A Late Role for bmp2b in the Morphogenesis of Semicircular Canal Ducts in the Zebrafish Inner Ear
A Late Role for bmp2b in the Morphogenesis of Semicircular Canal Ducts in the Zebrafish Inner Ear
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DOI：
10.1371/journal.pone.0004368
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发表时间：
2009-02-03
期刊：
影响因子：
3.7
通讯作者：
Whitfield, Tanya T.
中科院分区：
文献类型：
--
作者：
Hammond, Katherine L.;Loynes, Helen E.;Whitfield, Tanya T.
背景资料：骨形态发生蛋白（BMP）基因bmp 2和bmp 4在发育中的脊椎动物内耳中以高度保守的模式表达。然而，已经证明很难阐明骨形成蛋白在耳朵发育过程中的功能，因为这些基因的突变会导致早期胚胎死亡。以前的研究使用条件的方法在小鼠和鸡已经表明，BMP 4的半规管和嵴的发展中的作用，但目前还没有直接的证据BMP 2在发展中的内耳的作用。方法/主要发现：我们已经使用了RNA救援策略测试的作用BMP 2B在斑马鱼内耳直接。注射bmp 2b或smad 5 mRNA到纯合突变体漩涡（bmp 2b（-/-））胚胎拯救这些突变体的早期图案缺陷和鱼存活到成年。由于注射的RNA最多只能持续胚胎发生的前几天，所有后来的发育都是在没有bmp 2b功能的情况下发生的。虽然获救的漩涡成鱼是可行的，他们有平衡缺陷暗示前庭功能障碍。对这些鱼的内耳的分析显示，它们完全没有半规管，半规管是检测角运动的结构。耳的所有其他区域，包括壶腹和嵴，都存在并且看起来正常。在获救的漩涡胚胎耳发育的早期阶段也normal.Conclusions/Significance：我们的研究结果表明，BMP 2B在半规管在斑马鱼内耳的形态发生的关键后期作用。这是第一次证明任何基因在斑马鱼耳形态发生的胚胎后阶段的发育作用。尽管在半规管形成的早期阶段斑马鱼和BMP 2之间的差异，半规管管生长的作用可能是不同的脊椎动物物种之间的保守。
Background: The Bone Morphogenetic Protein (BMP) genes bmp2 and bmp4 are expressed in highly conserved patterns in the developing vertebrate inner ear. It has, however, proved difficult to elucidate the function of BMPs during ear development as mutations in these genes cause early embryonic lethality. Previous studies using conditional approaches in mouse and chicken have shown that Bmp4 has a role in semicircular canal and crista development, but there is currently no direct evidence for the role of Bmp2 in the developing inner ear.Methodology/Principal Findings: We have used an RNA rescue strategy to test the role of bmp2b in the zebrafish inner ear directly. Injection of bmp2b or smad5 mRNA into homozygous mutant swirl (bmp2b(-/-)) embryos rescues the early patterning defects in these mutants and the fish survive to adulthood. As injected RNA will only last, at most, for the first few days of embryogenesis, all later development occurs in the absence of bmp2b function. Although rescued swirl adult fish are viable, they have balance defects suggestive of vestibular dysfunction. Analysis of the inner ears of these fish reveals a total absence of semicircular canal ducts, structures involved in the detection of angular motion. All other regions of the ear, including the ampullae and cristae, are present and appear normal. Early stages of otic development in rescued swirl embryos are also normal.Conclusions/Significance: Our findings demonstrate a critical late role for bmp2b in the morphogenesis of semicircular canals in the zebrafish inner ear. This is the first demonstration of a developmental role for any gene during post-embryonic stages of otic morphogenesis in the zebrafish. Despite differences in the early stages of semicircular canal formation between zebrafish and amniotes, the role of Bmp2 in semicircular canal duct outgrowth is likely to be conserved between different vertebrate species.