bHLH-dependent and -independent modes of Ath5 gene regulation during retinal development
bHLH-dependent and -independent modes of Ath5 gene regulation during retinal development
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DOI：
10.1242/dev.01653
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发表时间：
2005-02-01
期刊：
影响因子：
4.6
通讯作者：
Vetter, ML
中科院分区：
文献类型：
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作者：
Hutcheson, DA;Hanson, MI;Vetter, ML
在广泛的脊椎动物物种中，bHLH转录因子Ath5与视网膜中神经发生的起始和视网膜神经节细胞的发生紧密相关。在这里，我们描述了至少两种模式的调节在视网膜发育过程中的Ath5的表达。我们已经发现，非洲爪蟾Ath5基因（Xath5）的近端顺式调控区在脊椎动物物种中是高度保守的，足以驱动视网膜特异性报告基因在转基因非洲爪蟾胚胎中的表达。Xath5近端转基因表达依赖于两个高度保守的bHLH因子结合位点（E盒）以及bHLH因子在体内的活性。然而，我们发现，bHLH活性是不需要一个更长的Xath5转基因的表达，这表明，其他机制有助于Xath5在体内的表达。与此一致，我们发现，一个更远的片段，不包括保守的近端区域是足以促进转基因表达在发育中的视网膜。在小鼠中，我们发现小鼠或非洲爪蟾Ath5基因的顺式调节区的较长片段是转基因表达所必需的，并且小鼠Math5（Atoh7）转基因的表达不依赖于自身调节。因此，尽管广泛的保护在近端区域，这些元素的重要性可能是物种依赖性。
In a wide range of vertebrate species, the bHLH transcription factor Ath5 is tightly associated with both the initiation of neurogenesis in the retina and the genesis of retinal ganglion cells. Here, we describe at least two modes of regulating the expression of Ath5 during retinal development. We have found that a proximal cis-regulatory region of the Xenopus Ath5 gene (Xath5) is highly conserved across vertebrate species and is sufficient to drive retinal-specific reporter gene expression in transgenic Xenopus embryos. Xath5 proximal transgene expression depended upon two highly conserved bHLH factor binding sites (E-boxes) as well as bHLH factor activity in vivo. However, we found that bHLH activity was not required for expression of a longer Xath5 transgene, suggesting that additional mechanisms contribute to Xath5 expression in vivo. Consistent with this, we showed that a more distal fragment that does not include the conserved proximal region is sufficient to promote transgene expression in the developing retina. In mouse, we found that a longer fragment of the cis-regulatory region of either the mouse or Xenopus Ath5 gene was necessary for transgene expression, and that expression of a mouse Math5 (Atoh7) transgene was not dependent upon autoregulation. Thus, despite extensive conservation in the proximal region, the importance of these elements may be species dependent.