Theodor Kocher Institute, University of Bern, Bern, Switzerland.
Laboratory of Tumor Immunology and Cell Therapy, Hyogo College of Medicine, Nishinomiya, Hyogo, Japan.
Sci Rep. 2019 Jan 18;9(1):203. doi: 10.1038/s41598-018-36731-3.
The tight junction protein claudin-3 has been identified as a transcriptional target of the Wnt/β-catenin signaling pathway regulating blood-brain barrier (BBB) maturation. In neurological disorders loss of claudin-3 immunostaining is observed at the compromised BBB and blood-cerebrospinal fluid barrier (BCSFB). Although these observations support a central role of claudin-3 in regulating brain barriers' tight junction integrity, expression of claudin-3 at the brain barriers has remained a matter of debate. This prompted us to establish claudin-3 C57BL/6J mice to study the role of claudin-3 in brain barrier integrity in health and neuroinflammation. Bulk and single cell RNA sequencing and direct comparative qRT-PCR analysis of brain microvascular samples from WT and claudin-3 mice show beyond doubt that brain endothelial cells do not express claudin-3 mRNA. Detection of claudin-3 protein at the BBB in vivo and in vitro is rather due to junctional reactivity of anti-claudin-3 antibodies to an unknown antigen still detected in claudin-3 brain endothelium. We confirm expression and junctional localization of claudin-3 at the BCSFB of the choroid plexus. Our study clarifies that claudin-3 is not expressed at the BBB and shows that absence of claudin-3 does not impair brain barrier function during health and neuroinflammation in C57BL/6J mice.
紧密连接蛋白 Claudin-3 已被确定为调节血脑屏障 (BBB) 成熟的 Wnt/β-连环蛋白信号通路的转录靶标。在神经疾病中，在受损的 BBB 和血脑脊髓液屏障 (BCSFB) 中观察到 Claudin-3 免疫染色的丢失。尽管这些观察结果支持 Claudin-3 在调节大脑屏障紧密连接完整性方面的核心作用，但 Claudin-3 在大脑屏障上的表达一直存在争议。这促使我们建立 Claudin-3 C57BL/6J 小鼠来研究 Claudin-3 在健康和神经炎症中的大脑屏障完整性中的作用。WT 和 Claudin-3 小鼠的大脑微血管样本的批量和单细胞 RNA 测序和直接比较 qRT-PCR 分析毫无疑问地表明，脑内皮细胞不表达 Claudin-3 mRNA。体内和体外 BBB 上 Claudin-3 蛋白的检测是由于抗 Claudin-3 抗体对 Claudin-3 脑内皮细胞中仍检测到的未知抗原的连接反应性所致。我们证实 Claudin-3 在脉络丛的 BCSFB 上的表达和连接定位。我们的研究阐明了 Claudin-3 不在 BBB 上表达，并表明 Claudin-3 的缺失不会在 C57BL/6J 小鼠的健康和神经炎症期间损害大脑屏障功能。
