Biology subjects

Keeley, S. D.

Publications and source records attributed to Keeley, S. D..

4 recordsLinked to original sources

bioRxiv2026

Tissue composition shapes differential skeletal integration strategies during axolotl limb regeneration

Limb regeneration requires rebuilding the missing structures and integrating them with stump tissues. Osteoclast-mediated tissue resorption is essential for skeletal integration during regeneration. However, it is unknown if skeletal tissue composition impacts its resorption and, if so, how it is regulated. Here, we show that osteoclast-mediated skeletal resorption is activated in amputations damaging the diaphysis, but not the epiphysis, of skeletal elements. We found that amputations in the calcified diaphysis trigger the sustained expression of RANKL and the chemokine Loc483, and that the latter is sufficient to induce osteoclast presence in non-resorbing amputations. Finally, our data suggests that the transcriptomic profile of the apical ectodermal cap is impacted by the tissues injured by the amputation. Overall, our work reveals that tissue composition at the amputation plane shapes adaptations of the regenerative program, which ultimately contribute to the near-seamless tissue integration of the regenerating axolotl limb regardless of the amputation position.

developmental biology↗

bioRxiv2025

Differential fates of vertebrate Kazald gene quartet, from ancestral roles in skeletogenesis and regeneration to putative innovations in fish and birds

Salamanders are known for their incredible regenerative abilities, but translating findings to mammals is complicated by unannotated genes and unclear orthology. An example highlighting this difficulty was a discovery in the axolotl (Ambystoma mexicanum) of a regeneration-associated gene that has been identified as either Kazald1 or Kazald2. Since orthology inference of genes across species is crucial to identifying gains and losses of gene functions, and thus if gene usage is likely to be consistent across species, we investigated the evolution of the axolotl genes using an extensive cross-species analysis. Molecular phylogeny inference conclusively identified the regeneration-associated gene as Kazald2, but also revealed an undescribed four-member Kazald gene family in jawed vertebrates. Moreover, synteny comparisons demonstrated that this family originated in the ancestral two-rounds of whole genome duplication. Additionally, we performed vertebrate-wide comparisons of Kazald gene expression profiles, employing available RNA-Seq which we validated in whole tissues of axolotl, zebrafish, and sharks. This uncovered seemingly ancestral connections conserved over jawed vertebrate evolution, such as Kazald1 with skeletogenesis and odontogenesis and Kazald2 with regeneration. It also suggested novel putative roles within specific lineages, including Kazald3 in teleost fish skeletogenesis and Kazald4 within avian brains. Our study thus demonstrates the establishment of a Kazald gene quartet in the jawed vertebrate ancestor, and elucidates the asymmetry of gene fates of its members, including deeply ancestral roles and comparably recent innovations. This provides a comprehensive report of this formerly undescribed gene family, offering a solid foundation for future studies of these genes in diverse species.

evolutionary biology↗

bioRxiv2024

Axolotl mandible regeneration occurs through mechanical gap closure and a shared regenerative program with the limb

The mandible plays an essential part in human life and, thus, defects in this structure can dramatically impair the quality of life in patients. Axolotls, unlike humans, are capable of regenerating their lower jaws; however, the underlying mechanisms and their similarity to those in limb regeneration are unknown. In this work, we used morphological, histological, and transcriptomic approaches to analyze the regeneration of lateral resection defects in the axolotl mandible. We found that this structure can regenerate all missing tissues in 90 days through gap minimization, blastema formation, and finally tissue growth, differentiation, and integration. Moreover, transcriptomic comparisons of regenerating mandibles and limbs showed that they share molecular phases of regeneration, that these similarities peak during blastema stages, and that mandible regeneration occurs at a slower pacing. Altogether, our study demonstrates the existence of a shared regenerative program used in two different regenerating body structures with different embryonic origins in the axolotl, and contributes to our understanding of the minimum requirements for a successful regeneration in vertebrates, bringing us closer to understand similar lesions in human mandibles.

developmental biology↗

bioRxiv2018

Hair Follicle Epidermal Stem Cells Define a Niche for Tactile Sensation

The heterogeneity and compartmentalization of stem cells is a common principle in many epithelia, and is known to function in epithelial maintenance, but its other physiological roles remain elusive. Here we show transcriptional and anatomical contributions of compartmentalized epidermal stem cells (EpSCs) in tactile sensory unit formation in the hair follicle (HF). EpSCs in the follicle upper-bulge, where mechanosensory lanceolate complexes (LCs) innervate, express a unique set of extracellular matrix (ECM) and neurogenesis-related genes. These EpSCs deposit an ECM protein EGFL6 into the collar matrix, a novel ECM that tightly ensheathes LCs. EGFL6 is required for the proper patterning, touch responses, and v integrin-enrichment of LCs. By maintaining a quiescent original EpSC niche, the old bulge, EpSCs provide anatomically stable HF-LC interfaces, irrespective of the stage of follicle regeneration cycle. Thus, compartmentalized EpSCs provide a niche linking the HF and the nervous system throughout the hair cycle.

developmental biology↗