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At least 19 recordsLinked to original sources
PubMed2026

Progress on the telomere-telomerase system in planarian neoblasts homeostasis and regeneration.

Planarians are flatworms with remarkable regenerative abilities, and their adult pluripotent stem cells, known as neoblasts, serve as the foundation for this regeneration. Neoblasts can rapidly migrate, proliferate, and undergo directed differentiation following tissue injury to complete regeneration. Telomeres are located at the ends of eukaryotic chromosomes and play a core role in maintaining chromosomal integrity. With each cell division, telomeres shorten. Telomerase is a reverse transcriptase that compensates for telomere loss during cell division by extending telomeric repeats. The telomere-telomerase system is one of the important mechanisms for maintaining stem cell homeostasis. As adult pluripotent stem cells of planarians, neoblasts are required to maintain a dynamic balance between high-frequency cell division and multilineage differentiation. The maintenance of their long-term proliferative capacity and genomic stability may depend on the precise regulation of the telomere-telomerase system. Thus, this system represents a critical entry point for understanding the remarkable regenerative ability of planarians. Integrating recent progress in regeneration, neoblast regulation, and the telomere-telomerase system, we systematically summarize the emerging evidence for telomere- telomerase involvement in neoblast homeostasis and regeneration. We aim to provide insights for research in regenerative medicine, stem cell regulation, and neural injury repair.

Animals↗
PubMed1978

The mechanism of anterior-posterior polarity control in planarians.

The substance which inhibits brain formation in the regenerating planarian Dugesia etrusca was found to be a large molecule, at least in part protein, which electrophoreses as an electronegative moiety in pH 6.8 buffer. A model is presented, based on this finding and previous studies, which proposes an electrochemical mechanism for the control of polarity and possibly for the maintenance of tissue organization in planarians. It is proposed that a bioelectric field exists and moves the electronegative brain-inhibiting substance in a posterior direction, establishing polarity. This model explains the polarity reversal experiments using external fields and many of the previously unexplained classical planarian experiments. Data are presented demonstrating the existence, magnitude, and polarity of this bioelectric field, which is not greatly altered upon decapitation, all in accord with predictions of the model.

Animals↗
PubMed2026

Conserved innate immunity components limit transgene expression in adult planarians.

The planarian flatworm Schmidtea mediterranea has become a powerful model for studying whole-body regeneration, tissue patterning, and stem cell regulation. Yet the absence of reliable tools for transgene expression still limits the elucidation of molecular mechanisms in in this system. Here, we establish a proof-of-principle system for plasmid-based expression of NanoLuciferase (NanoLuc) in S. mediterranea, employing commercially available transfection reagents and a panel of endogenous promoter sequences. Despite successful delivery, reporter expression remained low and transient. To identify biological barriers to robust transgene expression, we investigated the role of innate immune pathways. Candidate gene searches and biochemical pull-down of cytoplasmic DNA coupled to mass spectrometry identified several planarian homologs of conserved immune regulators and putative DNA sensors. Through RNA interference screening of conserved innate immune components, we uncover roles for S. mediterranea homologs of Tank-binding kinase 1 (TBK1) and macrophage mannose receptor 1 (MRC1) as potent repressors of transgene expression. Transcriptomic and functional analyses further implicate TBK1 in regulating broad innate immune and stress-response programs, akin to its vertebrate function. Together, our findings demonstrate that innate immune signaling limits transgene expression in S. mediterranea and suggest that modulating these pathways may be key to enabling stable and efficient genetic manipulation in planarians.

Animals↗
PubMed2025

Investigating the Functions of Hox Genes Using Planarian Asexual Reproduction.

Hox genes are highly conserved developmental regulators instrumental to the formation of a wide range of diverse body plans across metazoans. While significant progress in the field of Hox gene research has been made, persistent challenges in unraveling their mechanisms of action and full repertoire of functions remain. To date, investigations of Hox gene function have been primarily conducted in research models belonging to ecdysozoa and vertebrata. Herein we summarize recent findings on Hox genes' roles in the asexual reproduction of the regenerative flatworm planaria, a member of the understudied superphylum Spiralia. We detail our optimized methods for planarian culture, gene perturbation, and induction of asexual reproduction. We aim to provide an experimentally tractable means to dissect Hox gene adult tissue functions underlying planarian asexual reproduction with broader relevance to Hox genes' established and emerging roles in regulating cellular behaviors, developmental patterning, animal behavior, and tissue regeneration.

Animals↗
PubMed1979

Structure and regeneration of the planarian basal lamina: an ultrastructural study.

The structure and regeneration of the planarian subepidermal basement membrane or basal lamina have been electron microscopically examined, particularly in relation to the changes of extracellular products at the wounded area. The intact basal lamina consists of three structural elements; namely, an electron-lucent zone, a limiting layer and a microfibrillar layer. Ultrastructural changes during wound healing have suggested that the amorphous material secreted in the interspace between the epidermal cells and blastema contains precursors of the basal lamina. Within the amorphous zone two distinct phases of the basal lamina regeneration are observed: one is a reconstitution of the limiting layer and the other is a polymerization of the microfibrils. The limiting layer arises from areas subjacent to newly developed hemidesmosomes of epidermal cells. The unit microfibrils are formed from an accumulation of the precursors through transitional smaller microfibrils. At the late stage, individual mature microfibrils are regularly lined with the limiting layer and cell membranes of the newly differentiated muscle fibres. On the basis of these observations we suggest that the planarian basal lamina is regenerated by the interaction between epidermal cells and myoblasts.

Animals↗
PubMed1979

Analysis of the progress of hormone-receptor amplification during differentiation in regenerating planarians.

Planarians developing from isolated regenerates, when pretreated with epinephrine at different periods of their second regeneration, show a higher rate of sugar uptake than the controls, which were not treated with epinephrine. The hormone receptor development can be influenced most effectively by pretreatments performed during the 1--3 and 6--9 day periods, though some effect can be evoked at any time in the course of the second regeneration. The head regenerates developing from the anterior end of the original midpiece (and regenerating tails the second time, B1) were found to be most sensitive, while the similar regenerates developing from the hindpiece of the original planarian (C) showed the weakest reactivity. The experiments provide further evidence that the hormone receptors' activity can be amplified in the course of regenerative development, leading thus--at a later stage--to a more intense sugar uptake response of the cells.

Animals↗
PubMedDate not supplied

Content of mitochondrial protein in the planarian Polycelis nigra during starvation and feeding.

To discover the possible mechanisms determining the level of energy metabolism during changes in the body size of animals, the content of mitochondrial protein was studied in planarians during starvation and feeding. In the course of starvation, the relative content of mitochondrial protein decreases, whereas during feeding it increases. Comparison of the experimental results with previous observations on respiration of planarians under similar conditions shows that changes in the level of respiration during starvation and feeding correlate with the content of mitochondrial protein. However, the degree of the functional load on the mitochondria must be taken into account under these circumstances.

Animals↗
PubMed1976

[The effect of repeated amputations on planarian regeneration in the presence of the heat-stable toxin from Bacillus thuringiensis].

The exotoxin of Bacillus thuringiensis, which is an inhibitor of RNA synthesis, inhibits Planarian regeneration. Planarians which have been cut twice at the same level are able to regenerate after the second section in the presence of the toxin. This indicates that the first amputation stimulates a synthesis of stable RNAs which thus are available for regeneration at the moment of the second section.

Animals↗
PubMed1976

Use of the p-nitrophenyl phosphate method for the demonstration of acid phosphatase during starvation and cell autolysis in the planarian Polycelis tenuis Iijima.

Acid phosphatase activity is demonstrated employing p-nitrophenyl phosphate as substrate and lead acetate as coupler. The fine structural localization of the enzyme in starved planarian tissues is described. The method is used to pin-point starvation - induced acid phosphatase activity in relation to autophagy and crinophagy in the gland cells; autophagy, autolysis and cell death in parenchymal and gastrodermal cells and basement membrane lysis. Attention is also payed to the demonstration of muscle lysis. The histochemical implications of the method are discussed.

4-Nitrophenylphosphatase↗
PubMed1979

On the occurrence and significance of annulate lamellae in gastrodermal cells of regenerating planarians.

Cytoplasmic annulate lamellae have been observed to occur only in a subset of the gastrodermal cell population of regenerating planarians. They have not been found in the gastrodermal cells of intact, non-injured worms, nor in any other somatic cell type. These observations plus the presence of numerous chromatoid bodies in the same cells are consistent with the hypothesis that these cells are altering their state of differentiation and are preparing for division. It is further suggested that these cells are the precursors to the definitive somatic stem cells, the beta cells.

Animals↗
PubMed1976

[Control of the regeneration of small pieces of the planarian Dugesia tigrina by cylic AMP and GMP nucleotides].

The effects on regeneration of cyclic nucleotides AMP and GMP were studied on small pieces of the planarian worm Dugesia tigrina. db cAMP, 8Br cGMP and substances acting on their metabolism were used in this work (aminophylline, insulin, imidazole). It seems that these second messengers play a role in a mechanism of regulation in which cGMP has a promotive action and cAMP an inhibitive one.

Animals↗
PubMedDate not supplied

Change in ATP and ADP content of fasting and feeding planarians (Polycelis nigra).

The ATP and ADP content of planarians subjected to starvation for two weeks followed by feeding for the same period was investigated. The ATP and ADP content during fasting increased and then, after feeding, returned to normal. The ATP/ADP ratio varied in the same way, which is consistent with the view that the adenylic nucleotide pool is implicated in the regulation of the energy metabolism of the organism.

Adenosine Diphosphate↗
PubMed1978

[Toxic effects of essential oil of Cannabis sativa L. and main constituents on planarian (Dugesia tigrina) (author's transl)].

Regenerating pieces of planarian worms are able to absorbe insoluble substances deposited on the base of the vessels in which they are cultivated. This biological test was used to study the toxic effects of the essential oil of Cannabis sativa L. The hydrocarbons such as pinene (alpha and beta), caryophyllene and so on were not toxic. On the contrary caryophyllene oxide was highly toxic. It was not possible to detect any protection by 5-hydroxytryptamine as it was the case against delta 1-tétrahydro-cannabinol and cannabidiol.

Animals↗
PubMed1975

[Incorporation of 3H-5 uridine and 3H-5 leucine into cultured planarian cells, Polycelis tenuis (Iijima) in vitro].

RNA and protein synthesis in Planarian cells cultivated in vitro was studied by histoautoradiography. In the non-differentiated cells, uptake of precursor is intense from the beginning of the culture, and sensitive to addition of trophic factor known for their activating effect on mitosis and regeneration. On the contrary the rate of incorporation in differentiated cells is low and uniform, independently of the differents factors added to the medium.

Autoradiography↗
PubMed1977

Evidence against gastrointestinal pseudoparasitism by the land planarian, Bipalium kewense Moseley 1878.

The possibility of gastrointestinal pseudoparasitism by the free-living land planarian, Bipalium kewense, was tested by feeding and survival experiments. The intestinal tracts of three dogs were negative for B. kewense after the individual dogs were fed eight, three, and four large worms and autopsied at 12 h, 3 h, and 45 min, respectively. Survival of the worms in Warburg flasks, under N2, AT 27 C, was 2 h or less.. In Gas Pak jars (CO2 + H2) at 37 C, survival was less than 60 min. Aerobically, at 37 C, survival varied from 45 to 60 min. Attra-tion of the worms to stool material was examined by placing planaria inside square whose boundries were constructed of fecal smears. Bipalium kewense exposed to canine feces showed strong avoidance reactions. Urea, a nitrogen end product of these worms, was also shown to be a negative stimulus for B. kewense. Failure to establish even short term passage in the digestive tract, lethality of 37 C and anaerobic environments, and sensitivity to feces makes gastrointestinal pseudoparasitism unlikely in these organisms.

Anaerobiosis↗
PubMed1977

Characterization of an organ-specific differentiator substance in the planarian Dugesia etrusca.

A substance which inhibits brain formation in decapitated regenerating planarians (Dugesia etrusca) was characterized and partially purified. The substance's inhibitory activity was followed during each purification procedure by adding freshly decapitated animals of a standard size to each fraction, and later measuring the resultant regenerated brain volume. The inhibitory activity remained in the supernatant after a 10000 g centrifugation of a cell-free homogenate. Most of the activity sedimented when the 10000 g supernatant was centrifuged at 32000 g. The degree of inhibitory activity increased with increased numbers of animals in the initial homogenate. The substance has an apparent molecular weight between 2 X 10(5) and 4 X 10(5) daltons. Digestion by pronase destroyed the activity, but treatment with RNase, DNase I, or lipase had no significant effect. The inhibiting substance has an isoelectric point (pI) of between 4-75 and 5-38 and migrates to the anode when electrophorezed in pH 6-8 buffer.

Animals↗
PubMed2025

Multi-omics analyses reveal DjTcf4 critical for proper timing of differentiation in planarian regeneration.

The blastema is key to forming complete tissues in regenerating Dugesia japonica (D. japonica). However, the dynamic changes in cellular compositions and transcription landscapes in blastema during regeneration are understudied. Here, through genome reannotation, 3D spatial transcriptome construction, single-cell RNA sequencing (scRNA-seq), and single-cell assay for transposase-accessible chromatin sequencing (scATAC-seq) analyses of changes in gene expression and chromatin structures, we delineate key transcription factors regulating the developmental trajectories of major cell clusters in the regenerating head. Importantly, we find that the T cell factor 4 (DjTcf4)-positive cells highly accumulate at wound areas, and its gene network is critical for the proper timing of development during regeneration in multiple progenitor cells. Depletion of DjTcf4 and its target genes leads to singular eye and/or dull tail phenotypes and delays regeneration. Taken together, we build multi-omics atlases in D. japonica and reveal the noncanonical function of the DjTcf4 network in developmental pattern formation, laying a foundation for studies of regeneration in D. japonica.

Animals↗