Ectoderm cell--ECM interaction is essential for sea urchin embryo skeletogenesis

Area of Science:

• Developmental Biology
• Cell Biology
• Marine Biology

Background:

• Paracentrotus lividus sea urchin nectin (Pl-nectin) is an extracellular matrix protein found on the sea urchin embryo's ectoderm.
• Pl-nectin functions as an adhesive substrate for embryonic cells, playing a role in early development.

Purpose of the Study:

• To investigate the in vivo functions of Pl-nectin in sea urchin embryonic development.
• To determine the role of Pl-nectin in cell adhesion and morphogenesis.

Main Methods:

• A monoclonal antibody (McAb) against Pl-nectin was generated.
• Fab fragments (Fabs) of the McAb were applied to early sea urchin blastulae to assess in vivo effects.
• In vitro assays were used to measure the inhibition of blastula cell adhesion to Pl-nectin.

Main Results:

• External application of Pl-nectin McAb Fabs inhibited skeletal elongation and patterning in developing sea urchin embryos.
• Ingression of primary mesenchyme cells and endoderm development were not affected by the Fabs.
• Pigment cell migration was disrupted, with cells remaining clustered instead of dispersing.
• Injection of Fabs into the blastocoel did not affect skeletogenesis, indicating an indirect effect of the antibody.

Conclusions:

• Appropriate contact between ectodermal cells and outer extracellular matrix components, like Pl-nectin, is essential for correct morphogenesis of inner mesodermal structures in sea urchin embryos.
• Pl-nectin plays a critical, albeit indirect, role in regulating skeletal development and cell migration during sea urchin embryogenesis.