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Volume:16 Issue: 20 | Bio-protocol
Current Issue in 2026
Volume: 16, Issue: 20
Biochemistry
Preparation of Phosphoinositide-Containing Supported Lipid Bilayers and Quantitative Assessment of Protein Recruitment to Membrane Surfaces
Small GTPases and many other peripheral membrane proteins regulate essential cellular processes through dynamic interactions with cellular membranes. These interactions are often controlled by membrane composition, particularly phosphoinositides (PIPs), which modulate the recruitment of GTPases, their regulators, and their effectors. Quantitative characterization of protein recruitment to defined membrane environments remains technically challenging. Here, we describe a protocol for preparing supported lipid bilayers (SLBs) containing defined phosphoinositide compositions in polydimethylsiloxane (PDMS) chambers and monitoring protein recruitment by total internal reflection fluorescence (TIRF) microscopy. Purified fluorescently labeled proteins are incubated with SLBs to measure membrane association in real time under controlled biochemical conditions. The method enables quantitative analysis of membrane recruitment kinetics and comparison of protein binding across different lipid compositions or in the presence of partner proteins. Combining the biochemical precision of a reconstituted membrane system with the sensitivity of TIRF imaging, this protocol provides a robust and versatile platform for studying lipid-dependent membrane recruitment. Although developed to investigate small GTPase signaling, it is readily applicable to a wide range of peripheral membrane proteins and membrane-associated signaling mechanisms.
Bioinformatics and Computational Biology
Quantitative Colocalization Analysis in Fluorescence Microscopy
Spatial organization of macromolecules is fundamental to cellular function, with colocalization providing key insights into molecular interactions and biological processes. However, quantification remains challenging due to diverse localization patterns and irregular sample geometries. Here, we present a protocol for analyzing colocalization between two fluorescent probes using coAnalyzer, a MATLAB-based software package. coAnalyzer features a user-friendly graphical interface and supports region of interest (ROI) selection, image merging, line scanning, signal isolation, scatterplot generation, and quantitative analysis. coAnalyzer enables colocalization analysis of any two fluorophores, regardless of the proteins or dyes involved. Its broad applicability across a wide range of organisms and sample types demonstrates the robustness, flexibility, and versatility of the platform.
Cancer Biology
Microtube-Assisted Paraffin Embedding and Sectioning of Fragile 3D Tumor Spheroids for High-Quality Histology
Three-dimensional (3D) spheroid models have become essential in cancer biology, drug screening, and tissue engineering. However, their small size, fragile structure, and tendency to disintegrate during routine histoprocessing present persistent technical challenges. Conventional paraffin embedding often results in tissue fragmentation, loss of spatial orientation, and poor section quality, whereas cryosectioning often compromises cellular morphology. Here, we present a robust, cost-effective protocol for preserving and sectioning fragile 3D spheroids, resulting in high-quality histological sections with intact architecture and excellent cellular detail. The method involves optimized handling and embedding procedures that stabilize spheroids during standard formalin fixation, paraffin infiltration, and microtomy, eliminating mechanical distortion and preserving spherical integrity for consistent sectioning. We demonstrate the successful application of this protocol across different tumor spheroids derived from distinct tissue types, including MDA-MB-231 (breast carcinoma), Caco-2 (colorectal adenocarcinoma), and A549 (lung carcinoma) cell lines, with subsequent compatibility with hematoxylin and eosin (H&E) staining protocols. This protocol is compatible with immunohistochemistry (IHC) and immunofluorescence (IF). In our qualitative comparison with conventional methods, we found that our approach effectively limits sample loss, promotes consistent inter-section reproducibility, and preserves fine structural features, such as necrotic cores, proliferative zones, and extracellular matrix components. This protocol provides a reliable, accessible solution for routine histological analysis of fragile 3D spheroids, facilitating more accurate morphological assessment in translational research settings.
Antiangiogenic Drug Testing Using Proangiogenic and Hypoxia Zebrafish Model
Zebrafish is an excellent in vivo model for high-throughput antiangiogenic drug testing, commonly known as the zebrafish angiogenesis assay. Conventional zebrafish angiogenesis assays are performed in wild-type zebrafish to evaluate the vascular changes in intersegmental and subintestinal vessel regions of the zebrafish larvae at 2 and 3 dpf stages, respectively. However, wild-type zebrafish larvae do not adequately mimic the hypoxia microenvironment and ectopic vessel branching characteristics of cancer. To overcome this limitation, we developed a genetically engineered zebrafish model with constitutive activation of the hypoxia signaling pathway by targeting the vhl, a tumor suppressor, by negative regulation of the hypoxia pathway, using CRISPR mutagenesis. This model exhibits robust ectopic blood vessel branching throughout the larval body, thereby recapitulating pathological angiogenesis. The utility of this zebrafish model system for drug screening was validated with the sorafenib treatment, a known antiangiogenic tyrosine kinase inhibitor. Overall, this proangiogenic hypoxia zebrafish model provides a physiologically relevant platform for testing antiangiogenic drugs.
A Dissociation-Based Seahorse XF Workflow for Quantifying Averaged Bioenergetics in Anchorage-Independent Cancer Cell Clusters
Cell clustering during anchorage-independent growth (AIG) is a key hallmark of malignant progression, supporting survival under detachment during metastatic dissemination. However, bioenergetic profiling of cell clusters grown under AIG conditions remains technically challenging, in part because of steep nutrient and oxygen gradients and irregular cell cluster shapes that complicate Seahorse XF assay normalization. Here, we present a dissociation-based Seahorse XF96/XF Pro method that enables high-throughput quantification of the average bioenergetic state of anchorage-independent cancer cell clusters. In this workflow, clusters generated in ultra-low adherent plates are enzymatically and mechanically dissociated into a single-cell suspension immediately prior to Seahorse XF Mito Stress Test analysis on poly-D-lysine-coated 2D microplates. This approach ensures that all viable cells throughout each cluster contribute equally to oxygen consumption rate (OCR) measurements and reduces the need for complex post hoc normalization. We further apply this workflow to an in vitro metastasis model in which A549 lung cancer cells are studied as attached, detached (anchorageindependent), and reattached populations, mimicking primary tumor cells, circulating/clustered cells, and secondary lesions, respectively. Detached cells exhibit reduced mitochondrial membrane potential and diminished basal and maximal OCR, whereas reattached cells largely restore membrane potential and respiratory capacity to levels comparable to attached cells, demonstrating that detachment-induced mitochondrial dysfunction is reversible upon reattachment. These findings align with previous work showing that anchorage-independent and clustered cancer cells undergo reversible metabolic reprogramming, including suppression of oxidative metabolism, engagement of reductive pathways to support redox homeostasis, and altered ROS handling to facilitate metastatic colonization. Collectively, this dissociation-based Seahorse workflow provides a practical and accessible platform to interrogate metabolic adaptations to anchorage-independent growth and cell clustering and identify bioenergetic vulnerabilities of metastasis-relevant cancer cell states.
Cell Biology
Visualizing Cell Type–Specific Glycan Profiles in Tissue Sections With Glycan Painting
Glycans play critical roles in numerous biological processes. Therefore, visualizing the spatial distribution of glycans within cells and tissues is essential for understanding tissue architecture and cellular identity. Glycan painting is a novel tissue-staining method that employs three fluorescently labeled lectins with different glycan-binding specificities to visualize cell type–specific glycan profiles as unique color patterns. In this study, the protocol was validated using formalin-fixed paraffin-embedded sections of mouse embryos. Although Glycan painting is a qualitative method, each cell population that is difficult to distinguish with a single lectin can be differentiated as unique color patterns generated from the combined images of three fluorescent lectins. Moreover, because it does not require costly reagents or specialized equipment, Glycan painting provides a cost-effective and broadly accessible approach for full-color tissue imaging and cell-type discrimination.
Developmental Biology
PIC-RNA-seq for Region-Specific Transcriptomic Analysis of Chicken Limb Bud Progenitors
Region-specific RNA sequencing is a powerful approach for investigating tissue differentiation and dynamic changes in gene expression during embryonic development. The chicken embryo has long served as an important model system in developmental biology. However, the limited availability of tissue-specific reporter lines makes region-specific RNA-seq approaches particularly valuable in this organism. Here, we applied photo-isolation chemistry-based RNA sequencing (PIC-RNA-seq) to the somatic lateral plate mesoderm (sLPM) before the emergence of limb bud progenitor cells (LPCs) and to early LPCs in chicken embryos. These analyses revealed the upregulation of multiple genes, including Hox genes, in LPCs, suggesting the initiation of their regional patterning program. This workflow enables visualization of dynamic changes in the gene expression profile of LPCs and should also be applicable to other tissues in avian embryos.
Microbiology
An Improved Method for Rapid Unmarked Gene Deletion in Bacteria: Pseudomonas aeruginosa as an Example
The release and updating of whole-genome sequences of several representatives of the human opportunistic pathogen Pseudomonas aeruginosa have laid the ground for investigating the mechanisms of antibiotic resistance, biofilm formation, and virulence, while also offering opportunities for researchers to find new therapeutic targets to control this bacterium using a functional genomics approach. However, there is still a lack of detailed protocols describing gene inactivation methods in P. aeruginosa, resulting in failures and extra time spent designing in-house protocols. Here, we introduce a rapid, efficient, and unmarked deletion mutagenesis method combining overlap extension PCR, efficient conjugation, and the traditionally used sacB-based counter-selection procedure. Efficient generation of deletion mutants using this detailed protocol can be easily completed in one week using standard lab reagents. Importantly, this method may be adaptable to other bacteria where the sacB-based counter-selection system works.
Molecular Biology
Optimized Phenol–Chloroform–Isoamyl DNA Extraction Protocol for Single Fish Eggs
Reliable DNA extraction is essential for genetic research on marine species; however, obtaining sufficient DNA from single fish eggs remains challenging. Existing protocols often require optimization to achieve high PCR efficiency. The optimized phenol–chloroform–isoamyl extraction protocol presented in this paper improves DNA yield and quality from individual eggs of Atlantic bluefin tuna (Thunnus thynnus), bogue (Boops bops), saddled seabream (Oblada melanura), and painted comber (Serranus scriba) by modifying buffer volumes, incubation times, and washing steps, following prior micropuncturing of eggs on a glass slide. DNA quality is confirmed by spectrophotometry, PCR amplification of the mitochondrial COI gene, electrophoresis, and Sanger sequencing. This method provides a low-cost and effective approach for species identification from individual fish eggs.
Plant Science
An Optimized Protocol for TurboID-Based Proximity Labeling and Sample Preparation for Mass Spectrometry in Arabidopsis thaliana
Plant proximity labeling proteomics enables the identification of transient and weak intracellular protein interactions that are undetectable via traditional biochemical assays. Conventional enrichment pipelines suffer severe quantitative bias caused by urea-derived chemical artifacts and high mass spectrometry background signals from sample- and carrier-derived impurities. This protocol describes a complete standardized workflow for biotinylated protein extraction, enrichment, and LC-MS/MS sample preparation optimized for Arabidopsis seedlings. The procedure integrates controlled urea dilution and pre-desalting to suppress non-enzymatic protein modifications, introduces acetylation blocking of streptavidin magnetic beads to mitigate streptavidin degradation during on-bead digestion, and applies two-step on-bead trypsin digestion to improve peptide coverage. Multi-point sample retention and dual protein quantification are implemented throughout all experimental stages to ensure full-process quality control. Subsequent data processing pipelines using Spectronaut for data-independent acquisition (DIA) data and MaxQuant for data-dependent acquisition (DDA) data are also detailed for consistent proteome quantification. This workflow delivers higher protein recovery and better signal-to-noise ratios than standard protocols while offering flexible adaptation for various crop proximity labeling and affinity enrichment proteomic research.
Serial Cryosectioning for the Spatial Transcriptomics of Plant Tissues
Spatial transcriptomics enables genome-wide gene expression profiling while preserving tissue architecture, making it a powerful approach for studying plant developmental transitions. However, preparing small and structurally complex plant tissues for spatial transcriptomics remains technically challenging because samples must be rapidly preserved, precisely oriented, serially sectioned, and accurately positioned within the limited capture area of the Visium slides. Here, we describe an optimized workflow for cryo-embedding, serial cryosectioning, section placement, and data analysis of small plant samples for 10x Genomics Visium spatial transcriptomics. Using maize seedling shoot apices as the target, this protocol includes preparation of custom molds for optimal cutting temperature embedding, rapid fresh sample embedding, serial cryosectioning, section-position marking for Visium HD workflows, and morphological quality assessment of replicate tissue slides before transcript capture. The associated data analysis workflow includes Space Ranger processing, Seurat-based normalization and Harmony integration, anatomical domain annotation, pseudobulk and developmental trend analyses, RNA velocity, pseudotime analysis, transcription factor network analysis, single-cell reference mapping, and 3D transcriptome reconstruction. This computational workflow was developed and tested using maize Visium V1 data, but not Visium HD data. This protocol was used to generate serial spatial transcriptomes of maize shoot apices and developing leaf primordia, enabling reconstruction of gene expression transitions from the shoot apical meristem to sequential leaf developmental stages. The approach is also applicable to other small plant tissues, including Arabidopsis first true leaves and Marchantia thalli.
Stem Cell
Disease Modeling in iPSC-Derived Human Bone Marrow Organoids
Human bone marrow organoids provide a tractable three-dimensional platform for modeling hematopoiesis and hematologic disease in a human niche–like context. Here, we describe a stepwise protocol for utilizing human induced pluripotent stem cell (iPSC)-derived bone marrow organoids that support autonomous hematopoiesis for hematopoietic disease modeling, mouse xenograft hematopoiesis, and drug sensitivity testing. The workflow combines embryoid body formation, early mesoderm/angiogenic induction under hypoxia, hemogenic endothelial commitment, maturation within a collagen-containing hydrogel, and subsequent suspension culture as individual organoids. The resulting organoids contain endothelial, stromal, and hematopoietic components and reproduce key structural and cellular features of human marrow. We further describe procedures for engraftment of normal donor- or patient-derived CD34+ cells and implantation of mature organoids under the renal capsule of immunodeficient mice to assess in vivo hematopoietic maintenance. In prior applications of this platform, donor-derived CD34+ cells were shown to engraft within the organoid niche and undergo multilineage differentiation, enabling detection of selective erythroid defects caused by DDX41 deficiency and assessment of therapeutic suppression of JAK2V617F-mutant patient-derived hematopoietic cells in a human marrow–like microenvironment. This protocol, therefore, enables disease modeling, in vivo xenograft assessment, and ex vivo functional analysis of patient-derived hematopoietic cells using relatively small input samples.