Fig. 1

Two alleles of zebrafish bmp4. st37 (A–F) is an insertion allele of bmp4 isolated in a screen for dominant enhancers of vox and vent; st72 (G, H) is a null allele identified in a reverse genetic screen with a yeast-based truncation assay. (A) Physical map of an approximately 31 kb region on LG17 that contains the four known exons of bmp4. Noncoding exons are purple, coding exons are yellow. The location and number of recombinants in 7475 meioses is shown for the SNP markers used in high resolution mapping of st37. The red arrowhead denotes the insertion site. (B) RT-PCR on total RNA from 70% epiboly embryos, 24 hpf embryos, and dissected ovaries with primers in exon 1 and exon 4 (32 of the insertion) and primers in exon 3 and exon 4 (coding region) of bmp4. bmp4 mRNA is significantly reduced in st37 homozygous mutants at both 70% epiboly and 24 hpf as compared to wild-type and heterozygous embryos. The reduction of bmp4 mRNA is less extreme in st37 mutant ovaries when assayed with primers within the coding region of bmp4, suggesting the existence of bmp4 isoforms with alternate 5′ UTR in mutant ovaries. (C–F) bmp4 expression in bmp4^st37 homozygotes (D, F) and wild-type siblings (C, E). (C, D) Shield stage, animal pole view, dorsal to the right. (E, F) Bud stage, lateral view, dorsal to the right. (G) A sequencing trace from the st72 F1 heterozygous male identifies a G to T mutation in the fourth exon of bmp4 that changes Glu(209) to a stop. (H) Schematic representation of the BMP4 protein and the location of the st72 lesion. The bmp4^st72 lesion causes the BMP4 protein to truncate in the prodomain.