Project description:Amputation of the axolotl forelimb results in the formation of a blastema, a transient tissue where progenitor cells accumulate prior to limb regeneration. Connective tissue (CT) – skeleton, periskeleton, tendon, dermis, interstitial cells – contributes the vast majority of cells that populate the blastema, however it is unclear how individual CT cells may reprogram their fate in order to rebuild the tetrapod limb. Here we use a combination of Cre-loxP reporter lineage tracking and single-cell (sc) RNA-seq to molecularly track, for the first time, adult CT cell heterogeneity and its transition to a limb blastema state. We uncover a multi-phasic molecular program where CT cell types found in the uninjured adult limb revert to a relatively homogenous progenitor state that participates in inflammation and extracellular matrix disassembly prior to proliferation, establishment of positional information, and ultimately re-differentiation. While the early regeneration transcriptome states are unique to the blastema, the later stages recapitulate embryonic limb development. Notably, we do not find evidence of a pre-existing blastema-like precursor nor limb bud-like progenitors in the uninjured adult tissue. However, we find that distinct CT subpopulations in the adult limb differentially contribute to proximal and distal portions of the regenerated limb. Together, our data illuminates molecular and cellular reprogramming during complex organ regeneration in a vertebrate.
Project description:In this project, we studied the proteomic profiles of the early stages of blastema formation of neotenic and metamorphic axolotls after limb amputation by means of LC-MS/MS technology. We quantified a total of 714 proteins having an adjusted p < 0.01 with FC greater or equal to 2 between two conditions. Principal component analysis revealed a conspicuous clustering between neotenic and metamorphic samples at 7 days post-amputation. Different set of proteins was identified as differentially expressed at all of the time points (1, 4, and 7 days post-amputations against day0) for neotenic and metamorphic stages. Although functional enrichment analyses underline the presence of common pathways between regenerative and non-regenerative stages, cell proliferation and its regulation associated pathways, immune system related pathways and muscle tissue and ECM remodeling and degradation pathways were represented at different rate between both stages.
Project description:The salamander microRNA expression between mid-bud limb regenerating blastemas (17 days post amputation) and non-regenerating stump tissues was compared by microarray analysis. LC Sciences arrays: Six paired samples were analyzed: three mid-bud 17dpa blastemas (bl), and three non-regenerating stumps (st). Three arrays were hybridized comparing two paired samples each time. Biological dye-swaps were made by labeling bl samples once with Cy3 and twice with Cy5; st samples were labeled accordingly twice with Cy5 and once with Cy3. Multiple arrays averaged into a single Sample record. Supplementary files: GSE29727_LC_MultiArray_SimpleNormalizedData.txt.gz GSE29727_LC_signal_ratio_mean_SD.txt.gz GSE29727_LC_t-Test_st-vs-bl.txt.gz Exiqon arrays: Six paired samples were analyzed: three mid-bud 17dpa blastemas (bl), and three non-regenerating stumps (st). Six arrays were hybridized comparing each sample labeled with Hy3 against a common reference sample made by pooling all the samples and labeling it with Hy5. Multiple arrays not averaged, represented as multiple Sample records. Supplementary file: GSE29727_Exiqon_matrix_complete.txt