Jing M, Tactacan G B, Rodriguez-Lecompte J C, Kroeker A, House J D
Department of Animal Science, University of Manitoba, Winnipeg, Manitoba, Canada.
Poult Sci. 2009 Sep;88(9):1939-47. doi: 10.3382/ps.2009-00032.
The reduced folate carrier (RFC) has been postulated to be a major entity for folate transport activity in humans and other mammals. However, there are limited reports of the importance of RFC in an avian system. In the current study, therefore, the molecular cloning and tissue distribution of RFC, as well as the effect of dietary folate supplementation on the expression of this transporter, were investigated in the chicken. Shaver White laying hens (n=8 per diet) received 3 wheat-based diets containing the following: 1) no supplemental folate, 2) folic acid (10.00 mg/kg), or 3) 5-methyltetrahydrofolate (11.30 mg/kg) for 21 d. The mRNA expression levels were analyzed by quantitative real-time PCR. The results showed that the cloned partial RFC cDNA containing the full coding region from duodenum was 99% homologous to the reference gene available in GenBank. A broad expression profile of RFC transcripts was observed, with RFC mRNA detected in the brain, liver, kidney, spleen, lung, intestine, ovary, and testis, as well as other tissues. Real-time PCR analysis revealed that no significant differences (P>0.05) due to diet were found in the mRNA levels of RFC in the duodenum and cecum. However, compared with the basal diet, jejunal mRNA levels of RFC were decreased (P<0.05) in hens fed with the 5-methyltetrahydrofolate diet, but the reduction did not reach significance (P=0.077) in the hens fed the folic acid diet. Overall, the current study demonstrated that the RFC cDNA containing the full coding region was successfully cloned from the duodenum of laying hens. The wide tissue distribution of RFC transcripts is suggestive of an important role of RFC in the process of folate transport in the chicken. Moreover, dietary folate supplementation could downregulate the jejunal mRNA expression of RFC. Such findings will lay the foundation of future work involving the RFC in avian systems, including laying hens.
还原型叶酸载体（RFC）被认为是人类和其他哺乳动物中叶酸转运活性的主要载体。然而，关于RFC在禽类系统中的重要性的报道有限。因此，在本研究中，对鸡的RFC进行了分子克隆和组织分布研究，并研究了日粮添加叶酸对该转运蛋白表达的影响。将海兰白蛋鸡（每种日粮8只）分为3组，分别饲喂3种以小麦为基础的日粮，日粮分别含有：1）不添加叶酸；2）叶酸（10.00 mg/kg）；3）5-甲基四氢叶酸（11.30 mg/kg），持续21天。通过定量实时PCR分析mRNA表达水平。结果表明，从十二指肠克隆的包含完整编码区的部分RFC cDNA与GenBank中可用的参考基因有99%的同源性。观察到RFC转录本具有广泛的表达谱，在脑、肝、肾、脾、肺、肠、卵巢和睾丸以及其他组织中均检测到RFC mRNA。实时PCR分析显示，日粮对十二指肠和盲肠中RFC的mRNA水平没有显著影响（P>0.05）。然而，与基础日粮相比，饲喂5-甲基四氢叶酸日粮的母鸡空肠中RFC的mRNA水平降低（P<0.05），但饲喂叶酸日粮的母鸡中这种降低未达到显著水平（P=0.077）。总体而言，本研究表明成功从蛋鸡十二指肠克隆了包含完整编码区的RFC cDNA。RFC转录本广泛的组织分布表明RFC在鸡的叶酸转运过程中起重要作用。此外，日粮添加叶酸可下调空肠中RFC的mRNA表达。这些发现将为未来在禽类系统（包括蛋鸡）中研究RFC奠定基础。
