A progenitor with immature Bergmann glia-like characteristics in the developing cerebellar cortex

The cerebellum is an ancient brain component, conserved across mammalian species, that has classically played roles in regulating muscle tone, limb coordination, and equilibrium, as well as in non-motor functions, such as language, cognition, and emotion. Recently, we reported Nestin-expressing cells in the cerebellar cortex of ferret neonates that showed a proliferative potency defined by proliferating cell nuclear antigen (PCNA) immunostaining. We called these cells “internal granular progenitor (IGP).” IGPs were found to be abundant in the internal granular layer adjacent to the Purkinje cell layer and extended GFAP-immunopositive radials progressed through the molecular and external granular layers, forming an immature Bergmann glia-like morphology. The tracking of BrdU-labeling revealed that IGPs differentiated into granular neurons, Bergmann glia, and/or astrocytes. As such, we propose that IGPs may be neural progenitors with an immature Bergmann glia-like morphology that appear in the developing cerebellar cortex, and could serve as another source of granular neurons distinct from external granular progenitors. Further research on IGPs is expected to provide new perspectives for the future investigation of cerebellar corticohistogensis, particularly the difference between motor and non-motor cerebellar regions, and how the abnormal development of IGPs relates to neurodevelopmental disorders associated with non-motor cerebellar function, such as autism spectrum disorder.