The basal radial glia (bRG) is a type of progenitor in the subventricular zone (SVZ), which retains a basal process to the pial surface, sustains expression of radial glial markers and is capable of self-renewal. The bRGs occur at high relative abundance in the outer SVZ (OSVZ) of gyrencephalic animals, but lower of lissencephalic rodents, suggesting that the division of bRG in OSVZ is important to generate gyrencephalic brain. The common marmoset, Callithrix jacchus, is a primate which has a few gyrus and sulcus formations though the abundance of bRG cells is similar to that in human neocortex.
In order to study out the role of bRG in the developing marmoset brain, at first, we characterized the cell cycle of its bRG cells using the technique of thymidine analog labeling of the brain, in combination with immunofluorescent staining of brain slices. Secondary, we determined when the bRGs build up in the OSVZ in marmoset brain by histological analysis. The result is that its timing was later than those of gyrencephalic animals, such as human and macaque monkey, resulting in poor gyrification of marmoset brain. Furthermore, we labeled the dividing bRG with thymidine analogs when it is abundant in OSVZ according to previous data (Kelava et al., 2012). After birth, we performed histological analysis, showing that the bRG cells predominantly became the upper-layer neurons in the marmoset brain.