Fullerton Morgan D, Hakimuddin Fatima, Bakovic Marica
Department of Human Health and Nutirtionla Sciences, University of Guelph, Guelph, Ontario, Canada N1G 2W1.
Mol Cell Biol. 2007 May;27(9):3327-36. doi: 10.1128/MCB.01527-06. Epub 2007 Feb 26.
The CDP-ethanolamine pathway is responsible for the de novo biosynthesis of ethanolamine phospholipids, where CDP-ethanolamine is coupled with diacylglycerols to form phosphatidylethanolamine. We have disrupted the mouse gene encoding CTP:phosphoethanolamine cytidylyltransferase, Pcyt2, the main regulatory enzyme in this pathway. Intercrossings of Pcyt2(+/-) animals resulted in small litter sizes and unexpected Mendelian frequencies, with no null mice genotyped. The Pcyt2(-/-) embryos die after implantation, prior to embryonic day 8.5. Examination of mRNA expression, protein content, and enzyme activity in Pcyt2(+/-) animals revealed the anticipated 50% decrease due to the gene dosage effect but rather a 20 to 35% decrease. [(14)C]ethanolamine radiolabeling of hepatocytes, liver, heart, and brain corroborated Pcyt2 gene expression and activity data and showed a decreased rate of phosphatidylethanolamine biosynthesis in heterozygotes. Total phospholipid content was maintained in Pcyt2(+/-) tissues; however, this was not due to compensatory increases in the decarboxylation of phosphatidylserine. These results establish the necessity of Pcyt2 for murine development and demonstrate that a single Pcyt2 allele in heterozygotes can maintain phospholipid homeostasis.
CDP-乙醇胺途径负责乙醇胺磷脂的从头生物合成，在此过程中，CDP-乙醇胺与二酰基甘油结合形成磷脂酰乙醇胺。我们破坏了编码CTP：磷酸乙醇胺胞苷转移酶（Pcyt2）的小鼠基因，该酶是此途径中的主要调节酶。Pcyt2（+/-）动物的杂交产生了较小的窝仔数和意外的孟德尔频率，没有对纯合缺失小鼠进行基因分型。Pcyt2（-/-）胚胎在植入后、胚胎第8.5天之前死亡。对Pcyt2（+/-）动物的mRNA表达、蛋白质含量和酶活性的检测显示，由于基因剂量效应，预期会降低50%，但实际降低了20%至35%。用[（14）C]乙醇胺对肝细胞、肝脏、心脏和大脑进行放射性标记，证实了Pcyt2基因表达和活性数据，并显示杂合子中磷脂酰乙醇胺生物合成速率降低。Pcyt2（+/-）组织中的总磷脂含量保持不变；然而，这并不是由于磷脂酰丝氨酸脱羧作用的代偿性增加所致。这些结果证实了Pcyt2对小鼠发育的必要性，并表明杂合子中的单个Pcyt2等位基因可以维持磷脂稳态。
