The serotonin 5-HT6 receptor (5-HT6R) is a G protein-coupled receptor only expressed in the central nervous system. It is a promising target for treating cognitive deficits observed in neurodevelopmental diseases, such as autism spectrum disorders (ASD). Our team has demonstrated a crucial role for the 5-HT6R in neurodevelopment. It participates in neuronal migration, the initiation of neurite growth and dendritic arborization, through interactions with different protein partners. We also confirmed that this receptor is mainly expressed in the primary cilium of neurons and astrocytes, except for a period of 10 days after birth, when it is found in the somatodendritic compartment. However, the impact of this dynamic subcellular localization on the receptor’s neurodevelopmental roles remain unknown. We set to study how subcellular localization during development affects the receptor’s interactome, hence its functions. We use a 3D culture model of corticogenesis from mouse embryonic stem cells (ESC) that faithfully reproduces cortical development in vitro. We have designed ESC lines allowing inducible expression of wild-type or mutated receptor on its cilium targeting domains, but also used CRISPR/Cas9 gene editing to insert a turboID-tag in the endogenous 5-HT6R. For each cell line, we characterized the receptor's subcellular localization throughout differentiation by immunofluorescence. We will then use high resolution mass spectrometry after either affinity purification or proximity labeling assay to identify the receptor’s protein partners throughout development. Our work will therefore provide a better understanding of how the 5-HT6R subcellular localization and protein partners work together to control its neurodevelopmental functions.