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The evolution of robust development and homeostasis in artificial organisms.

Basanta D, Miodownik M, Baum B - PLoS Comput. Biol. (2008)

Bottom Line: An evolutionary analysis revealed that evolution itself contributed to the ability of this organism to maintain its form in the face of genetic and environmental perturbation, confirming the results of previous studies.In addition, the exceptional robustness of this organism to surface injury was found to result from an upward flux of cells, driven in part by cell divisions with a stable niche at the tissue base.Given the general nature of the model, our results lead us to suggest that many of the robust systems properties observed in real organisms, including scar-free wound-healing in well-protected embryos and the layered tissue architecture of regenerating epithelial tissues, may be by-products of the evolution of morphogenesis, rather than the direct result of selection.

View Article: PubMed Central - PubMed

Affiliation: Materials Research Group, Engineering Division, King's College London, London, United Kingdom.

ABSTRACT
During embryogenesis, multicellular animals are shaped via cell proliferation, cell rearrangement, and apoptosis. At the end of development, tissue architecture is then maintained through balanced rates of cell proliferation and loss. Here, we take an in silico approach to look for generic systems features of morphogenesis in multicellular animals that arise as a consequence of the evolution of development. Using artificial evolution, we evolved cellular automata-based digital organisms that have distinct embryonic and homeostatic phases of development. Although these evolved organisms use a variety of strategies to maintain their form over time, organisms of different types were all found to rapidly recover from environmental damage in the form of wounds. This regenerative response was most robust in an organism with a stratified tissue-like architecture. An evolutionary analysis revealed that evolution itself contributed to the ability of this organism to maintain its form in the face of genetic and environmental perturbation, confirming the results of previous studies. In addition, the exceptional robustness of this organism to surface injury was found to result from an upward flux of cells, driven in part by cell divisions with a stable niche at the tissue base. Given the general nature of the model, our results lead us to suggest that many of the robust systems properties observed in real organisms, including scar-free wound-healing in well-protected embryos and the layered tissue architecture of regenerating epithelial tissues, may be by-products of the evolution of morphogenesis, rather than the direct result of selection.

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The ability of homeostatic organisms (A) #11, (B) #17, and (C) #18 to withstand environmental perturbation was tested by inducing wounds at time step 100.The recovery process was then followed over time.
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pcbi-1000030-g003: The ability of homeostatic organisms (A) #11, (B) #17, and (C) #18 to withstand environmental perturbation was tested by inducing wounds at time step 100.The recovery process was then followed over time.

Mentions: Having tested the response of evolved organisms to genetic perturbation, we next tested their ability to maintain morphological homeostasis in the face of an environmental challenge. For this analysis, each organism was subjected to a systematic series of ‘gun-shot’ wounds in which ∼5% or more of the total cell population was removed at time-step 100 (Figure 3). As before, a 2-point correlation and a lineal path function were used to quantify any ensuing repair response. Remarkably, organisms of each type (dynamic, static or asymmetric) were able to heal wounds encompassing hundreds of cells within ∼30 time-steps (Figure 3A, 3B, and 3C and Videos S4, S5, and S6). This wound-healing response was most striking in the case of organism #11 (Figure 3A and Video S4), which during normal development undergoes a period of steady growth, followed by a period of stasis in which cell division and cell death rates fall to zero. Upon wounding, however, this organism mounted an effective repair-response; closing wounds to achieve a good restoration of the organism's original static form. Although normally static, this organism is therefore poised ready to respond appropriately to a variety of environmental insults and, as such, has achieved a relatively sophisticated form of homeostasis.


The evolution of robust development and homeostasis in artificial organisms.

Basanta D, Miodownik M, Baum B - PLoS Comput. Biol. (2008)

The ability of homeostatic organisms (A) #11, (B) #17, and (C) #18 to withstand environmental perturbation was tested by inducing wounds at time step 100.The recovery process was then followed over time.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2274883&req=5

pcbi-1000030-g003: The ability of homeostatic organisms (A) #11, (B) #17, and (C) #18 to withstand environmental perturbation was tested by inducing wounds at time step 100.The recovery process was then followed over time.
Mentions: Having tested the response of evolved organisms to genetic perturbation, we next tested their ability to maintain morphological homeostasis in the face of an environmental challenge. For this analysis, each organism was subjected to a systematic series of ‘gun-shot’ wounds in which ∼5% or more of the total cell population was removed at time-step 100 (Figure 3). As before, a 2-point correlation and a lineal path function were used to quantify any ensuing repair response. Remarkably, organisms of each type (dynamic, static or asymmetric) were able to heal wounds encompassing hundreds of cells within ∼30 time-steps (Figure 3A, 3B, and 3C and Videos S4, S5, and S6). This wound-healing response was most striking in the case of organism #11 (Figure 3A and Video S4), which during normal development undergoes a period of steady growth, followed by a period of stasis in which cell division and cell death rates fall to zero. Upon wounding, however, this organism mounted an effective repair-response; closing wounds to achieve a good restoration of the organism's original static form. Although normally static, this organism is therefore poised ready to respond appropriately to a variety of environmental insults and, as such, has achieved a relatively sophisticated form of homeostasis.

Bottom Line: An evolutionary analysis revealed that evolution itself contributed to the ability of this organism to maintain its form in the face of genetic and environmental perturbation, confirming the results of previous studies.In addition, the exceptional robustness of this organism to surface injury was found to result from an upward flux of cells, driven in part by cell divisions with a stable niche at the tissue base.Given the general nature of the model, our results lead us to suggest that many of the robust systems properties observed in real organisms, including scar-free wound-healing in well-protected embryos and the layered tissue architecture of regenerating epithelial tissues, may be by-products of the evolution of morphogenesis, rather than the direct result of selection.

View Article: PubMed Central - PubMed

Affiliation: Materials Research Group, Engineering Division, King's College London, London, United Kingdom.

ABSTRACT
During embryogenesis, multicellular animals are shaped via cell proliferation, cell rearrangement, and apoptosis. At the end of development, tissue architecture is then maintained through balanced rates of cell proliferation and loss. Here, we take an in silico approach to look for generic systems features of morphogenesis in multicellular animals that arise as a consequence of the evolution of development. Using artificial evolution, we evolved cellular automata-based digital organisms that have distinct embryonic and homeostatic phases of development. Although these evolved organisms use a variety of strategies to maintain their form over time, organisms of different types were all found to rapidly recover from environmental damage in the form of wounds. This regenerative response was most robust in an organism with a stratified tissue-like architecture. An evolutionary analysis revealed that evolution itself contributed to the ability of this organism to maintain its form in the face of genetic and environmental perturbation, confirming the results of previous studies. In addition, the exceptional robustness of this organism to surface injury was found to result from an upward flux of cells, driven in part by cell divisions with a stable niche at the tissue base. Given the general nature of the model, our results lead us to suggest that many of the robust systems properties observed in real organisms, including scar-free wound-healing in well-protected embryos and the layered tissue architecture of regenerating epithelial tissues, may be by-products of the evolution of morphogenesis, rather than the direct result of selection.

Show MeSH
Related in: MedlinePlus