Charakterisierung der Selenoproteine Thioredoxinreduktase 1 und 2 anhand von Knock-out-Mausmodellen Tierärztliche Fakultät - Digitale Hochschulschriften der LMU - Teil 01/07
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Thioredoxin Reductases (TR) are ubiquitously expressed Selenium-containing redox enzymes. By reducing different intracellular substrates they protect cells from oxidative stress. For mus musculus two members of the Thioredoxin Reductase gene family have been characterized so far: TR1 and TR2. Whereas the subcellular localization of TR1 is mainly cytoplasmatic, TR2 was only found in mitochondria. The protein functions of TR1 and TR2 were investigated by examining genetically engineered mice. Here I will present the establishment of a conditional TR1-knockout mouse strain and the phenotypical characterization of TR1- and of TR2-knockout mice, that have been established before. Both knockouts, TR1 and TR2, showed to be embryonically lethal. TR1 deficient mouse embryos died at day 9.5, whereas TR2 deficient mouse embryos died around day 13.0 of embryonic gestation. Total deficiency of TR1 leads to strong developmental retardation and malformations in organogenesis mostly affecting the turning of the embryo, closure of neural tube, formation of head structures and formation of somites. Thereby TR1 deficient embryos maximally reach the developmental stage of normal E8.5 wildtype embryos. Neuronal specific TR1 knockout mice show growth retardation and cerebellar hypoplasia. Starting at the postnatal age of 10-14 days they loose weight and show cerebellar ataxia and tremors. Recent results indicate that mice die at the age of approximately 4 weeks. TR2 deficient embryos can already be recognized at embryonic day E11.5 due to a smaller embryo size and paler colour. Mice are retarded in their status of organ differentiation and show malformations in heart and liver development, possibly leading to fatal heart failure or liver insufficiency. Besides that, TR2 deficient embryos show decreased proliferation rates of hematopoetic progenitor cells in the embryonic liver. Taken together these results indicate that TR1 plays an important role in embryonic growth and organogenesis. Besides, deficiency of TR2 is proposed to disturb primarily the integrity of mitochondria and as a consequence affect processes like cell proliferation and transdifferentiation – leading to embryonic death. The functions of Thioredoxin Reductases 1 and 2 in separate organ systems need to be further analyzed by using conditional ablation strategies.
Thioredoxin Reductases (TR) are ubiquitously expressed Selenium-containing redox enzymes. By reducing different intracellular substrates they protect cells from oxidative stress. For mus musculus two members of the Thioredoxin Reductase gene family have been characterized so far: TR1 and TR2. Whereas the subcellular localization of TR1 is mainly cytoplasmatic, TR2 was only found in mitochondria. The protein functions of TR1 and TR2 were investigated by examining genetically engineered mice. Here I will present the establishment of a conditional TR1-knockout mouse strain and the phenotypical characterization of TR1- and of TR2-knockout mice, that have been established before. Both knockouts, TR1 and TR2, showed to be embryonically lethal. TR1 deficient mouse embryos died at day 9.5, whereas TR2 deficient mouse embryos died around day 13.0 of embryonic gestation. Total deficiency of TR1 leads to strong developmental retardation and malformations in organogenesis mostly affecting the turning of the embryo, closure of neural tube, formation of head structures and formation of somites. Thereby TR1 deficient embryos maximally reach the developmental stage of normal E8.5 wildtype embryos. Neuronal specific TR1 knockout mice show growth retardation and cerebellar hypoplasia. Starting at the postnatal age of 10-14 days they loose weight and show cerebellar ataxia and tremors. Recent results indicate that mice die at the age of approximately 4 weeks. TR2 deficient embryos can already be recognized at embryonic day E11.5 due to a smaller embryo size and paler colour. Mice are retarded in their status of organ differentiation and show malformations in heart and liver development, possibly leading to fatal heart failure or liver insufficiency. Besides that, TR2 deficient embryos show decreased proliferation rates of hematopoetic progenitor cells in the embryonic liver. Taken together these results indicate that TR1 plays an important role in embryonic growth and organogenesis. Besides, deficiency of TR2 is proposed to disturb primarily the integrity of mitochondria and as a consequence affect processes like cell proliferation and transdifferentiation – leading to embryonic death. The functions of Thioredoxin Reductases 1 and 2 in separate organ systems need to be further analyzed by using conditional ablation strategies.
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