Gene Expression Profiles of Planarians after 6,000 Rads Irradiation
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ABSTRACT: The goal of the study was to identify genes expressed in the proliferative cell population (neoblasts) of adult planarians. Proliferating cells are rapidly and specifically eliminated following lethal irradiation. Genes expressed by neoblasts, therefore, were expected to show decreased level of expression following 6,000 rads, relative to control animals.
Project description:The goal of the study was to identify genes expressed in the proliferative cell population (neoblasts) of adult planarians. Proliferating cells are rapidly and specifically eliminated following lethal irradiation. Genes expressed by neoblasts, therefore, were expected to show decreased level of expression following 6,000 rads, relative to control animals. Total RNA was collected from control (unirradiated) animals and from animals 6, 12, 24, and 48 hours following 6,000 rads irradiation. Between three and five replicates were used for each sample
Project description:Throughout adulthood, the replacement of cells lost to physiological turnover or injury in planarians is sustained by the proliferation and differentiation of adult stem cells known as neoblasts. Because neoblasts are the only known mitotic cells in asexual planarians, they can be efficiently eliminated by irradiation without significantly affecting post-mitotic differentiated cells. We uncovered a cohort of transcripts specific to the stem cells and their division progeny by defining the expression profiles of wild type and irradiated animals at different time points after irradiation. RNA from wild type animals, or from animals 24 hours or seven days after exposure to radiation, were compared to a common reference.
Project description:Throughout adulthood, the replacement of cells lost to physiological turnover or injury in planarians is sustained by the proliferation and differentiation of adult stem cells known as neoblasts. Because neoblasts are the only known mitotic cells in asexual planarians, they can be efficiently eliminated by irradiation without significantly affecting post-mitotic differentiated cells. We uncovered a cohort of transcripts specific to the stem cells and their division progeny by defining the expression profiles of wild type and irradiated animals at different time points after irradiation.
Project description:The goal of this experiment is to identify target genes of Egf signaling which regulate recovery of the neoblast population following exposure to a sublethal dose of radiation. A large population of highly proliferative stem cells (neoblasts) is required for physiological tissue homeostasis and regeneration after injury in planarians. Recent studies indicate that survival of a few neoblasts after sublethal irradiation results in the clonal expansion of the surviving stem cells and the eventual restoration of tissue homeostasis and regenerative capacity. Many genes are known to be required for the normal function of neoblasts, but the precise mechanisms regulating the population dynamics of these adult pluripotent stem cells remain largely unknown. By coupling RNAi screening and sublethal irradiation, we uncovered a central role for Epidermal Growth Factor (EGF) signaling during in vivo neoblast expansion mediated by Smed-egfr-3 (egfr-3) and its putative ligand Smed-neuregulin-7 (nrg-7). Furthermore, the EGFR-3 protein localizes asymmetrically on the cytoplasmic membrane of neoblasts and the ratio of asymmetric to symmetric cell divisions decreases significantly in egfr-3(RNAi) worms. Our results not only provide the first molecular evidence of asymmetric stem cell divisions in planarian, but also demonstrate that EGF signaling likely functions as an essential regulator of neoblast clonal expansion.
Project description:Transcriptional profiling of Schmidtea mediterranea planarians that have been amputated transversely and left to regenerate for different time points (UNIRR); the same experiment was performed on irradiated - neoblast depleted animals (IRR). The purpose of this experiment was to identify transcriptional changes that are induced within the first 12h following amputation. In order to distinguish between gene expression changes in the differentiated tissue and the neoblasts, a second set of time course data was created from irradiated animals Two-color experiment, 3 replicates per condition (including 10 animals/replica)
Project description:Transcriptional profiling of Schmidtea mediterranea planarians that have been amputated transversely and left to regenerate for different time points (UNIRR); the same experiment was performed on irradiated - neoblast depleted animals (IRR). The purpose of this experiment was to identify transcriptional changes that are induced within the first 12h following amputation. In order to distinguish between gene expression changes in the differentiated tissue and the neoblasts, a second set of time course data was created from irradiated animals
Project description:Epimorphic regeneration commonly relies on the activation of quiescent stem cells to drive new cell production. The planarian Schmidtea mediterranea is among the best regenerators in nature, thanks to its large population of adult stem cells, called neoblasts. While neoblasts have long been known to drive regeneration, whether a subset of neoblasts is reserved for this purpose is unknown. Here, we revisited the idea of reserved neoblasts by approaching neoblast heterogeneity from a regulatory perspective. By implementing a new fluorescence-activated cell sorting strategy in planarians, we identified a population of neoblasts defined by low transcriptional activity. These RNAlow neoblasts are relatively slow-cycling at homeostasis and undergo a morphological regeneration response characterized by cell growth at 48 hours post-amputation. At this time, RNAlow neoblasts proliferated in a TOR-dependent manner. Additionally, knockdown of the tumour suppressor Lrig-1, which is enriched in RNAlow neoblasts, resulted in RNAlow neoblast growth and hyperproliferation at homeostasis, and ultimately delayed regeneration. We propose that slow-cycling RNAlow neoblasts represent a regeneration-reserved neoblast population.
Project description:Transcriptional profiling of Schmidtea mediterranea planarians that have been subjected to 2 weeks of runt-1 or control RNAi, amputated and RNA was directly collected at 5min, 9h, and 24h, or neoblasts (X1) were isolated from 9h wounded animals and subsequently RNA was extracted Two-color experiment, 3 replicates per condition (including 10 animals/replica)
Project description:Transcriptional profiling of Schmidtea mediterranea planarians that have been subjected to 2 weeks of runt-1 or control RNAi, amputated and RNA was directly collected at 5min, 9h, and 24h, or neoblasts (X1) were isolated from 9h wounded animals and subsequently RNA was extracted