Loss of ptr-6 restores eggshell integrity and embryonic viability in C. elegans fatty acid synthase mutants

Fatty acid synthase (FASN) is a key rate-limited, dimeric multi-enzyme complex in the de novo lipogenesis pathway. Each FASN monomer contains seven catalytic domains, which coordinate the stepwise conversion of acetyl-CoA into fatty acids. While FASN has been extensively studied in cultured cells, particularly for its oncogenic role, its functions in the germline and early embryonic development remain elusive. A major challenge is that the FASN dysfunction typically causes embryonic lethality in animal models, which complicates detailed functional analysis and the identification of compensatory genetic interactors during development. To overcome this limitation and identify novel genetic suppressors of the FASN gene, we utilized a temperature-sensitive allele, fasn-1(g43ts) (A1424T), in the genetically tractable model Caenorhabditis elegans, to conduct unbiased forward genetic screens. We isolated 22 suppressor lines that significantly restored embryonic viability in the fasn-1(g43ts) mutant at the non-permissive temperature. Using a combination of MIP-MAP genomic mapping and a customized bioinformatic pipeline, we identified six mutations in the ptr-6 gene, which encodes a protein containing a patched domain associated with the Hedgehog-like signaling pathway. To validate this genetic suppression, we recreated one of the loss-of-function mutations, ptr-6[W701*], in the fasn-1(g43ts) background using CRISPR/Cas9 gene editing. Notably, ptr-6[W701*] robustly rescued the embryonic lethality and permeability defects caused by fasn-1 loss-of-function. Taken together, our findings expand the genetic regulatory network of fatty acid synthase during early embryogenesis and highlight ptr-6 and Hedgehog-like signaling pathway as potential genetic modifiers of FASN-associated developmental and metabolic disorders.