Dynamic smad‐mediated BMP signaling revealed through transgenic zebrafish

Abstract

BMP signaling is fundamental to development, injury response, and homeostasis. We have developed transgenic zebrafish that report Smad-mediated BMP signaling in embryos and adults. These lines express either eGFP, destabilized eGFP, or destabilized KO2 under the wellcharacterized 'BMP Response Element' (BRE). These fluorescent proteins were found to be expressed dynamically in regions of known BMP signaling including the developing tailbud, hematopoietic lineage, dorsal eye, brain structures, heart, jaw, fins, and somites, as well as other tissues. Responsiveness to changes in BMP signaling was confirmed by observing fluorescence after activation in an hsp70:bmp2b transgenic background or by inhibition in an hsp70:nog3 background. We further demonstrated faithful reportage by the BRE transgenic lines following chemical repression of BMP signaling using an inhibitor of BMP receptor activity, dorsomorphin. Overall, these lines will serve as valuable tools to explore the mechanisms and regulation of BMP signal during embryogenesis, in tissue maintenance, and during disease.

Temporally coordinated signals progressively pattern the anteroposterior and dorsoventral body axes

“…For example, the intracellular transducer of BMP signaling is nuclear pSmad1/5, which can be directly visualized by immunofluorescence [129,139,244,245]. There are also various transgenic reporters in zebrafish for Wnt [221,246,247], FGF [248], Nodal [83], RA [99,249], and BMP signaling [144,250–252]. These reporter transgenes utilize sequences from a promoter that responds to the morphogen signal to drive reporter expression e.g.…”

Bmp signaling mediates endoderm pouch morphogenesis by regulating Fgf signaling in zebrafish

“…Previous work, using EGFP driven by a BRE, showed that both the endoderm and CNCCs are Bmp responsive during pharyngeal arch development . Our approach utilizing a BRE driving a destabilized form of GFP (Collery and Link, 2011) demonstrated that the endoderm and CNCCs receive Bmp signaling during different time windows, with the endoderm being Bmp responsive prior to the CNCCs. This Bmp response is highly dynamic, occurring in the prepouch endoderm and being rapidly downregulated in mature pouches.…”

“…To characterize the temporal and spatial dynamics of Bmp signaling in the pharyngeal arches, we utilized a destabilized form of GFP driven by a BRE derived from the mouse Id1 promoter, BRE:d2GFP (Collery and Link, 2011). Using double-transgenic embryos labeling the endoderm (sox17:dsRed) and Bmp-responsive cells (BRE:d2GFP) we found that the endoderm received canonical Bmp signaling as early as 14 hours post-fertilization (hpf) (Fig.…”

Glypican4 promotes cardiac specification and differentiation by attenuating canonical Wnt and Bmp signaling

“…To test whether, in kny/gpc4 mutants, the ectopic BMP activation observed at 20 hpf could be the consequence of enhanced canonical Wnt signaling, we crossed the Tg(hsp70:wnt8a-gfp) line with a BMP reporter line expressing an orange fluorescent protein, Tg(bre:dmKO2), and heat-shocked embryos at 16 hpf (Collery and Link, 2011). In contrast to later stages of heart development, we did not detect enhanced bre:dmKO2 activity in the cardiac disk or LPM of heat-shocked wnt8-gfp embryos (supplementary material Fig.…”