Clonal hematopoiesis (CH) is nearly universal in the elderly. The molecular and cellular mechanisms driving CH and the clinical consequences of carrying clonally derived mutant mature blood cells are poorly understood. We recently identified a C223Y mutation in the extracellular domain (ECD) of NOTCH3 as a putative CH driver in mice. Provocatively, germline NOTCH3 ECD mutations perturbing cysteine numbers cause Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL), a type of vascular dementia, suggesting an unexpected link between CADASIL and CH. Here, we formally demonstrated that mouse hematopoietic stem and progenitor cells (HSPCs) expressing CADASIL-related NOTCH3^C455R exhibit a proliferative advantage resulting in robust cellular expansion in vivo and in vitro. Co-expression of NOTCH3^C455R and Dnmt3a^R878H, homologous to a frequent human CH mutation, increased the fitness of NOTCH3^C455R HSPCs, demonstrating their functional cooperation. Surprisingly, the presence of NOTCH3^C455R hematopoietic cells supported the expansion of Dnmt3a^R878H HSPCs in a non-cell autonomous fashion in vivo, strongly suggesting that CADASIL patients and asymptomatic carriers can be highly predisposed to DNMT3A^R882H-driven CH. Considering that CADASIL-related NOTCH3 mutations are more frequent in the general population than anticipated (~1 carrier in 400 people), the effect of these NOTCH3 mutations on CH development should be considered.

克隆性造血 （CH） 在老年人中几乎普遍存在。驱动 CH 的分子和细胞机制以及携带克隆衍生突变成熟血细胞的临床后果知之甚少。我们最近在 NOTCH3 的胞外结构域 （ECD） 中发现 C223Y 突变是小鼠的推定 CH 驱动因素。令人发指的是，扰乱半胱氨酸数量的种系 NOTCH3 ECD 突变导致脑常染色体显性遗传性动脉病伴皮质下梗死和白质脑病 （CADASIL），一种血管性痴呆，表明 CADASIL 和 CH 之间存在意想不到的联系。在这里，我们正式证明，表达 CADASIL 相关 NOTCH3^C455R 的小鼠造血干细胞和祖细胞 （HSPC） 表现出增殖优势，导致体内和体外细胞的稳健扩增。NOTCH3^C455R 和 Dnmt3a^R878H 的共表达与常见的人类 CH 突变同源，增加了 NOTCH3^C455R HSPC 的适应性，证明了它们的功能合作。令人惊讶的是，NOTCH3^C455R 造血细胞的存在支持 Dnmt3a^R878H HSPCs 在体内以非细胞自主方式扩增，强烈表明 CADASIL 患者和无症状携带者可能高度易感于 DNMT3A^R882H 驱动的 CH。考虑到 CADASIL 相关的 NOTCH3突变在一般人群中比预期的更频繁（400 人中有 ~1 名携带者），应考虑这些 NOTCH3 突变对 CH 发展的影响。