|
Fig. 1
Schematic drawing of S&Z gastrulation model. a The organizer and the prospective neuroectoderm are originally established tandemly at the blastocoel roof of the blastula. b The organizer and the prospective neuroectoderm move downward. The organizer finally localizes at the blastocoel floor. c The prospective neuroectoderm progresses with downward movement. Accompanying that, the organizer is forcibly dragged down and makes a trench, which is termed “subduction movement.” Then, the organizer and the prospective neuroectoderm make physical contact from posterior (vegetal) toward anterior (equatorial), termed “zippering movement.” d As a result of subduction and zippering (S&Z) movement, “Anterior Contact Establishment (ACE)” occurs at the dorsal marginal zone of early gastrula. (e) The axial structure is formed toward the posterior during gastrulation. The red region and the blue region indicate the organizer and the prospective neuroectoderm, respectively
|
|
Fig. 2
ACE embryo lacking blastocoel roof and ventral two-thirds of the marginal zone developed the complete dorsal structures. a Schematic drawing of removal of the blastocoel roof and the ventral marginal zone at ACE. b The ACE embryo after removal of the blastocoel roof and ventral marginal zone. c The percentage of the embryo with dorsal structure after the removal of the indicated amount of the vegetal marginal zone at ACE. d, e The tailbud embryos developed from control and operated ACE embryo. Scale bars, 1 mm. f–y In situ hybridization of control and operated embryos. Scale bars, 500 µm. The expression of bf1 (f, g), otx2 (h, i), rx2a (j, k), pax6 (l, m), krox20 (n, o), hairy2 (p, q), gsc (r, s), and chd (t, u) in the neurula stage. The expression of myoD (v, w) and bra (x, y) in the tailbud stage
|
|
Fig. 3
ACE embryo lacking yolky endoderm developed the complete dorsal structures. a Schematic drawing of the yolky endoderm removal at ACE. b, c The tailbud embryos developed from control and operated ACE embryo. Scale bars, 1 mm. d–w In situ hybridization of control and operated embryos. Scale bars, 500 µm. The expression of bf1 (d, e), otx2 (f, g), rx2a (h, i), pax6 (j, k), krox20 (l, m), hairy2 (n, o), gsc (p, q), and chd (r, s) in the neurula stage. The expression of myoD (t, u) and bra (v, w) in the tailbud stage
|
|
Fig. 4
Transplantation of mGFP-labeled dorsal marginal zone at ACE into the ventral side of non-labeled ACE embryo. a Schematic drawing of the transplantation assay. b The whole-mount view of operated embryo at the tailbud stage. White arrowheads, mGFP-labeled secondary body axis. c The transverse section of head in the secondary body axis. White arrowhead, neural tube. Black arrowheads, eyes. d The transverse section of trunk region in the secondary body axis. White arrowhead, neural tube. Black arrowhead, notochord
|
|
Fig. 5
The explant of blastocoel roof of blastula developed an embryo only lacking yolk mass. a Schematic drawing of the blastocoel roof explant of blastula. b, c The tailbud embryos developed from control and operated blastocoel roof explant of blastula. Scale bars, 1 mm
|
|
Fig. 6
S&Z movement is conserved, whereas the amount and the location of yolk are varied, among chordates. a Amphioxus shows a hollow globular embryo which possesses only a small amount of yolk, but ACE has occurred by the simple invagination with little involution, which corresponds to S&Z movement. Thereafter, the A-P axis is elongated posteriorly. b Though vertebrate precursor might acquire the yolk on the vegetal side of the embryo, the gastrulation movement could be conserved. c Amphibians such as Xenopus laevis also store a certain amount of yolk within their dividing vegetal hemisphere. d Odorrana supranarina has a larger amount of yolk, which impedes cleavage, but the gastrulation movement, in which ACE occurs at the dorsal marginal zone and elongates the A-P axis posteriorly, is indeed confirmed. e In avian development such as that of Gallus gallus, the anterior end of the primitive streak regresses after the streak reaches its full length. The regression might lead to physical contact between the organizer and the prospective neuroectoderm, which could be referred to as the head process. The morphogenetic movement is similar to S&Z movement. Red region, the organizer. Blue region, the prospective neuroectoderm. Orange, yolk
|
|
Supplementary Fig. 1 Transplantation of non-labeled dorsal marginal zone at ACE into the ventral side of mGFP-labeled ACE embryo.
(a) Schematic drawing of the transplantation assay. (b) The lateral view of the operated embryo at tailbud stage. The non-labeled secondary body axis was formed at the ventral side. (c) The ventral view of the operated embryo. The head and the tail of the secondary body axis were completely non-labeled.
|
|
Supplementary Fig. 2 The explant of dorsal marginal zone at ACE developed into an embryoid possessing a complete dorsal structure
(a) Schematic drawing of dorsal marginal zone explant at ACE. (b) The explant of dorsal marginal zone at ACE. (c, d) The tailbud embryos developed from control and operated explant. Scale bars, 1 mm. (e-x) in situ hybridization of control and operated explant. Scale bars, 500 μm. The expression of bf1 (e, f), otx2 (g, h), rx2a (i, j), pax6 (k, l), krox20 (m, n), hairy2 (o, p), gsc (q, r), chd (s, t) in neurula stage. The expression of myoD (u, v), bra (w, x) in tailbud stage.
|
