Abstract
Despite a long history of research of cortical marginal zone (MZ) organization and development, a number of issues remain unresolved. One particular issue is the problem of Cajal–Retzius cells (C–R) identification. It is currently based on morphology and Reelin expression. The aim of this research is to investigate MZ cytoarchitectonics and Reelin-producing cells morphotypes in the superior temporal, pre- and postcentral cortex at GW24–26. We used Reelin (Reln) as the marker for C–R cells and microtubule-associated protein 2 (MAP2) and neurofilament heavy chain protein (N200) as markers of neuronal maturation. The MZ of all of the investigated areas had the distinct cytoarchitectonic of alternating cell sparse (MZP, SR) and cell dense (SGL, DGL) layers. The distribution of the neuromarkers across the MZ also showed layer specificity. MAP2-positive cells were only found in the SGL. N200 and Reelin-positive neurons in the MZP. N200-positive processes were forming a plexus at the DGL level. All of the N200-positive neurons found were in the MZP and had distinctive morphological features of C–R cells. All of the N200-positive neurons in MZ were also positive for Reelin, whereas MAP2-positive cells lack Reelin. Thus, the joint use of two immunomarkers allowed us to discern the C–R cells based on their morphotype and neurochemistry and indicate that the Reelin-positive cells of MZ at 24–26 GW were morphologically C–R cells. In the current study, we identified three C–R cells morphotypes. Using a 3D reconstruction, we made sure that all of them belonged to the single morphotype of triangular C–R cells. This approach will allow future studies to separate C–R cells from other Reelin-producing neurons which appear at later corticogenesis stages. In addition, our findings support the assumption that a plexus could be formed not only with C–R cells processes but also possibly by other cell processes by the poorly researched DGL, which is only allocated as a part of the human MZ.
Highlights
The marginal zone (MZ) of the cortex is the part of the early preplate that remains above the cortical plate (CP)
The joint use of two immunomarkers allowed us to discern the C–R cells based on their morphotype and neurochemistry and indicate that the Reelin-positive cells of MZ at 24–26 gestational week (GW) were morphologically C–R cells
Kostovic et al (2004) note that this complex organization is transitory (GW 18–28) and that in the course of CP neuron differentiation, the subpial granular layer (SGL) and deep granular layer (DGL) gradually disappear as the cell density in them decreases
Summary
The marginal zone (MZ) of the cortex is the part of the early preplate that remains above the cortical plate (CP). In the last decade a growing number of reviews have been devoted to this problem (Soriano and del Río, 2005; Meyer, 2010; Gil et al, 2014; Kirischuk et al, 2014; MartínezCerdeño and Noctor, 2014; Marín-Padilla, 2015) Despite such steadily growing interest, the morphological characteristics of C–R cells during corticogenesis are not sufficiently defined. C–R cells in mice and rats appear at the 10–11th embryonic day (E10–11) and peak in morphological complexity and diversity at the 4–7th postnatal day (P4–7; Radnikow et al, 2002; Hevner et al, 2003; CabreraSocorro et al, 2007; Anstötz et al, 2014; Ma et al, 2014) Their classification is based on dendrite number: ‘‘typical’’ C–R cells have one horizontal dendrite and ‘‘atypical’’ have multiple dendrites (Radnikow et al, 2002; Ma et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
