Forward genetics identifies cuticle and regulatory genes underlying cellular boundary integrity in C. elegans

Area of Science:

• Developmental Biology
• Genetics
• Cell Biology

Background:

• The C. elegans epidermis and cuticle form a crucial protective barrier against environmental insults.
• Proper development of cellular boundaries requires complex molecular interactions.
• Hermaphrodite tail tip defects in mutants suggest a sensitive model for studying boundary establishment.

Purpose of the Study:

• To identify novel genes and pathways involved in establishing cellular boundaries in C. elegans.
• To characterize the function of identified genes, particularly in relation to cuticle integrity and membrane permeability.

Main Methods:

• Conducted a forward genetics screen of approximately 800 ethyl methanesulfonate-mutagenized haploid genomes.
• Identified mutants exhibiting Tail End Defects in the hermaphrodite phenotype.
• Utilized whole genome sequencing and CRISPR/Cas9 to identify and confirm mutations in novel and known genes.
• Performed lipidomics analysis to assess membrane composition changes.

Main Results:

• Identified 21 mutants with Tail End Defects, with mutations in genes encoding cuticle structural components or regulatory proteins.
• Confirmed 6 novel alleles for genes including ptr-18, paqr-2, nab-1, ncam-1, vab-9, and efn-4.
• Characterized the ptr-18(et70) loss-of-function allele, revealing significant effects on growth, development, and increased membrane permeability.
• Lipidomics showed no major changes in membrane lipid composition, suggesting cuticle defects cause permeability issues.

Conclusions:

• The C. elegans tail tip serves as a sensitive model for identifying genes regulating cellular boundaries.
• Mutations in genes like ptr-18 disrupt cuticle integrity, leading to developmental defects and increased membrane permeability.
• Cuticle defects, rather than altered lipid composition, are implicated as the primary cause of increased membrane permeability in ptr-18 mutants.