The gene that encodes de novo DNA methyltransferase 3A (DNMT3A) is frequently mutated in acute myeloid leukemia genomes. Point mutations at position R882 have been shown to cause a dominant negative loss of DNMT3A methylation activity, but 15% of DNMT3A mutations are predicted to produce truncated proteins that could either have dominant negative activities or cause loss of function and haploinsufficiency. Here, we demonstrate that 3 of these mutants produce truncated, inactive proteins that do not dimerize with WT DNMT3A, strongly supporting the haploinsufficiency hypothesis. We therefore evaluated hematopoiesis in mice heterozygous for a constitutive null Dnmt3a mutation. With no other manipulations, Dnmt3a^+/– mice developed myeloid skewing over time, and their hematopoietic stem/progenitor cells exhibited a long-term competitive transplantation advantage. Dnmt3a^+/– mice also spontaneously developed transplantable myeloid malignancies after a long latent period, and 3 of 12 tumors tested had cooperating mutations in the Ras/MAPK pathway. The residual Dnmt3a allele was neither mutated nor downregulated in these tumors. The bone marrow cells of Dnmt3a^+/– mice had a subtle but statistically significant DNA hypomethylation phenotype that was not associated with gene dysregulation. These data demonstrate that haploinsufficiency for Dnmt3a alters hematopoiesis and predisposes mice (and probably humans) to myeloid malignancies by a mechanism that is not yet clear.

中文翻译：

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DNA甲基转移酶3A的单倍剂量不足使造血细胞易患骨髓恶性肿瘤

从头编码DNA甲基转移酶3A（DNMT3A）的基因经常在急性髓细胞白血病基因组中突变。R882位置的点突变已显示出导致DNMT3A甲基化活性显着负性损失，但据预测DNMT3A突变中有15％会产生截短的蛋白，这些蛋白可能具有显性负性活性或导致功能丧失和单倍性不足。在这里，我们证明了这些突变体中的3个产生不与WT DNMT3A二聚的截短的，无活性的蛋白质，强烈支持单倍体功能不足假设。因此，我们评估了杂合性小鼠虚构造血功能性Dnmt3a突变。在没有其他操作的情况下，Dnmt3a ^+/-随着时间的流逝，小鼠出现了髓样倾斜，其造血干/祖细胞表现出长期的竞争性移植优势。在长时间潜伏期后，Dnmt3a ^+/–小鼠也自发发展出可移植的骨髓恶性肿瘤，测试的12种肿瘤中有3种在Ras / MAPK途径中具有协同突变。在这些肿瘤中，残留的Dnmt3a等位基因既没有突变也没有下调。Dnmt3a ^+/–小鼠的骨髓细胞具有微妙但统计学上显着的DNA低甲基化表型，与基因失调无关。这些数据表明Dnmt3a的单倍剂量不足 通过尚不清楚的机制改变造血功能，并使小鼠（可能是人类）患上髓系恶性肿瘤。