Biology subjects

Lehoczky, J. A.

Publications and source records attributed to Lehoczky, J. A..

6 recordsLinked to original sources

bioRxiv2026

A conserved pituitary response to tissue loss controls regeneration across vertebrates

Regenerating complex tissues requires coordination between local cellular responses and body-wide systemic signals. As a central endocrine regulator, the pituitary is well positioned to coordinate this process. Here, we identify the pituitary as an injury-responsive regulator of axolotl limb and tilapia fin regeneration. Limb loss triggered sustained transcriptional responses in the axolotl pituitary. Single-cell transcriptomics linked pituitary loss to altered gene expression in prolactin- and growth hormone-responsive limb cells. Local disruption of the prolactin receptor impaired digit formation, whereas combined hormone treatment partially restored regeneration in hypophysectomized axolotls. In tilapia, pituitary removal impaired fin regeneration and prolactin-related signaling. Mouse digits differed from axolotls and tilapia in how and when they received pituitary signals during regeneration, suggesting pituitary-dependent regrowth is evolutionarily divergent among highly regenerative vertebrates.

systems biology↗

bioRxiv2025

Mouse digit AAV gene delivery into fibroblasts regulates regenerative outcome

The distal mouse digit tip regenerates post-amputation, while the proximal digit undergoes fibrosis. This study presents a comparative single-cell RNA sequencing-based analysis of regenerating and non-regenerating digits to computationally identify fibroblast subpopulations and genes associated with fibrosis and regeneration. To test the sufficiency of newly identified candidate genes to alter wound healing outcomes, we developed a robust adeno-associated virus gene delivery technique for digit fibroblasts. We found that overexpression of candidate pro-fibrotic genes Pcolce2 or Prelp in the blastema modifies normal regeneration and overexpression of candidate pro-regenerative factors Ccl2 or Mest in the proximal digit significantly increases bone deposition. These data demonstrate that the computational analysis combined with the AAV delivery approach presented in this study provides a powerful framework for identifying the driving factors of fibrosis and regeneration in the mammalian digit.

molecular biology↗

bioRxiv2024

Regeneration-specific promoter switching facilitates Mest expression in the mouse digit tip to modulate neutrophil response

The mouse digit tip regenerates following amputation, a process mediated by a cellularly heterogeneous blastema. We previously found the gene Mest to be highly expressed in mesenchymal cells of the blastema and a strong candidate pro-regenerative gene. We now show Mest digit expression is regeneration-specific and not upregulated in post-amputation fibrosing proximal digits. Mest homozygous knockout mice exhibit delayed bone regeneration though no phenotype is found in paternal knockout mice, inconsistent with the defined maternal genomic imprinting of Mest. We demonstrate that promoter switching, not loss of imprinting, regulates biallelic Mest expression in the blastema and does not occur during embryogenesis, indicating a regeneration-specific mechanism. Requirement for Mest expression is tied to modulating neutrophil response, as revealed by scRNAseq and FACS comparing wildtype and knockout blastemas. Collectively, the imprinted gene Mest is required for proper digit tip regeneration and its blastema expression is facilitated by promoter switching for biallelic expression.

developmental biology↗

bioRxiv2022

En1 and Lmx1b do not recapitulate embryonic dorsal-ventral limb patterning functions during mouse digit tip regeneration

The mouse digit tip is a complex tissue that is capable of regeneration after amputation. How the regenerated digit tip is patterned is unknown, but a long-standing hypothesis in the field of regeneration proposes that developmental patterning mechanisms are re-used during regeneration. The digit tip bone exhibits strong dorsal-ventral (DV) polarity, so we focus on Engrailed 1 (En1) and LIM homeobox transcription factor 1B (Lmx1b), two well-studied transcription factors necessary for DV patterning during limb development. We investigate if En1 and Lmx1b are re-expressed during regeneration in a developmental-like spatially restricted pattern, and if they direct DV morphology of the regenerated digit tip. We find that both En1 and Lmx1b are expressed in the regenerating mouse digit tip epithelium and mesenchyme, respectively, but without DV polarity. We use conditional genetics and quantitative analysis of digit tip bone morphology to determine that genetic deletion of En1 or Lmx1b in adult digit tip regeneration modestly reduces bone regeneration but does not affect DV patterning of the regenerate. Collectively, our data suggest that while En1 and Lmx1b are re-expressed during mouse digit tip regeneration, they do not define the DV axis during regeneration.

developmental biology↗

bioRxiv2021

LGR6 is necessary for attaining peak bone mass and regulates osteogenesis through differential ligand use

Leucine-rich repeat containing G-protein-coupled receptor 6 (LGR6) is a marker of osteoprogenitor cells and is dynamically expressed during in vitro osteodifferentation of mouse and human mesenchymal stem cells (MSCs). While the Lgr6 genomic locus has been associated with osteoporosis in human cohorts, the precise molecular function of LGR6 in osteogenesis and maintenance of bone mass are not yet known. In this study, we performed in vitro Lgr6 knockdown and overexpression experiments in murine osteoblastic cells and find decreased Lgr6 levels results in reduced osteoblast proliferation, differentiation, and mineralization. Consistent with these data, overexpression of Lgr6 in these cells leads to significantly increased proliferation and osteodifferentiation. To determine whether these findings are recapitulated in vivo, we performed microCT and ex vivo osteodifferentiation analyses using our newly generated CRISPR-Cas9 mediated Lgr6 mouse knockout allele (Lgr6-KO). We find that ex vivo osteodifferentiation of Lgr6-KO primary MSCs is significantly reduced, and 8 week-old Lgr6-KO mice have less trabecular bone mass as compared to Lgr6 wildtype controls, indicating that Lgr6 is necessary for normal osteogenesis and to attain peak bone mass. Toward mechanism, we analyzed in vitro signaling in the context of two LGR6 ligands, RSPO2 and MaR1. We find that RSPO2 stimulates LGR6-mediated WNT/{beta}-catenin signaling whereas MaR1 stimulates LGR6-mediated cAMP activity, suggesting two ligand-dependent functions for LGR6 receptor signaling during osteogenesis. Collectively, this study reveals that Lgr6 is necessary for wildtype levels of proliferation and differentiation of osteoblasts, and achieving peak bone mass.

developmental biology↗

bioRxiv2019

Cellular heterogeneity and lineage restriction during mouse digit tip regeneration at single cell resolution

Innate regeneration following digit tip amputation is one of the few examples of epimorphic regeneration in mammals. Digit tip regeneration is mediated by the blastema, the same structure invoked during limb regeneration in some lower vertebrates. By genetic lineage analyses in mice, the digit tip blastema has been defined as a population of heterogeneous, lineage restricted progenitor cells. These previous studies, however, do not comprehensively evaluate blastema heterogeneity or address lineage restriction of closely related cell types. In this report we present single cell RNA sequencing of over 38,000 cells from mouse digit tip blastemas and unamputated control digit tips and generate an atlas of the cell types participating in digit tip regeneration. We define the differentiation trajectories of vascular, monocytic, and fibroblastic lineages over regeneration, and while our data confirm broad lineage restriction of progenitors, our analysis reveals an early blastema fibroblast population expressing a novel regeneration-specific gene, Mest.

molecular biology↗