The central relay station in this flow of information is the thalamic complex in the diencephalon. During the development of this organ, highly differentiated, information-processing structures are formed - such as the cerebrum in the telencephalon, the tectum in the mesencephalon and the cerebellum in the rhombencephalon - which all have to be wired up with the information-generating sensory systems. The regionalisation and refinement of naìˆve neural tissue is a prerequisite for developing an elaborate structure such as the brain. We therefore propose that the ZLI is induced within the competence area established by Otx1l/2, and is posteriorly restricted by Irx1b. Furthermore, absence of thalamic Irx1b expression, in the presence of normal Otx1l/2 function, leads to a substantial caudal broadening of the ZLI by transformation of thalamic precursors. Conditional expression of Otx2 in these morphant embryos cell-autonomously rescues the formation of the ZLI at its correct location. Formation of both the ZLI and the Irx1b-positive thalamus require Otx1l/2 embryos impaired in Otx1l/2 function fail to form these areas, and,instead, the adjacent pretectum and, to a lesser extent, the prethalamus expand into the mis-specified area. Here we show that, before ZLI formation, both Otx1l and Otx2(collectively referred to as Otx1l/2) are expressed in spatially restricted domains. However, our understanding of the mechanisms responsible for positioning the ZLI along the neural axis is poor. Shh signalling from the ZLI confers regional identity of the flanking subregions of the ZLI, making it an important local signalling centre for regional differentiation of the diencephalon. The thalamic complex is the major sensory relay station in the vertebrate brain and comprises three developmental subregions: the prethalamus, the thalamus and an intervening boundary region - the zona limitans intrathalamica(ZLI).
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |