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Fig. 4 catastrophegw325 contains a copper sensitive mutation in the vacuolar (H+) ATPase Atp6.
(A–B) cto embryos are globally sensitive to copper deficiency. Wild-type embryos (A) in 2 μM neocuproine do not display notochord defects. In contrast, cto embryos (B) placed in this same dose of neocuproine have significant distortion of the notochord in a pattern consistent with loss of lysyl oxidase activity [12]. (C) Meotic mapping placed the cto mutation between markers z21519 (43.1cM) and z43308 (44.9cM) on chromosome 7. (D) Atp6v0d1 is highly conserved between zebrafish and mammals and is easily differentiated from ATP6V0D2 present in humans. The amino acid Q136 is changed to a stop in the mutant (asterisk). (E) The mutation in cto abolishes expression of the full length protein. Immunoblot analysis using a C-terminal polyclonal antibody shows no recognition of the 40 kD band in 48 hpf cto embryos. The identity of the band at 50 kD is unknown. Actin was used as a loading control (lower panel). (F) Model of the proposed quaternary structure of Atp6. The lower-case d subunit (yellow) forms part of a connecting stalk between the V1 and V0 subunits the presence of which is required for proper formation of the entire transporter [19].