State Key Laboratory of Mariculture Breeding, Key Laboratory of Marine Biotechnology of Fujian Province, College of Marine Sciences, Fujian Agriculture and Forestry University, Fuzhou, China.
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, China.
Front Immunol. 2024 Feb 9;15:1363426. doi: 10.3389/fimmu.2024.1363426. eCollection 2024.
In mammals, the transcription factor Pax5 is a key regulator of B cell development and maturation and specifically expressed in naive/mature B cells but repressed upon B cell activation. Despite the long-standing proposal that Pax5 repression is essential for proper B cell activation, the underlying mechanisms remain largely elusive. In this study, we used a teleost model to elucidate the mechanisms governing Pax5 repression during B cell activation. Treatment with lipopolysaccharide (LPS) and chitosan oligosaccharide (COS) significantly enhanced the antibody secreting ability and phagocytic capacity of IgM B cells in large yellow croaker (), coinciding with upregulated expression of activation-related genes, such as Bcl6, Blimp1, and sIgM, and downregulated expression of Pax5. Intriguingly, two CpG islands were identified within the promoter region of Pax5. Both CpG islands exhibited hypomethylation in naive/mature B cells, while CpG island1 was specifically transited into hypermethylation upon B cell activation. Furthermore, treatment with DNA methylation inhibitor 5-aza-2'-deoxycytidine (AZA) prevented the hypermethylation of CpG island1, and concomitantly impaired the downregulation of Pax5 and activation of B cells. Finally, through methylation experiments, we demonstrated that DNA methylation exerts an inhibitory effect on promoter activities of Pax5. Taken together, our findings unveil a novel mechanism underlying Pax5 repression during B cell activation, thus promoting the understanding of B cell activation process.
在哺乳动物中，转录因子 Pax5 是 B 细胞发育和成熟的关键调节因子，特异性表达于幼稚/成熟 B 细胞，但在 B 细胞激活时被抑制。尽管 Pax5 抑制对于 B 细胞激活是必需的这一观点由来已久，但潜在的机制仍很大程度上难以捉摸。在这项研究中，我们使用一种硬骨鱼类模型来阐明 B 细胞激活过程中 Pax5 抑制的调控机制。脂多糖（LPS）和壳寡糖（COS）处理显著增强了大黄鱼（）中 IgM B 细胞的抗体分泌能力和吞噬能力，同时上调了与激活相关的基因如 Bcl6、Blimp1 和 sIgM 的表达，下调了 Pax5 的表达。有趣的是，在 Pax5 启动子区域内鉴定出了两个 CpG 岛。在幼稚/成熟 B 细胞中，这两个 CpG 岛均表现出低甲基化，而 CpG 岛 1 在 B 细胞激活时特异性地转变为高甲基化。此外，用 DNA 甲基化抑制剂 5-氮杂-2'-脱氧胞苷（AZA）处理可防止 CpG 岛 1 的过度甲基化，并同时损害 Pax5 的下调和 B 细胞的激活。最后，通过甲基化实验，我们证明了 DNA 甲基化对 Pax5 启动子活性具有抑制作用。总之，我们的研究结果揭示了 B 细胞激活过程中 Pax5 抑制的新机制，从而促进了对 B 细胞激活过程的理解。
