Tbx16 cooperates with Wnt11 in assembling the zebrafish organizer

Area of Science:

• Developmental biology
• Embryology
• Molecular biology

Background:

• The organizer specifies vertebrate axial polarity and nervous system development.
• It is a dorsal midline mesodermal domain forming prechordal plate and anterior notochord.
• In zebrafish, the organizer's initial formation and assembly are not fully understood.

Purpose of the Study:

• To investigate the initial formation and cellular dynamics of the zebrafish organizer.
• To identify key molecular players involved in organizer assembly and symmetry.

Main Methods:

• Zebrafish embryo observation during gastrulation.
• Analysis of gene function using mutants for Tbx16 (Spadetail) and Wnt11 (Silberblick).
• Assay of organizer function via eye-field separation.

Main Results:

• The zebrafish organizer initially arises as two distinct cellular fields in the presumptive prechordal plate.
• Medial and anterior cell movements cause these fields to coalesce into a singular midline domain.
• Reduced Tbx16 or Papc function disrupts synchrony, leading to misshaped midline domains.
• Combined loss of Tbx16 and Wnt11 severely impairs coalescence and disrupts anterior cell movement and organizer function.

Conclusions:

• The zebrafish organizer is initially subdivided and requires cellular coalescence for proper formation.
• Tbx16, in conjunction with Wnt11, plays a critical role in the morphogenesis and initial assembly of the organizer.
• These factors are essential for establishing the symmetrical midline domain and subsequent organizer function.