Cdipt, also known as CDP-diacylglycerol-inositol 3-phosphatidyltransferase or phosphatidylinositol synthase, is a key enzyme in phosphatidylinositol (PI) synthesis. PI is a phospholipid molecule essential for generating seven different phosphoinositide lipids involved in diverse signaling and trafficking functions [2]. The synthesis of phosphatidylinositol by Cdipt catalyzes a reversible headgroup exchange reaction on its substrate liponucleotide CDP-diacylglycerol, incorporating inositol to generate phosphatidylinositol and release CMP. Genetic models, such as zebrafish mutants, are valuable for studying Cdipt's role.

In zebrafish, cdipt mutants have provided insights into its functions. The cdipt(lop/lop) mutant, with a missense mutation in the gene, lacks rod and cone photoreceptors and exhibits lens opacity by 7 days post-fertilization. Morpholino-mediated knockdown of cdipt phenocopies this mutant, and injection of wild-type cdipt mRNA reduces the lens opacity phenotype. Additionally, a cdipt retroviral-insertion allele shows similar lens and retinal abnormalities [1]. cdipt-deficient zebrafish also display endoplasmic reticulum (ER) stress and hepatic steatosis. Disruption of cdipt in hi559 mutants abrogates de novo PtdIns synthesis, leading to hepatomegaly, features of non-alcoholic fatty liver disease (NAFLD), and up-regulation of ER stress markers [4]. In zebrafish muscle, cdipt mutants have small but significant defects in triad size and decreased motor performance, suggesting a role in triad formation [3].

In conclusion, Cdipt is essential for phosphatidylinositol synthesis, which impacts various biological processes. Through model-based research, especially in zebrafish mutants, Cdipt has been shown to be crucial for photoreceptor and lens cell survival, triad formation in muscle, and maintaining ER homeostasis in the liver. Understanding Cdipt's functions may provide insights into diseases related to lipid metabolism, ER stress, and muscle development.