Vertebrate neural system development includes nueral induction, pattern formation and neurogenesis. At first, dorsal etctoderm is induced by the surrounding signals into neuro-ectoderm (neural plate), which is named neural induction; and then, the neuro-ectoderm is patterned along anterior-posterior and dorsal-ventral axis; at last, neural stem cells differentiate into many kinds of neural cell types. Here we studied the function of several genes involved in vertebrate neural development.The evolutionarily conserved Dbx homeodomain-containing proteins play important roles in the development of vertebrate central nervous system. In mouse, Dbx and Nkx6 have been suggested to be cross-repressive partners involved in the patterning of ventral neural tube. We isolated Xenopus Dbx2 and studied its developmental expression and function during neural development. From mid-neurula stage on, XDbx2 is expressed in stripes in the neural plate between the primary motoneurons and interneurons. At the tailbud stages, it is detected in the middle region of the neural tube. XDbx2 acts as a transcriptional repressor in vitro and over-expression of XDbx2 inhibits primary neurogenesis in Xenopus embryos. Over-expression of XDbx genes represses the expression of XNkx6.2 and vise versa. Knockdown of either XDbx1, XDbx2 or both by specific morpholinos induces lateral expansion of XNkx6.2 expression domains at neural stages. These data reveal conserved roles for Dbx in primary neurogenesis and dorsoventral neural patterning in Xenopus.The mid-hindbrain boundary (MHB) organizer is one of the best studied local organizers which patterns the midbrain and cerebellum in vertebrates.
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