Hsu Yi-Hua, Huang Hsin-Yi, Tsaur Meei-Ling
Institute of Neuroscience, National Yang-Ming University, Taipei, Taiwan 112, Republic of China.
Eur J Neurosci. 2003 Aug;18(3):601-12. doi: 10.1046/j.1460-9568.2003.02786.x.
Kv4.3, an A-type K+ channel, is the only channel molecule showing anterior-posterior (A-P) compartmentalization in the granular layer of mammalian cerebellum known so far. Kv4.3 mRNA has been detected from the posterior but not anterior granular layer in adult rat cerebellum. To characterize this A-P compartmentalization further, we examined Kv4.3 protein expression in rat cerebellum by immunohistochemistry at the embryonic, early postnatal and adult stages. Specificity of the Kv4.3 antibody was confirmed by both Western blot and immunoprecipitation analysis. In adulthood, Kv4.3 was detected from the somatodendritic domain of posterior granule cells, with a restriction boundary in the vermal lobule VI extending laterally to the hemispheric crus 1 ansiform lobules. At the early postnatal stage, this A-P pattern first appeared on postnatal day 8, when significant numbers of granule cells had migrated into the posterior granular layer and started to express Kv4.3. Similar Kv4.3 expression in the somatodendritic domain of post-migratory neurons in the cerebellum was also observed in basket cells, stellate cells, a subset of GABAergic deep neurons, Lugaro cells and, probably, deep Lugaro cells. However, none of them showed A-P compartmentalization. Strikingly, we found Kv4.3 in several clusters of migrating Purkinje cells with mediolateral compartmentalization. These Purkinje cells no longer expressed Kv4.3 after completing the migration. By contrasting the expression in migrating and post-migratory neurons, our results suggest that Kv4.3 may play an important role in the development of cerebellum, as well as in the mature cerebellum.
Kv4.3是一种A型钾离子通道，是目前已知的唯一一种在哺乳动物小脑颗粒层呈现前后区室化分布的通道分子。在成年大鼠小脑中，已在后侧颗粒层而非前侧颗粒层检测到Kv4.3信使核糖核酸。为了进一步表征这种前后区室化分布，我们通过免疫组织化学方法，在胚胎期、出生后早期和成年期三个阶段检测了大鼠小脑中Kv4.3蛋白的表达情况。通过蛋白质免疫印迹法和免疫沉淀分析，证实了Kv4.3抗体的特异性识别作用。在成年期小脑中，Kv4.3表达于后侧颗粒细胞的胞体树突区域，其限制边界在蚓部小叶VI，向外侧延伸至半球的小脑镰1和半月小叶。在出生后早期阶段，这种前后分布模式首次出现在出生后第8天，此时大量颗粒细胞已迁移至后侧颗粒层并开始表达Kv4.3。在篮状细胞、星状细胞、一部分γ-氨基丁酸能深部神经元、卢加罗细胞以及可能的深部卢加罗细胞中，也观察到小脑迁移后神经元的胞体树突区域存在类似的Kv4.3表达。然而，它们均未呈现前后区室化分布。令人惊讶的是，我们在几簇具有内外侧区室化分布的迁移中的浦肯野细胞中发现了Kv4.3。这些浦肯野细胞在完成迁移后不再表达Kv4.3。通过对比迁移中和迁移后神经元中的表达情况，我们的结果表明，Kv4.3可能在小脑发育以及成熟小脑中发挥重要作用。
