Roles of β-catenin in inner ear development in SD rat embryos

在脊椎动物中，内耳的发育始于表面外胚层被周围组织的信号诱导形成耳基板。在初步实验中，我们观察到高水平的β-连环蛋白出现在大鼠内耳短暂对应于其形态发生。在这项研究中，我们研究了β-catenin在大鼠胚胎内耳发育中的作用，通过免疫染色和反义实验。β-catenin在内耳发育过程中视杯内出现短暂的高水平表达。虽然在耳基板增厚的表面外胚层中尚未观察到β-连环蛋白积聚，但在耳杯的顶端表面检测到。然后从耳囊中消失。当胚胎用β-catenin反义寡脱氧核苷酸处理时，β-catenin在耳杯中的积累被抑制，并且处理的胚胎中的β-catenin蛋白水平显著低于对照。处理胚胎中耳杯中的细胞数量小于对照胚胎。在耳基板纳入溴脱氧尿苷的细胞在处理的胚胎数量比对照组少。在对照胚胎中，通过2 H3（抗神经丝165 KDa抗体）染色在听神经嵴复合体内检测到听神经元，而在处理胚胎的复合体中仅观察到少量2 H3染色。这些结果表明β-catenin在耳基板细胞增殖和听神经嵴复合体内听神经元的分化中起作用。

In vertebrates, inner-ear development begins when surface ectoderm is induced to form the otic placodes by signals from surrounding tissues. In preliminary experiments, we observed that high levels of β-catenin appear in rat inner ears transiently corresponding to their morphogenesis. In this study, we examined the roles of β-catenin in inner ear development in rat embryos using immunostaining and antisense experiments. High levels of β-catenin appeared transiently in the optic cup during inner ear development. While β-catenin accumulation was not yet observed in the thickened surface ectoderm at the otic placode, it became to be detected at the apical surface of the otic cup. Then it disappeared from the otocyst. When embryos were treated with the β-catenin antisense oligodeoxynucleotide, accumulation of β-catenin in the otic cup was suppressed and the β-catenin protein level was significantly less in treated embryos than in controls. The number of cells in the otic cup in treated embryos was smaller than in control embryos. Cells that incorporated bromodeoxyuridine in the otic placode were fewer in number in treated embryos than in controls. In control embryos, acoustic neurons were detected by 2H3 (anti-neurofilament 165 KDa antibody) staining within the acoustic neural crest complex, while only a little staining of 2H3 was observed in the complex of the treated embryos. These results suggested that β-catenin plays a role in cell proliferation in the otic placode and in differentiation of acoustic neurons within the acoustic neural crest complex.