Michio Yoshida1, Eriko Kajikawa1, Daisuke Kurokawa1,2, Tomoyuki Tokunaga3, Akira Onishi4, Shigenobu Yonemura5, Kensaku Kobayashi6, Hiroshi Kiyonari6, Shinichi Aizawa1,6. 1. Laboratory for Vertebrate Body Plan, Center for Developmental Biology (CDB), RIKEN Kobe, Chuo-ku, Kobe, Japan. 2. Misaki Marine Biological Station, Graduate School of Science, The University of Tokyo, Misaki, Miura, Kanagawa, Japan. 3. Animal Development and Differentiation Research Unit, Animal Research Division, National Institute of Agrobiological Sciences (NIAS), Tsukuba-shi, Ibaraki, Japan. 4. Laboratory of Animal Reproduction, Department of Animal Science and Resources, Nihon University College of Bioresource Sciences, Fujisawa, Kanagawa, Japan. 5. Ultrastructural Research Team, Biosystem Dynamics Group, Division of Bio-function Dynamics Imaging, RIKEN Center for Life Science Technologies (CLST), Chuo-ku, Kobe, Japan. 6. Laboratory for Animal Resources and Genetic Engineering, Center for Developmental Biology (CDB), RIKEN Kobe, Chuo-ku, Kobe, Japan.
Abstract
BACKGROUND: Mouse embryos are cup shaped, but most nonrodent eutherian embryos are disk shaped. Extraembryonic ectoderm (ExEc), which may have essential roles in anterior-posterior (A-P) axis formation in mouse embryos, does not develop in many eutherian embryos. To assess A-P axis formation in eutherians, comparative analyses were made on rabbit, porcine, and Suncus embryos. RESULTS: All embryos examined expressed Nodal initially throughout epiblast and visceral endoderm; its expression became restricted to the posterior region before gastrulation. Anterior visceral endoderm (AVE) genes were expressed in Otx2-positive visceral endoderm, with Dkk1 expression being most anterior. The mouse pattern of AVE formation was conserved in rabbit embryos, but had diverged in porcine and Suncus embryos. No structure that was molecularly equivalent to Bmp-positive ExEc, existed in rabbit or pig embryos. In Suncus embryos, A-P axis was determined at prehatching stage, and these embryos attached to uterine wall at future posterior side. CONCLUSIONS: Nodal, but not Bmp, functions in epiblast and visceral endoderm development may be conserved in eutherians. AVE functions may also be conserved, but the pattern of its formation has diverged among eutherians. Roles of BMP and NODAL gradients in AVE formation seem to have been established in a subset of rodents.
BACKGROUND:Mouse embryos are cup shaped, but most nonrodent eutherian embryos are disk shaped. Extraembryonic ectoderm (ExEc), which may have essential roles in anterior-posterior (A-P) axis formation in mouse embryos, does not develop in many eutherian embryos. To assess A-P axis formation in eutherians, comparative analyses were made on rabbit, porcine, and Suncus embryos. RESULTS: All embryos examined expressed Nodal initially throughout epiblast and visceral endoderm; its expression became restricted to the posterior region before gastrulation. Anterior visceral endoderm (AVE) genes were expressed in Otx2-positive visceral endoderm, with Dkk1 expression being most anterior. The mouse pattern of AVE formation was conserved in rabbit embryos, but had diverged in porcine and Suncus embryos. No structure that was molecularly equivalent to Bmp-positive ExEc, existed in rabbit or pig embryos. In Suncus embryos, A-P axis was determined at prehatching stage, and these embryos attached to uterine wall at future posterior side. CONCLUSIONS: Nodal, but not Bmp, functions in epiblast and visceral endoderm development may be conserved in eutherians. AVE functions may also be conserved, but the pattern of its formation has diverged among eutherians. Roles of BMP and NODAL gradients in AVE formation seem to have been established in a subset of rodents.
Authors: Jessica van Leeuwen; Pisana Rawson; Debra K Berg; David N Wells; Peter L Pfeffer Journal: Proc Natl Acad Sci U S A Date: 2020-06-29 Impact factor: 11.205