Université Paris Cité, CNRS, Institut Jacques Monod, F-75013 Paris, France.
Department of Experimental, Diagnostic and Specialty Medicine (DIMES), Alma Mater Studiorum University of Bologna, Bologna, Italy.
PLoS Genet. 2022 May 23;18(5):e1009782. doi: 10.1371/journal.pgen.1009782. eCollection 2022 May.
The hallmarks of the alveolar subclass of rhabdomyosarcoma are chromosomal translocations that generate chimeric PAX3-FOXO1 or PAX7-FOXO1 transcription factors. Overexpression of either PAX-FOXO1s results in related cell transformation in animal models. Yet, in patients the two structural genetic aberrations they derived from are associated with distinct pathological manifestations. To assess the mechanisms underlying these differences, we generated isogenic fibroblast lines expressing either PAX-FOXO1 paralog. Mapping of their genomic recruitment using CUT&Tag revealed that the two chimeric proteins have distinct DNA binding preferences. In addition, PAX7-FOXO1 binding results in greater recruitment of the H3K27ac activation mark than PAX3-FOXO1 binding and is accompanied by greater transcriptional activation of neighbouring genes. These effects are associated with a PAX-FOXO1-specific alteration in the expression of genes regulating cell shape and the cell cycle. Consistently, PAX3-FOXO1 accentuates fibroblast cellular traits associated with contractility and surface adhesion and limits entry into S phase. In contrast, PAX7-FOXO1 drives cells to adopt an amoeboid shape, reduces entry into M phase, and causes increased DNA damage. Altogether, our results argue that the diversity of rhabdomyosarcoma manifestation arises, in part, from the divergence between the genomic occupancy and transcriptional activity of PAX3-FOXO1 and PAX7-FOXO1.
横纹肌肉瘤肺泡亚型的特征是染色体易位，导致嵌合 PAX3-FOXO1 或 PAX7-FOXO1 转录因子的产生。在动物模型中，过表达任何一种 PAX-FOXO1 都会导致相关的细胞转化。然而，在患者中，它们衍生自的两种结构遗传异常与不同的病理表现相关。为了评估这些差异的潜在机制，我们生成了表达 PAX-FOXO1 同源物的同基因成纤维细胞系。使用 CUT&Tag 对其基因组募集进行映射，揭示了这两种嵌合蛋白具有不同的 DNA 结合偏好。此外，PAX7-FOXO1 结合导致 H3K27ac 激活标记的募集程度大于 PAX3-FOXO1 结合，并且伴随着邻近基因的转录激活增加。这些效应与调节细胞形状和细胞周期的基因的 PAX-FOXO1 特异性表达改变相关。一致地，PAX3-FOXO1 强调与收缩和表面黏附相关的成纤维细胞特征，并限制进入 S 期。相比之下，PAX7-FOXO1 驱动细胞采用阿米巴样形状，减少进入 M 期，并导致 DNA 损伤增加。总的来说，我们的结果表明，横纹肌肉瘤表现的多样性部分源自 PAX3-FOXO1 和 PAX7-FOXO1 的基因组占据和转录活性的分歧。
