Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.|Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.|Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.|Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.|Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.|Department of Molecular Biology, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.