an organ or tissue in its earliest recognizable stage of development. Cells of the primordium are called primordial cells. A primordium is the simplest set of cells capable of ...

. In the rat cortex, they appear at embryonic day (E) 11.5 in the lateral aspect of the

telencephalic The cerebrum, telencephalon or endbrain is the largest part of the brain containing the cerebral cortex (of the two cerebral hemispheres), as well as several subcortical structures, including the hippocampus, basal ganglia, and olfactory bulb. In ...

vesicle and cover its whole surface on E12. These cells, which show intense immunoreactivity for

calbindin Calbindins are three different calcium-binding proteins: calbindin, calretinin and S100G. They were originally described as vitamin D-dependent calcium-binding proteins in the intestine and kidney in the chick and mammals. They are now classi ...

and

calretinin Calretinin, also known as calbindin 2 (formerly 29 kDa calbindin), is a calcium-binding protein involved in calcium signaling. In humans, the calretinin protein is encoded by the ''CALB2'' gene. Function This gene encodes an intracellular ...

, are characterized by their large size and axonal projection. They remain in the marginal zone after the formation of the

cortical plate The cerebral cortex, also known as the cerebral mantle, is the outer layer of neural tissue of the cerebrum of the brain in humans and other mammals. The cerebral cortex mostly consists of the six-layered neocortex, with just 10% consisting of ...

; they project first into the ventricular zone, and then into the

subplate The subplate, also called the subplate zone, together with the marginal zone and the cortical plate, in the fetus represents the developmental anlage of the mammalian cerebral cortex. It was first described, as a separate transient fetal zone ...

and the

internal capsule The internal capsule is a white matter structure situated in the inferomedial part of each cerebral hemisphere of the brain. It carries information past the basal ganglia, separating the caudate nucleus and the thalamus from the putamen and the ...

. Therefore, these cells are the origin of the earliest efferent pathway of the developing cortex.

Function

It is thought that axons of pioneer neurons,

pioneer axon Pioneer axon is the classification given to axons that are the first to grow in a particular region. They originate from pioneer neurons, and have the main function of laying down the initial growing path that subsequent growing axons, dubbed follo ...

s, serve as a pathway for additional neurons that develop later in the embryo and project their axons to the appropriate target. In many systems pioneer neurons are eliminated by programmed cell-death and are not present in the adult.

External links

*
Neuronal Migration and Formation of Cellular Patterns During Brain Development
- from the site of the University of Texas. * {{cite journal , vauthors=Meyer G, Goffinet AM, Fairén A , title=What is a Cajal-Retzius cell? A reassessment of a classical cell type based on recent observations in the developing neocortex , journal=Cereb. Cortex , volume=9 , issue=8 , pages=765–75 , date=December 1999 , pmid=10600995 , doi=10.1093/cercor/9.8.765 , doi-access=free Authors of the article propose new criteria to distinguish between different cell types in the developing cortex. Developmental neuroscience

Function

See also

External links