Staying in shape: Planarians as a model for understanding regenerative morphology

Birkholz, Taylor R.; Huizen, Alanna V. Van; Beane, Wendy S.

doi:10.1016/j.semcdb.2018.04.014

Cited by 17 publications

(18 citation statements)

References 110 publications

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“…The rate of brain regeneration that we observed was consistent with results from other research groups in various planarians species (Reviewed in Birkholz et al, 2019;Brown andPearson, 2017, Cebrià 2007;Cebrià et al, 2018;Fraguas et al, 2012;Inoue et al, 2004;Ivankovic et al, 2019;Ross et al, 2017). Our experiments show that intact planarians, as expected, displayed a constant response to 1 mM cytisine exposure over a period of nine days, in contrast to decapitated planarians, which did not significantly respond to this cytisine treatment until day four, when they began to display pSLMs, indicating a gradual recovery of function, which was complete by day 9 (Fig.…”

Section: Cytisinesupporting

confidence: 92%

Measuring functional brain recovery in regenerating planarians by assessing the behavioral response to the cholinergic compound cytisine

Pagán

Baker²,

Deats³

et al. 2020

Int. J. Dev. Biol.

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Planarians are traditional model invertebrates in regeneration and developmental biology research that also display a variety of quantifiable behaviors useful to screen for pharmacologically active compounds. One such behavior is the expression of seizure-like movements (pSLMs) induced by a variety of substances. Previous work from our laboratory showed that cocaine, but not nicotine, induced pSLMs in intact but not decapitated planarians. Interestingly, as decapitated planarians regenerated their heads, they gradually recovered their sensitivity to cocaine. These results suggested a method to assess planarian brain regeneration and a possible way of identifying compounds that could enhance or hold back brain regeneration. In the present work, we demonstrate that the cholinergic agent cytisine is a suitable reference compound to apply our method. Cytisine induces pSLMs in a concentration-dependent manner in intact (but not decapitated) planarians of the species Girardia tigrina. Based on our data, we developed a behavioral protocol to assess planarian brain regeneration over time. We tested this method to measure the effect of ethanol on G. tigrina’s brain regeneration. We found that ethanol slows down the rate of planarian brain regeneration in a concentration-dependent manner, consistently with data from other research groups that tested ethanol effects on planarian brain regeneration using different behavioral protocols. Thus, here we establish a general method using cytisine-induced pSLMs as an indicator of brain regeneration in planarians, a method that shows potential for assessing the effect of pharmacologically active compounds in this process.

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Section: Cytisinesupporting

confidence: 92%

Measuring functional brain recovery in regenerating planarians by assessing the behavioral response to the cholinergic compound cytisine

Pagán

Baker²,

Deats³

et al. 2020

Int. J. Dev. Biol.

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“…The best-understood group of these worms is the freshwater type, particularly the ones belonging to the family Dugesiidae, which includes the genera Girardia, Dugesia and Schmidtea, comprising more than one hundred formally described species [15]. The most striking characteristic of many of these planarian species is their remarkable capacity for regeneration [16,17]. As an example royalsocietypublishing.org/journal/rstb Phil.…”

Section: The First Brainmentioning

confidence: 99%

The brain: a concept in flux

Pagán

2019

Phil. Trans. R. Soc. B

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One of the most important aspects of the scientific endeavour is the definition of specific concepts as precisely as possible. However, it is also important not to lose sight of two facts: (i) we divide the study of nature into manageable parts in order to better understand it owing to our limited cognitive capacities and (ii) definitions are inherently arbitrary and heavily influenced by cultural norms, language, the current political climate, and even personal preferences, among many other factors. As a consequence of these facts, clear-cut definitions, despite their evident importance, are oftentimes quite difficult to formulate. One of the most illustrative examples about the difficulty of articulating precise scientific definitions is trying to define the concept of a brain. Even though the current thinking about the brain is beginning to take into account a variety of organisms, a vertebrocentric bias still tends to dominate the scientific discourse about this concept. Here I will briefly explore the evolution of our ‘thoughts about the brain’, highlighting the difficulty of constructing a universally (or even a generally) accepted formal definition of it and using planarians as one of the earliest examples of organisms proposed to possess a ‘traditional’, vertebrate-style brain. I also suggest that the time is right to attempt to expand our view of what a brain is, going beyond exclusively structural and taxa-specific criteria. Thus, I propose a classification that could represent a starting point in an effort to expand our current definitions of the brain, hopefully to help initiate conversations leading to changes of perspective on how we think about this concept. This article is part of the theme issue ‘Liquid brains, solid brains: How distributed cognitive architectures process information’.

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“…Typically, whole-body axis regeneration occurs through a combination of remodeling of existing tissue and growth of new tissue through cell proliferation. Regenerates resulting from whole-body axis regeneration are typically smaller than the pre-amputated animal but display correct proportionality [ 1 – 7 ], suggesting that rescaling of some tissues and organ systems is part of the normal regenerative response [ 4 , 7 ]. Many species are able to alter their adult size based on environmental conditions.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the dynamics and variability of neuronal subtype responses during growth, degrowth, and regeneration of Nematostella vectensis

et al. 2021

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Background The ability to regenerate body parts is a feature of metazoan organisms and the focus of intense research aiming to understand its basis. A number of mechanisms involved in regeneration, such as proliferation and tissue remodeling, affect whole tissues; however, little is known on how distinctively different constituent cell types respond to the dynamics of regenerating tissues. Preliminary studies suggest that a number of organisms alter neuronal numbers to scale with changes in body size. In some species with the ability of whole-body axis regeneration, it has additionally been observed that regenerates are smaller than their pre-amputated parent, but maintain the correct morphological proportionality, suggesting that scaling of tissue and neuronal numbers also occurs. However, the cell dynamics and responses of neuronal subtypes during nervous system regeneration, scaling, and whole-body axis regeneration are not well understood in any system. The cnidarian sea anemone Nematostella vectensis is capable of whole-body axis regeneration, with a number of observations suggesting the ability to alter its size in response to changes in feeding. We took advantage of Nematostella’s transparent and “simple” body plan and the NvLWamide-like mCherry fluorescent reporter transgenic line to probe the response of neuron populations to variations in body size in vivo in adult animals during body scaling and regeneration. Results We utilized the previously characterized NvLWamide-like::mCherry transgenic reporter line to determine the in vivo response of neuronal subtypes during growth, degrowth, and regeneration. Nematostella alters its size in response to caloric intake, and the nervous system responds by altering neuronal number to scale as the animal changes in size. Neuronal numbers in both the endodermal and ectodermal nerve nets decreased as animals shrunk, increased as they grew, and these changes were reversible. Whole-body axis regeneration resulted in regenerates that were smaller than their pre-amputated size, and the regenerated nerve nets were reduced in neuronal number. Different neuronal subtypes had distinct responses during regeneration, including consistent, not consistent, and conditional increases in number. Conditional responses were regulated, in part, by the size of the remnant fragment and the position of the amputation site. Regenerates and adults with reduced nerve nets displayed normal behaviors, indicating that the nerve net retains functionality as it scales. Conclusion These data suggest that the Nematostella nerve net is dynamic, capable of scaling with changes in body size, and that neuronal subtypes display differential regenerative responses, which we propose may be linked to the scale state of the regenerating animals.

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Staying in shape: Planarians as a model for understanding regenerative morphology

Cited by 17 publications

References 110 publications

Measuring functional brain recovery in regenerating planarians by assessing the behavioral response to the cholinergic compound cytisine

Measuring functional brain recovery in regenerating planarians by assessing the behavioral response to the cholinergic compound cytisine

The brain: a concept in flux

Characterization of the dynamics and variability of neuronal subtype responses during growth, degrowth, and regeneration of Nematostella vectensis

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