Disease-causing Mutations in Human Enzymes of the CDP-Ethanolamine and CDP-Choline Pathways Cause Distinct Growth and Phospholipid Synthesis Phenotypes in Saccharomyces cerevisiae

Abstract

Phosphatidylcholine and phosphatidylethanolamine are two of the most abundant phospholipids present in eukaryotic cells. In mammalian cells, these are mainly synthesized through the Kennedy pathways. PCYT1A is the gene that codes for the rate-limiting step in the CDP-choline pathway. Three rare inherited diseases have been associated with mutations in this gene. EPT1 is the gene that codes for the final step in the CDP-ethanolamine pathway and new patient-derived mutation has been associated with complex hereditary spastic paraplegia. I sought to better understand how these mutations affect the protein function using yeast as a model organism. Using serial dilution pinning assays, I discovered that some of the mutations in PCYT1A cause altered growth compared to the wild type when exposed to certain cell stressors. By studying the novel patient-derived mutation in EPT1 using metabolic radiolabelling of the CDP-ethanolamine pathway, I determined that this mutation causes a decrease in enzyme activity.