| 1. Domain | 1.1 Scope of the Domain | Boundaries | The range of phenomena the science includes and excludes. | Focuses on how cells generate, maintain, and remodel their shape, and how they move through space using cytoskeletal systems, adhesion structures, force generation, and polarity. Includes actin/microtubule dynamics, protrusion formation, contraction, migration modes, shape transitions, and mechanical–biochemical coupling. Excludes organism-level locomotion, tissue-scale movement, or whole-organ shape changes except where rooted in single-cell behaviors. |
| | Scale | The spatial, temporal, or organizational level at which the science operates (e.g., quantum, cellular, social, cosmic). | Operates at nanometer scales (filament subunits), micrometer scales (whole-cell morphology), and timescales ranging from milliseconds (actin polymerization, motor stepping) to minutes/hours (cell migration, shape remodeling). |
| 1.2 Ontological Commitments | Entities | The kinds of things assumed to exist within the domain (particles, organisms, agents, fields, etc.). | Actin filaments, microtubules, intermediate filaments, motor proteins (myosin, kinesin, dynein), focal adhesions, integrins, Rho-family GTPases, membrane protrusions (lamellipodia, filopodia, blebs), contractile networks, polarity complexes. |
| | Properties | The fundamental attributes these entities possess (mass, charge, genotype, preference, etc.). | Polymerization rate, depolymerization rate, filament stiffness, adhesion strength, contractility, cortical tension, membrane elasticity, polarity state, diffusion coefficients of regulators, protrusion velocity, traction force. |
| | Categories | The basic ontological types used to classify domain elements (substances, processes, relations, structures). | Motility modes (mesenchymal, amoeboid, collective, swimming), protrusion types (lamellipodia, filopodia, blebs), cytoskeletal systems (actin, microtubules, intermediate filaments), adhesion classes (focal adhesions, nascent adhesions), polarity regimes (front–rear, rotational, multi-axial). |
| 1.3 State-Variables | Variables | The measurable or definable properties that describe system conditions. | Cell shape descriptors (area, curvature, aspect ratio), protrusion dynamics, actin density, microtubule organization, cortical tension, adhesion number and size, polarity vector, traction-force distribution, migration speed, persistence. |
| | Parameterization | How variables encode and represent the system’s state. | State encoded through quantitative morphometrics, time-series protrusion maps, filament-density profiles, force-distribution fields, polarity vectors, stochastic stepping rates, and migration trajectories. |
| 1.4 Admissible Idealizations | Simplifications | Conceptual reductions used to make the domain tractable (point masses, rational agents, perfect gases). | Modeling cells as viscoelastic droplets; treating cytoskeletal networks as continuous gels; simplifying shape to 2D outlines; representing protrusions as idealized geometries; ignoring intracellular heterogeneity; linearizing motor-generated forces. |
| | Validity Conditions | The limits and contexts in which idealizations hold or break down. | Breaks down when cells exhibit highly irregular shapes, switch motility modes, undergo rapid polarity changes, experience spatially heterogeneous environments, or when filament networks behave strongly nonlinearly. |
| 1.5 Domain Assumptions | Structural Assumptions | Background ontological stances such as determinism, continuity, randomness, discreteness. | Motility relies on regulated cytoskeletal assembly and force generation; polarity emerges from biochemical gradients; adhesions transmit traction; morphology reflects mechanical–biochemical equilibrium; movement integrates protrusion + adhesion + contraction cycles. |
| | Implicit Commitments | Unstated but necessary assumptions that shape the field’s conceptual structure. | Assumes cytoskeletal integrity, reliable polymerization dynamics, stable regulatory gradients, consistent adhesion–force coupling, and predictable membrane mechanics across motility cycles. |
| 1.6 Internal Coherence Requirements | Consistency | The demand that domain concepts do not contradict one another. | Cytoskeletal mechanics, adhesion dynamics, polarity regulation, and force-generation models must not contradict each other; shape transitions must align with known biochemical constraints. |
| | Compatibility | The requirement that entities, variables, and assumptions fit together into a unified descriptive framework. | Adhesion systems, cytoskeletal networks, motor proteins, polarity regulators, membrane mechanics, and migration trajectories must integrate into a unified framework describing how cells adopt and change shape while generating motion. |
| 2. Evidence Layer | 2.1 Observable Phenomena | Observables | The aspects of the domain that can produce detectable signals accessible to measurement. | Protrusion dynamics (lamellipodia, filopodia, blebs), actin polymerization waves, focal-adhesion formation and turnover, cytoskeletal reorganization, migration trajectories, cell-shape transitions, traction-force patterns, polarity establishment and switching, microtubule dynamics. |
| | Detection Limits | The boundaries of what can be resolved or sensed by current instruments or methods. | Spatial limits of optical and super-resolution imaging (~200 nm → ~20–50 nm); temporal limits of high-speed imaging for fast protrusions (ms–s); sensitivity of force sensors; difficulties detecting low-density actin structures or rapid, transient shape fluctuations. |
| 2.2 Measurement Systems | Units | Standardized quantifications (meters, seconds, volts, decibels, dollars, etc.) necessary for consistent comparison. | µm, nm (shape/morphology), seconds–minutes (motility events), µm/s (migration speed), pN–nN (traction force), curvature units, fluorescence intensity (cytoskeletal density), step-size distributions for motor activity. |
| | Instruments | Devices and tools (microscopes, spectrometers, sensors, surveys, detectors) used to produce measurements. | Live-cell fluorescence microscopy, confocal and super-resolution systems (STED, SIM, PALM/STORM), TIRF microscopes, traction-force microscopy setups, AFM, micropipette aspiration, lattice light-sheet microscopes, automated morphometric analysis platforms, cytoskeletal reporters. |
| 2.3 Operational Definitions | Definitions | Terms defined by specific measurement procedures, ensuring empirical clarity. | Morphology defined by curvature, area, and protrusion metrics; motility defined by speed, persistence, and directional bias; adhesion turnover defined by lifetime of focal contacts; polarity defined by localization of regulatory proteins and force asymmetry. |
| | Procedures | The explicit steps required to perform a measurement in a reproducible way. | Time-lapse microscopy of cytoskeletal reporters, traction-force measurement protocols, automated shape segmentation, single-cell tracking, motor stepping assays, actin-flow mapping, focal-adhesion marker imaging, membrane-deformation measurements. |
| 2.4 Data Acquisition | Protocols | Formal processes for gathering data under controlled or standardized conditions. | Standardized imaging intervals, consistent expression levels of reporters, controlled substrate stiffness, stable environmental conditions, replicate time-lapse recordings, parallel control groups, high-sensitivity detection for dynamic cytoskeletal events. |
| | Sampling | Rules determining which subset of the domain is measured and how representative it is. | Choosing representative cells, capturing sufficient timepoints for dynamic shape/migration events, sampling across regions of varying mechanical conditions, avoiding selection bias from highly motile or highly static subpopulations. |
| 2.5 Data Character & Format | Data Types | The form raw evidence takes (time series, spectra, images, counts, qualitative records). | Time-lapse image stacks, protrusion-speed maps, traction-force fields, migration trajectories, shape-descriptor matrices, cytoskeletal density heatmaps, filament-orientation maps, step-size distributions, morphodynamic feature vectors. |
| | Resolution | The granularity or precision with which data is captured. | Spatial resolution set by imaging platform; temporal resolution determined by acquisition rate; mechanical-resolution determined by force-sensor sensitivity; segmentation and tracking resolution constrained by SNR in fluorescence channels. |
| 2.6 Reliability & Calibration | Calibration | Adjustment procedures ensuring instruments produce accurate results. | AFM cantilever calibration, traction-gel stiffness calibration, fluorescent reporter intensity calibration, microscope alignment checks, drift correction, uniformity checks for substrate coating, motor stepping calibration using known standards. |
| | Error Characterization | Identification and quantification of noise, uncertainty, bias, and measurement error. | Identifying noise from motion blur, segmentation errors, photobleaching, fluorophore blinking, variations in substrate stiffness, tracking inaccuracies, camera noise, and cytoskeletal signal heterogeneity; distinguishing random vs systematic error. |
| 3. Structural Layer | 3.1 Patterns & Regularities | Laws / Relations | Stable, repeatable patterns governing how observables behave across conditions. | Protrusion formation correlates with actin polymerization at the leading edge; traction forces scale with adhesion size and substrate stiffness; migration speed and persistence follow conserved polarity–adhesion–contraction relationships; microtubule orientation predicts directionality; shape change follows mechanical equilibrium between cortex tension and cytoskeletal forces. |
| | Invariants | Quantities or properties that remain constant under transformations (symmetries, conservation laws). | Conserved actin–myosin contractile units; stable polarity axes during persistent migration; characteristic filament organization patterns; fixed relationships between adhesion size and traction force; reproducible cycles of protrusion → adhesion → contraction → rear retraction. |
| 3.2 Causal Architecture | Mechanisms | Underlying processes or structures that produce the observed regularities. | Actin polymerization generates pushing forces for protrusion; myosin contractility drives rear retraction; integrins form mechanical linkages enabling traction; Rho-family GTPases regulate polarity and cytoskeletal assembly; microtubules coordinate long-range force balance and intracellular transport; membrane tension regulates protrusion competition. |
| | Pathways | Organized sequences of interactions forming a causal chain or network. | Actin-driven motility pathway (Rac → Arp2/3 → branched actin); contraction pathway (RhoA → ROCK → myosin II); adhesion assembly/disassembly cycle; polarity-establishment circuits (Cdc42/Rac/Rho); protrusion competition pathways; mechanical feedback loops integrating traction and actin flow. |
| 3.3 Theoretical Vocabulary | Concepts | Core terms that encode the domain’s structure (force, gene, equilibrium, field). | Protrusion, contraction, polarity, tension, actin flow, focal adhesion, lamellipodia, filopodia, blebbing, persistence, cortical stiffness, cytoskeletal remodeling, motility modes, force balance. |
| | Classifications | Taxonomies, categories, or typologies that organize entities and relations. | Motility modes (mesenchymal, amoeboid, collective, bleb-driven), protrusion types (lamellipodia, filopodia, blebs), adhesion classes (nascent, focal, fibrillar), polarity regimes (front–rear, rotational, multi-axial), cytoskeletal systems (actin, microtubules, intermediate filaments). |
| 3.4 Formal Representations | Equations | Mathematical constructs expressing laws, relations, or mechanisms. | Force–balance equations for cell shape; polymerization–depolymerization kinetics; reaction–diffusion equations for polarity regulators; traction–stress equations; membrane-tension models; motility equations linking speed to adhesion, force, and protrusion rate. |
| | Models | Structured representations—mathematical, computational, or conceptual—used to predict and explain phenomena. | Actin-network mechanical models; polarity reaction–diffusion models; agent-based motility simulations; continuum models of the cytoskeleton; force-balance cell-shape models; protrusion–adhesion–contraction cycle models; microtubule-guided directionality models. |
| 3.5 Idealized Structures | Simplified Models | Purposeful abstractions that capture essential dynamics while omitting irrelevant detail. | Treating cells as viscoelastic droplets; modeling the cytoskeleton as a uniform gel; assuming a single dominant polarity axis; simplifying protrusions to ideal geometric shapes; linearizing contractile forces; ignoring subcellular heterogeneity and complex 3D morphology. |
| | Limit Conditions | Regimes where specific models or approximations hold (classical vs. quantum, linear vs. nonlinear). | Fail in highly irregular or rapidly changing shapes, multi-protrusion states, 3D-confined environments, mechanically heterogeneous substrates, extreme actin remodeling rates, or when motility mode switches occur (e.g., amoeboid ↔ mesenchymal). |
| 3.6 Integrative Frameworks | Unifying Theories | Higher-order structures that connect disparate laws or mechanisms under a coherent whole. | Motility as an integrated system coupling actin polymerization, adhesion mechanics, polarity circuits, and contractile forces; morphology as the emergent equilibrium of biochemical regulation, force generation, and membrane mechanics; migration governed by coordinated protrusion–adhesion–contraction cycles. |
| | Interdisciplinary Links | Points where the theory connects to adjacent sciences or larger explanatory systems. | Connects to biophysics (force mechanics, polymer physics), biomechanics (cell–substrate mechanics), developmental biology (morphogenetic movements), immunology (immune-cell motility), cancer biology (invasion modes), and materials science (engineered substrates). |
| 4. Method Layer | 4.1 Inquiry Design | Experimental Design | Structured plans for manipulating variables to test causal claims. | Perturbing actin or microtubule dynamics, inhibiting or activating Rho-family GTPases, altering substrate stiffness, modulating adhesion-ligand density, manipulating membrane tension, or expressing motility reporters to determine causal effects on shape, protrusion dynamics, and migration behavior. |
| | Observational Design | Systematic approaches for gathering non-manipulated data (surveys, field studies, natural experiments). | Tracking spontaneous cell-shape fluctuations, natural migration trajectories, endogenous protrusion cycles, unperturbed adhesion turnover, cytoskeletal remodeling, and polarity switching without applied interventions. |
| 4.2 Testing & Validation | Hypothesis Testing | Procedures for evaluating whether evidence supports or contradicts specific claims. | Evaluating predicted effects of perturbations on migration speed, directionality, persistence, protrusion rate, traction-force distribution, or polarity stability; testing whether specific regulators drive expected morphological transitions. |
| | Replication | The requirement that results be independently reproducible under similar conditions. | Repeating migration assays, traction-force measurements, shape-segmentation analyses, cytoskeletal reporter imaging, and mechanical perturbation experiments under identical conditions to ensure reproducibility. |
| 4.3 Inference & Evaluation | Statistical Inference | Rules for drawing conclusions from noisy or incomplete data. | Quantifying variability in protrusion dynamics, migration trajectories, adhesion lifetimes, force maps, and polarity fluctuations; determining significance of observed differences between conditions or motility modes. |
| | Model Comparison | Criteria (fit, simplicity, predictive accuracy, robustness) used to evaluate competing models. | Comparing force-balance models, reaction–diffusion polarity models, agent-based motility simulations, actin-network mechanical models, and shape-evolution models based on predictive accuracy, robustness, and goodness of fit. |
| 4.4 Error Management | Error Analysis | Identification and quantification of random and systematic errors. | Identifying errors from segmentation failures, motion blur, photobleaching, drift, inaccurate force calibration, uneven substrate coating, tracking noise, and fluctuations in cytoskeletal reporter expression. |
| | Bias Control | Methods for minimizing subjective, instrumental, or procedural biases. | Standardizing imaging conditions, substrate preparation, reporter expression, force-calibration methods, and blinding migration or morphometric analyses; validating probe specificity and mechanical-sensor accuracy. |
| 4.5 Adjudication & Revision | Peer Scrutiny | Collective evaluation of claims through critique, review, and debate. | Reviewing interpretations of motility modes, shape transitions, protrusion–adhesion–contraction cycles, force-generation mechanisms, and polarity dynamics through lab peer review, replication attempts, and external literature comparisons. |
| | Theory Revision | Procedures for modifying, replacing, or discarding models based on new evidence. | Updating mechanical, biochemical, or shape-evolution models when new evidence reveals alternative motility modes, unexpected force asymmetries, novel polarity circuits, or non-canonical cytoskeletal behaviors. |
| 4.6 Integrity Conditions | Transparency | Requirements to disclose methods, data, assumptions, and limitations. | Full disclosure of imaging parameters, segmentation algorithms, force-calibration methods, substrate conditions, perturbation schemes, tracking pipelines, normalization procedures, and all modeling assumptions. |
| | Ethical Standards | Norms ensuring responsible conduct in experimentation, data handling, and publication. | Ensuring responsible use of engineered substrates, accurate representation of motility data, avoiding misinterpretation or selective omission, maintaining safe and ethical handling of cell lines and motility reporters. |