no tail integrates two modes of mesoderm induction

Area of Science:

• Developmental Biology
• Molecular Genetics
• Zebrafish Embryogenesis

Background:

• The nodal signaling pathway is critical for patterning early zebrafish embryos into germ layers.
• No tail (ntl) gene expression, induced by nodal signaling, is essential for mesoderm formation.
• Ntl expression exhibits both nodal-dependent and independent regulation, suggesting complex control mechanisms.

Purpose of the Study:

• To elucidate the regulatory elements governing nodal-dependent and nodal-independent expression of the no tail (ntl) gene in zebrafish embryos.
• To understand the distinct mechanisms of mesoderm formation mediated by different enhancers of ntl.
• To investigate the role of nodal-independent ntl regulation in tail formation.

Main Methods:

• Mapping of genetic elements responsible for ntl gene expression in the zebrafish embryo margin.
• Analysis of ntl enhancer activity in response to nodal, Wnt, and BMP signaling pathways.
• Functional studies involving misexpression of signaling ligands and assessment of ntl-dependent processes.

Main Results:

• Identified two distinct enhancers controlling ntl expression: one nodal-dependent and one responsive to Wnt and BMP signaling.
• Demonstrated that nodal-independent regulation of ntl is essential for tail formation, independent of nodal signaling.
• Showed that Wnt/BMP-mediated, nodal-independent tail formation requires ntl function and can induce ectopic tails.

Conclusions:

• Zebrafish mesoderm formation and tail development are regulated by at least two distinct enhancers controlling ntl expression.
• Nodal-independent pathways, involving Wnt and BMP signaling, play a crucial role in tail development through ntl.
• The identified enhancers provide insights into the complex genetic networks governing early embryonic patterning and organogenesis.