Fig. S7

BMP2b is the BMP family member in zebrafish that accounts for the BMP activity at the epidermis/neural ectoderm border that is dependent on SNW1.

(A) Comparison of BMP2b, BMP4, and BMP7 expression in zebrafish embryos at 11 hpf (2–3 somite stage) using WISH. BMP2b transcripts are enriched at the epidermis/neural ectoderm border (arrows). In contrast, BMP4 is enriched in the anterior prechordal plate and the tailbud, while BMP7 appears to be expressed in the endoderm. (B) Transgenic BRE-mRFP embryos were injected with 15 ng of control MO or MoZFSNW1. They were fixed at 11 hpf, when WISH was performed for mRFP. SNW1 knockdown results in the strong loss of BMP activity at the epidermis/neural ectoderm border, as seen with mRFP WISH in BRE-mRFP embryos. Notably, some of the posterior mRFP staining is preserved in the SNW1 morphant, which is likely because of BMP4 activity. BMP2b expression, however, appears unaltered in SNW1 morphants, suggesting that SNW1 does not induce BMP activity at the epidermis/neural ectoderm border through the transcriptional regulation of BMP2b. Note that the same batch of injected embryos was stained for mRFP or BMP2b.