Universidad Nacional de Córdoba, Facultad de Ciencias Químicas, Departamento de Bioquímica Clínica, Ciudad Universitaria, X5000HUA, Córdoba, Argentina; Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET), Centro de Investigaciones en Bioquímica Clínica e Inmunología (CIBICI), Ciudad Universitaria, X5000HUA, Córdoba, Argentina.
Servicio de Ginecología y Obstetricia, Hospital Privado Universitario de Córdoba, X5000HUA, Córdoba, Argentina.
Placenta. 2022 Jan;117:139-149. doi: 10.1016/j.placenta.2021.12.006. Epub 2021 Dec 4.
Villous cytotrophoblast (vCTB) cells fuse to generate and maintain the syncytiotrophoblast layer required for placental development and function. Krüppel-like factor 6 (KLF6) is a ubiquitous transcription factor with an N-terminal acidic transactivation domain and a C-terminal zinc finger DNA-binding domain. KLF6 is highly expressed in placenta, and it is required for proper placental development. We have demonstrated that KLF6 is necessary for cell fusion in human primary vCTBs, and in the BeWo cell line.
Full length KLF6 or a mutant lacking its N-terminal domain were expressed in BeWo cells or in primary vCTB cells isolated from human term placentas. Cell fusion, gene and protein expression, and cell proliferation were analyzed. Moreover, Raman spectroscopy and atomic force microscopy (AFM) were used to identify biochemical, topography, and elasticity cellular modifications.
The increase in KLF6, but not the expression of its deleted mutant, is sufficient to trigger cell fusion and to raise the expression of β-hCG, syncytin-1, the chaperone protein 78 regulated by glucose (GRP78), the ATP Binding Cassette Subfamily G Member 2 (ABCG2), and Galectin-1 (Gal-1), all molecules involved in vCTB differentiation. Raman and AFM analysis revealed that KLF6 reduces NADH level and increases cell Young's modulus. KLF6-induced differentiation correlates with p21 upregulation and decreased cell proliferation. Remarkable, p21 silencing reduces cell fusion triggered by KLF6 and the KLF6 mutant impairs syncytialization and decreases syncytin-1 and β-hCG expression.
KLF6 induces syncytialization through a mechanism that involves its regulatory transcriptional domain in a p21-dependent manner.
绒毛滋养层细胞（vCTB）融合生成并维持合胞滋养层，这是胎盘发育和功能所必需的。Krüppel 样因子 6（KLF6）是一种普遍存在的转录因子，具有 N 端酸性转录激活结构域和 C 端锌指 DNA 结合结构域。KLF6 在胎盘组织中高表达，对于胎盘的正常发育是必需的。我们已经证明 KLF6 对于人原代 vCTB 和 BeWo 细胞系中的细胞融合是必需的。
全长 KLF6 或缺失其 N 端结构域的突变体在 BeWo 细胞或从人足月胎盘分离的原代 vCTB 细胞中表达。分析细胞融合、基因和蛋白表达以及细胞增殖。此外，还使用拉曼光谱和原子力显微镜（AFM）来鉴定生化、形貌和弹性细胞修饰。
KLF6 的增加而不是其缺失突变体的表达足以触发细胞融合并提高β-hCG、syncytin-1、葡萄糖调节蛋白 78（GRP78）、ATP 结合盒亚家族 G 成员 2（ABCG2）和半乳糖凝集素-1（Gal-1）的表达，这些分子都参与 vCTB 的分化。拉曼和 AFM 分析表明 KLF6 降低 NADH 水平并增加细胞杨氏模量。KLF6 诱导的分化与 p21 上调和细胞增殖减少有关。值得注意的是，p21 沉默可减少 KLF6 触发的细胞融合，而 KLF6 突变体则损害合胞化并降低 syncytin-1 和β-hCG 的表达。
KLF6 通过依赖于 p21 的机制诱导合胞化，该机制涉及其调节转录结构域。
