Up‐regulation of HP 1γ expression during neuronal maturation promotes axonal and dendritic development in mouse embryonic neocortex

Immature neurons undergo morphological and physiological changes including axonal and dendritic development to establish neuronal networks. As the transcriptional status changes at a large number of genes during neuronal maturation, global changes in chromatin modifiers may take place in this process. We now show that the amount of heterochromatin protein 1γ ( HP 1γ) increases during neuronal maturation in the mouse neocortex. Knockdown of HP 1γ suppressed axonal and dendritic development in mouse embryonic neocortical neurons in culture, and either knockdown or knockout of HP 1γ impaired the projection of callosal axons of superficial layer neurons to the contralateral hemisphere in the developing neocortex. Conversely, forced expression of HP 1γ facilitated axonal and dendritic development, suggesting that the increase of HP 1γ is a rate limiting step in neuronal maturation. These results together show an important role for HP 1γ in promoting axonal and dendritic development in maturing neurons.