Xiong Z, O'Hanlon D, Becker L E, Roder J, MacDonald J F, Marks A
Department of Physiology, University of Toronto, Toronto, Ontario, M5S 1A8, Canada.
Exp Cell Res. 2000 Jun 15;257(2):281-9. doi: 10.1006/excr.2000.4902.
S100B is the major low-affinity Ca(2+)-binding protein in astrocytes. In order to study the role of S100B in the maintenance of Ca(2+) homeostasis, we generated S100B null mice by a targeted inactivation of the S100B gene. Absence of S100B expression was demonstrated by Northern and Western blotting for S100B mRNA and protein, respectively, and immunoperoxidase staining of sections of various brain regions. S100B null mice were viable, fertile, and exhibited no overt behavioral abnormalities up to 12 months of age. On the basis of light microscopy and immunohistochemical staining, there were no discernable alterations in the distribution and morphology of astrocytes or neurons in sections of adult brains of these mice. Astrocytes in cerebellar cultures derived from 6-day-old S100B null mice exhibited enhanced Ca(2+) transients in response to treatment with KCl or caffeine. On the other hand, granule neurons, in the same cultures, exhibited normal Ca(2+) transients in response to treatment with KCl, caffeine, or N-methyl-d-aspartate. These results demonstrate a specific decrease in Ca(2+)-handling capacity in astrocytes derived from S100B null mice and suggest that S100B plays a role in the maintenance of Ca(2+) homeostasis in astrocytes.
S100B是星形胶质细胞中主要的低亲和力钙结合蛋白。为了研究S100B在维持钙稳态中的作用，我们通过靶向灭活S100B基因培育出了S100B基因敲除小鼠。分别通过对S100B mRNA和蛋白质进行Northern印迹和Western印迹，以及对各个脑区切片进行免疫过氧化物酶染色，证实了S100B表达缺失。S100B基因敲除小鼠能够存活、繁殖，在12个月龄之前未表现出明显的行为异常。基于光学显微镜和免疫组织化学染色，这些小鼠成年脑切片中的星形胶质细胞或神经元的分布和形态没有明显改变。来自6日龄S100B基因敲除小鼠的小脑培养物中的星形胶质细胞在用氯化钾或咖啡因处理后表现出增强的钙瞬变。另一方面，同一培养物中的颗粒神经元在用氯化钾、咖啡因或N-甲基-D-天冬氨酸处理后表现出正常的钙瞬变。这些结果表明，源自S100B基因敲除小鼠的星形胶质细胞中钙处理能力特异性降低，提示S100B在星形胶质细胞钙稳态的维持中发挥作用。
