Huang, A. Z. | bioRxiv Science

bioRxiv2026

Synthetic budding morphogenesis by optogenetic receptor tyrosine kinase signaling

The mammalian kidney relies on a branched network of collecting ducts for fluid transport and homeostasis. Replicating this network in vitro would parallelize function in synthetic replacement kidneys, yet current organoids have limited branching capacity. Here, we establish a developmentally-informed strategy to control organoid budding through optogenetic control of a receptor tyrosine kinase, RET. We first show pharmacological manipulation of RET signaling controls the extent of branching in mouse embryonic kidneys and human stem cell-derived kidney organoids. Next, we develop an optogenetic RET receptor (optoRET) that signals in a ligand-independent manner via blue light-mediated clustering. Epithelial cells expressing optoRET reproduce stereotyped RET signaling, scattering, and symmetry breaking in response to blue light. Human kidney organoids undergo budding with controllable orientation in response to spatially patterned optoRET stimulation. Our results establish ligand-free optogenetic control of branching and inspire new synthetic biology strategies for epithelial organoid design. HighlightsGDNF-RET controls branching and tip cell state in mouse and human kidney tissues. OptoRET reproduces endogenous RET signaling and morphogenesis in cell lines. OptoRET enables ligand-free budding in human renal epithelial organoids. Spatially patterned optoRET stimulation controls budding orientation.

bioengineering↗

bioRxiv2024

Engineering kidney developmental trajectory using culture boundary conditions

Kidney explant cultures are traditionally carried out at air-liquid interfaces, which disrupts 3D tissue structure and limits interpretation of developmental data. To overcome this limitation, we developed a 3D culture technique using hydrogel embedding to capture morphogenesis in real time. We show that 3D culture better approximates in vivo-like niche spacing and dynamic tubule tip rearrangement, as well as in vivo-like presentation of branching defects under perturbations to glial cell-derived neurotrophic factor (GDNF)-REarranged during Transfection (RET) tyrosine kinase signaling. We find that the concentration of the embedding matrix influences the number of nephrons per ureteric bud (UB) tip and the spacing between tips. To isolate the effect of specific material properties on explant development, we introduce engineered acrylated hyaluronic acid hydrogels that allow independent tuning of stiffness and adhesion. We find that sufficient stiffness and adhesion are both required to maintain kidney shape. Matrix stiffness has a "Goldilocks effect" on the nephron per UB tip balance centered at [~]2 kPa, while higher matrix adhesion increases nephron per UB tip ratio. Our technique captures large-scale, in vivo-like tissue morphogenesis in 3D, providing a platform suited to contrasting normal and congenital disease contexts. Moreover, understanding the impact of boundary condition mechanics on kidney development benefits fundamental renal research and advances the engineering of next-generation kidney replacement tissues.

developmental biology↗