The Balance Between Self-Renewal and Differentiation of Human Neural Stem Cells Requires the Amyloid Precursor Protein

Abstract

The approximately 16 billion neurons of the human neocortex are derived from a relatively limited number of developmental neural stem cells (NSCs). During embryogenesis, human cortical NSCs initially generate neurons at a particularly slow rate while preserving their progenitor state for a relatively long time. How this balance between the progenitor state and neurogenic state is regulated, and whether it contributes to species-specific brain patterning, is poorly understood. Here we show that the characteristic potential of human NSCs to remain in a progenitor state as they generate neurons for a prolonged amount of time requires the Amyloid Precursor Protein (APP). In contrast, APP is dispensable in mouse NSCs, which undergo neurogenesis at a much faster rate. Mechanistically, loss of APP cell-autonomously accelerates neurogenesis through activation of the AP-1 transcription factor and repression of WNT signaling. We propose that the fine balance between self-renewal and differentiation is homeostatically regulated by APP, which may contribute to human-specific temporal patterns of neurogenesis.