Multiple sequence alignments and phylogenetic trees from: Co-option of the limb patterning program in cephalopod eye development

Background Across the Metazoa, similar genetic programs are found in the development of analogous, independently evolved, morphological features. The functional significance of this reuse and the underlying mechanisms of co-option remain unclear. Cephalopods have evolved a highly acute visual system with a cup shaped retina and a novel refractive lens in the anterior, important for a number of sophisticated behaviors including predation, mating and camouflage. Almost nothing is known about the molecular-genetics of lens development in the cephalopod. Results Here we identify the co-option of the canonical bilaterian limb pattering program during cephalopod lens development, a functionally unrelated structure. We show radial expression of transcription factors SP6-9/sp1, Dlx/dll, Pbx/exd, Meis/hth, and a Prdl homolog in the squid Doryteuthis pealeii, similar to expression required in Drosophila limb development. We assess the role of Wnt signaling in the cephalopod lens, a posit...研究背景 在后生动物（Metazoa）各分支中，独立演化形成的同类形态特征的发育过程里，均存在相似的保守遗传程序。该遗传程序复用的功能意义，以及共选择（co-option）的潜在作用机制仍未明晰。头足类演化出了高度敏锐的视觉系统，其拥有杯状视网膜与前部的新型屈光晶状体，这对于捕食、交配、伪装等诸多复杂行为至关重要。目前学界对头足类晶状体发育的分子遗传调控机制仍知之甚少。 研究结果 本研究鉴定发现，在头足类晶状体——一种功能上与肢体无关的结构——的发育过程中，存在对经典两侧对称动物肢体模式形成（limb patterning）程序的共选择。我们在佩氏枪乌贼（Doryteuthis pealeii）中观察到，转录因子（transcription factor）SP6-9/sp1、Dlx/dll、Pbx/exd、Meis/hth以及Prdl同源基因的表达呈放射状分布，该表达模式与果蝇肢体发育所需的基因表达特征高度一致。我们对Wnt信号通路（Wnt signaling）在头足类晶状体发育中的调控作用进行了评估，初步研究结果为……