Project description:Background: Freshwater planarians are well known for their regenerative abilities. Less well known is how planarians maintain spatial patterning in long-lived adult animals or how they re-pattern tissues during regeneration. HOX genes are good candidates to regulate planarian spatial patterning, yet the full complement or genomic clustering of planarian HOX genes has not yet been described, primarily because only a few have been detectable by in situ hybridization, and none have given morphological phenotypes when knocked down by RNAi. Results: Because the planarian Schmidtea mediterranea (S. med) is unsegmented, appendage-less, and morphologically simple, it has been proposed that it may have a simplified HOX gene complement. Here we argue against this hypothesis and show that S. med has a total of 13 HOX genes, which represent homologs to all major axial categories, and can be detected by whole-mount in situ hybridization using a highly-sensitive method. In addition, we show that planarian HOX genes do not cluster in the genome, yet 5/13 have retained aspects of axially-restricted expression. Finally, we confirm HOX gene axial expression by RNA-deep-sequencing 6 anterior-to-posterior “zones” of the animal, which we provide as a dataset to the community to discover other axially-restricted transcripts. Conclusions: Freshwater planarians have an unappreciated HOX gene complexity, with all major axial categories represented. However, we conclude based on adult expression patterns that planarians have a derived body plan and their asexual lifestyle may have allowed for large changes in HOX expression from the last common ancestor between arthropods, flatworms, and vertebrates. Using our in situ method and axial zone RNAseq data, it should be possible to further understand the pathways that pattern the anterior-posterior axis of adult planarians.
Project description:Combining the exposure to the human carcinogen cadmium to in silico and proteomic top-down approaches the conserved function of two novel tumor suppressor genes in planarians were disclosed.
Project description:Adult stem cells are tissue-specific cells with the capacity to self-renew and differentiate to continually replace cells lost to normal physiological turnover or injury. Neoblasts, the planarian stem cells, are widely distributed throughout the body mesenchyme, driving constitutive renewal of tissues during homeostasis and endowing planarians with the remarkable capacity to regenerate wholly from tiny tissue fragments. Neoblasts are the only dividing cells in planarians and are believed to be collectively comprised of both a heterogeneous population of pluripotent cells with broad differentiation potential and also lineage-committed progenitor cells that give rise to specific tissues. Recent technology has allowed one to isolate stem cells so we used a well-established method to isolate planarian stem cells by Hoechst blue staining and flow cytometry. To understand the molecular mechanisms underlying neoblast differentiation, we performed an RNA-Seq analysis of X1 and Xins cells looking at the differentially expressed genes between the two populations. Examine gene expression profiles of adult flatwormâ??s X1 and Xins cell types. The experiment was performed in quadruplicate yielding a total of 8 samples.