Notum1a Inhibition promotes neurogenesis in the adult zebrafish brain.

Notum is a carboxylesterase enzyme that modulates extracellular signaling by hydrolyzing palmitoleoyl residues from proteins, thereby influencing key pathways involved in cell differentiation, survival, and proliferation. While notum1 expression has been identified in the brain, its role in adult neurogenesis remains poorly understood. Using the adult zebrafish brain as a model system, we demonstrate that the notum1a homolog is broadly expressed across various brain cell types but is absent in undifferentiated radial glial cells. Pharmacological inhibition of Notum activity with the small molecule inhibitor ABC99 stimulates activation of radial glial cells, leading to increased neurogenesis. A BrdU pulse-chase assay confirms that ABC99-induced proliferation enhances the production of mature neurons. Despite Notum's established role in Wnt signaling, transcriptional analysis following ABC99 treatment reveals no sustained impact on Wnt pathway targets, suggesting that Notum may regulate neurogenesis through alternative mechanisms. Our findings highlight notum1a as a potential modulator of neural progenitor cell dynamics in the adult brain and suggest that targeting Notum could represent a novel therapeutic strategy for neurodegenerative conditions characterized by impaired neurogenesis.