Fig. 3

whz encodes Tbox transcription factor 20 (tbx20).

(A) Integrated genetic and physical map of the whz locus on zebrafish chromosome 16. The whz mutation interval is flanked by the microsatellite markers z1215 and z6240 and encodes 2 open reading frames, zebrafish tbx20 and herpud2. (B) Missense mutation of Adenine to Cytosine of the stop codon of tbx20 results in the loss of the original stop codon and the termination of tbx20 transcription after 87 additional nucleotides. (C) Partial amino acid alignment of the C-terminus of zebrafish whz and wt as well as human and murine Tbx20. Tbx20 is highly conserved cross-species and the whz mutant Tbx20 protein is extended by 29 additional amino acids. (D, E) Tbx20-specific whole-mount antisense RNA in situ hybridization detects unaltered expression of zebrafish tbx20 in whz mutant embryos compared to wild-types. (F) Quantitative RT-PCR analysis showing similar relative mRNA levels of tbx20 in wt and whz embryos at 72 hpf (n = 4; p = 0.5957). (G, H) Tbx20 protein levels are significantly reduced in whz mutant embryos compared to wild-type littermates (n = 4; p = 0.0286).