UASt regulatory sequences drive expression of BicD that has been mutated to carry the S103L amino acid replacement (this is equivalent to p.BICD2Ser107Leu in the human BICD2 ortholog, which is identified as a frequent mutation in individuals with autosomal dominant lower extremity-predominant spinal muscular atrophy 2). The protein is tagged at the C-terminal end with one copy of Tag:FLAG.