Chronic lymphocytic leukemia (CLL) is characterized by disordered DNA methylation, suggesting these epigenetic changes might play a critical role in disease onset and progression. The methyltransferase DNMT3A is a key regulator of DNA methylation. Although DNMT3A somatic mutations in CLL are rare, we found that low DNMT3A expression is associated with more aggressive disease. A conditional knockout mouse model showed that homozygous depletion of Dnmt3a from B cells results in the development of CLL with 100% penetrance at a median age of onset of 5.3 months, and heterozygous Dnmt3a depletion yields a disease penetrance of 89% with a median onset at 18.5 months, confirming its role as a haploinsufficient tumor suppressor. B1a cells were confirmed as the cell of origin of disease in this model, and Dnmt3a depletion resulted in focal hypomethylation and activation of Notch and Myc signaling. Amplification of chromosome 15 containing the Myc gene was detected in all CLL mice tested, and infiltration of high- Myc –expressing CLL cells in the spleen was observed. Notably, hyperactivation of Notch and Myc signaling was exclusively observed in the Dnmt3a CLL mice, but not in three other CLL mouse models tested ( Sf3b1-Atm , Ikzf3 , and MDR ), and Dnmt3a -depleted CLL were sensitive to pharmacologic inhibition of Notch signaling in vitro and in vivo . Consistent with these findings, human CLL samples with lower DNMT3A expression were more sensitive to Notch inhibition than those with higher DNMT3A expression. Altogether, these results suggest that Dnmt3a depletion induces CLL that is highly dependent on activation of Notch and Myc signaling. Significance: Loss of DNMT3A expression is a driving event in CLL and is associated with aggressive disease, activation of Notch and Myc signaling, and enhanced sensitivity to Notch inhibition.

中文翻译：

---

通过 B 细胞限制性 Dnmt3a 消耗激活 Notch 和 Myc 信号传导产生慢性淋巴细胞白血病的一致小鼠模型

慢性淋巴细胞白血病 (CLL) 的特征是 DNA 甲基化紊乱，这表明这些表观遗传变化可能在疾病发作和进展中起关键作用。甲基转移酶 DNMT3A 是 DNA 甲基化的关键调节因子。尽管 CLL 中的 DNMT3A 体细胞突变很少见，但我们发现低 DNMT3A 表达与更具侵袭性的疾病有关。条件性敲除小鼠模型显示，B 细胞中 Dnmt3a 的纯合耗竭导致 CLL 的发展，其中位发病年龄为 5.3 个月，外显率为 100%，杂合 Dnmt3a 耗竭产生 89% 的疾病外显率，中位发病年龄为18.5 个月，证实了其作为单倍体不足的肿瘤抑制因子的作用。B1a细胞在该模型中被确认为疾病的起源细胞，和 Dnmt3a 消耗导致局灶性低甲基化和 Notch 和 Myc 信号传导的激活。在所有测试的 CLL 小鼠中检测到含有 Myc 基因的 15 号染色体扩增，并观察到脾脏中高表达 Myc 的 CLL 细胞浸润。值得注意的是，仅在 Dnmt3a CLL 小鼠中观察到 Notch 和 Myc 信号的过度激活，但在测试的其他三种 CLL 小鼠模型（Sf3b1-Atm、Ikzf3 和 MDR）中未观察到，并且 Dnmt3a 耗尽的 CLL 对 Notch 信号的药理学抑制敏感体外和体内。与这些发现一致，DNMT3A 表达较低的人类 CLL 样本比 DNMT3A 表达较高的人类 CLL 样本对 Notch 抑制更敏感。总而言之，这些结果表明 Dnmt3a 消耗诱导 CLL，其高度依赖于 Notch 和 Myc 信号的激活。