Molecular Basis For The Morphogenesis Of The Inner Ear

内耳形态发生的分子基础

• 批准号: 7593329
• 负责人: Doris Wu
• 金额: $ 183.45万
• 依托单位: NATIONAL INSTITUTE ON DEAFNESS AND OTHER COMMUNICATION DISORDERS
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7593329
• 关键词: Activator Appliances; Alleles; Animal Model; Ankylosis; Area; Auditory; Bone Morphogenetic Proteins; Branchial arch structure; Chickens; Cochlear duct; Complex; Conductive hearing loss; Defect; Development; Disease; Distal; Dorsal; Ear; Ear ossicles; Embryo; Embryonic Development; Equilibrium; Erinaceidae; Exons; Floor; Genes; Genetic; Goals; Human; Knock-out; Knockout Mice; Labyrinth; Manuscripts; Modeling; Molecular; Morphogenesis; Mus; Mutant Strains Mice; Mutation; Organ; Paper; Patients; Phenotype; Positioning Attribute; Proteins; Publishing; Role; Saccule structure; Sensory; Signal Transduction; Skeletal system; Source; Specific qualifier value; Stapes; Stapes Surgery; Structure; Syndrome; Testing; Tympanic cavity; Vestibule; base; bone; deafness; design; hearing impairment; hindbrain; malformation; middle ear; mutant; otoconia; outcome forecast; prospective; sample fixation; sound

Our major accomplishments are in the following areas: 1) Inner ear analyses of Noggin knockout mouse embryos (manuscript published) Mutations of the NOGGIN gene in humans are associated with several autosomal dominant disorders such as symphalangism and multiple synotoses. These syndromes are characterized by skeletal defects and synotoses, which include conductive hearing loss. Noggin encodes a protein that antagonizes activities of Bone morphogenetic proteins (BMP). To understand the role of Noggin in ear development, we analyzed the ear phenotypes of Noggin homozygous mice. We published a paper this year describing the inner ears of Noggin knockout embryos. We show that the inner ear phenotypes observed in Noggin knockout embryos are largely due to a misalignment of the otocysts with the hindbrain during early embryogenesis. We propose that this misalignment disrupted the normal hindbrain signaling that is required for proper inner ear morphogenesis. We tested this hypothesis by generating similar misalignment in chicken embryo surgically as what was observed in Noggin -/- embryos. The resulting inner ear phenotypes in chicken resemble those in Noggin mutants, in particularly the saccule and cochlear duct malformations. These results indicate that the inner ear phenotypes observed in Noggin mutants are largely attributed to improper formation of the body axis. 2) Noggin heterozygous mice an animal model for conductive hearing loss (manuscript submitted) We conducted a study in the Noggin heterozygous mice. We show that the Noggin heterozygous mice suffer from conductive hearing loss, similar to the human patients with NOGGIN mutations. Since Noggin is a single exon gene, our results strongly suggest that the autosomal dominant disorders associated with NOGGIN mutations in humans are due to haploinsufficiency of NOGGIN. We discovered that the heterozygous mice with hearing loss have an ectopic bone fragment connecting one of the middle ear ossicles, the stapes, to the wall of the tympanum. This fixation most likely impedes the mobility of the stapes during sound conduction leading to hearing loss. We concluded from our analyses that the ectopic bone fragment is not due to de novo synthesis. Most likely, the extra bone formed by an incomplete separation of the prospective stapes from its precursor in the second branchial arch due to unopposed BMP activities. Since the long-term prognosis is not ideal for patients with NOGGIN mutations who underwent corrective surgery for stapes ankylosis, these Noggin mutant mice will continue to serve as a good model for exploring better strategies to alleviate hearing loss. 3) Roe of Sonic hedgehog (Shh) and Gli proteins in inner ear development (manuscript published) From the analyses of mouse mutants with various genetic combinations of mutant alleles such as Shh, Gli2, Gli3, and Gli3 delta699, we show that several mechanisms are involved in Shh signal transduction in the inner ear. The formation of the distal cochlear duct, which is positioned closest to the source of Shh in the notchord and floor plate, requires robust Gli2 and Gli3 activator functions. The proximal region of the cochlear duct requires less Shh signaling to antagonize Gli3 repressors. The dorsal vestibule of the inner ear requires little Shh signaling but Gli3 repressor is important for the formation of this region. Thus the graded Shh signaling from the ventral midline specifies various inner ear structures along the dorsal-ventral axis.

我们的主要成就是在以下领域： 1）Noggin基因敲除小鼠胚胎的内耳分析（手稿发布） 人类中的Noggin基因的突变与几种常染色体显性疾病（例如交响乐和多种同步疾病）有关。 这些综合征的特征是骨骼缺陷和总结作用，其中包括导电性听力损失。 Noggin编码拮抗骨形态发生蛋白（BMP）活性的蛋白质。 为了了解Noggin在耳朵发育中的作用，我们分析了Noggin纯合小鼠的耳朵表型。 我们今年发表了一篇论文，描述了Noggin敲除胚胎的内耳。 我们表明，在Noggin基因敲除胚胎中观察到的内耳表型很大程度上是由于早期胚胎发生期间耳ot囊与后脑的未对准。 我们建议这种未对准破坏了适当的内耳形态发生所需的正常后脑信号传导。 我们通过手术中与Noggin - / - 胚胎中观察到的相似的鸡胚胎中的相似未对准来测试了这一假设。 鸡肉中所得的内耳表型类似于Noggin突变体的表型，尤其是在扫月和耳蜗管道畸形中。 这些结果表明，在Noggin突变体中观察到的内耳表型主要归因于身体轴的不当形成。 2）Noggin杂合小鼠是导电性听力损失的动物模型（手稿提交） 我们在Noggin杂合小鼠中进行了一项研究。 我们表明，Noggin杂合小鼠患有导电性听力损失，类似于患有Noggin突变的患者。 由于Noggin是单个外显子基因，因此我们的结果强烈表明，与人类Noggin突变相关的常染色体显性疾病是由于Noggin的单倍弥漫性引起的。 我们发现，听力损失的杂合小鼠具有异位骨碎片，将中耳耳的一个，stapes连接到鼓膜的壁。 这种固定最有可能阻碍声音传导过程中stap的活动性，从而导致听力损失。 我们从分析得出的结论是，异位骨碎片不是由于从头综合而引起的。 最有可能的是，由于没有反对的BMP活性而导致的前弓与其前体的前瞻性分离不完全分离而形成的额外骨骼。 由于长期预后对接受stapes ancylosis矫正手术的Noggin突变患者而言并不理想，因此这些Noggin突变小鼠将继续成为探索更好的策略来减轻听力损失的良好模型。 3）内耳发育中的Sonic刺猬（SHH）和GLI蛋白的ROE（手稿） 从对突变等位基因（例如SHH，GLI2，GLI3和GLI3 Delta699）的各种遗传组合的小鼠突变体的分析中，我们表明内耳中的SHH信号转导涉及几种机制。 远端耳蜗的形成，位于距离和地板板中最接近SHH的源的位置，需要强大的GLI2和GLI3激活仪的功能。 人工耳管的近端区域需要更少的SHH信号传导来拮抗GLI3阻遏物。 内耳的背部前庭几乎不需要SHH信号传导，但GLI3阻遏物对于该区域的形成很重要。 因此，来自腹部中线的分级SHH信号传导指定沿背腹侧轴的各种内耳结构。