Abstract: The adult subventricular zone of the lateral ventricles and the subgranular zone in the hippocampal dentate gyrus (DG) are the two brain regions where neurogenesis occurs throughout life in the adult mammalian brain (Ming and Song, 2011). Adult quiescent hippocampal neural stem cells (NSCs) are bona fide stem cells and, when activated, give rise to newborn granule neurons in the adult brain, which play vital roles in learning, memory, mood, and affective cognition (Bonaguidi et al., 2011; Ming and Song, 2011). Dysregulation of this process is often associated with brain disorders in both patients and various animal models (Christian et al., 2014). The proper establishment of a quiescent adult NSC pool is essential to sustain life-long continuous neurogenesis (Urban et al., 2019). Clonal lineagetracing in mice has identified a common neural precursor population that originates from the dentate neuroepithelium and migrates to primitive DG during the embryonic stage, and continuously contributes to the generation of dentate granule neurons from early embryonic stages to adulthood (Berg et al., 2019; Figure 1A). Furthermore, a subpopulation of proliferating DG NSCs undergoes a transition to quiescence during the early postnatal stage and adopts adult NSC-like quiescent properties to establish the quiescent adult DG NSC pool in mice (Berg et al., 2019; Bond et al., 2021; Figure 1A). Importantly, disturbances in the quiescence acquisition and fate determination of DG NSCs are closely associated with abnormal postnatal DG neurogenesis and neuronal circuitry formation during development, which would impair hippocampal function (Zhang et al., 2023, 2024; Jimenez-Cyrus et al., 2024). A better understanding of the fundamental mechanisms underlying adult neurogenesis and the establishment of a quiescent NSC pool is necessary to harness this striking intrinsic regenerative capacity in the adult mammalian brain for regeneration and repair. While the mechanisms regulating the activation and quiescence maintenance of adult DG NSCs have been widely investigated (Urban et al., 2019), research into cellular and molecular mechanisms governing the establishment of the adult NSC pool during development remains in its infancy.