PDF(Pubmed)
Abstract：
BACKGROUND: The evolution of central nervous systems (CNSs) is a fascinating and complex topic; further work is needed to understand the genetic and developmental homology between organisms with a CNS. Research into a limited number of species suggests that CNSs may be homologous across Bilateria. This hypothesis is based in part on similar functions of BMP signaling in establishing fates along the dorsal-ventral (D-V) axis, including limiting neural specification to one ectodermal region. From an evolutionary-developmental perspective, the best way to understand a system is to explore it in a wide range of organisms to create a full picture.
METHODS: Here, we expand our understanding of BMP signaling in Spiralia, the third major clade of bilaterians, by examining phenotypes after expression of a dominant-negative BMP Receptor 1 and after knock-down of the putative BMP antagonist Chordin-like using CRISPR/Cas9 gene editing in the annelid Capitella teleta (Pleistoannelida).
RESULTS: Ectopic expression of the dominant-negative Ct-BMPR1 did not increase CNS tissue or alter overall D-V axis formation in the trunk. Instead, we observed a unique asymmetrical phenotype: a distinct loss of left tissues, including the left eye, brain, foregut, and trunk mesoderm. Adding ectopic BMP4 early during cleavage stages reversed the dominant-negative Ct-BMPR1 phenotype, leading to a similar loss or reduction of right tissues instead. Surprisingly, a similar asymmetrical loss of left tissues was evident from CRISPR knock-down of Ct-Chordin-like but concentrated in the trunk rather than the episphere.
CONCLUSIONS: Our data highlight a novel asymmetrical phenotype, giving us further insight into the complicated story of BMP\'s developmental role. We further solidify the hypothesis that the function of BMP signaling during the establishment of the D-V axis and CNS is fundamentally different in at least Pleistoannelida, possibly in Spiralia, and is not required for nervous system delimitation in this group.
METHODS: Here, we expand our understanding of BMP signaling in Spiralia, the third major clade of bilaterians, by examining phenotypes after expression of a dominant-negative BMP Receptor 1 and after knock-down of the putative BMP antagonist Chordin-like using CRISPR/Cas9 gene editing in the annelid Capitella teleta (Pleistoannelida).
RESULTS: Ectopic expression of the dominant-negative Ct-BMPR1 did not increase CNS tissue or alter overall D-V axis formation in the trunk. Instead, we observed a unique asymmetrical phenotype: a distinct loss of left tissues, including the left eye, brain, foregut, and trunk mesoderm. Adding ectopic BMP4 early during cleavage stages reversed the dominant-negative Ct-BMPR1 phenotype, leading to a similar loss or reduction of right tissues instead. Surprisingly, a similar asymmetrical loss of left tissues was evident from CRISPR knock-down of Ct-Chordin-like but concentrated in the trunk rather than the episphere.
CONCLUSIONS: Our data highlight a novel asymmetrical phenotype, giving us further insight into the complicated story of BMP\'s developmental role. We further solidify the hypothesis that the function of BMP signaling during the establishment of the D-V axis and CNS is fundamentally different in at least Pleistoannelida, possibly in Spiralia, and is not required for nervous system delimitation in this group.
摘要：
背景：中枢神经系统（CNSs）的进化是一个令人着迷且复杂的主题；需要进一步的工作来了解具有CNS的生物体之间的遗传和发育同源性。对数量有限的物种的研究表明，CNSs可能在Bilateria中同源。该假设部分基于BMP信号在沿背-腹侧（D-V）轴建立命运中的类似功能，包括将神经规范限制在一个外胚层区域。从进化发展的角度来看，了解一个系统的最好方法是在广泛的生物体中探索它，以创造一个完整的画面。
方法：这里，我们扩展了我们对Spiralia中BMP信号的理解，双边主义者的第三大分支，通过在环状Capitellateleta（Pleistoannelida）中使用CRISPR/Cas9基因编辑来检查显性阴性BMP受体1表达后和推定的BMP拮抗剂脊索蛋白样敲除后的表型。
结果：显性阴性Ct-BMPR1的异位表达并未增加CNS组织或改变躯干中整体D-V轴的形成。相反，我们观察到一种独特的不对称表型：左侧组织明显丧失，包括左眼,大脑,前肠,和树干中胚层。在卵裂阶段早期添加异位BMP4逆转了显性阴性Ct-BMPR1表型，导致类似的右组织丢失或减少。令人惊讶的是,从Ct-Chordin样的CRISPR敲除中可以明显看出左组织的类似不对称损失，但集中在躯干而不是半球。
结论：我们的数据突出了一种新的不对称表型，让我们进一步深入了解BMP的发展作用的复杂故事。我们进一步巩固了以下假设：在D-V轴和CNS的建立过程中，BMP信号传导的功能至少在Pleistoannelida中是根本不同的。可能在Spiralia,并且在该组中不需要进行神经系统划界。
方法：这里，我们扩展了我们对Spiralia中BMP信号的理解，双边主义者的第三大分支，通过在环状Capitellateleta（Pleistoannelida）中使用CRISPR/Cas9基因编辑来检查显性阴性BMP受体1表达后和推定的BMP拮抗剂脊索蛋白样敲除后的表型。
结果：显性阴性Ct-BMPR1的异位表达并未增加CNS组织或改变躯干中整体D-V轴的形成。相反，我们观察到一种独特的不对称表型：左侧组织明显丧失，包括左眼,大脑,前肠,和树干中胚层。在卵裂阶段早期添加异位BMP4逆转了显性阴性Ct-BMPR1表型，导致类似的右组织丢失或减少。令人惊讶的是,从Ct-Chordin样的CRISPR敲除中可以明显看出左组织的类似不对称损失，但集中在躯干而不是半球。
结论：我们的数据突出了一种新的不对称表型，让我们进一步深入了解BMP的发展作用的复杂故事。我们进一步巩固了以下假设：在D-V轴和CNS的建立过程中，BMP信号传导的功能至少在Pleistoannelida中是根本不同的。可能在Spiralia,并且在该组中不需要进行神经系统划界。
