FORWARD GENETICS IN C. ELEGANS REVEALS GENETIC ADAPTATIONS TO POLYUNSATURATED FATTY ACID DEFICIENCY

Area of Science:

• Cell Biology
• Genetics
• Biochemistry

Background:

• Polyunsaturated fatty acids (PUFAs) are essential for mammalian health, but their primary function remains unclear.
• Unlike mammals, *C. elegans* can synthesize PUFAs via the Δ12 desaturase FAT-2.
• FAT-2 activity is crucial for *C. elegans* viability, with null mutants being non-viable and near-null mutants exhibiting severe sickness.

Purpose of the Study:

• To investigate the essential function of PUFAs in *C. elegans*.
• To identify genetic mechanisms that compensate for PUFA deficiency.
• To understand how PUFA deficiency impacts membrane fluidity and stress responses.

Main Methods:

• Utilized fluorescence recovery after photobleaching (FRAP) to assess membrane rigidity in *fat-2(wa17)* mutants.
• Performed forward genetics screens to isolate suppressors of *fat-2(wa17)*.
• Analyzed the impact of suppressor mutations on PUFA levels and stress response pathways (daf-16, UPR^er, UPR^mt).

Main Results:

• *fat-2(wa17)* mutants display rigid membranes, which are rescued by dietary PUFAs but not by fluidizing agents or mutations.
• Forward genetics screen identified mutations in *fat-2* and the HIF-1 pathway as suppressors of PUFA deficiency.
• Suppressors increase endogenous PUFA levels and ameliorate the activation of stress response pathways in *fat-2(wa17)* worms.
• HIF-1 pathway mutations (in *egl-9*, *ftn-2*, *hif-1*) are hypothesized to increase Fe²⁺ levels, thereby enhancing desaturase activity.

Conclusions:

• PUFA deficiency in *C. elegans* leads to rigid membranes and activated stress responses.
• Genetic compensation for PUFA deficiency occurs primarily by increasing endogenous PUFA synthesis.
• PUFAs cannot be genetically substituted; their essential role necessitates endogenous production or dietary intake.