Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA, USA.
Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA.
Nat Immunol. 2020 Sep;21(9):1082-1093. doi: 10.1038/s41590-020-0713-6. Epub 2020 Jun 29.
Memory B cells (MBCs) are essential for long-lived humoral immunity. However, the transcription factors involved in MBC differentiation are poorly defined. Here, using single-cell RNA sequencing analysis, we identified a population of germinal center (GC) B cells in the process of differentiating into MBCs. Using an inducible CRISPR-Cas9 screening approach, we identified the hematopoietically expressed homeobox protein Hhex as a transcription factor regulating MBC differentiation. The corepressor Tle3 was also identified in the screen and was found to interact with Hhex to promote MBC development. Bcl-6 directly repressed Hhex in GC B cells. Reciprocally, Hhex-deficient MBCs exhibited increased Bcl6 expression and reduced expression of the Bcl-6 target gene Bcl2. Overexpression of Bcl-2 was able to rescue MBC differentiation in Hhex-deficient cells. We also identified Ski as an Hhex-induced transcription factor involved in MBC differentiation. These findings establish an important role for Hhex-Tle3 in regulating the transcriptional circuitry governing MBC differentiation.
记忆 B 细胞（MBC）是长寿命体液免疫所必需的。然而，参与 MBC 分化的转录因子尚未完全明确。在此，我们通过单细胞 RNA 测序分析，鉴定了生发中心（GC）B 细胞向 MBC 分化过程中的一个群体。通过诱导型 CRISPR-Cas9 筛选方法，我们鉴定了造血表达的同源盒蛋白 Hhex 作为调节 MBC 分化的转录因子。在筛选中还鉴定到了共抑制因子 Tle3，它被发现与 Hhex 相互作用以促进 MBC 发育。Bcl-6 在 GC B 细胞中直接抑制 Hhex。反过来，Hhex 缺陷的 MBC 表现出 Bcl6 表达增加和 Bcl-6 靶基因 Bcl2 表达减少。Bcl-2 的过表达能够挽救 Hhex 缺陷细胞中的 MBC 分化。我们还鉴定到 Ski 作为 Hhex 诱导的参与 MBC 分化的转录因子。这些发现确立了 Hhex-Tle3 在调节 MBC 分化的转录调控回路中的重要作用。
