Fig. S3

bmp4 Transcripts are Expressed Throughout the Zebrafish Trunk, Found Polarised Under the Ventral Wall of the Dorsal Aorta During the Initiation of Definitive Haematopoiesis and Chordin Transcripts are Present Within the Pronephric Duct Progenitors and the Pronephric Duct.

a) Whole-mount in situ hybridisation with riboprobe to bmp4 in 23hpf wild-type embryo. bmp4 transcripts are present in the pronephric duct (PND) in the anterior trunk (blue arrowhead) and in the ventral mesenchyme under the DA (red arrowhead) in the posterior trunk. 10μm thick sections are shown in panels b, c and e. b) Transverse section through 24hpf embryo subjected to in situ hybridisation for bmp4 illustrating polarisation of bmp4 transcripts within the ventral mesenchyme under the DA (red arrowheads). c) Transverse section of 22hpf embryo stained for chordin (chd). Expression of chd within the pronephric ducts is illustrated (blue arrowheads). d) Flat mounted 5s embryo stained for pax2.1 and chd. Co-expression of pax2.1 and chd is illustrated within pronephric duct progenitors (blue arrowheads). e) Transverse section of 10s embryo subjected stained for chd. Expression of chd within the pronephric duct progenitors is illustrated (blue arrowheads). f) Flat mounted 10s embryo stained for scl and chd. chd is found lateral to scl within pronephric duct progenitors (blue arrows). No co-expression of chd and scl was detected. AV, axial vein; DA, dorsal aorta; NT, neural tube; NC, notochord; PND, pronephric duct; S, somite; VM, ventral mesenchyme.