Selective amputation of the pharynx identifies a FoxA-dependent regeneration program in planaria
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ABSTRACT: Planarian flatworms can regenerate every organ after amputation. Adult pluripotent stem cells drive the ability to regenerate, but how injury activates these cells and directs them into the appropriate lineages is not understood. To study the regeneration response in a simplified context, we selectively induced the ejection of the planarian pharynx by briefly exposing animals to sodium azide followed by microarray analysis. Tissue surrounding the wound site was examined at 6, 12, 18, 24, 48, and 72 hours post amputation by comparison to tissue isolated immediately after amputation (time zero). Stem cells are required for the regeneration process, and can be eradicated by exposure to radiation. A parallel time course was also performed on worms that had been irradiated with 10k rads of gamma irradiation.
Project description:Planarian flatworms can regenerate every organ after amputation. Adult pluripotent stem cells drive the ability to regenerate, but how injury activates these cells and directs them into the appropriate lineages is not understood. To study the regeneration response in a simplified context, we selectively induced the ejection of the planarian pharynx by briefly exposing animals to sodium azide followed by microarray analysis. Tissue surrounding the wound site was examined at 6, 12, 18, 24, 48, and 72 hours post amputation by comparison to tissue isolated immediately after amputation (time zero). Stem cells are required for the regeneration process, and can be eradicated by exposure to radiation. A parallel time course was also performed on worms that had been irradiated with 10k rads of gamma irradiation. Two time courses consisting of irradiated or unirradiated worms following chemical amputation of the pharynx. Tissue samples taken at 6, 12, 18, 24, 48 and 72 hours are each compared to a reference sample at time zero. The experiment was performed in triplicate for a total of 42 samples on 36 arrays.
Project description:Variability of regenerative potential among animals has long perplexed biologists. Based on their amazing regenerative abilities, planarians have become important models for understanding the molecular basis of regeneration; however, planarian species with limited regenerative abilities are also found. Despite the importance of understanding the differences between closely related, regenerating and non-regenerating organisms, few studies have focused on the evolutionary loss of regeneration, and the molecular mechanisms leading to such regenerative loss remain obscure. Here we examine Procotyla fluviatilis, a planarian with restricted ability to replace missing tissues, utilizing next-generation sequencing to define the gene expression programs active in regeneration-permissive and regeneration-deficient tissues. We found that Wnt signaling is aberrantly activated in regeneration-deficient tissues. Remarkably, down-regulation of canonical Wnt signaling in regeneration-deficient regions restores regenerative abilities: blastemas form and new heads regenerate in tissues that normally never regenerate. This work reveals that manipulating a single signaling pathway can reverse the evolutionary loss of regenerative potential. RNA-seq experiments to identify gene expression changes following amputation in body regions with variable regenerative potential. Adult Procotyla fluviatilis were amputated at sites either anterior or posterior to the pharynx. After 24 hours post-amputation, tissues near the amputation site were excised and RNA was extracted. Similar tissues were excised from uncut control animals. Samples were processed for RNA-seq using Illumina procedures. We generated a de novo P. fluviatilis transcriptome and used RNA sequencing (RNA-seq) to characterize transcripts from excised tissue fragments in Reg+ and Reg- body regions 24 hours post-amputation. We performed parallel analyses on tissues excised from intact animals at identical body regions to account for regional differences in transcripts, thereby identifying changes resulting from amputation. Samples A1-A3 = Regeneration-proficient (Reg+) tissue excision 24 hours after amputation. Samples B1-B3 = Tissue excision from regeneration-proficient (Reg+) region but not amputated. Samples C1-C3 = Tissue excision from regeneration-deficient (Reg-) tissues 24 hours after amputation. Samples D1, D3-D4 = Tissue excision from regeneration-deficient (Reg-) region that was not amputated.
Project description:Stem cells integrate extracellular cues with downstream transcriptional responses to channel their differentiation, but the underlying mechanisms responsible remain unclear. Planarians possess distinct organs embedded in a vast pool of pluripotent stem cells that maintain tissue turnover and drive whole-body regeneration. This unique configuration provides an ideal model for exploring how pluripotent stem cells sense tissue boundaries, guiding appropriate differentiation. Here, we use the planarian pharynx to define the cell lineages that originate from stem cells expressing the pioneer transcription factor foxA. The anatomical restriction of pharynx-specific lineages is disrupted by knockdown of the Roundabout receptor roboA, leading to ectopic pharynx neurons (EPNs) emerging in the brain. An RNAi screen for genes that phenocopy roboA identifies the extracellular protein anosmin-1, a gene responsible for Kallmann syndrome, as a potential partner of roboA. Aberrant induction of EPNs in the brain requires foxA, while knockdown of foxA induces head-specific neurons in the pharynx, revealing a latent plasticity in stem cells to adopt alternative fates. Together, we propose that RoboA and Anos1 act as fate-reinforcing genes (FRGs) that suppress inappropriate cell fates, maintaining organ integrity and enabling stem cell plasticity during regeneration.
Project description:To investigate the role of alx-3 in activating wound-induced transciptional programs during anterior regneneraiton, control(RNAi) and alx-3(RNAi) planarians were amputated below the pharynx and were allowed to regenerate for 0.5 hours post-amputation (HPA), 6HPA, 24HPA, 48HPA and 72HPA. Intact animals were are also included.Tissue from tail fragments and intact animals was collected at each time point for RNA extraction and cDNA synthesis. Gene expression profiling analysis was performed using data obtained from RNA-seq of planarian tissues at 5 timepoints after regeneraiton and in uninjured animals .
Project description:The planarian Dugesia japonica has amazing ability to regenerate a head from the anterior ends of the amputated stump with maintenance of the original anterior-posterior polarity. Although planarians present an attractive system for molecular investigation of regeneration and research has focused on clarifying the molecular mechanism of regeneration initiation in planarians, but proteomic studies are still in the early stages. Here, a global proteomics analysis of regenerating head fragments in planarians at 0h, 2h and 6h after amputation was performed using isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics coupled with LC-MS/MS strategy. Then the significantly changed proteins were identified. The correlation betwwen protein expression profiles and signaling pathways/biological processes was analyzed by bioinformatics and systems biology.
Project description:Variability of regenerative potential among animals has long perplexed biologists. Based on their amazing regenerative abilities, planarians have become important models for understanding the molecular basis of regeneration; however, planarian species with limited regenerative abilities are also found. Despite the importance of understanding the differences between closely related, regenerating and non-regenerating organisms, few studies have focused on the evolutionary loss of regeneration, and the molecular mechanisms leading to such regenerative loss remain obscure. Here we examine Procotyla fluviatilis, a planarian with restricted ability to replace missing tissues, utilizing next-generation sequencing to define the gene expression programs active in regeneration-permissive and regeneration-deficient tissues. We found that Wnt signaling is aberrantly activated in regeneration-deficient tissues. Remarkably, down-regulation of canonical Wnt signaling in regeneration-deficient regions restores regenerative abilities: blastemas form and new heads regenerate in tissues that normally never regenerate. This work reveals that manipulating a single signaling pathway can reverse the evolutionary loss of regenerative potential. RNA-seq experiments to identify gene expression changes following amputation in body regions with variable regenerative potential.
Project description:Adult zebrafish hearts have the ability to regenerate. The roles of non-myocytes in this process have remained elusive. Here, we have performed 2 scRNAseq experiments on interstitial cells. Experiment 1 (E1) included interstitial cells obtained from uninjured, regenerating (3 days, 7 days and 14 days post-apical amputation). Experiment 2 (E2) included cells from uninjured, sham-operated (abdomen opened) and regenerating (3 days post-amputation) with and without MMP inhibitor (NSC40520) treatment. Cells were obtained by heart dissection followed by enzymatic dissociation and FACS sorting of single, viable nucleated cells.
Project description:We used Nimblegen arrays with design 2007-11-06_Smed_ESTs_4_exp to measure changes in gene expression during a timecourse of regeneration of one side of the head in Schmidtea mediterranea flatworms. Following amputation of one side of the head, samples were collected from both the regeneration blastema and non-regenerating side of the head on days 2, 3, and 4 post-amputation. Gene expression in these samples was compared to that in non-regenerating control samples collected at the time of amputation.
Project description:The roles of extracellular vesicles in animal models of regeneration are poorly characterized. The goal of this study was to identify differentially expressed transcripts in planarian flatworms after injection of buffer only or extracellular vesicles compared to uninjected animals.
Project description:Adult zebrafish can completely regenerate their caudal fin following amputation. This complex process is initiated by the formation of an epithelial would cap over the amputation site by 12 hours post amputation (hpa). Once the cap is formed, mesenchymal cells proliferate and migrate from sites distal to the wound plane and accumulate under the epithelial cap forming the blastemal structure within 48 hpa. Blastemal cells proliferate and differentiate, replacing the amputated tissues, which are populated with angiogenic vessels and innervating nerves during the regenerative outgrowth phase which is completed around 14 days post amputation (dpa). Regenerative outgrowth does not occur in TCDD-exposed zebrafish. To identify the molecular pathways that are perturbed by TCDD exposure, male zebrafish were i.p. injected with 50 ng/g TCDD or vehicle and caudal fins were amputated. Regenerating fin tissue was collected at 1, 3 and 5 dpa for mRNA abundance analysis. Microarray analysis and quantitative real time PCR revealed that wound healing and regeneration alone altered the expression of nearly 900 genes by at least two fold between 1 and 5 dpa. TCDD altered the abundance of 370 genes at least two fold. Among these, several known aryl hydrocarbon responsive genes were identified in addition to several genes involved in extracellular matrix composition and metabolism. The profile of misexpressed genes is suggestive of impaired cellular differentiation and extracellular matrix composition potentially regulated by Sox9b. Keywords: Time course and TCDD exposure response