ABSTRACT

Histone lysine-to-methionine (K-to-M) mutations have been identified as driver mutations in human cancers. Interestingly, these ‘oncohistone’ mutations inhibit the activity of histone methyltransferases. Therefore, they can potentially be used as versatile tools to investigate the roles of histone modifications. In this study, we generated a genetically engineered mouse line in which an H3.3K36M mutation could be induced in the endogenous H3f3b gene. Since H3.3K36M has been identified as a causative mutation of human chondroblastoma, we induced this mutation in the chondrocyte lineage in mouse embryonic limbs. We found that H3.3K36M causes a global reduction in H3K36me2 and defects in chondrocyte differentiation. Importantly, the reduction of H3K36me2 was accompanied by a collapse of normal H3K27me3 distribution. Furthermore, the changes in H3K27me3, especially the loss of H3K27me3 at gene regulatory elements, were associated with the mis-regulated expression of a set of genes important for limb development, including HoxA cluster genes. Thus, through the in vivo induction of the H3.3K36M mutation, we reveal the importance of maintaining the balance between H3K36me2 and H3K27me3 during chondrocyte differentiation and limb development.

摘要

组蛋白赖氨酸到蛋氨酸 (K-to-M) 突变已被确定为人类癌症的驱动突变。有趣的是，这些“癌组蛋白”突变抑制了组蛋白甲基转移酶的活性。因此，它们可以潜在地用作研究组蛋白修饰作用的通用工具。在这项研究中，我们生成了一个基因工程小鼠系，其中可以在内源性H3f3b中诱导 H3.3K36M 突变基因。由于 H3.3K36M 已被确定为人类软骨母细胞瘤的致病突变，我们在小鼠胚胎肢体的软骨细胞谱系中诱导了这种突变。我们发现 H3.3K36M 导致 H3K36me2 整体减少和软骨细胞分化缺陷。重要的是，H3K36me2 的减少伴随着正常 H3K27me3 分布的崩溃。此外，H3K27me3 的变化，尤其是基因调控元件中 H3K27me3 的缺失，与一组对肢体发育很重要的基因（包括 HoxA 簇基因）的错误调节表达有关。因此，通过体内诱导 H3.3K36M 突变，我们揭示了在软骨细胞分化和肢体发育过程中维持 H3K36me2 和 H3K27me3 之间平衡的重要性。