The phagocytic cyst cells in Drosophila testis eliminate germ cell progenitors via phagoptosis

Area of Science:

• Cell Biology
• Developmental Biology
• Genetics

Background:

• Phagoptosis is a non-autonomous cell death pathway where viable cells are eliminated by phagocytes.
• The precise molecular mechanisms and sequence of events initiating phagoptosis, particularly the role of phosphatidylserine (PS) signals, remain incompletely understood.

Purpose of the Study:

• To elucidate the sequential events and molecular players involved in phagoptosis of progenitor germ cells by cyst cells in Drosophila testes.
• To investigate the role of specific cellular components, including endosomes, lysosomes, and phagocytic receptors, in this process.

Main Methods:

• Live imaging of Drosophila testes using multiple fluorescent markers.
• Genetic manipulation, including knockdown of specific genes (Rab5, Lamp1) in cyst cells.
• Immunohistochemistry to detect phagocytic receptor expression (Draper).

Main Results:

• Progenitor germ cells in Drosophila testes undergo spontaneous removal by neighboring cyst cells via phagoptosis.
• Cyst cell-derived endosomes and lysosomes fuse with and acidify live germ cells prior to DNA fragmentation and PS exposure.
• The phagocytic receptor Draper is essential for this phagoptosis process.
• Knockdown of Rab5 or Lamp1 in cyst cells significantly blocks germ cell death.

Conclusions:

• Cyst cells actively participate in the removal of live germ cell progenitors through a phagoptosis pathway.
• The study reveals a novel sequence of events in phagoptosis, involving early endosomal and lysosomal involvement preceding PS exposure.
• This work highlights the critical role of phagocytic cyst cells in maintaining tissue homeostasis by eliminating viable germ cells.