Editing Reelin (section)

== Tissue distribution and secretion ==
Studies show that reelin is absent from [[synaptic vesicle]]s and is secreted via [[secretory pathway|constitutive secretory pathway]], being stored in [[Golgi apparatus|Golgi]] secretory vesicles.<ref name="golgi" /> Reelin's release rate is not regulated by [[depolarization]], but strictly depends on its synthesis rate. This relationship is similar to that reported for the secretion of other [[extracellular matrix]] proteins.{{citation needed|date=January 2016}}

During the brain development, reelin is secreted in the cortex and hippocampus by the so-called [[Cajal-Retzius cell]]s, Cajal cells, and Retzius cells.<ref name="cr_cells" /> Reelin-expressing cells in the prenatal and early postnatal brain are predominantly found in the marginal zone (MZ) of the cortex and in the temporary [[subpial granular layer]] (SGL), which is manifested to the highest extent in human,<ref name="pmid9671277" /> and in the hippocampal [[stratum lacunosum-moleculare]] and the upper marginal layer of the [[dentate gyrus]].

In the developing [[cerebellum]], reelin is expressed first in the external [[granule cell]] layer (EGL), before the granule cell migration to the internal granule cell layer (IGL) takes place.<ref name="Schiffmann" />

Having peaked just after the birth, the synthesis of reelin subsequently goes down sharply, becoming more diffuse compared with the distinctly laminar expression in the developing brain. In the adult brain, reelin is expressed by [[GABA]]-ergic [[interneuron]]s of the cortex and glutamatergic cerebellar neurons,<ref name="Interneurons" /> the glutamatergic stellate cells and fan cells in the superficial [[entorhinal cortex]] that are supposed to carry a role in encoding new [[episodic memories]],<ref>{{cite journal | vauthors = Kovács KA | title = Episodic Memories: How do the Hippocampus and the Entorhinal Ring Attractors Cooperate to Create Them? | journal = Frontiers in Systems Neuroscience | volume = 14 | pages = 68 | date = September 2020 | doi = 10.3389/fnsys.2020.559186 | pmid = 33013334 | pmc = 7511719 | doi-access = free }}</ref> and by the few extant Cajal-Retzius cells. Among GABAergic interneurons, reelin seems to be detected predominantly in those expressing [[calretinin]] and [[calbindin]], like [[bitufted neuron|bitufted]], [[horizontal neurons|horizontal]], and [[Martinotti cell]]s, but not [[parvalbumin]]-expressing cells, like [[chandelier cell|chandelier]] or [[basket neuron]]s.<ref name="Regional_patterns_1998" /><ref name="No_parvalbumin_1999" /> In the white matter, a minute proportion of [[interstitial neuron]]s has also been found to stain positive for reelin expression.<ref name="pmid19543540" />

[[File:Schema of the Reelin protein vertical en.png|thumb|Schema of the reelin protein]]
Outside the brain, reelin is found in adult mammalian blood, [[liver]], pituitary [[pars intermedia]], and adrenal [[chromaffin cell]]s.<ref name="bodyexpr" /> In the liver, reelin is localized in [[hepatic stellate cell]]s.<ref name="liver2" /> The expression of reelin increases when the liver is damaged, and returns to normal following its repair.<ref name="Kobold_2002_liver1" />
In the eyes, reelin is secreted by [[retinal ganglion cell]]s and is also found in the [[Corneal endothelium|endothelial layer of the cornea]].<ref name="pmid17120005" /> Just as in the liver, its expression increases after an injury has taken place.{{citation needed|date=January 2016}}

The protein is also produced by the [[odontoblast]]s, which are cells at the margins of the dental pulp. Reelin is found here both during odontogenesis and in the mature tooth.<ref name="pmid10980418" /> Some authors suggest that odontoblasts play an additional role as sensory cells able to [[Transduction (physiology)|transduce]] pain signals to the nerve endings.<ref name="pmid16831873" /> According to the hypothesis, reelin participates in the process<ref name="Reelin_book_2008" /> by enhancing the contact between odontoblasts and the nerve terminals.<ref name="pmid15464360" />