Multiple pathways for reestablishing PAR polarity in C. elegans embryo.

Area of Science:

• Developmental Biology
• Cell Biology
• Genetics

Background:

• Asymmetric cell divisions are crucial for development, producing daughter cells with distinct fates.
• PAR polarity proteins mediate symmetry breaking in many asymmetric divisions.
• The one-cell C. elegans embryo is a model for PAR polarity, but subsequent divisions are less understood.

Purpose of the Study:

• Investigate the mechanisms of PAR polarity establishment in the P1 cell of the two-cell C. elegans embryo.
• Identify key proteins and pathways involved in early and late polarization events.

Main Methods:

• Utilized C. elegans embryos for studying cell division and polarity.
• Employed genetic mutations (par-1, plk-1) to analyze the roles of specific kinases.
• Observed polarization dynamics, centrosome maturation, and actomyosin flow.

Main Results:

• A posterior PAR-2 domain forms rapidly in the P1 cell, strengthening over time.
• Early polarization depends on PAR-1 and PKC-3 kinases, and MEX-5/PLK-1 regulators.
• Loss of PAR-1 or PLK-1 delays polarization, which correlates with centrosome maturation and myosin flow.

Conclusions:

• PAR polarity in the P1 cell is established by at least two redundant pathways.
• An early pathway involves PAR-1, PKC-3, and cytoplasmic factors.
• A late pathway resembles one-cell embryo symmetry breaking, requiring PKC-3, AIR-1, and myosin flow.