Project description:Salamander limb regeneration is an accurate process which gives rise exclusively to the missing structures, irrespective of the amputation level. This suggests that cells in the stump have an awareness of their spatial location, a property termed ‘positional identity’. Little is known about how positional identity is encoded, in salamanders or other biological systems. Through single-cell RNAseq analysis, we identified Tig1/RARRES1 as a potential determinant of proximal identity. Tig1 encodes a conserved cell surface molecule, is regulated by retinoic acid and exhibits a graded expression along the proximo-distal axis of the limb. Its overexpression leads to regeneration defects in the distal elements and elicits proximal displacement of blastema cells, while its neutralisation blocks proximo-distal cell surface interactions. Critically, Tig1 reprogrammes distal cells to a proximal identity, upregulating Prod1 and inhibiting HoxA13 and distal transcriptional networks. Thus, Tig1 is a central cell surface determinant of proximal identity in the salamander limb.
Project description:The salamander limb regenerates only the missing portion. Each limb segment can only form segments equivalent to- or more distal to their own identity, relying on a property termed “positional information”. How positional information is encoded in limb cells has been unknown. By cell-type-specific chromatin profiling of upper arm, lower arm, and hand, we found segment-specific levels of histone H3K27me3 at limb homeoprotein gene loci but not their upstream regulators, constituting an intrinsic segment information code. During regeneration, regeneration-specific regulatory elements became active prior to the re-appearance of developmental regulatory elements. This means that, in the hand segment, the permissive chromatin state of the hand homeoprotein gene HoxA13 engages with regeneration regulatory elements, bypassing the upper limb program. Profiling chromatin accessibility (ACRs) of Axoltol limb connective tissue cells, and compare among developmental limb buds, and mature limb at different segments and regeneration time points.
Project description:The salamander limb regenerates only the missing portion. Each limb segment can only form segments equivalent to- or more distal to their own identity, relying on a property termed “positional information”. How positional information is encoded in limb cells has been unknown. By cell-type-specific chromatin profiling of upper arm, lower arm, and hand, we found segment-specific levels of histone H3K27me3 at limb homeoprotein gene loci but not their upstream regulators, constituting an intrinsic segment information code. During regeneration, regeneration-specific regulatory elements became active prior to the re-appearance of developmental regulatory elements. This means that, in the hand segment, the permissive chromatin state of the hand homeoprotein gene HoxA13 engages with regeneration regulatory elements, bypassing the upper limb program. Profiling histone marks of Axoltol limb connective tissue cells, and comparing among limb different limb segments and mature vs regeneration time points.
Project description:The salamander limb regenerates only the missing portion. Each limb segment can only form segments equivalent to- or more distal to their own identity, relying on a property termed “positional information”. How positional information is encoded in limb cells has been unknown. By cell-type-specific chromatin profiling of upper arm, lower arm, and hand, we found segment-specific levels of histone H3K27me3 at limb homeoprotein gene loci but not their upstream regulators, constituting an intrinsic segment information code. During regeneration, regeneration-specific regulatory elements became active prior to the re-appearance of developmental regulatory elements. This means that, in the hand segment, the permissive chromatin state of the hand homeoprotein gene HoxA13 engages with regeneration regulatory elements, bypassing the upper limb program. We performed Differential Gene expression analysis using data obtained from RNA-seq of two mature limb segments (mature arm vs hand). Therefore, we performed libraries from the mature arm and 5, 9, 13 dpa regenerating arm blastema.
Project description:Tissue regeneration is widely distributed across the tree of life. Among vertebrates, salamanders possess an exceptional ability to regenerate amputated limbs and other complex structures. Thus far, molecular insights about limb regeneration have come from a relatively limited number of species from two closely related salamander families. To gain broader perspective on the molecular basis of limb regeneration and enhance the molecular toolkit of an emerging plethodontid salamander (Bolitoglossa ramosi), we used RNA-seq to generate transcript sequence data and identify 602 genes that are differentially expressed during limb regeneration. This list was further processed to identify a core set of genes that exhibit conserved expression changes between B. ramosi and the Mexican axolotl (Ambystoma mexicanum), and presumably their common ancestor approximately 180 million years ago. Our study highlights the importance of developing comparative gene expression data for studies of limb regeneration among salamanders. All animals used in this work were collected under the Contract on Genetic Access for scientific research for non commercial profit (Contrato de acceso a recursos genéticos para la investigación científica sin interés commercial) to Resources number 118–2015.
Project description:Transcriptome studies are revealing the complex gene expression basis of limb regeneration in the primary salamander model – Ambystoma mexicanum (axolotl). To better understand this complexity, there is need to extend analyses to additional salamander species. Using microarray and RNA-Seq, we performed a comparative transcriptomic study using A. mexicanum and two other ambystomatid salamanders: A. andersoni, and A. maculatum. Salamanders were administered forelimb amputations and RNA was isolated and analyzed to identify 405 non-redundant genes that were commonly, differentially expressed 24 hours post amputation. Many of the upregulated genes are predicted to function in wound healing and developmental processes, while many of the downregulated genes are typically expressed in muscle. The conserved transcriptional changes identified in this study provide a high-confidence dataset for identifying factors that simultaneous orchestrate wound healing and regeneration processes in response to injury, and more generally for identifying genes that are essential for salamander limb regeneration.
Project description:Transcriptome studies are revealing the complex gene expression basis of limb regeneration in the primary salamander model – Ambystoma mexicanum (axolotl). To better understand this complexity, there is need to extend analyses to additional salamander species. Using microarray and RNA-Seq, we performed a comparative transcriptomic study using A. mexicanum and two other ambystomatid salamanders: A. andersoni, and A. maculatum. Salamanders were administered forelimb amputations and RNA was isolated and analyzed to identify 405 non-redundant genes that were commonly, differentially expressed 24 hours post amputation. Many of the upregulated genes are predicted to function in wound healing and developmental processes, while many of the downregulated genes are typically expressed in muscle. The conserved transcriptional changes identified in this study provide a high-confidence dataset for identifying factors that simultaneous orchestrate wound healing and regeneration processes in response to injury, and more generally for identifying genes that are essential for salamander limb regeneration.
Project description:Here we report the results of a robust microarray experiment that examined the first 28 days of axolotl forelimb regeneration. At each of 20 post-amputation time points, we estimated gene expression for 10 replicate RNA samples that were isolated from 1m of heterogeneous tissue collected from the distal limb tip. The distal 1.0mm of heterogeneous tissue from regenerating limb tip were removed and used for RNA extraction. 10 samples were collected for each of 20 time points.
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.
Project description:Here we report the results of a robust microarray experiment that examined the first 28 days of axolotl forelimb regeneration. At each of 20 post-amputation time points, we estimated gene expression for 10 replicate RNA samples that were isolated from 1m of heterogeneous tissue collected from the distal limb tip.