Biology subjects

Walker, L. J.

Publications and source records attributed to Walker, L. J..

3 recordsLinked to original sources

bioRxiv2025

Xeno-free human iPSC-derived prostate organoid platform for multilineage differentiation and genetic manipulation

Current prostate organoid models rely on tissue-derived material or animal components and lack epithelial and stromal complexity. We defined a xeno-free system to generate human prostate organoids from induced pluripotent stem cells with consistent multilineage differentiation. Floating organoids self-organize into epithelial and stromal domains with basal, luminal, neuroendocrine, fibroblast, and smooth muscle markers. In an alternative modular co-culture system, engineered epithelial progenitors are aggregated with wild-type mesenchymal progenitors, enabling compartment-specific manipulation. Androgen receptor-overexpressing organoids showed increased epithelial AR and PSA expression and proliferation. Single-cell transcriptomics, together with qPCR and immunostaining, confirmed prostate lineage specification and tissue organization. This new xeno-free platform provides a reproducible, scalable, and genetically tractable model to study in-vitro prostate lineage programs, epithelial-stromal interactions, and disease biology. Graphic AbstractThis study describes the generation of prostate organoids from human iPSCs. iPSCs, including those reprogrammed from patients carrying germline mutations, can be differentiated into prostate organoids either through monoculture or by co-culturing endodermal cells with mesenchymal progenitors. Genetic manipulation can be introduced before endoderm specification to model cancer drivers. The resulting multi-lineage organoids exhibit distinct epithelial (AR, NKX3.1, PSA, CK8/18) and stromal (VIM, -SMA) compartments, providing a versatile platform for developmental studies, disease modelling, drug screening, and biomarker discovery. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/683654v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1cc13eborg.highwire.dtl.DTLVardef@12fe2a4org.highwire.dtl.DTLVardef@c89d64org.highwire.dtl.DTLVardef@d541e0_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2023

A glia cell dependent mechanism at a peripheral nerve plexus critical for target-selective axon regeneration

A critical step for functional recovery from peripheral nerve injury is for regenerating axons to connect with their pre-injury targets. Reestablishing pre-injury target specificity is particularly challenging for limb-innervating axons as they encounter a plexus, a network where peripheral nerves converge, axons from different nerves intermingle, and then re-sort into target-specific bundles. Here, we examine this process at a plexus located at the base of the zebrafish pectoral fin, equivalent to tetrapod forelimbs. Using live cell imaging and sparse axon labeling, we find that regenerating motor axons from three nerves coalesce into the plexus. There, they intermingle and sort into distinct branches, and then navigate to their original muscle domains with high fidelity that restores functionality. We demonstrate that this regeneration process includes selective retraction of mistargeted axons, suggesting active correction mechanisms. Moreover, we find that Schwann cells are enriched and associate with axons at the plexus, and that Schwann cell ablation during regeneration causes profound axonal mistargeting. Our data provide the first real time account of regenerating vertebrate motor axons navigating a nerve plexus and reveal a previously unappreciated role for Schwann cells to promote axon sorting at a plexus during regeneration.

neuroscience↗

bioRxiv2021

Agrin/Lrp4 signal constrains MuSK activity during neuromuscular synapse development in appendicular muscle

The receptor tyrosine kinase MuSK, its co-receptor Lrp4 and the Agrin ligand constitute a signaling pathway critical in axial muscle for neuromuscular synapse development, yet whether this pathway functions similarly in appendicular muscle is unclear. Here, using the larval zebrafish pectoral fin, equivalent to tetrapod forelimbs, we show that like axial muscle, developing appendicular muscles develop aneural acetylcholine receptor (AChR) clusters prior to innervation. As motor axons arrive, neural AChR clusters form, eventually leading to functional synapses in a MuSK-dependent manner. Surprisingly, we find that loss of Agrin or Lrp4 function, which abolishes synaptic AChR clusters in axial muscle, results in enlarged presynaptic nerve endings and progressively expanding appendicular AChR clusters, mimicking the consequences of motoneuron ablation. Moreover, musk depletion in lrp4 mutants partially restores synaptic AChR patterning. Combined, our results provide compelling evidence that, in contrast to axial muscle in which Agrin/Lrp4 stimulates MuSK activity, Agrin/Lrp4 signaling in appendicular muscle constrains MuSK activity to organize neuromuscular synapses. Thus, we reveal a previously unappreciated role for Agrin/Lrp4 signaling, thereby highlighting distinct differences between axial and appendicular synapse development.

neuroscience↗