Cytological and hitological analyses of essential Wnt 1 gene in morphogenesis of the central nervous system

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A detailed comparison of the cerebellum and midbrain (superior and inferior colliculi) between UNC5h3rcm and Wnt -1sw mice was performed in order to define role of Wnt -1 gene. The midbrain and cerebellum of UNC5h3rcm mouse as well wildtype mouse were present at E14 ; in "contrast, the midbrain and cerebellum of West-1sw mouse were considerably reduced in size at this stage." "However, by postnatal day 5 the posterior cereblellum and superior colliculus of Wnt-1sw mouse were" "similar in size to wildtype. From these findings, we suggest that generation and differentiation of midbrain or" cerebellum in Wnt-1sw mouse is delayed in comparison with wildtype and UNC5h3rcm mice. A fusion of the cerebellum and midbrain in UNC5h3rcm mouse was observed. This fusion created a merger of the anterior cerebellum and inferior colliculus and produced ectopic. Purkinje and ectopic granule cells "in the border zone. In Wnt -1sw mouse fusions of the cerebellum and midbrain were also present. These fusions, " "however, were variable in size and asymmetric. In some cases the entire inferior colliculus was missing and" "the anterior cerebellum was directly merged with the superior colliculus. In such cases, many ectopic " Purkinje cells and ectopic granule cells were present. No fusions were found in wildtype mice. From these "findings, we suggest that in UNC5h3rcm mouse the fusion of midbrain and cerebellum was induced by" "disruption between netrin and its receptor, whereas in Wnt -1sw mouse the fusion of midbrain and cerebellum " was induced by a massive disruption of the border between midbrain and cerebellum.