Planarians require ced-12/elmo-1 to clear dead cells by excretion through the gut

Area of Science:

• Cell biology
• Regenerative medicine
• Animal development and homeostasis

Background:

• Cell corpse removal is essential for development and tissue homeostasis across the animal kingdom.
• While engulfment and digestion are known mechanisms, cell clearance dynamics in adult tissues are poorly understood.

Purpose of the Study:

• To investigate the mechanisms of cell corpse clearance in adult planarian flatworms (Schmidtea mediterranea).
• To elucidate the role of gut phagocytes and specific molecular pathways in eliminating dead cells in adult tissues.

Main Methods:

• Induction of cell death in adult planarians using light exposure.
• Tracking the fate of dead pigment cells within the planarian body.
• Utilizing genetic analysis to identify key genes and cell types involved, including the ELMO pathway.

Main Results:

• Pigment cell corpses were observed to transit to the planarian gut and be excreted.
• Gut phagocytes, typically involved in food uptake, are crucial for directing dead cells into the gut lumen.
• The planarian engulfment and cell motility (ELMO) gene is essential for phagocytosis and gut-mediated clearance of cell corpses.

Conclusions:

• A novel mechanism for cell clearance in adult organisms involves the transport of dead cells to the gut.
• Gut phagocytes and the ELMO pathway facilitate the removal of cell debris through excretion.
• This study provides insights into tissue homeostasis and regeneration in adult animals.