Generation and characterization ofSema6aΔcytconditional knockout mice

Abstract

ABSTRACTThe axon guidance molecule Semaphorin-6A (SEMA6A) plays a key role during nervous system development. SEMA6A, classically known as a ligand for Plexin-A2 and -A4, is a transmembrane protein that can also elicit signaling via its intracellular domainin vitro. However, the physiological relevance of this ‘reverse’ signaling route is largely unknown. We generated a new transgenic mouse model,Sema6aΔcytfl/fl, in which the cytosolic part of SEMA6A can be conditionally removed usingCre-recombination. UponSema6aΔcytmutation, SEMA6A can only act as a ligand andreversesignaling is perturbed. Germline deletion of SEMA6A’s intracellular part results in developmental defects in axon pathfinding and neuron migration that partially phenocopy defects observed in fullSema6aknockout mice. These defects include disorganization of the anterior commissure, piriform cortex, lateral olfactory tract, thalamocortical and corticospinal white matter tracts, and defected neuron migration in the neocortex and cerebellum. Intriguingly, the hippocampal malformation described inSema6afull knockout mice was not reproduced, suggesting a specific role for SEMA6Aforwardsignaling in hippocampal development. Our results indicate that the intracellular domain of SEMA6A is essential for proper axon targeting and neuron migration, and provide the first proof of a SEMA6Areversesignaling pathwayin vivo.