Biology Department, Texas A&M University, College Station, TX, United States.
Department of Biology and Biochemistry, University of Houston, Houston, TX, United States.
Dev Biol. 2022 Dec;492:139-153. doi: 10.1016/j.ydbio.2022.10.004. Epub 2022 Oct 14.
In zebrafish, sensory epithelia and neuroblasts of the inner ear form simultaneously in abutting medial and lateral domains, respectively, in the floor of the otic vesicle. Previous studies support regulatory roles for Fgf and Wnt, but how signaling is coordinated is poorly understood. We investigated this problem using pharmacological and transgenic methods to alter Fgf or Wnt signaling from early placodal stages to evaluate later changes in growth and patterning. Blocking Fgf at any stage reduces proliferation of otic tissue and terminates both sensory and neural specification. Wnt promotes proliferation in the otic vesicle but is not required for sensory or neural development. However, sustained overactivation of Wnt laterally expands sensory epithelia and blocks neurogenesis. pax2a, sp5a and sp5l are coregulated by Fgf and Wnt and show overlapping expression in the otic placode and vesicle. Gain- and loss-of-function studies show that these genes are together required for Wnt's suppression of neurogenesis, as well as some aspects of sensory development. Thus, pax2a, sp5a and sp5l are critical for mediating Fgf and Wnt signaling to promote spatially localized sensory and neural development.
在斑马鱼中,内耳的感觉上皮和神经母细胞分别在耳泡的内侧和外侧毗邻区域同时形成。先前的研究支持 Fgf 和 Wnt 的调节作用,但信号如何协调还知之甚少。我们使用药理学和转基因方法研究了这个问题,以改变早期颅嵴阶段的 Fgf 或 Wnt 信号,从而评估后期生长和模式形成的变化。在任何阶段阻断 Fgf 都会减少耳组织的增殖,并终止感觉和神经特化。Wnt 促进耳泡中的增殖,但对感觉或神经发育不是必需的。然而,Wnt 的持续过度激活会使感觉上皮侧向扩张并阻止神经发生。pax2a、sp5a 和 sp5l 受 Fgf 和 Wnt 的共同调节,在耳嵴和耳泡中有重叠表达。获得和丧失功能的研究表明,这些基因共同需要 Wnt 抑制神经发生,以及感觉发育的某些方面。因此,pax2a、sp5a 和 sp5l 对于介导 Fgf 和 Wnt 信号以促进空间定位的感觉和神经发育至关重要。
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