A molecular pathway determining left-right asymmetry in chick embryogenesis

Area of Science:

• Developmental Biology
• Embryogenesis
• Molecular Genetics

Background:

• Early embryonic axis specification (antero-posterior, dorso-ventral) is well-understood.
• The cellular and molecular basis of left-right (LR) asymmetry in animal morphogenesis remains largely unknown.

Purpose of the Study:

• To investigate the molecular mechanisms underlying left-right (LR) asymmetry in chick embryo development.
• To identify key genes and their expression patterns involved in establishing LR differences.

Main Methods:

• Examined expression patterns of activin receptor IIa, Sonic hedgehog (Shh), and cNR-1 in chick embryos.
• Analyzed gene interactions during and after gastrulation.
• Manipulated activin protein and Shh expression to observe effects on heart situs.

Main Results:

• Identified asymmetric expression of activin receptor IIa, Shh, and cNR-1 during and after gastrulation.
• Demonstrated a sequential regulatory pathway among these genes.
• Showed that altering activin or Shh sidedness impacts heart situs, confirming their role in LR determination.

Conclusions:

• A cascade of molecular asymmetry involving activin receptor IIa, Shh, and cNR-1 dictates morphological LR asymmetry in chick embryos.
• This pathway is crucial for establishing fundamental body plan asymmetries during development.