Ilyanassa Notch signaling implicated in dynamic signaling between all three germ layers

Area of Science:

• Developmental Biology
• Cell Signaling
• Marine Invertebrate Zoology

Background:

• Two specific cells (3D and 4d) in the mud snail Ilyanassa obsoleta are known to induce proper cell fate.
• Notch signaling is a conserved pathway involved in cell-cell communication during development.

Purpose of the Study:

• To investigate the role of Notch signaling in multiple developmental stages of Ilyanassa obsoleta.
• To determine if Notch signaling is involved in endoderm formation and the function of 3D/4d cells and their sublineages.

Main Methods:

• Analyzing expression patterns of Notch, Delta, and Suppressor of Hairless (SuH).
• Treating veligers with DAPT (a Notch inhibitor) and observing developmental defects.
• Utilizing Ilyanassa Delta siRNA to inhibit Delta function and assess phenotypic mimicry.

Main Results:

• Notch signaling components' expression patterns support its role in endoderm formation and 4d sublineage development.
• DAPT treatment resulted in loss of endodermal structures and defects in 4d inductive signaling targets.
• Delta siRNA injection mimicked DAPT-induced defects, suggesting Notch/Delta pathway involvement.
• Notch signaling is required for both early inductive events and later cell fate maintenance.

Conclusions:

• Notch signaling is essential for specifying endoderm fates and 4d sublineages in Ilyanassa obsoleta.
• The Notch pathway plays a continuous role throughout development, from initial induction to maintaining cell fates.
• A model is proposed where Notch signaling specifies and maintains cell fates induced by 4d cells.