Budding-specific lectin induced in epithelial cells is an extracellular matrix component for stem cell aggregation in...

Area of Science:

• Marine Biology
• Developmental Biology
• Biochemistry

Background:

• Tunicates exhibit complex budding processes involving stem cell differentiation.
• Extracellular matrix (ECM) components play vital roles in developmental processes.
• Lectins are proteins known for their specific carbohydrate-binding properties and diverse biological functions.

Purpose of the Study:

• To investigate the expression, localization, and function of a specific lectin from the budding tunicate, Polyandrocarpa misakiensis.
• To elucidate the role of this lectin in the context of bud morphogenesis and stem cell behavior.
• To determine the lectin's interaction with hemoblasts (pluripotent stem cells) and the extracellular matrix during development.

Main Methods:

• Immunocytochemical analysis was used to detect lectin expression and localization.
• Purification of a calcium-dependent, galactose-binding lectin (14 x 10^3 Mr) from P. misakiensis.
• In vivo bioassays were conducted to assess the lectin's functional role in stem cell migration and aggregation, including experiments with galactose and anti-lectin antibodies.

Main Results:

• The lectin was observed in granules within epithelial cells and secreted into the mesenchymal space, forming an ECM during budding.
• Granular leucocytes also produced and secreted the lectin.
• The lectin exhibited high binding affinity for hemoblast precursors and was essential for their migration towards the epithelium, but not for cell-cell adhesion.
• Anti-lectin antibodies inhibited hemoblast spreading and migration on the ECM.

Conclusions:

• Polyandrocarpa lectin is an ECM component specifically induced during tunicate budding.
• The lectin plays a significant role in bud morphogenesis by regulating the migration of pluripotent stem cells.
• This lectin directs hemoblast precursors to the epithelium, facilitating organ rudiment formation.