Reduced expression of the Nodal co-receptor Oep causes loss of mesendodermal competence in zebrafish

Area of Science:

• Developmental biology
• Molecular signaling
• Gene expression regulation

Background:

• Cellular competence to signals is crucial for gene activation but its regulation is poorly understood.
• The molecular basis for the loss of cellular competence over time remains largely unknown.
• Nodal signaling pathways play vital roles in embryonic development.

Purpose of the Study:

• To determine the time window of competence loss in zebrafish prospective ectoderm towards Nodal signals.
• To elucidate the molecular mechanisms underlying this loss of competence.
• To investigate the role of the Nodal co-receptor One-eyed pinhead (Oep) in regulating competence.

Main Methods:

• Time-course analysis of zebrafish prospective ectoderm's response to Nodal signals.
• Quantification of One-eyed pinhead (Oep) levels during ectoderm development.
• Experimental manipulation of Oep levels and Nodal signaling using photoactivatable receptors and Oep-independent ligands.

Main Results:

• Zebrafish prospective ectoderm loses competence to Nodal signals within a specific time window.
• This loss of competence correlates with a decrease in One-eyed pinhead (Oep) levels.
• Bypassing Oep or extending its presence modulated the duration of Nodal target gene activation and cellular competence.

Conclusions:

• Decreasing levels of the Nodal co-receptor One-eyed pinhead (Oep) are a primary cause for the loss of responsiveness in prospective ectoderm.
• The temporal regulation of Oep levels directly controls the window of cellular competence to Nodal signals.
• This provides a simple molecular mechanism for regulating mesendodermal competence during early embryonic development.