Morphogenetic signaling by retinoic acid and its regulation during inner ear development

脊椎动物内耳发育对维甲酸(RA)信号的变化很敏感，但RA及其分子靶点控制的形态发生过程在很大程度上还没有被探索。哺乳动物在内耳中共表达三种视黄醛脱氢酶，而斑马鱼发育中的内耳和两侧组织中分别存在ALDH1a3和Aldh1a2。因此，对斑马鱼耳囊RA功能进行简单的遗传分析是可行的。我们的目标有三个：1)我们将使用遗传学和化学遗传学的方法来检验RA信号模式在内耳上皮细胞的投影和耳囊形成所需的假说；2)在微阵列分析中，我们已经确定了受RA信号上调和下调的候选靶基因；我们将表征它们在内耳中的表达谱和RA敏感性，并将通过基因敲除来检测它们的功能；3)为了推进内耳形态发生的可视化和剖析细胞动力学，我们将建立转基因斑马鱼系，它将在体内概括RA介导的基因激活和RA合成的动力学。总之，拟议的研究将揭示RA介导的基因活性控制的作用，并将使我们能够将分子遗传相互作用与内耳发育中的形态变化联系起来。

Vertebrate inner ear development is sensitive to alterations in retinoic acid (RA) signaling, but the morphogenetic processes that are controlled by RA and its molecular targets are largely unexplored. Whereas mammals co-express three retinaldehyde-dehydrogenases within the inner ear, only Aldh1a3 and Aldh1a2 are present in the zebrafish developing inner ear and in flanking tissues, respectively. It is thus feasible to accomplish a straightforward genetic analysis of RA function in the zebrafish otic vesicle. Our goals are threefold: 1) We will use genetic and chemical genetic methods to examine the hypothesis that RA signaling patterns epithelial projections in the inner ear and is required for the formation of the otic capsule; 2) In a microarray analysis we have identified candidate target genes that are up- and down-regulated by RA signaling; we will characterize their expression profiles and RA-sensitivity in the inner ear and will examine their function by gene knockdown; 3) To advance the visualization and to dissect the cellular dynamics of inner ear morphogenesis, we will develop transgenic zebrafish lines that recapitulate RA-mediated gene activation and the dynamics of RA synthesis within the inner ear in vivo. Together, the proposed studies will unravel the roles of RA-mediated control of gene activity and will allow us to associate molecular genetic interactions with morphological change in the developing inner ear.