Dynamic microtubules at the vegetal cortex predict the embryonic axis in zebrafish

Area of Science:

• Developmental biology
• Cell biology
• Genetics

Background:

• Maternal dorsal determinants are crucial for embryonic axis formation in zebrafish.
• Their transport after fertilization relies on microtubules, but early organization and dynamics remain unclear.

Purpose of the Study:

• To investigate the organization and dynamics of early microtubules in zebrafish embryos.
• To understand the role of microtubules in axis formation and maternal determinant transport.

Main Methods:

• Live imaging of zebrafish embryos.
• Analysis of microtubule organization (perpendicular bundles and parallel arrays).
• Tracking of vegetal cytoplasmic granules and wnt8a RNA localization.

Main Results:

• Identified two distinct microtubule populations: perpendicular bundles and parallel arrays, oriented at the vegetal cortex.
• Microtubule orientation at 20 minutes post-fertilization predicts dorsal structure formation.
• Parallel arrays colocalize with wnt8a RNA and mediate vegetal granule displacement, suggesting a cortical rotation-like process.
• Parallel array formation depends on calcium signaling.

Conclusions:

• Microtubule polarity and organization are key predictors of the zebrafish embryonic axis.
• A cortical rotation-like process, mediated by parallel microtubule arrays, contributes to asymmetric maternal determinant transport.
• Such processes may be more widespread in early development than previously recognized.