UASt regulatory sequences drive expression of a mutated form of the fusion protein associated with the mouse 'Wld[S]' mutation. The 'Wld[S]' fusion protein is composed of the N-terminal 70 amino acids of Mmus\Ube4b, a unique 18 amino acid domain generated during the fusion event and the full-length sequence of Mmus\Nmnat1. In this transgene, an H24A amino acid replacement has been introduced into the fusion protein sequence (this mutation largely abolishes Mmus\Nmnat1 enzymatic activity). The coding sequence is tagged at the C-terminal end with 6xTag:MYC.