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Savage AM, Alberio R, Johnson AD. Germline competent mesoderm: the substrate for vertebrate germline and somatic stem cells? Biol Open 2021; 10:272478. [PMID: 34648017 PMCID: PMC8524722 DOI: 10.1242/bio.058890] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
In vitro production of tissue-specific stem cells [e.g. haematopoietic stem cells (HSCs)] is a key goal of regenerative medicine. However, recent efforts to produce fully functional tissue-specific stem cells have fallen short. One possible cause of shortcomings may be that model organisms used to characterize basic vertebrate embryology (Xenopus, zebrafish, chick) may employ molecular mechanisms for stem cell specification that are not conserved in humans, a prominent example being the specification of primordial germ cells (PGCs). Germ plasm irreversibly specifies PGCs in many models; however, it is not conserved in humans, which produce PGCs from tissue termed germline-competent mesoderm (GLCM). GLCM is not conserved in organisms containing germ plasm, or even in mice, but understanding its developmental potential could unlock successful production of other stem cell types. GLCM was first discovered in embryos from the axolotl and its conservation has since been demonstrated in pigs, which develop from a flat-disc embryo like humans. Together these findings suggest that GLCM is a conserved basal trait of vertebrate embryos. Moreover, the immortal nature of germ cells suggests that immortality is retained during GLCM specification; here we suggest that the demonstrated pluripotency of GLCM accounts for retention of immortality in somatic stem cell types as well. This article has an associated Future Leaders to Watch interview with the author of the paper. Summary: Recent findings that germline and stem cell specification may differ between species may have important implications for regenerative medicine and the future of stem cell biology.
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Affiliation(s)
- Aaron M Savage
- School of Pharmacy, Division of Stem Cell and Regenerative Medicine, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
| | - Ramiro Alberio
- School of Biosciences, Stem Cell Biology, Reprogramming and Pluripotency, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK
| | - Andrew D Johnson
- School of Life Sciences, Division of Cells, Organisms and Molecular Genetics, University of Nottingham, Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK
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Ricci L, Cabrera F, Lotito S, Tiozzo S. Redeployment of germ layers related TFs shows regionalized expression during two non-embryonic developments. Dev Biol 2016; 416:235-248. [PMID: 27208394 DOI: 10.1016/j.ydbio.2016.05.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 05/11/2016] [Accepted: 05/12/2016] [Indexed: 11/26/2022]
Abstract
In all non-vertebrate metazoan phyla, species that evolved non-embryonic developmental pathways as means of propagation or regeneration can be found. In this context, new bodies arise through asexual reproduction processes (such as budding) or whole body regeneration, that lack the familiar temporal and spatial cues classically associated with embryogenesis, like maternal determinants, or gastrulation. The molecular mechanisms underlying those non-embryonic developments (i.e., regeneration and asexual reproduction), and their relationship to those deployed during embryogenesis are poorly understood. We have addressed this question in the colonial ascidian Botryllus schlosseri, which undergoes an asexual reproductive process via palleal budding (PB), as well as a whole body regeneration by vascular budding (VB). We identified early regenerative structures during VB and then followed the fate of differentiating tissues during both non-embryonic developments (PB and VB) by monitoring the expression of genes known to play key functions in germ layer specification with well conserved expression patterns in solitary ascidian embryogenesis. The expression patterns of FoxA1, GATAa, GATAb, Otx, Bra, Gsc and Tbx2/3 were analysed during both PB and VB. We found that the majority of these transcription factors were expressed during both non-embryonic developmental processes, revealing a regionalization of the palleal and vascular buds. Knockdown of GATAa by siRNA in palleal buds confirmed that preventing the correct development of one of these regions blocks further tissue specification. Our results indicate that during both normal and injury-induced budding, a similar alternative developmental program operates via early commitment of epithelial regions.
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Affiliation(s)
- Lorenzo Ricci
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06230 Villefranche sur-mer, France
| | - Fabien Cabrera
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06230 Villefranche sur-mer, France
| | - Sonia Lotito
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06230 Villefranche sur-mer, France
| | - Stefano Tiozzo
- Sorbonne Universités, UPMC Univ. Paris 06, CNRS, Laboratoire de Biologie du Développement de Villefranche-sur-mer (LBDV), 06230 Villefranche sur-mer, France.
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Multicellular Mathematical Modelling of Mesendoderm Formation in Amphibians. Bull Math Biol 2016; 78:436-67. [PMID: 26934886 DOI: 10.1007/s11538-016-0150-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 01/04/2016] [Indexed: 10/22/2022]
Abstract
The earliest cell fate decisions in a developing embryo are those associated with establishing the germ layers. The specification of the mesoderm and endoderm is of particular interest as the mesoderm is induced from the endoderm, potentially from an underlying bipotential group of cells, the mesendoderm. Mesendoderm formation has been well studied in an amphibian model frog, Xenopus laevis, and its formation is driven by a gene regulatory network (GRN) induced by maternal factors deposited in the egg. We have recently demonstrated that the axolotl, a urodele amphibian, utilises a different topology in its GRN to specify the mesendoderm. In this paper, we develop spatially structured mathematical models of the GRNs governing mesendoderm formation in a line of cells. We explore several versions of the model of mesendoderm formation in both Xenopus and the axolotl, incorporating the key differences between these two systems. Model simulations are able to reproduce known experimental data, such as Nodal expression domains in Xenopus, and also make predictions about how the positional information derived from maternal factors may be interpreted to drive cell fate decisions. We find that whilst cell-cell signalling plays a minor role in Xenopus, it is crucial for correct patterning domains in axolotl.
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Parfitt DE, Shen MM. From blastocyst to gastrula: gene regulatory networks of embryonic stem cells and early mouse embryogenesis. Philos Trans R Soc Lond B Biol Sci 2015; 369:rstb.2013.0542. [PMID: 25349451 DOI: 10.1098/rstb.2013.0542] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
To date, many regulatory genes and signalling events coordinating mammalian development from blastocyst to gastrulation stages have been identified by mutational analyses and reverse-genetic approaches, typically on a gene-by-gene basis. More recent studies have applied bioinformatic approaches to generate regulatory network models of gene interactions on a genome-wide scale. Such models have provided insights into the gene networks regulating pluripotency in embryonic and epiblast stem cells, as well as cell-lineage determination in vivo. Here, we review how regulatory networks constructed for different stem cell types relate to corresponding networks in vivo and provide insights into understanding the molecular regulation of the blastocyst-gastrula transition.
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Affiliation(s)
- David-Emlyn Parfitt
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA Department of Genetics and Development, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA Department of Urology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA Department of Systems Biology, Herbert Irving Comprehensive Cancer Center, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | - Michael M Shen
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA Department of Genetics and Development, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA Department of Urology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA Department of Systems Biology, Herbert Irving Comprehensive Cancer Center, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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Kaufman-Francis K, Goh HN, Kojima Y, Studdert JB, Jones V, Power MD, Wilkie E, Teber E, Loebel DAF, Tam PPL. Differential response of epiblast stem cells to Nodal and Activin signalling: a paradigm of early endoderm development in the embryo. Philos Trans R Soc Lond B Biol Sci 2015; 369:rstb.2013.0550. [PMID: 25349457 DOI: 10.1098/rstb.2013.0550] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Mouse epiblast stem cells (EpiSCs) display temporal differences in the upregulation of Mixl1 expression during the initial steps of in vitro differentiation, which can be correlated with their propensity for endoderm differentiation. EpiSCs that upregulated Mixl1 rapidly during differentiation responded robustly to both Activin A and Nodal in generating foregut endoderm and precursors of pancreatic and hepatic tissues. By contrast, EpiSCs that delayed Mixl1 upregulation responded less effectively to Nodal and showed an overall suboptimal outcome of directed differentiation. The enhancement in endoderm potency in Mixl1-early cells may be accounted for by a rapid exit from the progenitor state and the efficient response to the induction of differentiation by Nodal. EpiSCs that readily differentiate into the endoderm cells are marked by a distinctive expression fingerprint of transforming growth factor (TGF)-β signalling pathway genes and genes related to the endoderm lineage. Nodal appears to elicit responses that are associated with transition to a mesenchymal phenotype, whereas Activin A promotes gene expression associated with maintenance of an epithelial phenotype. We postulate that the formation of definitive endoderm (DE) in embryoid bodies follows a similar process to germ layer formation from the epiblast, requiring an initial de-epithelialization event and subsequent re-epithelialization. Our results show that priming EpiSCs with the appropriate form of TGF-β signalling at the formative phase of endoderm differentiation impacts on the further progression into mature DE-derived lineages, and that this is influenced by the initial characteristics of the cell population. Our study also highlights that Activin A, which is commonly used as an in vitro surrogate for Nodal in differentiation protocols, does not elicit the same downstream effects as Nodal, and therefore may not effectively mimic events that take place in the mouse embryo.
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Affiliation(s)
- Keren Kaufman-Francis
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia
| | - Hwee Ngee Goh
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia
| | - Yoji Kojima
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia Institute of Integrated Cell-Material Science, Kyoto University, Kyoto 606-8501, Japan
| | - Joshua B Studdert
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia
| | - Vanessa Jones
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia
| | - Melinda D Power
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia
| | - Emilie Wilkie
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia Bioinformatics Group, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia
| | - Erdahl Teber
- Bioinformatics Group, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia
| | - David A F Loebel
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia Sydney Medical School, University of Sydney, Sydney, New South Wales 2008, Australia
| | - Patrick P L Tam
- Embryology Unit, Children's Medical Research Institute, Westmead, New South Wales 2145, Australia Sydney Medical School, University of Sydney, Sydney, New South Wales 2008, Australia
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Abstract
Systems biology has gained a tremendous amount of interest in the last few years. This is partly due to the realization that traditional approaches focusing only on a few molecules at a time cannot describe the impact of aberrant or modulated molecular environments across a whole system. Furthermore, a hypothesis-driven study aims to prove or disprove its postulations, whereas a hypothesis-free systems approach can yield an unbiased and novel testable hypothesis as an end-result. This latter approach foregoes assumptions which predict how a biological system should react to an altered microenvironment within a cellular context, across a tissue or impacting on distant organs. Additionally, re-use of existing data by systematic data mining and re-stratification, one of the cornerstones of integrative systems biology, is also gaining attention. While tremendous efforts using a systems methodology have already yielded excellent results, it is apparent that a lack of suitable analytic tools and purpose-built databases poses a major bottleneck in applying a systematic workflow. This review addresses the current approaches used in systems analysis and obstacles often encountered in large-scale data analysis and integration which tend to go unnoticed, but have a direct impact on the final outcome of a systems approach. Its wide applicability, ranging from basic research, disease descriptors, pharmacological studies, to personalized medicine, makes this emerging approach well suited to address biological and medical questions where conventional methods are not ideal.
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Affiliation(s)
- Scott W Robinson
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, BHF Glasgow Cardiovascular Research Centre, 126 University Place, Glasgow G12 8TA, UK
| | - Marco Fernandes
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, BHF Glasgow Cardiovascular Research Centre, 126 University Place, Glasgow G12 8TA, UK
| | - Holger Husi
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, BHF Glasgow Cardiovascular Research Centre, 126 University Place, Glasgow G12 8TA, UK
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