Development studies of the inner ear

描述（由申请人提供）：形态发生素是在发育胚胎中作为梯度起作用的分子，根据形态发生素暴露的持续时间和/或浓度赋予细胞不同的命运。已知在其他系统中作为形态发生剂起作用的几种分泌配体存在于鸟类和哺乳动物的发育中的内耳中，包括Wnt基因家族中的分子。Wnt转录本在胚胎耳蜗的径向轴上呈不对称分布。目前的研究表明，这种本地化的表达在体内的异位基因转移的破坏可以改变细胞的命运在发育中的鸡胚耳蜗。这一新出现的证据表明Wnt形态原可能在耳蜗中活跃，导致3条调查线。在目标1中，将进行转录物的深度测序，以比较对照耳与其中听力器官的腹侧已通过异位Wnt递送转化为神经侧命运的耳。这有望揭示在感觉器官两侧差异使用的基因，其中一些将有能力直接影响径向身份的各个方面，如细胞分裂的时间调节，细胞类型的选择，以及轴突神经支配的分布和类别。越来越多的新证据表明，以转录抑制靶转录物的能力而闻名的microRNA可以与癌细胞和胚胎中参与Wnt信号通路的分子形成相互作用网络。在目标2中，microRNA谱的变化将与异位Wnt递送诱导的鸡听觉器官径向轴上的细胞类型转化有关。这应该提供与Wnt通路相互作用以形成反馈或前馈网络的特定候选microRNA，从而影响听觉器官径向轴上的细胞表型。目标3将转向研究发育中的小鼠耳蜗，以确定哪些Wnt信号分子以与该物种中形态发生功能一致的方式分布。然后，阻断所有Wnt配体分泌的可用小鼠突变体将提供有价值的资源，以揭示特定Wnt配体是否与特定microRNA形成子网络。为了实现这一点，将在不同Wnt配体的存在下培养缺乏Wnt分泌的胚胎耳蜗，并比较受这些处理影响的下游microRNA。这些研究的总体意义在于，它们可以更好地了解有助于形成和形成耳蜗细胞类型的基因网络，其长期目标是为人类患者听力损失的生物治疗的设计和实施提供信息。

DESCRIPTION (provided by applicant): Morphogens are molecules that operate as gradients in developing embryos to endow cells with different fates depending upon the duration and/or concentration of morphogen exposure. Several secreted ligands known to function as morphogens in other systems are present in the developing inner ears of birds and mammals, including molecules in the Wnt gene family. Wnt transcripts are asymmetrically distributed across the radial axis of the embryonic cochlea. Current research reveals that disruption of this localized expression in vivo by ectopic gene transfer can transform cell fates in the developing cochlea of the chicken embryo. This emerging evidence that a Wnt morphogen may be active in the cochlea leads to 3 lines of inquiry. In Aim 1, deep-sequencing of transcripts will be undertaken to compare control ears to those in which the abneural-side of the hearing organ has been converted to a neural-side fate by ectopic Wnt delivery. This is expected to reveal genes that are differentially employed on the two sides of the sensory organ, some of which will have the ability to directly influence aspects of radial identity, such as the temporal regulation f cell division, the choice of cell types, and the distribution and class of axonal innervation. Accumulating new evidence suggests that microRNAs, known for their ability to transcriptionally repress target transcripts, can form interacting networks with molecules involved in the Wnt signaling pathway in cancer cells and in embryos. In Aim 2, changes in the microRNA profile will be linked to the transformation of cell types across the radial axis of the chicken hearing organ that are induced by ectopic Wnt delivery. This should provide specific candidate microRNAs that interact with the Wnt pathway to form either feedback or feedforward networks and thereby influence cellular phenotypes across the radial axis of the hearing organ. Aim 3 will switch to studying the developing mouse cochlea to identify which Wnt signaling molecules are distributed in a manner consistent with a morphogen function in this species. Then, available mouse mutants that block the secretion of all Wnt ligands will provide a valuable resource to reveal whether specific Wnt ligands form sub-networks with specific microRNAs. To accomplish this, embryonic cochleas lacking Wnt secretion will be cultured in the presence of different Wnt ligands and the downstream microRNAs affected by these treatments will be compared. The overall significance of these studies is that they may offer a better understanding of the gene networks that contribute to forming and patterning cochlear cell types, with a long-term goal of informing the design and implementation of biological-based treatments of hearing loss in human patients.