Department of Pharmacology, University of Iowa Carver College of Medicine, Iowa City, IA.
Department of Veterinary Pathology, Iowa State University, Ames, IA.
J Am Heart Assoc. 2017 Oct 27;6(11):e007038. doi: 10.1161/JAHA.117.007038.
Congenital heart defects are the most common birth defects worldwide. Although defective Notch signaling is the major cause of mouse embryonic death from cardiovascular defects, how Notch signaling is regulated during embryonic vasculogenesis and heart development is poorly understood.
Regulator of G protein signaling 6 (RGS6)/Ca/calmodulin-dependent protein kinase II (CaMKII) double mutant mice were developed by crossing RGS6 mice with mice expressing an oxidation-resistant CaMKIIδ (CaMKII), and the resulting embryonic defects/lethality were investigated using E7.5 to E15.5 embryos. While loss of either RGS6 or oxidized CaMKIIδ does not alter embryogenesis, their combined loss causes defective Notch signaling, severe cardiovascular defects, and embryonic lethality (≈E10.5-11.5). Embryos lacking RGS6 and expressing oxidation-resistant CaMKIIδ exhibit reduced myocardial wall thickness, abnormal trabeculation, and arterial specification defects. Double mutants show vascular remodeling defects, including reduced neurovascularization, delayed neural tube maturation, and small dorsal aortae. These striking cardiovascular defects were accompanied by placental and yolk sac defects in angiogenesis, hematopoiesis, and vascular remodeling similar to what is seen with defective Notch1 signaling. Double mutant hearts, embryos, and yolk sacs exhibit profound downregulation of Notch1, Jagged 1, and Notch downstream target genes Hey1, Hey2, and Hey1L as well as impaired Notch1 signaling in embryos/hearts.
RGS6 and oxidized CaMKIIδ together function as novel critical upstream modulators of Notch signaling required for normal cardiovascular development and embryo survival. Their combined need indicates that they function in parallel pathways needed for Notch1 signaling in yolk sac, placenta and embryos. Thus, dysregulated embryonic RGS6 expression and oxidative activation of CaMKII may potentially contribute to congenital heart defects.
先天性心脏缺陷是全球最常见的出生缺陷。尽管 Notch 信号转导缺陷是导致心血管缺陷的小鼠胚胎死亡的主要原因，但 Notch 信号转导在胚胎血管生成和心脏发育过程中是如何被调控的，目前还知之甚少。
通过将 RGS6 小鼠与表达氧化型 CaMKIIδ（CaMKII）的小鼠杂交，培育出了 RGS6/Ca/钙调蛋白依赖性蛋白激酶 II（CaMKII）双突变小鼠，并使用 E7.5 至 E15.5 胚胎研究了由此产生的胚胎缺陷/致死性。虽然缺失任一种 RGS6 或氧化型 CaMKIIδ 都不会改变胚胎发生，但它们的联合缺失会导致 Notch 信号转导缺陷、严重的心血管缺陷和胚胎致死性（≈E10.5-11.5）。缺乏 RGS6 但表达氧化型 CaMKIIδ 的胚胎表现出心肌壁厚度变薄、异常小梁化和动脉特化缺陷。双突变体显示出血管重塑缺陷，包括减少神经血管化、延迟神经管成熟和小背主动脉。这些明显的心血管缺陷伴随着胎盘和卵黄囊在血管生成、造血和血管重塑方面的缺陷，类似于 Notch1 信号转导缺陷所观察到的。双突变体心脏、胚胎和卵黄囊表现出 Notch1、Jagged 1 及其下游靶基因 Hey1、Hey2 和 Hey1L 的显著下调，以及胚胎/心脏中 Notch1 信号转导受损。
RGS6 和氧化型 CaMKIIδ 共同作为 Notch 信号转导的新型关键上游调节剂，对于正常心血管发育和胚胎存活是必需的。它们的共同需要表明，它们在卵黄囊、胎盘和胚胎中 Notch1 信号转导所需的平行途径中发挥作用。因此，胚胎 RGS6 表达失调和 CaMKII 的氧化激活可能潜在地导致先天性心脏缺陷。
