TSPAN5 and Intellectual disability: Importantly, we found that TSPAN5 exerts this function by interacting with AP4, a member of the adaptor protein complex family (Boehm and Bonifacino, 2001; Bonifacino, 2014; Robinson and Bonifacino, 2001), which coding genes are mutated in a syndrome characterised by spastic paraplegia and intellectual disability (Sanger et al., 2019).