SETD4 cells contribute to brain development and maintain adult stem cell reservoir for neurogenesis.

Cellular quiescence facilitates maintenance of neural stem cells (NSCs) and their subsequent regenerative functions in response to brain injury and aging. However, the specification and maintenance of NSCs in quiescence from embryo to adulthood remain largely unclear. Here, using Set domain-containing protein 4 (SETD4), an epigenetic determinant of cellular quiescence, we mark a small but long-lived NSC population in deep quiescence in the subventricular zone of adult murine brain. Genetic lineage tracing shows that SETD4 cells appear before neuroectoderm formation and contribute to brain development. In the adult, conditional knockout of Setd4 resulted in quiescence exit of NSCs, generating newborn neurons in the olfactory bulb and contributing to damage repair. However, long period deletion of SETD4 lead to exhaustion of NSC reservoir or SETD4 overexpression caused quiescence entry of NSCs, leading to suppressed neurogenesis. This study reveals the existence of long-lived deep quiescent NSCs and their neurogenetic capacities beyond activation.