Endogenous Expression and Subcellular Localization of Core Apoptosis Regulators Reveal Key Differences Between...

Area of Science:

• Cell Biology
• Developmental Biology
• Genetics

Background:

• Apoptosis, or programmed cell death, is crucial for development and tissue homeostasis.
• The core apoptosis pathway in C. elegans involves EGL-1, CED-9, CED-4, and CED-3.
• Despite extensive study, the precise regulation of apoptosis, including tissue-specific induction and protein localization, remains incompletely understood.

Purpose of the Study:

• To generate and utilize CRISPR/Cas9 reporters for all core apoptosis genes in C. elegans.
• To systematically analyze the expression patterns and subcellular localization of apoptosis proteins in the germline and embryo.
• To elucidate the distinct mechanisms governing apoptosis in different developmental contexts.

Main Methods:

• CRISPR/Cas9 gene editing to create transcriptional and translational reporters for egl-1, ced-9, ced-4, and ced-3.
• Systematic analysis of gene expression and protein localization in C. elegans germline and embryos.
• Mutant analysis (brc-1, syp-2) to investigate meiotic surveillance pathways.

Main Results:

• Somatic apoptosis is driven by lineage-specific egl-1 activation, while ced-9, ced-4, and ced-3 are ubiquitously expressed.
• DNA damage induces egl-1 broadly in the germline, but apoptosis is restricted to specific meiotic cells.
• Distinct meiotic surveillance pathways converge on egl-1 induction, and intron1 of egl-1 is essential for CEP-1-dependent activation.
• Dynamic, tissue-specific subcellular localizations of CED-9, CED-4, and CED-3 were observed, refining the classical apoptosis model.
• CED-4 localizes to mitochondria later in embryogenesis, and CED-3 localization varies with developmental stage.

Conclusions:

• C. elegans apoptosis is regulated by two distinct programs: lineage-specific egl-1 activation in embryos and checkpoint-mediated egl-1 activation in the germline.
• The germline program involves unidentified pathways that restrict apoptotic execution.
• The generated reporters provide a valuable tool for studying apoptosis and non-apoptotic functions of conserved apoptotic machinery in vivo.