Faculty Opinions recommendation of Decoupling of amniote gastrulation and streak formation reveals a morphogenetic unity in vertebrate mesoderm induction.

Several protocols exist for generating megakaryocytes (MKs) and platelets from human induced pluripotent stem cells (hiPSCs) with limited efficiency. We observed previously that mesoderm induction improved endothelial and stromal differentiation. We, therefore, hypothesized that a protocol modification prior to hemogenic endothelial cell (HEC) differentiation will improve MK progenitor (MKP) production and increase platelet output. We further asked if basic media composition affects MK maturation. In an iterative process, we first compared two HEC induction protocols. We found significantly more HECs using the modified protocol including activin A and CHIR99021, resulting in significantly increased MKs. MKs released comparable platelet amounts irrespective of media conditions. In a final validation phase, we obtained five-fold more platelets per hiPSC with the modified protocol (235 ± 84) compared to standard conditions (51 ± 15; p < 0.0001). The regenerative potency of hiPSC-derived platelets was compared to adult donor-derived platelets by profiling angiogenesis-related protein expression. Nineteen of 24 angiogenesis-related proteins were expressed equally, lower or higher in hiPSC-derived compared to adult platelets. The hiPSC-platelet’s coagulation hyporeactivity compared to adult platelets was confirmed by thromboelastometry. Further stepwise improvement of hiPSC-platelet production will, thus, permit better identification of platelet-mediated regenerative mechanisms and facilitate manufacture of sufficient amounts of functional platelets for clinical application.

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Expression of a novel FGF in the Xenopus embryo. A new candidate inducing factor for mesoderm formation and anteroposterior specification

Development ◽

10.1242/dev.114.3.711 ◽

1992 ◽

Vol 114 (3) ◽

pp. 711-720 ◽

Cited By ~ 46

Author(s):

H.V. Isaacs ◽

D. Tannahill ◽

J.M. Slack

Keyword(s):

Specific Activity ◽

Biological Properties ◽

The Body ◽

Mesoderm Induction ◽

Gastrula Stage ◽

Blastula Stage ◽

Mesoderm Formation ◽

Low Levels

We have cloned and sequenced a new member of the fibroblast growth factor family from Xenopus laevis embryo cDNA. It is most closely related to both mammalian kFGF (FGF-4) and FGF-6 but as it is not clear whether it is a true homologue of either of these genes we provisionally refer to it as XeFGF (Xenopus embryonic FGF). Two sequences were obtained, differing by 11% in derived amino acid sequence, which probably represent pseudotetraploid variants. Both the sequence and the behaviour of in vitro translated protein indicates that, unlike bFGF (FGF-2), XeFGF is a secreted molecule. Recombinant XeFGF protein has mesoderm-inducing activity with a specific activity similar to bFGF. XeFGF mRNA is expressed maternally and zygotically with a peak during the gastrula stage. Both probe protection and in situ hybridization showed that the zygotic expression is concentrated in the posterior of the body axis and later in the tailbud. Later domains of expression were found near the midbrain/hindbrain boundary and at low levels in the myotomes. Because of its biological properties and expression pattern, XeFGF is a good candidate for an inducing factor with possible roles both in mesoderm induction at the blastula stage and in the formation of the anteroposterior axis at the gastrula stage.

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Xenopus Embryo: Mesoderm Induction

Encyclopedia of Life Sciences ◽

10.1002/9780470015902.a0029258 ◽

2021 ◽

pp. 1-10

Author(s):

Leslie Dale ◽

Fiona C Wardle

Keyword(s):

Xenopus Embryo ◽

Mesoderm Induction

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Mechanism of anteroposterior axis specification in vertebrates. Lessons from the amphibians

Development ◽

10.1242/dev.114.2.285 ◽

1992 ◽

Vol 114 (2) ◽

pp. 285-302 ◽

Cited By ~ 33

Author(s):

J.M. Slack ◽

D. Tannahill

Keyword(s):

Molecular Markers ◽

Expression Patterns ◽

Signal Transduction Pathway ◽

Homeobox Gene ◽

Neural Induction ◽

High Sensitivity ◽

Neural Plate ◽

Mesoderm Induction ◽

Inducing Factors ◽

Almost All

Interest in the problem of anteroposterior specification has quickened because of our near understanding of the mechanism in Drosophila and because of the homology of Antennapedia-like homeobox gene expression patterns in Drosophila and vertebrates. But vertebrates differ from Drosophila because of morphogenetic movements and interactions between tissue layers, both intimately associated with anteroposterior specification. The purpose of this article is to review classical findings and to enquire how far these have been confirmed, refuted or extended by modern work. The “pre-molecular” work suggests that there are several steps to the process: (i) Formation of anteroposterior pattern in mesoderm during gastrulation with posterior dominance. (ii) Regional specific induction of ectoderm to form neural plate. (iii) Reciprocal interactions from neural plate to mesoderm. (iv) Interactions within neural plate with posterior dominance. Unfortunately, almost all the observable markers are in the CNS rather than in the mesoderm where the initial specification is thought to occur. This has meant that the specification of the mesoderm has been assayed indirectly by transplantation methods such as the Einsteckung. New molecular markers now supplement morphological ones but they are still mainly in the CNS and not the mesoderm. A particular interest attaches to the genes of the Antp-like HOX clusters since these may not only be markers but actual coding factors for anteroposterior levels. We have a new understanding of mesoderm induction based on the discovery of activins and fibroblast growth factors (FGFs) as candidate inducing factors. These factors have later consequences for anteroposterior pattern with activin tending to induce anterior, and FGF posterior structures. Recent work on neural induction has implicated cAMP and protein kinase C (PKC) as elements of the signal transduction pathway and has provided new evidence for the importance of tangential neural induction. The regional specificity of neural induction has been reinvestigated using molecular markers and provides conclusions rather similar to the classical work. Defects in the axial pattern may be produced by retinoic acid but it remains unclear whether its effects are truly coordinate ones or are concentrated in certain regions of high sensitivity. In general the molecular studies have supported and reinforced the “pre-molecular ones”. Important questions still remain: (i) How much pattern is there in the mesoderm (how many states?) (ii) How is this pattern generated by the invaginating organizer? (iii) Is there one-to-one transmission of codings to the neural plate? (iv) What is the nature of the interactions within the neural plate? (v) Are the HOX cluster genes really the anteroposterior codings?

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