Alternative Splicing Controls Teneurin-3 Compact Dimer Formation for Neuronal Recognition

Neuronal network formation is facilitated by recognition between synaptic cell adhesion molecules (CAMs) at the cell surface. Alternative splicing of CAMs provides additional specificity in forming neuronal connections. For the teneurin family of CAMs, alternative splicing of the EGF-repeats and NHL domain controls protein-protein interactions at the synapse. Here we present a 3.2 Å cryo-EM structure of the compact dimeric ectodomain of teneurin-3 harbouring both splice inserts. This dimer is stabilised by an EGF8-ABD contact between subunits. Cryo-EM reconstructions of all four splice variants, together with SAXS and negative stain EM, reveal compacted dimers for each, with variant-specific dimeric arrangements. This results in specific trans-cellular interactions, as tested in cell clustering and stripe assays. The compact conformations provide a structural basis for teneurin homo- and heterophilic interactions. Altogether, our findings demonstrate how alternative splicing results in rearrangements of the dimeric subunits, influencing neuronal recognition and circuit wiring.