Planarian brain regeneration as a model system for developmental neurotoxicology

Hagstrom, Danielle; Cochet‐Escartin, Olivier; Collins, Eva‐Maria S.

doi:10.1002/reg2.52

Cited by 72 publications

(69 citation statements)

References 81 publications

(187 reference statements)

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“…As the peripheral site may play a role in aspects of OP toxicity (Kousba et al 2004), the differences in the DjChE peripheral site, as compared to mammalian AChE, provides an opportunity to distinguish between these effects. The unique regenerative capabilities of planarians allows one not only to compare toxicity on adult and developing animals in parallel (Hagstrom et al 2016), but also bears the potential to delineate how OP-induced neurological damage could be repaired.…”

Section: Discussionmentioning

confidence: 99%

“…We have recently shown that the freshwater planarian Dugesia japonica is a valuable in vivo model for neurotoxicity studies (Hagstrom et al 2015; Hagstrom et al 2016). The planarian’s capacity to regenerate after asexual reproduction or amputation - due to its large population of stem cells - make it well suited to study perturbations in neurodevelopment (Hagstrom et al 2016).…”

Section: Introductionmentioning

confidence: 99%

“…The planarian’s capacity to regenerate after asexual reproduction or amputation - due to its large population of stem cells - make it well suited to study perturbations in neurodevelopment (Hagstrom et al 2016). Because full and regenerating worms are of similar size, the planarian system allows for a direct comparison of the effects of neurotoxicants on brain development and function using the same behavioral endpoints (Hagstrom et al 2015; Hagstrom et al 2016). Using a custom planarian screening platform (Hagstrom et al 2015), we found that planarians are sensitive to OPs.…”

Section: Introductionmentioning

confidence: 99%

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Planarian cholinesterase: in vitro characterization of an evolutionarily ancient enzyme to study organophosphorus pesticide toxicity and reactivation

et al. 2016

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The freshwater planarian Dugesia japonica has recently emerged as an animal model for developmental neurotoxicology and found to be sensitive to organophosphorus (OP) pesticides. While previous activity staining of D. japonica, which possess a discrete cholinergic nervous system, has shown acylthiocholine catalysis, it is unknown whether this is accomplished through an acetylcholinesterase (AChE), butyrylcholinesterase (BChE), or a hybrid esterase and how OP exposure affects esterase activity. Here, we show that the majority of D. japonica cholinesterase (DjChE) activity departs from conventional AChE and BChE classifications. Inhibition by classic protonable amine and quaternary reversible inhibitors (ethopropazine, donepezil, tacrine, edrophonium, BW284c51, propidium) shows that DjChE is far less sensitive to these inhibitors than human AChE, suggesting discrete differences in active center and peripheral site recognition and structures. Additionally, we find that different OPs (chlorpyrifos oxon, paraoxon, dichlorvos, diazinon oxon, malaoxon) and carbamylating agents (carbaryl, neostigmine, physostigmine, pyridostigmine) differentially inhibit DjChE activity in vitro. DjChE was most sensitive to diazinon oxon and neostigmine and least sensitive to malaoxon and carbaryl. Diazinon oxon-inhibited DjChE could be reactivated by the quaternary oxime, pralidoxime (2-PAM), and the zwitterionic oxime, RS194B, with RS194B being significantly more potent. Sodium fluoride (NaF) reactivates OP-DjChE faster than 2-PAM. As one of the most ancient true cholinesterases, DjChE provides insight into the evolution of a hybrid enzyme before the separation into distinct AChE and BChE enzymes found in higher vertebrates. The sensitivity of DjChE to OPs and capacity for reactivation validate the use of planarians for OP toxicology studies.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Planarian cholinesterase: in vitro characterization of an evolutionarily ancient enzyme to study organophosphorus pesticide toxicity and reactivation

et al. 2016

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“…Planarians have also been the subject of recent work in toxicology, as well as behavioral, ecological, and evolutionary biology research (Alvarez-Presas et al, 2008; Hagstrom et al, 2016, 2015; Hicks et al, 2006; Inoue et al, 2015; Levin et al, 2016; Lombardo et al, 2011; Majdi et al, 2014; Shomrat and Levin, 2013), broadening their use as a model beyond fields related to developmental biology. In the classroom, these charismatic organisms have been an important component in K-12 science education and tools are being developed to modernize their use in college level courses (Accorsi et al, 2017; Eberhardt et al, 2015; Pagan et al, 2009; Valverde, 2015).…”

Section: Introductionmentioning

confidence: 99%

Girardia dorotocephala transcriptome sequence, assembly, and validation through characterization of piwi homologs and stem cell progeny markers

Almazan

Lesko

Markey

et al. 2018

Developmental Biology

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Planarian flatworms are popular models for the study of regeneration and stem cell biology in vivo. Technical advances and increased availability of genetic information have fueled the discovery of molecules responsible for stem cell pluripotency and regeneration in flatworms. Unfortunately, most of the planarian research performed worldwide utilizes species that are not natural habitants of North America, which limits their availability to newcomer laboratories and impedes their distribution for educational activities. In order to circumvent these limitations and increase the genetic information available for comparative studies, we sequenced the transcriptome of Girardia dorotocephala, a planarian species pandemic and commercially available in North America. A total of 254,802,670 paired sequence reads were obtained from RNA extracted from intact individuals, regenerating fragments, as well as freshly excised auricles of a clonal line of G. dorotocephala (MA-C2), and used for de novo assembly of its transcriptome. The resulting transcriptome draft was validated through functional analysis of genetic markers of stem cells and their progeny in G. dorotocephala. Akin to orthologs in other planarian species, G. dorotocephala Piwi1 (GdPiwi1) was found to be a robust marker of the planarian stem cell population and GdPiwi2 an essential component for stem cell-driven regeneration. Identification of G. dorotocephala homologs of the early stem cell descendent marker PROG-1 revealed a family of lysine-rich proteins expressed during epithelial cell differentiation. Sequences from the MA-C2 transcriptome were found to be 98–99% identical to nucleotide sequences from G. dorotocephala populations with different chromosomal number, demonstrating strong conservation regardless of karyotype evolution. Altogether, this work establishes G. dorotocephala as a viable and accessible option for analysis of gene function in North America.

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“…The freshwater planarian Dugesia japonica has recently emerged as a valuable in vivo model for neurotoxicity studies, with particular focus on neurodevelopment (Hagstrom et al 2015; Hagstrom et al 2016). This asexual species naturally reproduces through transverse fission.…”

Section: Introductionmentioning

confidence: 99%

Planarian cholinesterase: molecular and functional characterization of an evolutionarily ancient enzyme to study organophosphorus pesticide toxicity

Hagstrom

Zhang

et al. 2017

Arch Toxicol

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The asexual freshwater planarian Dugesia japonica has emerged as a medium-throughput alternative animal model for neurotoxicology. We have previously shown that D. japonica are sensitive to organophosphorus pesticides (OPs) and characterized the in vitro inhibition profile of planarian cholinesterase (DjChE) activity using irreversible and reversible inhibitors. We found that DjChE has intermediate features of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Here, we identify two candidate genes (Djche1 and Djche2) responsible for DjChE activity. Sequence alignment and structural homology modeling with representative vertebrate AChE and BChE sequences confirmed our structural predictions, and show that both DjChE enzymes have intermediate sized catalytic gorges and disrupted peripheral binding sites. Djche1 and Djche2 were both expressed in the planarian nervous system, as anticipated from previous activity staining, but with distinct expression profiles. To dissect how DjChE inhibition affects planarian behavior, we acutely inhibited DjChE activity by exposing animals to either an OP (diazinon) or carbamate (physostigmine) at 1 µM for 4 days. Both inhibitors delayed the reaction of planarians to heat stress. Simultaneous knockdown of both Djche genes by RNAi similarly resulted in a delayed heat stress response. Furthermore, chemical inhibition of DjChE activity increased the worms' ability to adhere to a substrate. However, increased substrate adhesion was not observed in Djche1/Djche2 (RNAi) animals or in inhibitor-treated day 11 regenerates, suggesting this phenotype may be modulated by other mechanisms besides ChE inhibition. Together, our study characterizes DjChE expression and function, providing the basis for future studies in this system to dissect alternative mechanisms of OP toxicity.

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Planarian brain regeneration as a model system for developmental neurotoxicology

Cited by 72 publications

References 81 publications

Planarian cholinesterase: in vitro characterization of an evolutionarily ancient enzyme to study organophosphorus pesticide toxicity and reactivation

Planarian cholinesterase: in vitro characterization of an evolutionarily ancient enzyme to study organophosphorus pesticide toxicity and reactivation

Girardia dorotocephala transcriptome sequence, assembly, and validation through characterization of piwi homologs and stem cell progeny markers

Planarian cholinesterase: molecular and functional characterization of an evolutionarily ancient enzyme to study organophosphorus pesticide toxicity

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