Expanded expression of Sonic Hedgehog in Astyanax cavefish:: multiple consequences on forebrain development and evolution
Expanded expression of Sonic Hedgehog in Astyanax cavefish:: multiple consequences on forebrain development and evolution
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DOI：
10.1242/dev.02780
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发表时间：
2007-03-01
期刊：
影响因子：
4.6
通讯作者：
Retaux, Sylvie
中科院分区：
文献类型：
--
作者：
Menuet, Arnaud;Alunni, Alessandro;Retaux, Sylvie
脑中线Sonic Hedgehog（Shh）信号传导对于胚胎前脑的生长和形成至关重要。在这里，我们报告如何增强的Shh中线信号影响端脑和间脑神经元图案在盲洞穴鱼Astyanax mexicanus，硬骨鱼密切相关的斑马鱼的演变。洞穴和表面居住形式的Astyanax之间的比较表明，洞穴鱼显示更大的Shh在整个发展的所有前中线域的表达。这并不影响整体前脑区域模式，但对特定区域和神经元群体有几个重要的后果。首先，我们发现洞穴鱼基底间脑和下丘脑中Nkx2.1a表达增强，细胞增殖水平更高。第二，我们发现了Nkx 2. 1b-Lhx 6-GABA阳性迁移途径从软腭下的嗅球，这是在洞穴鱼类的大小增加。最后，我们观察到异时性和扩大Lhx 7在洞穴鱼基底前脑的表达。嗅觉和下丘脑前脑成分的这些特定增加是Shh依赖的，因此将端脑中线组织者置于通过发育事件调节前脑进化的关键位置，并在前脑神经元模式中产生多样性。
Ventral midline Sonic Hedgehog ( Shh) signalling is crucial for growth and patterning of the embryonic forebrain. Here, we report how enhanced Shh midline signalling affects the evolution of telencephalic and diencephalic neuronal patterning in the blind cavefish Astyanax mexicanus, a teleost fish closely related to zebrafish. A comparison between cave- and surface-dwelling forms of Astyanax shows that cavefish display larger Shh expression in all anterior midline domains throughout development. This does not affect global forebrain regional patterning, but has several important consequences on specific regions and neuronal populations. First, we show expanded Nkx2.1a expression and higher levels of cell proliferation in the cavefish basal diencephalon and hypothalamus. Second, we uncover an Nkx2.1b-Lhx6-GABA-positive migratory pathway from the subpallium to the olfactory bulb, which is increased in size in cavefish. Finally, we observe heterochrony and enlarged Lhx7 expression in the cavefish basal forebrain. These specific increases in olfactory and hypothalamic forebrain components are Shh-dependent and therefore place the telencephalic midline organisers in a crucial position to modulate forebrain evolution through developmental events, and to generate diversity in forebrain neuronal patterning.