Quantitative analysis of FMO gene mRNA levels in human tissues

The developmentally and tissue-specific expression of flavin-con-taining monooxygenase (FMO) enzymes has been previously char-acterized in a number of animal species, including humans, mice, rats, and rabbits. In this study, we used sensitive real-time reverse transcription-polymerase chain reaction methodology to system-atically quantify the steady-state mRNA levels of FMO1, 2, 3, 4, and 5 in human tissues. We examined the developmental regulation of these enzymes in brain tissue. FMO1 was found to be down-regulated in human adult brain. The amount of other FMO mRNAs in human brains in different age groups was not significantly dif-ferent. The study also provided a systematic quantitative compar-ison of the steady-state mRNA levels of FMO1 to 5 in several major human organs (i.e., liver, lung, kidney, small intestine, and brain). The nature of the quantitative analysis allowed a comprehensive comparison of each FMO mRNA in different tissues as well a