XB-ART-28272Dev Biol. February 1, 1987; 119 (2): 560-78.
Fates of the blastomeres of the 16-cell stage Xenopus embryo.
The fate of each of the blastomeres in the 16-cell stage Xenopus embryo which had been carefully selected for stereotypic cleavages was determined by intracellularly marking a single blastomere with horseradish peroxidase and identifying the labeled progeny in the tailbud embryo by histochemistry. Each blastomere populated all three primary germ layers. The progeny of each blastomere were distributed characteristically both in phenotype and in location. For example, most organs were populated by the descendants of particular sets of blastomeres. Furthermore, within an organ the progeny of a single blastomere were restricted to defined spatial addresses. This study describes the fates of identified 16-cell stage blastomeres and demonstrates that they are distinct and predictable if embryos are preselected for stereotypic cleavages.
PubMed ID: 3803718
Article link: Dev Biol.
Grant support: NS20604 NINDS NIH HHS , NS23158 NINDS NIH HHS
Article Images: [+] show captions
|Fig. 1. The names of the blastomeres of the 16-cell stage Xenopus embryo, as assigned by Hirose and Jacobson (1979). Although Xenopus embryos need not cleave in this pattern, the embryos used in this study all did.|
|FIG. 2. The distribution of HRP-labeled cells in head sections of tailbud embryos (st. 32-34) after HRP was injected into a blastomere. The HRP reaction product is brown and natural melanin pigmentation is black. However, in these and the following black and white photomicrographs, the two colors have very similar densities. A natural distribution of melanin in the head is demonstrated in D, G, and H, in which there are no HRP labeled cells. (A) D1.1: Labeled cells were located bilaterally in the ventral mesencephalon, dorsal head mesenchyme, and retina. Labeled cells lined the pharynx and were in the core of the branchial mesoderm. The dark pigmentation surrounding the entire tissue section and the eyes is melanin. X60. (B) 01.2: Labeled cells were in the lens, dorsal head mesenchyme, and branchial mesoderm, but not in pharynx or notochord. Pigmented cells that also contained HRP were in the epidermis, cement gland, and dorsal mesencephalon (arrow). X60. (C) D2.1: One labeled cell was in the forebrain (bracket) in this specimen, although similar labeled cells were not in any other embryos in this group. Dorsal head mesoderm and the central core of each branchial arch contained labeled cells. Many cells in the pharynx were labeled. X53. (D) D.&B: No labeled cells were in the rostra1 head. All coloration is due to melanin granules. X50. (E) V1.l: The only labeled cells in this section were in the lens, dorsal branchial mesoderm, and epidermis. X60. (F) Vl.2: Labeled epidermal cells were scattered over the rostra1 head, within the cement gland and lens. All branchial arches contained many labeled cells. x60. (G) V.. I; No HRP-labeled cells were in head sections. All coloration is due to melanin granules. X56. (H) VZ.2: No HRP-labeled cells were in most head sections, although branchial arches caudal to this section contained some labeled cells. All coloration is due to melanin granules. X60. Abbreviations used in this and other figures as follows: a, archenteron roof; b, branchial arch; c, central trunk somite; cg, cranial ganglion; cm, cement gland; d, dorsal trunk somite; df, dorsal tailfin; dh, dorsal head mesenchyme; e, epidermis; fg, foregut; h, heart; hg, hindgut; hs, head somite; 1,lens; li, liver; lp, lateral plate; m, mesencephalon; n, notochord; nc, neural crest; ne, nephrotome; o, otic vesicle; p, prosencephalon; ph, pharynx; r, retina; rh, rhombencephalon; s, spinal cord; so, somite; v, ventral somite.|
|IG. 3. The distribution of HRP-labeled cells in rostra1 trunk sections of tailbud embryos. (A) Dl.1: Labeled cells were located bilaterally in the central region of the somite and in the ventral spinal cord. Notochord cells were labeled faintly. One ventral hindgut cell was labeled in this section. X52. (B) 01.2: In a caudal head section, labeled cells were in the trigeminal ganglion (cg), ventral retina, and lens. Ventral pharynx and branchial arch mesoderm contained several labeled cells. Arrow points to a single cell in the dorsal rhombencephalon. X56. (C) 02.1: In a section near the spinomedullary junction labeled cells were in the head somite, foregut, and heart. X54. (D) 02.2: In a section near the spinomedullary junction, large numbers of labeled neural crest cells migrated along the rhombencephalon and otocyst. The entire head somite was labeled. Caudal branchial mesoderm, dorsal foregut, and heart contained labeled cells. X66. (E) V1.1: In the midtrunk region numerous labeled epidermal cells were scattered over the ventral and lateral regions. Neural crest cells, dorsal and ventral myotubes, and ventrolateral hindgut cells were labeled. X59. (F) V1.2: In a section near the spinomedullary junction, numerous neural crest cells, cranial ganglion cells, brachial mesoderm cells, heart cells, and epidermal cells were labeled. X60. (G) V2.1: In a section near the spinomedullary junction, labeled cells only were in the dorsal region of the lateral plate mesoderm and in the nephric tubules. X55. (H) V2.2: In a section near the spinomedullary junction, labeled cells were in the neural crest, lateral plate mesoderm, and nephrotome. A few labeled cells were in the head somite at this level. X51. Abbreviations as in Fig. 2.|
|IG. 4. The distribution of HRP-labeled cells in caudal trunk or tail sections of tailbud embryos. (A) D1.1: Labeled cells in the tail region were in the central somite, ventral spinal cord and notochord. The dark coloration in the epidermis and hindgut is due to melanin granules, not to the HRP reaction product. X57. (B) Dl.2: Labeled neurons were located throughout the ipsilateral spinal cord and central somite. Labeled neural crest cells, dorsal to the spinal cord and betwen it and the somites were located bilaterally. A few labeled cells were in the dorsal fin epidermis. X55. (C) 02.1: Labeled cells were only in the neural crest and ventral hindgut at this level. X53. (D) 02.2: Labeled cells were in the intermediate and ventral spinal cord, mostly the central somite, the neural crest, and ventral hindgut. X57. (E) Vl.1: In the tail, labeled cells in the epidermis and ventral somite occurred bilaterally in some embryos. The only labeled cells in the spinal cord were Rohon-Beard neurons (arrow). X79. (F) Irl.~: Many cells in the lateral plate mesoderm, epidermis, and dorsal somite were labeled. A few cells were labeled in the hindgut, neural crest, and dorsal spinal cord. Arrow points to a labeled Rohon-Beard neuron. X59. (G) VZ.1:Many labeled cells were in the dorsal and ventral somite, neural crest, lateral plate mesoderm, and hindgut. X52. (H) V2.2:Labeled myotubes were mostly in dorsal and ventral somite at this level, but more caudally they were mostly in the central somite. Labeled neural crest were between the epidermis and somite. Arrow points to a labeled dorsal commissural neuron in the spinal cord. Large regions of the hindgut, including archenteron roof, were labeled. X52. Abbreviations as in Fig. 2.|