Christensen Rikke, Alhonen Leena, Wahlfors Jarmo, Jakobsen Maria, Jensen Thomas G
Department of Human Genetics, University of Aarhus, Aarhus, Denmark.
Exp Dermatol. 2005 Jul;14(7):535-42. doi: 10.1111/j.0906-6705.2005.00326.x.
Phenylketonuria (PKU) is a metabolic disease causing increased levels of phenylalanine in blood and body fluids. Circulating phenylalanine is normally cleared by phenylalanine hydroxylase (PAH) expressed in the liver. The aim of this study is to exploit the skin as a 'metabolic sink' removing phenylalanine from the blood. We have previously showed that the overexpression of PAH and GTP cyclohydrolase I (GTP-CH), the rate-limiting enzyme in the synthesis of the cofactor for PAH, leads to high levels of phenylalanine clearance in primary human keratinocytes. In this study, we have investigated the 'metabolic sink' strategy in an in vivo model by developing three lines of transgenic mice expressing PAH and GTP-CH in various layers of the skin. The promoters used were keratin 14 (K14), involucrin (INV) and a truncated variant of Keratin 1 (K1). The mice were crossbred to a mouse model of human PKU, the PAH(enu2) mouse, in order to obtain mice that do not express PAH in the liver and the kidney. Transgenic mice containing the INV and K14 promoters expressed PAH and GTP-CH in the epidermis. However, the K1 promoter did not lead to detectable gene expression. Analysis of the mice showed that no phenotypic effect was observed in mice expressing PAH and GTP-CH from the INV promoter. However, low level of phenylalanine clearance was observed in mice expressing PAH and GTP-CH from the K14 promoter, suggesting that the skin can be genetically engineered to function as a 'metabolic sink'.
苯丙酮尿症（PKU）是一种代谢性疾病，会导致血液和体液中苯丙氨酸水平升高。循环中的苯丙氨酸通常由肝脏中表达的苯丙氨酸羟化酶（PAH）清除。本研究的目的是利用皮肤作为“代谢库”，从血液中清除苯丙氨酸。我们之前已经表明，PAH和GTP环水解酶I（GTP-CH，PAH辅因子合成中的限速酶）的过表达会导致原代人角质形成细胞中苯丙氨酸的高清除率。在本研究中，我们通过培育在皮肤各层表达PAH和GTP-CH的三系转基因小鼠，在体内模型中研究了“代谢库”策略。使用的启动子是角蛋白14（K14）、内披蛋白（INV）和角蛋白1（K1）的截短变体。将这些小鼠与人类PKU的小鼠模型PAH(enu2)小鼠杂交，以获得在肝脏和肾脏中不表达PAH的小鼠。含有INV和K14启动子的转基因小鼠在表皮中表达PAH和GTP-CH。然而，K1启动子未导致可检测到的基因表达。对小鼠的分析表明，从INV启动子表达PAH和GTP-CH的小鼠未观察到表型效应。然而，从K14启动子表达PAH和GTP-CH的小鼠中观察到低水平的苯丙氨酸清除，这表明皮肤可以通过基因工程改造来发挥“代谢库”的作用。
