| Summary: | 碩士 === 國立陽明大學 === 神經科學研究所 === 90 === Kv4.3, a voltage-gated potassium channel alpha subunit, can evoke A-current in Xenopus oocytes. Previous studies showed that Kv4.3 mRNA exhibited an anterior-posterior (A-P) compartmentalization in granular layer of rat cerebel- lum. Kv4.3 mRNA was highly expressed in the posterior lobules, but at low levels in the anterior lobules. Kv4.3 has been the only ion channel subunit exhibiting A-P compartmentalization in mammalian cerebellum known so far. However, details related to this A-P compartmentalization, as well as the spatial and temporal expression of Kv4.3 in the cerebellum, remained unclear. In this study, with immunohistochemistry and double immunofluorescent staining, we found that granule cell is the only cell type responsible for the A-P compartmen- talization. Kv4.3 was expressed in the somata of posterior granule cells soon after they migrated from the external germinal layer into the internal granular layer at early postnatal stage. Kv4.3 was concentrated on the dendrites after granule cell maturation. Kv4.3 was not expressed in the germinal trigone or the external germinal layer, where granule cell precursors are located. Interestingly, we found that Kv4.3 was transiently expressed in migrating Purkinje cells at em- bryonic stage, and the expression pattern was complementary to calbindin staining. In contrast, in the basket cells, stellate cells, Lugaro cells, a subpopu- lation of Golgi cells, and a subset of deep neurons, expression of Kv4.3 was started soon after they arrived at their final destinations and continued through- out adulthood. Kv4.3 was selectively expressed in posterior but not anterior granule cells, suggesting that anterior and posterior granule cells are derived from two different populations of precursors. Transient expression of Kv4.3 in migrating Purkinje cells suggests that Kv4.3 may be important for the migration of Purkinje cells. Expression of Kv4.3 in many types of cerebellar inter- neurons suggests that Kv4.3 could be crucial for modulating signals in the cerebellum.
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