A pcyt-1 allelic series reveals in vivo consequences of reduced phosphatidylcholine synthesis in C. elegans.

Qvist A, Kaper D, Henricsson M, Stjernman A, Borén J, Pilon M

G3 (Bethesda) 16 (8) - [2026-08-05; online 2026-07-04]

Phosphatidylcholine (PC) is the most abundant phospholipid in eukaryotic membranes and is synthesized in part via the rate-limiting enzyme PCYT1A. In humans, hypomorphic PCYT1A variants cause diverse disorders. To define how graded reductions in PC synthesis affect organismal physiology, we generated and characterized a series of mutant alleles in the Caenorhabditis elegans homolog pcyt-1, including variants corresponding to disease-causing human mutations, as well as an auxin-inducible degradation allele. We identify a clear allelic hierarchy. The V146M variant is embryonic lethal, whereas A97T is largely benign. P154A is temperature-sensitive, and C211Y causes growth delay, reduced brood size, sterility, and lengthened lifespan at standard temperature. Phenotypes of C211Y are rescued by choline, CDP-choline, or PC supplementation, supporting reduced enzymatic function. Lipidomic profiling reveals that decreased PC synthesis consistently increases long-chain polyunsaturated fatty acids (LCPUFAs) in both PCs and phosphatidylethanolamine (PEs) at the expense of shorter saturated species, without markedly altering the PC/PE ratio at 20 °C. At elevated temperature, the P154A variant exhibits protein instability and a decreased PC/PE ratio. Despite significant lipid remodeling, canonical ER, mitochondrial, and metabolic stress GFP-based reporters are not activated; only the oxidative stress response is elevated, consistent with increased peroxidation-prone LCPUFAs in the pcyt-1 mutant. Acute auxin-induced degradation of PCYT-1 in larvae causes developmental arrest, while acute PCYT-1 degradation in adults disrupts oogenesis, demonstrating a continuous requirement for PC synthesis. Together, these findings establish a functional pcyt-1 allelic series and show that limiting PC synthesis drives compensatory remodeling toward LCPUFA-enriched membranes while rendering the germline particularly vulnerable.

Integrated Microscopy Technologies Gothenburg [Service]

PubMed 42400359

DOI 10.1093/g3journal/jkag161

Crossref 10.1093/g3journal/jkag161

pmc: PMC13439949
pii: 8724733