Institute of Mammalian Genetics, GSF-National Research Center for Environment and Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany.|Institute of Mammalian Genetics, GSF-National Research Center for Environment and Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany.|Institute of Mammalian Genetics, GSF-National Research Center for Environment and Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany.|Institute of Mammalian Genetics, GSF-National Research Center for Environment and Health, Ingolstaedter Landstrasse 1, D-85764 Neuherberg, Germany.