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Spatial Transcriptomics

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1,607prerequisites beneath it

RNA-seq Analysis Pipeline Single-Cell RNA Sequencing→

Core Idea

Spatial transcriptomics measures gene expression while preserving the spatial location of each measurement within a tissue section. Sequencing-based methods (10x Visium, Slide-seq) capture mRNA on spatially barcoded arrays, providing transcriptome-wide coverage at defined locations. Imaging-based methods (MERFISH, seqFISH) use multiplexed fluorescence in situ hybridization to detect hundreds to thousands of genes at single-molecule resolution within intact tissue. By retaining spatial context that scRNA-seq loses during dissociation, spatial transcriptomics reveals how gene expression varies across tissue architecture, identifies spatial domains and niches, and maps cell-cell communication patterns.

How It's Best Learned

Analyze a 10x Visium dataset from a mouse brain section using Squidpy or Scanpy: visualize gene expression overlaid on the tissue image, identify spatially variable genes, and map clusters to anatomical regions. Compare to a dissociated scRNA-seq dataset from the same tissue and note what spatial information was lost in the scRNA-seq.

Common Misconceptions

10x Visium spots are not single cells — each 55-micrometer spot captures RNA from approximately 1-10 cells, requiring computational deconvolution to estimate cell type composition per spot.
Spatial transcriptomics does not yet provide the same transcriptome-wide coverage at single-cell resolution in a single technology — there is a tradeoff between the number of genes measured and spatial resolution.

Explainer

Single-cell RNA sequencing revealed that tissues are composed of diverse cell types with distinct transcriptional programs. But by dissociating tissue into single cells, scRNA-seq destroys the very thing that makes a tissue a tissue: the spatial organization of cells. Which cells are next to which? How does gene expression change from the center to the edge of a tumor? Where exactly in the brain is a particular gene expressed? Spatial transcriptomics answers these questions by measuring gene expression in situ — within intact tissue sections.

Sequencing-based methods work by placing a tissue section onto a surface printed with spatially barcoded oligonucleotides. When RNA is released from the tissue (by permeabilization), it hybridizes to the barcoded probes, which capture it at known locations. After reverse transcription and sequencing, each read carries both the gene identity and the spatial barcode, enabling reconstruction of a spatial gene expression map. 10x Genomics Visium, the most widely used platform, prints ~5,000 spots (each 55 micrometers in diameter, spaced 100 micrometers apart) on a capture area. This provides transcriptome-wide coverage but at multi-cell resolution — each spot captures RNA from several cells. Newer methods like Slide-seq (10-micrometer beads) and Stereo-seq (sub-cellular resolution) are pushing spatial resolution finer.

Imaging-based methods take the opposite approach: they visualize individual RNA molecules in situ using multiplexed FISH. MERFISH (Multiplexed Error-Robust Fluorescence In Situ Hybridization) encodes each RNA species with a unique combination of fluorescent probes across multiple rounds of imaging. A gene detected in rounds 1, 3, and 5 (but not 2, 4, and 6) has a unique binary barcode that identifies it. Error-robust encoding schemes tolerate missed or false hybridizations. seqFISH uses a sequential barcoding strategy for similar results. These methods achieve single-molecule, subcellular resolution but are limited in gene number (hundreds to low thousands) and require specialized microscopy.

The analytical challenge is integrating spatial and molecular information. Spatially variable gene detection identifies genes whose expression shows significant spatial patterns (gradients, hot spots, domain boundaries). Spatial domain identification segments the tissue into regions with coherent expression programs, often corresponding to anatomical structures. Deconvolution (for multi-cell-resolution data like Visium) estimates the cell type composition of each spot by combining the spatial data with a scRNA-seq reference. Cell-cell communication analysis maps ligand-receptor interactions between spatially adjacent cells. These analyses are producing spatial cell atlases of organs in health and disease, revealing how tissue microenvironments shape cell behavior in ways that dissociated studies could never capture.

Practice Questions 3 questions

Prerequisite Chain

Understanding Zero → The Number Zero → Counting to Five → Counting to 10 → One-to-One Correspondence → Counting a Set of Objects Up to 20 → Cardinality: The Last Number Counted → Matching Numerals to Quantities → Subitizing Small Quantities → Addition Within 10 → Making 10 as an Addition Strategy → Addition Within 20 → Doubles and Near Doubles → Doubles Facts Within 10 → Near Doubles Facts Within 20 → Mental Math Strategies for Addition → Mental Math: Adding and Subtracting Tens → Addition Within 100 → Repeated Addition as Multiplication → Multiplication as Equal Groups → Multiplication: Arrays → Basic Multiplication Facts (0s, 1s, 2s, 5s, 10s) → Multiplication Facts Within 100 → Division as Equal Sharing → Division as Grouping (Measurement Division) → Division: Grouping (Repeated Subtraction) Model → Division: Fair Sharing Model → Division as Equal Sharing → Division as Grouping → Basic Division Facts → Division Facts Within 100 → Multiplication and Division Fact Families → Relationship Between Multiplication and Division → Division Facts as Inverse of Multiplication → Remainders and Quotients in Division → Division Word Problems → Multi-Step Word Problems → Solving Multi-Step Word Problems → Multiplication Word Problems → Division Word Problems → Introduction to Long Division → Factors and Multiples → Prime and Composite Numbers → Equivalent Fractions → Relating Fractions and Decimals → Decimal Place Value → Integers and the Number Line → Comparing and Ordering Integers → Absolute Value → Adding Integers → Subtracting Integers → Multiplying Integers → Dividing Integers → Unit Rates → Proportions → Percent Concept → Converting Between Fractions, Decimals, and Percents → Operations with Rational Numbers → Two-Step Equations → Solving Multi-Step Equations → Equations with Variables on Both Sides → Angle Pairs: Complementary, Supplementary, and Vertical → Parallel Lines and Transversals → Corresponding Angles → Alternate Interior Angles → Triangle Angle Sum Theorem → Exterior Angle Theorem → Triangle Inequality Theorem → Similar Triangles: AA Similarity → Similar Triangles: SSS and SAS Similarity → Proportions in Similar Triangles → Right Triangle Trigonometry Introduction → Sine, Cosine, and Tangent Ratios → Trigonometric Ratios Review → Radian Measure → Converting Between Degrees and Radians → The Unit Circle → Graphing Sine and Cosine → Graphing Tangent and Reciprocal Trigonometric Functions → Derivatives of Trigonometric Functions → Antiderivatives → Iterated Integrals and Fubini's Theorem → Double Integrals in Cartesian Coordinates → Double Integrals in Polar Coordinates → Double Integrals in Polar Coordinates → Double Integrals: Definition and Setup → Iterated Integrals and Fubini's Theorem → Double Integrals over Rectangular Regions → Double Integrals over General Regions → Applications of Double Integrals: Area, Mass, and Moments → Triple Integrals in Cartesian Coordinates → Triple Integrals in Cylindrical and Spherical Coordinates → Change of Variables and the Jacobian Determinant → Applications of Triple Integrals: Volume and Mass → Vector Fields and Their Representations → Line Integrals of Vector Fields → Work and Circulation → Line Integrals of Scalar and Vector Functions → Fundamental Theorem for Line Integrals → Conservative Vector Fields → Conservative Vector Fields and Potential Functions → Curl and Divergence of Vector Fields → Curl and Divergence → Divergence Theorem → Electric Flux and Divergence Theorem → Gauss's Law: Integral Form and Meaning → Solving Problems with Gauss's Law → Conductors in Electrostatic Equilibrium → Capacitance and Capacitors → Dielectrics → Dielectric Constant and Relative Permittivity → Electric Field Inside Dielectric Materials → Dielectric Materials and Polarization → Dielectric Susceptibility and Permittivity → Energy Density in Electric Fields → Electric Current and Current Density → Electrical Resistance and Resistivity → Ohm's Law and Circuit Elements → Electromotive Force (EMF) and Batteries → Kirchhoff's Circuit Laws: Voltage and Current → DC Circuit Network Analysis Methods → Transient Response in RC Circuits → RC Circuits → LC and RLC Circuits → AC Circuits: Fundamentals → Impedance and Reactance → AC Power and Resonance → Electromagnetic Waves → Postulates of Special Relativity → Time Dilation → Length Contraction → Lorentz Transformation → Relativistic Velocity Addition → Relativistic Momentum and Energy → Mass-Energy Equivalence and E=mc² → Photons as Particles with Energy and Momentum → Planck-Einstein Relation: Energy and Frequency → Photoelectric Effect → The Photon: Light as Quanta → Compton Scattering → Wave-Particle Duality → de Broglie Wavelength → The Schrödinger Equation → State Vectors and Wavefunctions → Quantum Superposition → The Measurement Problem → Interpretations of Quantum Mechanics → Postulates of Quantum Mechanics → Observables and Quantum Operators → Commutators and Commutation Relations → Quantum Angular Momentum → Quantum Mechanical Treatment of Hydrogen → Solving the Schrödinger Equation for Hydrogen Atom → Quantum Numbers → Electron Configuration → Periodic Trends → Covalent Bonding → Electronegativity and Bond Polarity → Ionic Bonding → Lewis Structures → VSEPR Theory and Molecular Geometry → Molecular Geometry and Electron Pair Geometry → Molecular Polarity and Dipole Moments → Intermolecular Forces → States of Matter and Phase Changes: Melting, Boiling, and Sublimation → Gas Laws and the Ideal Gas Equation → Gas Stoichiometry and Volume-Volume Calculations → Thermochemistry and Enthalpy → Heat Capacity and Calorimetry → Entropy and Molecular Disorder → Spontaneity and ΔG → Entropy and Gibbs Free Energy → Chemical Equilibrium → Acid-Base Chemistry → Weak Acid Ionization → Weak Base Ionization → Acid and Base Strength: Ka, Kb, and Ionization → Leaving Groups and Nucleofugality → SN2 Substitution Reactions → SN1 Substitution Reactions → E1 Elimination Reactions → Alcohols and Ethers: Structure, Properties, and Nomenclature → Reactions of Alcohols → Aldehydes and Ketones: Structure and Reactivity → Oxidation Reactions in Organic Chemistry → Oxidation of Alcohols to Aldehydes and Ketones → Aldehyde and Ketone Structure and Nomenclature → Nucleophilic Addition to Aldehydes and Ketones → Carboxylic Acids and Their Derivatives → IUPAC Nomenclature of Carbonyls and Carboxylic Acids → IUPAC Nomenclature of Alkenes → Electrophilic Addition to Alkenes → Aromaticity and Benzene → Electrophilic Aromatic Substitution (EAS) → Nucleophilic Aromatic Substitution (SNAr) → Nucleophilic Acyl Substitution → Amines: Structure, Basicity, and Reactions → Amine Reactivity: Nucleophilicity and Basicity → Amino Acid Structure and Properties → Peptide Bonds and Polypeptide Formation → Protein Primary Structure → Protein Secondary Structure → Protein Tertiary Structure → Enzyme Structure and Function → Transcription: DNA to RNA → RNA Types and Structure → RNA Structure and Intramolecular Base Pairing → RNA Processing and Splicing → Translation: RNA to Protein → Ribosomes: Protein Synthesis Machines → Translation: Initiation and Elongation → Post-Translational Modifications → Proteasomal Degradation and Ubiquitin-Mediated Marking → Cell Cycle Regulation and Checkpoints → Mitosis → Cytokinesis → Meiosis → Chromosomal Theory of Inheritance → Mendelian Genetics → Dominance, Recessiveness, and Allelic Interactions → Sex-Linked Inheritance → Non-Mendelian Inheritance Patterns → Population Genetics and Hardy-Weinberg Equilibrium → Natural Selection → Adaptation and Fitness → Life History Strategies: r- and K-Selection → Predator-Prey Dynamics and the Lotka-Volterra Model → Community Ecology: Structure and Organization → Species Interactions: Competition, Predation, Mutualism, and Parasitism → Trophic Levels and Food Webs → Energy Flow and Ecological Efficiency → Biogeochemical Cycles: Carbon, Nitrogen, and Phosphorus → Nitrogen Fixation, Availability, and Cycling → Phosphorus Cycling and Freshwater-Marine Differences → Nucleotide Structure and Nomenclature → Purine Biosynthesis → Nucleotide Salvage Pathways → Nucleotide Synthesis Pathways (De Novo and Salvage) → Transcription Initiation and Gene Regulation → Gene Regulation in Eukaryotes → Promoters, Enhancers, Silencers, and Cis-Acting Elements → Chromatin Remodeling Complexes and Histone Acetylation → Genome Structure and Organization → Gene Prediction and Annotation → RNA-seq Analysis Pipeline → Differential Gene Expression Analysis → Single-Cell RNA Sequencing → Spatial Transcriptomics

Longest path: 248 steps · 1607 total prerequisite topics

Prerequisites (2)

Single-Cell RNA Sequencinghard RNA-seq Analysis Pipelinehard

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