RESUMO
Adult regeneration restores patterning of orthogonal body axes after damage in a post-embryonic context. Planarians regenerate using distinct body-wide signals primarily regulating each axis dimension: anteroposterior Wnts, dorsoventral BMP, and mediolateral Wnt5 and Slit determinants. How regeneration can coordinate perpendicular tissue axes without symmetry-breaking embryonic events is not fully understood. Here, we report that the planarian dorsoventral regulator bmp4 suppresses the posterior determinant wnt1 to provide patterning input to the anteroposterior axis. Double-FISH identified distinct anteroposterior domains within dorsal midline muscle that express either bmp4 or wnt1. Homeostatic inhibition bmp4 and smad1 expanded the wnt1 expression anteriorly, while elevation of BMP signaling through nog1;nog2 RNAi reduced the wnt1 expression domain and elevated bmp4 expression. Homeostatic BMP signal perturbation broadly affected anteroposterior identity as measured by expression of posterior Wnt pathway factors, and caused mislocalization of AP-regionalized pharynx progenitors, without strongly affecting expression domains of anterior regulators. Additionally, wnt1 inhibition elevated bmp4 expression in the tip of the tail. Therefore, dorsal BMP signals and posterior wnt1 mutually antagonize for patterning the tail. Furthermore, homeostatic bmp4 RNAi caused medial expansion of the lateral determinant wnt5 and reduced expression of the medial regulator slit. By contrast, nog1;nog2 RNAi restricted wnt5 expression. Double RNAi of bmp4 and wnt5 resulted in lateral ectopic eye phenotypes, suggesting bmp4 acts upstream of wnt5 to pattern the mediolateral axis. These results indicate bmp4 controls dorsoventral information and also, through suppression of Wnt signals, influences anteroposterior and mediolateral identity. Based on related functions across vertebrates and Cnidarians, Wnt and BMP cross-regulation could form an ancient mechanism for coordinating orthogonal axis patterning.
Assuntos
Planárias , Animais , Planárias/genética , Regulação da Expressão Gênica no Desenvolvimento , Transdução de Sinais , Vertebrados/genética , Interferência de RNA , Proteínas Wnt/genética , Proteínas Wnt/metabolismo , Padronização Corporal/genéticaRESUMO
Tissue identity determination is crucial for regeneration, and the planarian anteroposterior (AP) axis uses positional control genes expressed from body wall muscle to determine body regionalization. Canonical Wnt signaling establishes anterior versus posterior pole identities through notum and wnt1 signaling, and two Wnt/FGFRL signaling pathways control head and trunk domains, but their downstream signaling mechanisms are not fully understood. Here, we identify a planarian Src homolog that restricts head and trunk identities to anterior positions. src-1(RNAi) animals formed enlarged brains and ectopic eyes and also duplicated trunk tissue, similar to a combination of Wnt/FGFRL RNAi phenotypes. src-1 was required for establishing territories of positional control gene expression in Schmidtea mediterranea, indicating that it acts at an upstream step in patterning the AP axis. Double RNAi experiments and eye regeneration assays suggest src-1 can act in parallel to at least some Wnt and FGFRL factors. Co-inhibition of src-1 with other posterior-promoting factors led to dramatic patterning changes and a reprogramming of Wnt/FGFRLs into controlling new positional outputs. These results identify src-1 as a factor that promotes robustness of the AP positional system that instructs appropriate regeneration.
Assuntos
Planárias , Animais , Padronização Corporal/genética , Regulação da Expressão Gênica no Desenvolvimento , Planárias/fisiologia , Proteínas Wnt/genética , Proteínas Wnt/metabolismo , Via de Sinalização Wnt/genéticaRESUMO
How animals establish and pattern the primary body axis is one of the most fundamental problems in biology. Data from diverse deuterostomes (frog, fish, mouse, and amphioxus) and from planarians (protostomes) suggest that Wnt signaling through beta-catenin controls posterior identity during body plan formation in most bilaterally symmetric animals. Wnt signaling also influences primary axis polarity of pre-bilaterian animals, indicating that an axial patterning role for Wnt signaling predates the evolution of bilaterally symmetric animals. The use of posterior Wnt signaling and anterior Wnt inhibition might be a unifying principle of body plan development in most animals.
Assuntos
Padronização Corporal , Transdução de Sinais , Proteínas Wnt/metabolismo , Animais , beta Catenina/metabolismoRESUMO
Wnt signaling regulates primary body axis formation across the Metazoa, with high Wnt signaling specifying posterior identity. Whether a common Wnt-driven transcriptional program accomplishes this broad role is poorly understood. We identified genes acutely affected after Wnt signaling inhibition in the posterior of two regenerative species, the planarian Schmidtea mediterranea and the acoel Hofstenia miamia, which are separated by >550 million years of evolution. Wnt signaling was found to maintain positional information in muscle and regional gene expression in multiple differentiated cell types. sp5, Hox genes, and Wnt pathway components are down-regulated rapidly after ß-catenin RNAi in both species. Brachyury, a vertebrate Wnt target, also displays Wnt-dependent expression in Hofstenia. sp5 inhibits trunk gene expression in the tail of planarians and acoels, promoting separate tail-trunk body domains. A planarian posterior Hox gene, Post-2d, promotes normal tail regeneration. We propose that common regulation of a small gene set-Hox, sp5, and Brachyury-might underlie the widespread utilization of Wnt signaling in primary axis patterning across the Bilateria.
Assuntos
Padronização Corporal/genética , Genes Homeobox/genética , Planárias/genética , Regeneração/genética , Animais , Diferenciação Celular/genética , Regulação da Expressão Gênica no Desenvolvimento/genética , Desenvolvimento Muscular/genética , Proteínas Nucleares/genética , Planárias/crescimento & desenvolvimento , Proteínas Wnt/genética , Via de Sinalização Wnt/genéticaRESUMO
Animals capable of adult regeneration require specific signaling to control injury-induced cell proliferation, specification and patterning, but comparatively little is known about how the regeneration blastema assembles differentiating cells into well-structured functional tissues. Using the planarian Schmidtea mediterranea as a model, we identify ß1-integrin as a crucial regulator of blastema architecture. ß1-integrin(RNAi) animals formed small head blastemas with severe tissue disorganization, including ectopic neural spheroids containing differentiated neurons normally found in distinct organs. By mimicking aspects of normal brain architecture but without normal cell-type regionalization, these spheroids bore a resemblance to mammalian tissue organoids synthesized in vitro We identified one of four planarian integrin-alpha subunits inhibition of which phenocopied these effects, suggesting that a specific receptor controls brain organization through regeneration. Neoblast stem cells and progenitor cells were mislocalized in ß1-integrin(RNAi) animals without significantly altered body-wide patterning. Furthermore, tissue disorganization phenotypes were most pronounced in animals undergoing brain regeneration and not homeostatic maintenance or regeneration-induced remodeling of the brain. These results suggest that integrin signaling ensures proper progenitor recruitment after injury, enabling the generation of large-scale tissue organization within the regeneration blastema.
Assuntos
Encéfalo/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Integrina beta1/fisiologia , Planárias/fisiologia , Regeneração , Células-Tronco/citologia , Animais , Padronização Corporal/genética , Diferenciação Celular , Proliferação de Células , Neurogênese , Neurônios/citologia , Interferência de RNA , Transdução de SinaisRESUMO
Mechanisms determining final organ size are poorly understood. Animals undergoing regeneration or ongoing adult growth are likely to require sustained and robust mechanisms to achieve and maintain appropriate sizes. Planarians, well known for their ability to undergo whole-body regeneration using pluripotent adult stem cells of the neoblast population, can reversibly scale body size over an order of magnitude by controlling cell number. Using quantitative analysis, we showed that after injury planarians perfectly restored brain:body proportion by increasing brain cell number through epimorphosis or decreasing brain cell number through tissue remodeling (morphallaxis), as appropriate. We identified a pathway controlling a brain size set-point that involves feedback inhibition between wnt11-6/wntA/wnt4a and notum, encoding conserved antagonistic signaling factors expressed at opposite brain poles. wnt11-6/wntA/wnt4a undergoes feedback inhibition through canonical Wnt signaling but is likely to regulate brain size in a non-canonical pathway independently of beta-catenin-1 and APC. Wnt/Notum signaling tunes numbers of differentiated brain cells in regenerative growth and tissue remodeling by influencing the abundance of brain progenitors descended from pluripotent stem cells, as opposed to regulating cell death. These results suggest that the attainment of final organ size might be accomplished by achieving a balance of positional signaling inputs that regulate the rates of tissue production.
Assuntos
Encéfalo/citologia , Encéfalo/crescimento & desenvolvimento , Diferenciação Celular , Esterases/metabolismo , Retroalimentação Fisiológica , Planárias/citologia , Proteínas Wnt/metabolismo , Animais , Encéfalo/anatomia & histologia , Contagem de Células , Modelos Biológicos , Neurônios/citologia , Tamanho do Órgão , Regeneração , Transdução de Sinais , Células-Tronco/citologiaRESUMO
Regeneration requires that the identities of new cells are properly specified to replace missing tissues. The Wnt signaling pathway serves a central role in specifying posterior cell fates during planarian regeneration. We identified a gene encoding a homolog of the Teashirt family of zinc-finger proteins in the planarian Schmidtea mediterranea to be a target of Wnt signaling in intact animals and at posterior-facing wounds. Inhibition of Smed-teashirt (teashirt) by RNA interference (RNAi) resulted in the regeneration of heads in place of tails, a phenotype previously observed with RNAi of the Wnt pathway genes ß-catenin-1, wnt1, Dvl-1/2 or wntless. teashirt was required for ß-catenin-1-dependent activation of posterior genes during regeneration. These findings identify teashirt as a transcriptional target of Wnt signaling required for Wnt-mediated specification of posterior blastemas.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento/fisiologia , Proteínas de Homeodomínio/metabolismo , Planárias/fisiologia , Regeneração/fisiologia , Via de Sinalização Wnt/fisiologia , Dedos de Zinco/fisiologia , Animais , Regulação da Expressão Gênica no Desenvolvimento/genética , Cabeça/fisiologia , Proteínas de Homeodomínio/genética , Hibridização In Situ , Planárias/genética , Análise de Componente Principal , Interferência de RNA , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Cauda/metabolismo , Cauda/fisiologia , Dedos de Zinco/genéticaRESUMO
Mechanisms that enable injury responses to prompt regenerative outgrowth are not well understood. Planarians can regenerate essentially any tissue removed by wounding, even after decapitation, due to robust regulation of adult pluripotent stem cells of the neoblast population. Formation of pole signaling centers involving Wnt inhibitors or Wnt ligands promotes head or tail regeneration, respectively, and this process requires the use of neoblasts early after injury. We used expression profiling of purified neoblasts to identify factors needed for anterior pole formation. Using this approach, we identified zic-1, a Zic-family transcription factor, as transcriptionally activated in a subpopulation of neoblasts near wound sites early in head regeneration. As head regeneration proceeds, the Wnt inhibitor notum becomes expressed in the newly forming anterior pole in zic-1-expressing cells descended from neoblasts. Inhibition of zic-1 by RNAi resulted in a failure to express notum at the anterior pole and to regenerate a head, but did not affect tail regeneration. Both injury and canonical Wnt signaling inhibition are required for zic-1 expression, and double-RNAi experiments suggest zic-1 inhibits Wnt signaling to allow head regeneration. Analysis of neoblast fate determinants revealed that zic-1 controls specification of notum-expressing cells from foxD-expressing neoblasts to form the anterior pole, which organizes subsequent outgrowth. Specialized differentiation programs may in general underlie injury-dependent formation of tissue organizing centers used for regenerative outgrowth.
Assuntos
Proteínas de Helminto/genética , Células-Tronco Pluripotentes , Regeneração/genética , Transdução de Sinais/genética , Proteínas Wnt/genética , Animais , Diferenciação Celular , Regulação da Expressão Gênica no Desenvolvimento , Cabeça/crescimento & desenvolvimento , Planárias/genética , Cauda/crescimento & desenvolvimento , Fatores de TranscriçãoRESUMO
14-3-3 proteins are crucial in a wide variety of cellular responses including cell cycle progression, DNA damage checkpoints and apoptosis. One particular 14-3-3 isoform, sigma, is a p53-responsive gene, the function of which is frequently lost in human tumours, including breast and prostate cancers as a result of either hypermethylation of the 14-3-3sigma promoter or induction of an oestrogen-responsive ubiquitin ligase that specifically targets 14-3-3sigma for proteasomal degradation. Loss of 14-3-3sigma protein occurs not only within the tumours themselves but also in the surrounding pre-dysplastic tissue (so-called field cancerization), indicating that 14-3-3sigma might have an important tumour suppressor function that becomes lost early in the process of tumour evolution. The molecular basis for the tumour suppressor function of 14-3-3sigma is unknown. Here we report a previously unknown function for 14-3-3sigma as a regulator of mitotic translation through its direct mitosis-specific binding to a variety of translation/initiation factors, including eukaryotic initiation factor 4B in a stoichiometric manner. Cells lacking 14-3-3sigma, in marked contrast to normal cells, cannot suppress cap-dependent translation and do not stimulate cap-independent translation during and immediately after mitosis. This defective switch in the mechanism of translation results in reduced mitotic-specific expression of the endogenous internal ribosomal entry site (IRES)-dependent form of the cyclin-dependent kinase Cdk11 (p58 PITSLRE), leading to impaired cytokinesis, loss of Polo-like kinase-1 at the midbody, and the accumulation of binucleate cells. The aberrant mitotic phenotype of 14-3-3sigma-depleted cells can be rescued by forced expression of p58 PITSLRE or by extinguishing cap-dependent translation and increasing cap-independent translation during mitosis by using rapamycin. Our findings show how aberrant mitotic translation in the absence of 14-3-3sigma impairs mitotic exit to generate binucleate cells and provides a potential explanation of how 14-3-3sigma-deficient cells may progress on the path to aneuploidy and tumorigenesis.
Assuntos
Biomarcadores Tumorais/metabolismo , Citocinese , Exonucleases/metabolismo , Mitose , Proteínas de Neoplasias/metabolismo , Biossíntese de Proteínas , Proteínas 14-3-3 , Biomarcadores Tumorais/deficiência , Linhagem Celular Tumoral , Fatores de Iniciação em Eucariotos/metabolismo , Exonucleases/deficiência , Exorribonucleases , Regulação Neoplásica da Expressão Gênica , Humanos , Proteínas de Neoplasias/deficiência , Neoplasias/genética , Neoplasias/metabolismo , Neoplasias/patologia , Capuzes de RNA/genética , Capuzes de RNA/metabolismoRESUMO
Regeneration abilities are widespread among animals and select species can restore any body parts removed by wounds that sever the major body axes. This capability of whole-body regeneration as exemplified in flatworm planarians, Acoels, and Cnidarians involves initial responses to injury, the assessment of wound site polarization, determination of missing tissue and programming of blastema fate, and patterned outgrowth to restore axis content and proportionality. Wnt signaling drives many shared and conserved aspects of the biology of whole-body regeneration in the planarian species Schmidtea mediterranea and Dugesia japonica, in the Acoel Hofstenia miamia, and in Cnidarians Hydra and Nematostella. These overlapping mechanisms suggest whole-body regeneration might be an ancestral property across diverse animal taxa.
Assuntos
Hydra , Planárias , Animais , Via de Sinalização Wnt , Planárias/fisiologiaRESUMO
Adult regeneration restores patterning of orthogonal body axes after damage in a post-embryonic context. Planarians regenerate using distinct body-wide signals primarily regulating each axis dimension: anteroposterior Wnts, dorsoventral BMP, and mediolateral Wnt5 and Slit determinants. How regeneration can consistently form perpendicular tissue axes without symmetry-breaking embryonic events is unknown, and could either occur using fully independent, or alternatively, integrated signals defining each dimension. Here, we report that the planarian dorsoventral regulator bmp4 suppresses the posterior determinant wnt1 to pattern the anteroposterior axis. Double-FISH identified distinct anteroposterior domains within dorsal midline muscle that express either bmp4 or wnt1 . Homeostatic inhibition bmp4 and smad1 expanded the wnt1 expression anteriorly, while elevation of BMP signaling through nog1;nog2 RNAi reduced the wnt1 expression domain. BMP signal perturbation broadly affected anteroposterior identity as measured by expression of posterior Wnt pathway factors, without affecting head regionalization. Therefore, dorsal BMP signals broadly limit posterior identity. Furthermore, bmp4 RNAi caused medial expansion of the lateral determinant wnt5 and reduced expression of the medial regulator slit . Double RNAi of bmp4 and wnt5 resulted in lateral ectopic eye phenotypes, suggesting bmp4 acts upstream of wnt5 to pattern the mediolateral axis. Therefore, bmp4 acts at the top of a patterning hierarchy both to control dorsoventral information and also, through suppression of Wnt signals, to regulate anteroposterior and mediolateral identity. These results reveal that adult pattern formation involves integration of signals controlling individual orthogonal axes. Author Summary: Systems that coordinate long-range communication across axes are likely critical for enabling tissue restoration in regenerative animals. While individual axis pathways have been identified, there is not yet an understanding of how signal integration allows repatterning across 3-dimensions. Here, we report an unanticipated linkage between anteroposterior, dorsoventral, and mediolateral systems in planarians through BMP signaling. We find that dorsally expressed BMP restricts posterior and lateral identity by suppressing distinct Wnt signals in adult planarians. These results demonstrate that orthogonal axis information is not fully independent and suggest a potentially ancient role of integrated axis patterning in generating stable 3-dimensional adult forms.
RESUMO
Regeneration requires specification of the identity of new tissues to be made. Whether this process relies only on intrinsic regulative properties of regenerating tissues or whether wound signaling provides input into tissue repatterning is not known. The head-versus-tail regeneration polarity decision in planarians, which requires Wnt signaling, provides a paradigm to study the process of tissue identity specification during regeneration. The Smed-wntP-1 gene is required for regeneration polarity and is expressed at the posterior pole of intact animals. Surprisingly, wntP-1 was expressed at both anterior- and posterior-facing wounds rapidly after wounding. wntP-1 expression was induced by all types of wounds examined, regardless of whether wounding prompted tail regeneration. Regeneration polarity was found to require new expression of wntP-1. Inhibition of the wntP-2 gene enhanced the polarity phenotype due to wntP-1 inhibition, with new expression of wntP-2 in regeneration occurring subsequent to expression of wntP-1 and localized only to posterior-facing wounds. New expression of wntP-2 required wound-induced wntP-1. Finally, wntP-1 and wntP-2 expression changes occurred even in the absence of neoblast stem cells, which are required for regeneration, suggesting that the role of these genes in polarity is independent of and instructive for tail formation. These data indicate that wound-induced input is involved in resetting the normal polarized features of the body axis during regeneration.
Assuntos
Proteínas de Helminto/genética , Planárias/genética , Regeneração/genética , Proteínas Wnt/genética , Animais , Polaridade Celular/genética , Polaridade Celular/fisiologia , Perfilação da Expressão Gênica , Proteínas de Helminto/metabolismo , Imuno-Histoquímica , Hibridização In Situ , Planárias/citologia , Planárias/fisiologia , Interferência de RNA , Regeneração/fisiologia , Estresse Mecânico , Fatores de Tempo , Proteínas Wnt/metabolismo , Proteína Wnt1/genética , Proteína Wnt1/metabolismo , Proteína Wnt2/genética , Proteína Wnt2/metabolismo , beta Catenina/genética , beta Catenina/fisiologiaRESUMO
Regeneration is initiated by wounding, but it is unclear how injury-induced signals precisely convey the identity of the tissues requiring replacement. In the planarian Schmidtea mediterranea, the first event in head regeneration is the asymmetric activation of the Wnt inhibitor notum in longitudinal body-wall muscle cells, preferentially at anterior-facing versus posterior-facing wound sites. However, the mechanism driving this early symmetry-breaking event is unknown. We identify a noncanonical Wnt11 and Dishevelled pathway regulating notum polarization, which opposes injury-induced notum-activating Wnt/ß-catenin signals and regulates muscle orientation. Using expression analysis and experiments to define a critical time of action, we demonstrate that Wnt11 and Dishevelled signals act prior to injury and in a growth-dependent manner to orient the polarization of notum induced by wounding. In turn, injury-induced notum dictates polarization used in the next round of regeneration. These results identify a self-reinforcing feedback system driving the polarization of blastema outgrowth and indicate that regeneration uses pre-existing tissue information to determine the outcome of wound-induced signals.
Assuntos
Planárias , Animais , Planárias/genética , Padronização Corporal/fisiologia , Transdução de Sinais/fisiologia , Via de Sinalização WntRESUMO
Regeneration involves regulating tissue proportionality across considerable size ranges through unknown mechanisms. In planarians, which scale reversibly over 40× through regeneration, we identify the Striatin-interacting phosphatase and kinase (STRIPAK) complex as a potent negative regulator of axis length. Inhibition of two proteins in the STRIPAK complex, mob4 and striatin, dramatically increased posterior length, through expansion of a posterior wnt1+ signaling center within midline muscle cells. wnt1 was required for tail expansion after mob4 inhibition and dynamically reestablishes proportionality after amputation in normal animals, indicating STRIPAK represses Wnt signaling for scaling. Regulation of wnt1 expansion was stem cell dependent, demonstrating that control of signaling-center production through stem cell differentiation underlies proportional growth in adult regenerative tissue.
Assuntos
Padronização Corporal/genética , Diferenciação Celular/genética , Proteínas de Helminto/genética , Planárias/genética , Células-Tronco/citologia , Via de Sinalização Wnt/fisiologia , Animais , Proteínas de Helminto/metabolismo , Planárias/citologia , Planárias/crescimento & desenvolvimento , Planárias/metabolismoRESUMO
Negative regulators of adult neurogenesis are of particular interest as targets to enhance neuronal repair, but few have yet been identified. Planarians can regenerate their entire CNS using pluripotent adult stem cells, and this process is robustly regulated to ensure that new neurons are produced in proper abundance. Using a high-throughput pipeline to quantify brain chemosensory neurons, we identify the conserved tyrosine kinase tec-1 as a negative regulator of planarian neuronal regeneration. tec-1RNAi increased the abundance of several CNS and PNS neuron subtypes regenerated or maintained through homeostasis, without affecting body patterning or non-neural cells. Experiments using TUNEL, BrdU, progenitor labeling, and stem cell elimination during regeneration indicate tec-1 limits the survival of newly differentiated neurons. In vertebrates, the Tec kinase family has been studied extensively for roles in immune function, and our results identify a novel role for tec-1 as negative regulator of planarian adult neurogenesis.
Assuntos
Neurogênese/genética , Planárias , Proteínas Tirosina Quinases , Regeneração/genética , Animais , Encéfalo/citologia , Encéfalo/metabolismo , Encéfalo/fisiologia , Química Encefálica , Neurônios/metabolismo , Planárias/genética , Planárias/metabolismo , Proteínas Tirosina Quinases/genética , Proteínas Tirosina Quinases/metabolismo , Interferência de RNARESUMO
Most animals undergo homeostatic tissue maintenance, yet those capable of robust regeneration in adulthood use mechanisms significantly overlapping with homeostasis. Here we show in planarians that modulations to body-wide patterning systems shift the target site for eye regeneration while still enabling homeostasis of eyes outside this region. The uncoupling of homeostasis and regeneration, which can occur during normal positional rescaling after axis truncation, is not due to altered injury signaling or stem cell activity, nor specific to eye tissue. Rather, pre-existing tissues, which are misaligned with patterning factor expression domains, compete with properly located organs for incorporation of migratory progenitors. These observations suggest that patterning factors determine sites of organ regeneration but do not solely determine the location of tissue homeostasis. These properties provide candidate explanations for how regeneration integrates pre-existing tissues and how regenerative abilities could be lost in evolution or development without eliminating long-term tissue maintenance and repair.
Assuntos
Padronização Corporal/fisiologia , Olho/crescimento & desenvolvimento , Planárias/fisiologia , Regeneração/fisiologia , Animais , Padronização Corporal/genética , Movimento Celular/genética , Olho/citologia , Olho/metabolismo , Homeostase/genética , Hibridização In Situ/métodos , Organogênese/genética , Planárias/genética , Planárias/crescimento & desenvolvimento , Interferência de RNA , Regeneração/genética , Células-Tronco/citologia , Células-Tronco/metabolismoRESUMO
The processes that trigger regeneration after injury and link new and old tissue are not fully understood. New findings indicate that, after decapitation, planarians build an organizing center from stem cells at the old midline that directs head patterning and outgrowth.
Assuntos
Planárias , Animais , Padronização Corporal , Cabeça , Regeneração , Células-TroncoRESUMO
All animals must detect noxious stimuli to initiate protective behavior, but the evolutionary origin of nociceptive systems is not well understood. Here we show that noxious heat and irritant chemicals elicit robust escape behaviors in the planarian Schmidtea mediterranea and that the conserved ion channel TRPA1 is required for these responses. TRPA1-mutant Drosophila flies are also defective in noxious-heat responses. We find that either planarian or human TRPA1 can restore noxious-heat avoidance to TRPA1-mutant Drosophila, although neither is directly activated by heat. Instead, our data suggest that TRPA1 activation is mediated by H2O2 and reactive oxygen species, early markers of tissue damage rapidly produced as a result of heat exposure. Together, our data reveal a core function for TRPA1 in noxious heat transduction, demonstrate its conservation from planarians to humans, and imply that animal nociceptive systems may share a common ancestry, tracing back to a progenitor that lived more than 500 million years ago.
Assuntos
Nociceptividade/fisiologia , Planárias/fisiologia , Espécies Reativas de Oxigênio/farmacologia , Canal de Cátion TRPA1/efeitos dos fármacos , Animais , Aprendizagem da Esquiva/efeitos dos fármacos , Comportamento Animal/efeitos dos fármacos , Drosophila , Proteínas de Drosophila/genética , Peróxido de Hidrogênio/farmacologia , Canais Iônicos , Nociceptividade/efeitos dos fármacos , Técnicas de Patch-Clamp , Interferência de RNA , Canal de Cátion TRPA1/genéticaRESUMO
Mechanisms enabling positional identity re-establishment are likely critical for tissue regeneration. Planarians use Wnt/beta-catenin signaling to polarize the termini of their anteroposterior axis, but little is known about how regeneration signaling restores regionalization along body or organ axes. We identify three genes expressed constitutively in overlapping body-wide transcriptional gradients that control trunk-tail positional identity in regeneration. ptk7 encodes a trunk-expressed kinase-dead Wnt co-receptor, wntP-2 encodes a posterior-expressed Wnt ligand, and ndl-3 encodes an anterior-expressed homolog of conserved FGFRL/nou-darake decoy receptors. ptk7 and wntP-2 maintain and allow appropriate regeneration of trunk tissue position independently of canonical Wnt signaling and with suppression of ndl-3 expression in the posterior. These results suggest that restoration of regional identity in regeneration involves the interpretation and re-establishment of axis-wide transcriptional gradients of signaling molecules.
Assuntos
Padronização Corporal/genética , Regulação da Expressão Gênica , Proteínas de Helminto/genética , Planárias/genética , Receptores Proteína Tirosina Quinases/genética , Receptores de Fatores de Crescimento de Fibroblastos/genética , Proteínas Wnt/genética , Animais , Diferenciação Celular , Proteínas de Helminto/metabolismo , Planárias/metabolismo , Planárias/ultraestrutura , Receptores Proteína Tirosina Quinases/metabolismo , Receptores de Fatores de Crescimento de Fibroblastos/metabolismo , Receptores Wnt/genética , Receptores Wnt/metabolismo , Regeneração/genética , Células-Tronco/citologia , Células-Tronco/metabolismo , Transcrição Gênica , Proteínas Wnt/metabolismo , Via de Sinalização Wnt , beta Catenina/genética , beta Catenina/metabolismoRESUMO
Regeneration involves precise control of cell fate to produce an appropriate complement of tissues formed within a blastema. Several chromatin-modifying complexes have been identified as required for regeneration in planarians, but it is unclear whether this class of molecules uniformly promotes the production of differentiated cells. We identify a function for p66, encoding a DNA-binding protein component of the NuRD (nucleosome remodeling and deacetylase) complex, as well as the chromodomain helicase chd4, in suppressing production of photoreceptor neurons (PRNs) in planarians. This suppressive effect appeared restricted to PRNs because p66 inhibition did not influence numbers of eye pigment cup cells (PCCs) and decreased numbers of brain neurons and epidermal progenitors. PRNs from p66(RNAi) animals differentiated with some abnormalities but nonetheless produced arrestin+ projections to the brain. p66 inhibition produced excess ovo+otxA+ PRN progenitors without affecting numbers of ovo+otxA- PCC progenitors, and ovo and otxA were each required for the p66(RNAi) excess PRN phenotype. Together these results suggest that p66 acts through the NuRD complex to suppress PRN production by limiting expression of lineage-specific transcription factors.