Organization of radial glia reveals growth pattern in the telencephalon of a percomorph fish Astatotilapia burtoni

• Published in: Journal of comparative neurology (1911) Vol. 529; no. 10; pp. 2813 - 2823
• Main Authors: Mack, Andreas F., DeOliveira‐Mello, Laura, Mattheus, Ulrich, Neckel, Peter H.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01.07.2021; Wiley Subscription Services, Inc
• Subjects: Animals; Astatotilapia burtoni; astrocyte; Astrocytes; Brain; Cell differentiation; cell proliferation; Cichlids - growth & development; doublecortin; Doublecortin protein; Ependymoglial Cells - physiology; Female; Glial cells; Growth patterns; Immunocytochemistry; Male; Neurogenesis - physiology; Neuronal-glial interactions; Pallium; Proliferating cell nuclear antigen; radial glia; Radial glial cells; Sox2; Stem cells; Telencephalon; Telencephalon - growth & development; tissue clearing; Ventricle; Sox2; doublecortin; radial glia; cell proliferation; pallium; tissue clearing; telencephalon; astrocyte
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.25126

In the brain of teleost fish, radial glial cells are the main astroglial cell type. To understand how radial glia structures are adapting to continuous growth of the brain, we studied the astroglial cells in the telencephalon of the cichlid fish Astatotilapia burtoni in small fry to large specimens. These animals grow to a standard length of 10–12 cm in this fish species, corresponding to a more than 100‐fold increase in brain volume. Focusing on the telencephalon where glial cells are arranged radially in the everted (dorsal) pallium, immunocytochemistry for glial markers revealed an aberrant pattern of radial glial fibers in the central division of the dorsal pallium (DC, i.e., DC4 and DC5). The main glial processes curved around these nuclei, especially in the posterior part of the telencephalon. This was verified in tissue‐cleared brains stained for glial markers. We further analyzed the growth of radial glia by immunocytochemically applied stem cell (proliferating cell nuclear antigen [PCNA], Sox2) and differentiation marker (doublecortin) and found that these markers were expressed at the ventricular surface consistent with a stacking growth pattern. In addition, we detected doublecortin and Sox2 positive cells in deeper nuclei of DC areas. Our data suggest that radial glial cells give rise to migrating cells providing new neurons and glia to deeper pallial regions. This results in expansion of the central pallial areas and displacement of existing radial glial. In summary, we show that radial glial cells can adapt to morphological growth processes in the adult fish brain and contribute to this growth. The orientation of radial glia in the dorsal telencephalon of teleost fish follows a morphogenetic process called eversion. We studied the radial glia in the cichlid fish Astatotilapia burtoni and found that glial processes get increasingly displaced by central pallial areas during growth. New cells are added to the growing brain subventricularly consistent with a stacking growth pattern (Cell Addition I). In addition, our data suggest that radial glial cells give rise to migrating astroglial cells providing new neurons and glia to deeper pallial regions (Cell Addition II).