Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA.
Dis Model Mech. 2013 Sep;6(5):1246-59. doi: 10.1242/dmm.012005. Epub 2013 May 29.
Mutations in the human NOTCH3 gene cause CADASIL syndrome (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). CADASIL is an inherited small vessel disease characterized by diverse clinical manifestations including vasculopathy, neurodegeneration and dementia. Here we report two mutations in the zebrafish notch3 gene, one identified in a previous screen for mutations with reduced expression of myelin basic protein (mbp) and another caused by a retroviral insertion. Reduced mbp expression in notch3 mutant embryos is associated with fewer oligodendrocyte precursor cells (OPCs). Despite an early neurogenic phenotype, mbp expression recovered at later developmental stages and some notch3 homozygous mutants survived to adulthood. These mutants, as well as adult zebrafish carrying both mutant alleles together, displayed a striking stress-associated accumulation of blood in the head and fins. Histological analysis of mutant vessels revealed vasculopathy, including: an enlargement (dilation) of vessels in the telencephalon and fin, disorganization of the normal stereotyped arrangement of vessels in the fin, and an apparent loss of arterial morphological structure. Expression of hey1, a well-known transcriptional target of Notch signaling, was greatly reduced in notch3 mutant fins, suggesting that Notch3 acts via a canonical Notch signaling pathway to promote normal vessel structure. Ultrastructural analysis confirmed the presence of dilated vessels in notch3 mutant fins and revealed that the vessel walls of presumed arteries showed signs of deterioration. Gaps in the arterial wall and the presence of blood cells outside of vessels in mutants indicated that compromised vessel structure led to hemorrhage. In notch3 heterozygotes, we found elevated expression of both notch3 itself and target genes, indicating that specific alterations in gene expression due to partial loss of Notch3 function might contribute to the abnormalities observed in heterozygous larvae and adults. Our analysis of zebrafish notch3 mutants indicates that Notch3 regulates OPC development and mbp gene expression in larvae, and maintains vascular integrity in adults.
人类 NOTCH3 基因突变导致 CADASIL 综合征（伴有皮质下梗死和白质脑病的常染色体显性脑动脉病）。CADASIL 是一种遗传性小血管疾病，其特征是临床表现多样，包括血管病变、神经退行性变和痴呆。在这里，我们报告了斑马鱼 notch3 基因的两个突变，一个是在前一个髓鞘碱性蛋白（mbp）表达降低的筛选中发现的，另一个是由逆转录病毒插入引起的。 notch3 突变胚胎中 mbp 表达减少与少突胶质前体细胞（OPC）减少有关。尽管存在早期神经发生表型，但 mbp 表达在后期发育阶段恢复，一些 notch3 纯合突变体存活至成年。这些突变体，以及携带两个突变等位基因的成年斑马鱼，表现出与应激相关的头部和鳍部血液积聚。突变血管的组织学分析显示血管病变，包括：端脑和鳍中的血管扩张（扩张），鳍中正常的血管刻板排列紊乱，以及动脉形态结构的明显丧失。 Notch 信号通路的已知转录靶标 hey1 的表达在 notch3 突变鳍中大大降低，表明 Notch3 通过经典 Notch 信号通路发挥作用，促进正常血管结构。超微结构分析证实了 notch3 突变鳍中存在扩张的血管，并显示假定动脉的血管壁有恶化的迹象。突变体中动脉壁的间隙和血管外的血细胞存在表明血管结构受损导致出血。在 notch3 杂合子中，我们发现 notch3 本身和靶基因的表达都升高，表明 Notch3 功能部分缺失导致的基因表达的特定改变可能导致杂合子幼虫和成年个体的异常。我们对斑马鱼 notch3 突变体的分析表明，Notch3 调节幼虫中 OPC 的发育和 mbp 基因表达，并在成年期维持血管完整性。
