The Notch pathway is an ancient intercellular signaling system with crucial roles in numerous cell-fate decision processes across species. While the canonical pathway is activated by ligand-induced cleavage and nuclear localization of membrane-bound Notch, Notch can also exert its activity in a ligand/transcription-independent fashion, which is conserved in Drosophila, Xenopus, and mammals. However, the noncanonical role remains poorly understood in in vivo processes. Here we show that increased levels of the Notch intracellular domain (NICD) in the early mesoderm inhibit heart development, potentially through impaired induction of the second heart field (SHF), independently of the transcriptional effector RBP-J. Similarly, inhibiting Notch cleavage, shown to increase noncanonical Notch activity, suppressed SHF induction in embryonic stem cell (ESC)-derived mesodermal cells. In contrast, NICD overexpression in late cardiac progenitor cells lacking RBP-J resulted in an increase in heart size. Our study suggests that noncanonical Notch signaling has stage-specific roles during cardiac development.

Notch 通路是一种古老的细胞间信号系统，在许多跨物种的细胞命运决定过程中起着至关重要的作用。虽然经典途径被配体诱导的裂解和膜结合 Notch 的核定位激活，但 Notch 也可以以配体/转录非依赖性方式发挥其活性，这在果蝇、非洲爪蟾和哺乳动物中是保守的。然而，在体内的非规范作用仍然知之甚少过程。在这里，我们表明早期中胚层中 Notch 细胞内结构域 (NICD) 水平的增加会抑制心脏发育，这可能是通过第二心脏场 (SHF) 的诱导受损，与转录效应子 RBP-J 无关。类似地，抑制 Notch 裂解（显示可增加非经典 Notch 活性）可抑制胚胎干细胞 (ESC) 衍生的中胚层细胞中的 SHF 诱导。相反，在缺乏 RBP-J 的晚期心脏祖细胞中 NICD 过表达导致心脏大小增加。我们的研究表明，非经典 Notch 信号在心脏发育过程中具有阶段特异性作用。