Analysis of extraembryonic mesodermal structure formation in the absence of morphological primitive streak. (8th June 2016)

• Record Type: Journal Article
• Authors: Jin, Jiu‐Zhen; Zhu, Yuanqi; Warner, Dennis; Ding, Jixiang
• Is Part Of: Development growth and differentiation. Volume 58:Number 6(2016)
• Page Start: 522
• Page End: 529
• Publication Date: 2016-06-08
• Subjects: allantois -- blood island -- Cripto -- Drap1 -- Lefty2 -- primitive streak; Embryology -- Periodicals; Developmental biology -- Periodicals; Growth -- Periodicals; 574.3
• DOI: 10.1111/dgd.12294
• Languages: English
• ISSNs: 0012-1592

Abstract

Abstract : During mouse gastrulation, the primitive streak is formed on the posterior side of the embryo. Cells migrate out of the primitive streak to form the future mesoderm and endoderm. Fate mapping studies revealed a group of cell migrate through the proximal end of the primitive streak and give rise to the extraembryonic mesoderm tissues such as the yolk sac blood islands and allantois. However, it is not clear whether the formation of a morphological primitive streak is required for the development of these extraembryonic mesodermal tissues. Loss of the Cripto gene in mice dramatically reduces, but does not completely abolish, Nodal activity leading to the absence of a morphological primitive streak. However, embryonic erythrocytes are still formed and assembled into the blood islands. In addition, Cripto mutant embryos form allantoic buds. However, Drap1 mutant embryos have excessive Nodal activity in the epiblast cells before gastrulation and form an expanded primitive streak, but no yolk sac blood islands or allantoic bud formation. Lefty2 embryos also have elevated levels of Nodal activity in the primitive streak during gastrulation, and undergo normal blood island and allantois formation. We therefore speculate that low level of Nodal activity disrupts the formation of morphological primitive streak on the posterior side, but still allows the formation of primitive streak cells on the proximal side, which give rise to the extraembryonic mesodermal tissues formation. Excessive Nodal activity in the epiblast at pre‐gastrulation stage, but not in the primitive streak cells during gastrulation, disrupts extraembryonic mesoderm development. Abstract : Cripto mutant mouse embryos form blood islands without morphological primitive streak. Drap1 is a Nodal inhibitor expressed in the epiblast and Drap1 mutant mouse embryos form excess primitive streak, but do not form blood islands or allantois. Lefty2 is also a Nodal antagonist expressed in the primitive streak, and Lefty2 mutant embryos displayed an expanded primitive streak and gave rise to normal blood islands and allantois.