Yoshida Michio, Kajikawa Eriko, Kurokawa Daisuke, Noro Miyuki, Iwai Tatsuhiro, Yonemura Shigenobu, Kobayashi Kensaku, Kiyonari Hiroshi, Aizawa Shinichi
Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan.
Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, 2-2-3 Minatojima Minami-machi, Chuo-ku, Kobe 650-0047, Japan; Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, 1024 Koajiro, Misaki, Miura, Kanagawa 238-0225, Japan.
Dev Biol. 2016 Jul 1;415(1):122-142. doi: 10.1016/j.ydbio.2016.05.005. Epub 2016 May 9.
The processes of development leading up to gastrulation have been markedly altered during the evolution of amniotes, and it is uncertain how the mechanisms of axis formation are conserved and diverged between mouse and chick embryos. To assess the conservation and divergence of these mechanisms, this study examined gene expression patterns during the axis formation process in Chinese soft-shell turtle and Madagascar ground gecko preovipositional embryos. The data suggest that NODAL signaling, similarly to avian embryos but in contrast to eutherian embryos, does not have a role in epiblast and hypoblast development in reptilian embryos. The posterior marginal epiblast (PME) is the initial molecular landmark of axis formation in reptilian embryos prior to primitive plate development. Ontogenetically, PME may be the precursor of the primitive plate, and phylogenetically, Koller's sickle and posterior marginal zone in avian development may have been derived from the PME. Most of the genes expressed in the mouse anterior visceral endoderm (AVE genes), especially signaling antagonist genes, are not expressed in the hypoblast of turtle and gecko embryos, though they are expressed in the avian hypoblast. This study proposes that AVE gene expression in the hypoblast and the visceral endoderm could have been independently established in avian and eutherian lineages, similar to the primitive streak that has been independently acquired in these lineages.
在羊膜动物的进化过程中，导致原肠胚形成的发育过程发生了显著变化，目前尚不清楚小鼠和鸡胚胎之间轴形成的机制是如何保守和分化的。为了评估这些机制的保守性和差异性，本研究检测了中华鳖和马达加斯加地壁虎产卵前胚胎轴形成过程中的基因表达模式。数据表明，与鸟类胚胎相似但与真兽类胚胎不同，NODAL信号在爬行类胚胎的上胚层和下胚层发育中不起作用。后缘上胚层（PME）是爬行类胚胎在原板发育之前轴形成的初始分子标志。从个体发育角度来看，PME可能是原板的前体，从系统发育角度来看，鸟类发育中的科勒镰刀和后缘区可能源自PME。大多数在小鼠前内脏内胚层中表达的基因（AVE基因），尤其是信号拮抗剂基因，在龟和壁虎胚胎的下胚层中不表达，尽管它们在鸟类下胚层中表达。本研究提出，下胚层和内脏内胚层中的AVE基因表达可能在鸟类和真兽类谱系中独立建立，类似于这些谱系中独立获得的原条。
