Sustained Bmp signaling is essential for cloaca development in zebrafish

Area of Science:

• Developmental biology
• Molecular signaling
• Zebrafish embryogenesis

Background:

• Bone morphogenetic protein (Bmp) signaling is vital for ventral mesoderm development, including blood, vasculature, and kidney cells.
• The temporal roles of Bmp signaling in regulating ventral mesoderm patterning during gastrulation and somitogenesis remain largely uncharacterized.

Purpose of the Study:

• To investigate the temporal roles of Bmp signaling in ventral mesoderm patterning during zebrafish development.
• To elucidate the function of Bmp signaling in cloaca development and its implications for excretory system formation.

Main Methods:

• Utilized a transgenic inducible dominant-negative Bmp receptor line in zebrafish.
• Developed a novel assay to assess cloacal function in larvae.
• Analyzed gene expression patterns related to the excretory system and cloacal morphogenesis.

Main Results:

• Bmp signaling from mid-gastrula through early somitogenesis excludes blood and vascular precursors from the extreme ventral mesoderm.
• Reduced mid-gastrula Bmp signaling leads to defective cloaca development, impaired waste excretion, and altered excretory system gene expression.
• HrT, a Bmp-regulated T-box transcription factor, is essential for cloaca development.

Conclusions:

• Sustained Bmp signaling is critical for zebrafish cloaca specification by maintaining extreme ventral cell fate during gastrulation and early somitogenesis.
• Disruptions in Bmp signaling may contribute to anorectal malformations in human embryogenesis.