IDENTIFICATION OF THE GENE(S) RESPONSIBLE FOR ALAGILLE

Jagged1(JAG1)基因编码Notch受体的配体，JAG1基因的突变导致Alagille综合征(AGS)。Notch通路许多其他成员的突变也被发现与人类疾病和小鼠的表型有关。斑马鱼是脊椎动物发育的极好模型，因此我们开始努力探索锯齿状基因在斑马鱼发育和阿拉格尔综合症等发育性疾病中的作用。作为这项工作的一部分，我们从斑马鱼中分离并鉴定了锯齿状的同源基因。分离并鉴定了三个基因，分别命名为锯齿状的1、2和3，以及它们的染色体定位和表达。锯齿状RNA的异位表达导致“心灵炸弹”(MIB)突变胚胎中神经元的减少，在这种突变胚胎中，侧抑制的减少允许过多的神经前体细胞分化为神经元。定位克隆表明，MIB是Notch途径中的一个新基因，它编码一种环状泛素连接酶，它是Delta有效激活Notch所必需的。针对Jaggeds 1、2和3产生的反义寡核苷酸(Morpholino衍生物)正被用于探索它们在肝脏发育中的作用。锯齿和缺口基因敲除的组合以一种与AGS表型相适应的方式改变斑马鱼的胆管发育。

Jagged1 (JAG1) gene encodes a ligand for a Notch receptor, and mutations in the JAG1 are responsible for Alagille syndrome (AGS). Mutations in many other members of the Notch pathway have also been found to be associated with human diseases and mouse phenotypes. Zebrafish is an excellent model for vertebrate development, and therefore we have initiated efforts to explore the role of jagged genes in zebrafish development and in developmental diseases like Alagille syndrome. As a part of this effort, we have isolated and characterized Jagged homologous genes from zebrafish. Three genes termed jagged 1, 2 and 3 were isolated and characterized, along with their chromosomal location and expression. Ectopic expression of jagged RNAs leads to a reduction of neurons in "mind bomb" (mib) mutant embryos in which reduced lateral inhibition permits too many neural progenitors to differentiate into neurons. Positional cloning revealed that the mib is a novel gene in the Notch pathway, which encodes a RING Ubiquitin ligase that is essential for efficient activation of Notch by Delta. Antisense oligonucleotides (Morpholino derivatives) generated for Jaggeds 1, 2 and 3 are being used to explore their role in liver development. Combinations of jagged and notch gene knockdowns alter zebrafish biliary development in a manner compatible with an AGS phenocopy.