The specification of anterior neuroectoderm is controlled by a highly conserved molecular mechanism in bilaterians. A forkhead family gene, foxQ2, is known to be one of the pivotal regulators, which is zygotically expressed in this region during embryogenesis of a broad range of bilaterians. However, what controls the expression of this essential factor has remained unclear to date. To reveal the regulatory mechanism of foxQ2, we performed cis‐regulatory analysis of two foxQ2 genes, foxQ2a and foxQ2b, in a sea urchin Hemicentrotus pulcherrimus. In sea urchin embryos, foxQ2 is initially expressed in the entire animal hemisphere and subsequently shows narrower expression restricted to the anterior pole region. In this study, as a first step to understand the foxQ2 regulation, we focused on the later restricted expression and analyzed the upstream cis‐regulatory sequences of foxQ2a and foxQ2b by using the constructs fused to short half‐life green fluorescent protein. Based on deletion and mutation analyses of both foxQ2, we identified each of the five regulatory sequences, which were 4–9 bp long. Neither of the regulatory sequences contains any motifs for ectopic activation or spatial repression, suggesting that later mRNA localization is regulated in situ. We also suggest that the three amino acid loop extension‐class homeobox gene Meis is involved in the maintenance of foxQ2b, the expression of which is dominant during embryogenesis.

中文翻译：

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顺式调控分析海胆胚胎中前神经外胚层特异性foxQ2表达后期的过程。

前神经外胚层的规格是受双语者中高度保守的分子机制控制的。已知叉头家族基因foxQ2是关键调节子之一，在广泛的双语者的胚胎发生过程中在该区域合子表达。然而，至今仍不清楚什么因素控制该基本因子的表达。为了揭示foxQ2的调控机制，我们在海胆Hemicentrotus pulcherrimus中对两个foxQ2基因foxQ2a和foxQ2b进行了顺式调控分析。在海胆胚胎中，foxQ2最初在整个动物半球中表达，随后显示出局限于前极区的较窄表达。在这项研究中，作为了解foxQ2调控的第一步，我们集中于后来的限制性表达，并通过使用融合了半衰期短的绿色荧光蛋白的构建体分析了foxQ2a和foxQ2b的上游顺式调控序列。基于对两个foxQ2的缺失和突变分析，我们确定了5个调控序列中的每一个，序列长4–9 bp。这两个调控序列均不包含异位激活或空间抑制的任何基序，这表明以后的mRNA定位是原位调控的。我们还建议，三个氨基酸环延伸级同源盒基因Meis参与foxQ2b的维持，其表达在胚胎发生过程中占主导地位。