HTT and Huntington disease: Huntingtin (HTT), the protein mutated in HD, is an adaptor for kinesin and dynein to either directly or indirectly link these motors to various cargo and cargo-adaptor complexes in neurons (Engelender et al, 1997; Li et al, 1998; Gauthier et al, 2004; Caviston et al, 2007; Vitet et al, 2020, 2023; Cason et al, 2021).