Institut de recherches cliniques de Montréal, Montreal, H2W 1R7, QC, Canada.
Department of Anatomy and Cell Biology, McGill University, Montréal, QC, H3A 0C7, Canada.
Nat Commun. 2019 Mar 20;10(1):1270. doi: 10.1038/s41467-019-09273-z.
Gfi1b is a transcriptional repressor expressed in hematopoietic stem cells (HSCs) and megakaryocytes (MKs). Gfi1b deficiency leads to expansion of both cell types and abrogates the ability of MKs to respond to integrin. Here we show that Gfi1b forms complexes with β-catenin, its co-factors Pontin52, CHD8, TLE3 and CtBP1 and regulates Wnt/β-catenin-dependent gene expression. In reporter assays, Gfi1b can activate TCF-dependent transcription and Wnt3a treatment enhances this activation. This requires interaction between Gfi1b and LSD1 and suggests that a tripartite β-catenin/Gfi1b/LSD1 complex exists, which regulates Wnt/β-catenin target genes. Consistently, numerous canonical Wnt/β-catenin target genes, co-occupied by Gfi1b, β-catenin and LSD1, have their expression deregulated in Gfi1b-deficient cells. When Gfi1b-deficient cells are treated with Wnt3a, their normal cellularity is restored and Gfi1b-deficient MKs regained their ability to spread on integrin substrates. This indicates that Gfi1b controls both the cellularity and functional integrity of HSCs and MKs by regulating Wnt/β-catenin signaling pathway.
Gfi1b 是一种在造血干细胞（HSCs）和巨核细胞（MKs）中表达的转录抑制因子。Gfi1b 缺失会导致这两种细胞类型的扩增，并使 MKs 丧失对整合素的反应能力。在这里，我们表明 Gfi1b 与 β-catenin 形成复合物，其共同因子包括 Pontin52、CHD8、TLE3 和 CtBP1，并调节 Wnt/β-catenin 依赖性基因表达。在报告基因实验中，Gfi1b 可以激活 TCF 依赖性转录，而 Wnt3a 处理增强了这种激活。这需要 Gfi1b 与 LSD1 之间的相互作用，表明存在一个三组分的 β-catenin/Gfi1b/LSD1 复合物，它调节 Wnt/β-catenin 靶基因。一致地，许多典型的 Wnt/β-catenin 靶基因，被 Gfi1b、β-catenin 和 LSD1 共同占据，其在 Gfi1b 缺失细胞中的表达被失调。当 Gfi1b 缺失的细胞用 Wnt3a 处理时，它们的正常细胞密度得到恢复，Gfi1b 缺失的 MKs 恢复了在整合素底物上扩散的能力。这表明 Gfi1b 通过调节 Wnt/β-catenin 信号通路来控制 HSCs 和 MKs 的细胞密度和功能完整性。
