Metamorphic pitx2 expression in the left habenula correlated with lateralization of eye‐sidedness in flounder
Metamorphic pitx2 expression in the left habenula correlated with lateralization of eye‐sidedness in flounder
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DOI：
10.1111/j.1440-169x.2009.01139.x
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发表时间：
2009-10
期刊：
影响因子：
4.6
通讯作者：
Tohru Suzuki;Youhei Washio;M. Aritaki;Y. Fujinami;D. Shimizu;S. Uji;H. Hashimoto
中科院分区：
文献类型：
--
作者：
Tohru Suzuki;Youhei Washio;M. Aritaki;Y. Fujinami;D. Shimizu;S. Uji;H. Hashimoto
比目鱼幼体的两侧对称性在形态发生过程中发生变化，在变态时产生外部不对称性。该过程的特征在于一只眼睛的侧向迁移和眼侧的色素沉着。左眼或右眼分别迁移产生右旋或左旋形式，通常在一个物种内是固定的。在这里，我们提出了一种通过比目鱼中的nodal-lefty-pitx 2（NLP）通路介导偏侧化的机制，其中pitx 2，NLP通路的最终左右决定因素，在变态前在左缰中重新表达。在左侧pitx 2重新表达开始后，眼睛开始迁移，此时缰在左侧比目鱼（Paralichthys olivaceus）腹侧间脑上的位置向右移动，在右侧比目鱼（Verasper variegatus）中向左移动。此外，在这两个物种中，右侧缰的大小相对于左侧缰增加。pitx 2重新表达的缺失诱导眼侧性的随机化，表现为正常、反向或双侧对称，与正常比目鱼相比，反向比目鱼的缰结构不对称的偏侧性完全颠倒。因此，比目鱼pitx 2似乎在变态时在左侧缰中重新表达，通过侧化缰的形态不对称性直接向眼侧化。
The bilateral symmetry of flounder larvae changes through the process of morphogenesis to produce external asymmetry at metamorphosis. The process is characterized by the lateral migration of one eye and pigmentation at the ocular side. Migration of the left or right eye to produce either dextral or sinistral forms, respectively, is usually fixed within a species. Here we propose a mechanism for the mediation of lateralization by the nodal‐lefty‐pitx2 (NLP) pathway in flounders, in which pitx2, the final left‐right determinant of the NLP pathway, is re‐expressed in the left habenula at pre‐metamorphosis. After the initiation of left‐sided pitx2 re‐expression, the eye commences migration, when the habenulae shift their position on the ventral diencephalon rightwards in sinistral flounder (Paralichthys olivaceus) and leftwards in dextral flounder (Verasper variegatus). In addition, the right habenula increases in size relative to the left habenula in both species. Loss of pitx2 re‐expression induces randomization of eye‐sidedness, manifesting as normal, reversed or bilateral symmetry, with laterality of the structural asymmetry of habenulae being entirely inverted in reversed flounders compared with normal ones. Thus, flounder pitx2 appears to be re‐expressed in the left habenula at metamorphosis to direct eye‐sidedness by lateralizing the morphological asymmetry of the habenulae.