Neurexin-Neuroligin Cell Adhesion Complexes Contribute to Synaptotropic Dendritogenesis via Growth Stabilization Mechanisms In Vivo

SummaryCell adhesion molecules are well characterized for mediating synapse initiation, specification, differentiation, and maturation, yet their contribution to directing dendritic arborization during early brain circuit formation remains unclear. Using two-photon time-lapse imaging of growing neurons within intact and awake embryonic Xenopus brain, we examine roles of β-neurexin (NRX) and neuroligin-1 (NLG1) in dendritic arbor development. Using methods of dynamic morphometrics for comprehensive 3D quantification of rapid dendritogenesis, we find initial trans-synaptic NRX-NLG1 adhesions confer transient morphologic stabilization independent of NMDA receptor activity, whereas persistent stabilization requires NMDA receptor-dependent synapse maturation. Disrupting NRX-NLG1 function destabilizes filopodia while reducing synaptic density and AMPA receptor mEPSC frequency. Altered dynamic growth culminates in reduced dendritic arbor complexity as neurons mature over days. These results expand the synaptotropic model of dendritogenesis to incorporate cell adhesion molecule-mediated morphological stabilization necessary for directing normal dendritic arborization, providing a potential morphological substrate for developmental cognitive impairment associated with cell adhesion molecule mutations.Video Abstract Help with MOV filesOptionsDownload video (104945 K)

► Rapid imaging in awake brain shows role for NRX-NLG1 in dendritogenesis
► NRX-NLG1 interactions direct rapid and long-term dendritic arbor growth
► NRX-NLG1 induce transient dendritic stabilization via activity-independent adhesions
► NRX-NLG1 induce persistent stabilization via activity-dependent synaptogenesis