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Fig. 2 Genetic identification of the love sofa mutation. A, Alignment of amino acid sequences of AChR δ subunit from human, rat, torpedo, Xenopus, wild-type zebrafish, and the love sofa mutant. The putative mutation of love sofa is located at the shadowed amino acid. In wild-type zebrafish, the amino acid is leucine, whereas in other species isoleucine or phenylalanine is found. In love sofa, it is changed to proline. The location of the L332P mutation in the δ subunit protein is shown in the right panel. B, The wild-type δ subunit was expressed in mosaic fashion by injecting the gene construct into the love sofa mutant at one cell stage. Muscle fibers expressing the transgene, as marked by the cytoplasmic GFP (green), displayed distributed synapses (arrowheads) as marked by α-BTX (magenta). C, When the δ subunit harboring the L332P mutation was expressed in the sofa potato mutant, α-BTX staining visualized myoseptal synapses (arrowheads) but failed to exhibit distributed synapses. Magenta represents α-BTX; green represents cytoplasmic GFP. Scale bar, 50 μm.