Spinal Cord Regeneration in the Leopard Gecko: Activation and Heterogeniety of Ependymal Layer Cells
Bibliographic record
Abstract
Among species capable of spinal cord regeneration, mounting evidence points towards a crucial role for a population of cells lining the central canal, herein referred to as ependymal layer cells (ELCs). In addition to their role in circulating cerebrospinal fluid, it is now understood that ELCs include a population of resident neural stem/progenitor cells (NSPCs) within the spinal cord. In taxa such as urodeles and zebrafish, ELCs are recruited in response to injury to replace lost or damaged neurons and support cells. Among other species capable of spontaneous spinal cord regeneration less is known. Here we characterized ELCs in the tail‐regenerating lizard Eublepharis macularius , the leopard gecko. As for many lizards, geckos are able to self‐detach their tail to avoid predation and then regenerate a replacement. The replacement tail includes a regenerated spinal cord with a relatively simple morphology: a monolayer of ELCs surrounded by nerve tracts. We hypothesized that ELCs of the original spinal cord include populations of NSPCs that are activated following tail loss. We conducted a detailed spatiotemporal characterization of ELCs before, during, and after tail regeneration. Prior to injury, ELCs express the hallmark NSPC marker SOX2. Following tail loss, ELCs in the original stump of the tail become highly proliferative and express an expanded panel of NSPC and lineage‐restricted progenitor cell markers, including Vimentin, MSI‐1, SOX9 and TUJ1. We also found that cells within the ependymal layer represent at least two distinct populations. Most ELCs are SOX2+, GFAP+, HuC/D−. We interpret these cells as ependymo‐radial glia. A second subset of ELCs are SOX2+, GFAP−, HuC/D+, which we identify as a neuronal‐like population of cerebrospinal fluid‐contacting cells. This complex assemblage of cells, in combination with the activation of an endogenous NSPC population may explain the remarkable regenerative abilities of the spinal cord in this species. We propose that spinal cord regeneration proceeds along a trajectory similar to development and that the completeness of the program varies across species. Ultimately, the degree with which a species is capable of progressing along the trajectory determines the degree of structural and functional fidelity is re‐established following injury.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".