The function of a newly identified retinal homeobox-containing gene, Xenopus RxL in retinal development Dissertation zur Erlangung des akademischen Grades doctor rerum naturalium (Dr. rer. nat.) vorgelegt der Naturwissenschaftlichen Fakultät I Biowissenschaften der Martin-Luther-Universität Halle-Wittenberg von Huiyuan Wu M.Sc. of Microbial Pharmacy geb. am 06.04.1973 in Inner Mongolia, P.R.China Gutachter: 1. Prof. Dr. Thomas Hollemann 2. Prof. Dr. Elmar Wahle 3. Prof. Dr. Michael Kuhl verteidigt am 29.08.2008 urn:nbn:de:gbv:3-000014661[http://nbn-resolving.de/urn/resolver.pl?urn=nbn%3Ade%3Agbv%3A3-000014661] To my parents ????Table of Contents I Table of Contents Table of Contents I List of Figures V List of Tables VI Abbreviation VII Abstract XI 1 Introduction 1 1.1 Xenopus laevis as model system for developmental biology 1 1.2 Retina- the perception of light 1 1.3 Neural induction - the prelude of eye formation 3 1.4 The early patterning of vertebrate eye 6 1.4.1 The eye field specification in the anterior neural plate 6 1.4.2 The early morphogenesis of the eye 7 1.5 The cell-specification of retina cells 10 1.5.1 The extrinsic cues for retinal cell specification 10 1.5.2 The intrinsic clues for retinal cells specification 11 1.5.3 The intrinsic signals involved in photoreceptor cell specification 12 1.6 Rx genes in eye development 13 1.