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A continuous membrane. A flexible scaffold. Growth through local interaction.
Separate mechanics test. Experimental 2.5-D model, not validated biological predictions. Whole-cell crawling remains weak. Existing cell-growth laboratories are unchanged.
Material length excludes elastic stretch. Soma height comes from a reduced volume constraint.
Computed activity, not a prescribed moving marker. Horizontal position is normalized arclength as the process grows.
The reference video could not be loaded. Open the original eLife videos. The simulation does not depend on video availability.
Reference films streamed on demand from the publisher’s video host · Winans, Collins & Meyer (2016), eLife 5:e12387 · CC BY 4.0. Experimental sample times differ from video playback times.
No pixel-level tracking or fit was performed. These films guide which mechanisms to test, not a claim that this engine reproduces their measured dynamics.
The first round-to-spread cell is an engineering experiment. These videos mostly begin with already-formed neurites.
This is a new independent mechanics prototype. It is not the earlier fixed-centerline transport demonstration and does not replace the deployed Cell Growth Lab.
A 48-site deformable cortical ring encloses an oblate soma. Adhesive spreading competes with effective cortical tension and area elasticity. A finite nucleus supplies a minimum soma-height constraint. Structural outgrowth withdraws volume from the body approximation.
Bookkeeping conserves a reduced body + shaft volume proxy. The rendered irregular skin, widening waves and filopodia are not independently volume-integrated. Membrane area/exocytosis are not yet conserved.
Each neurite is an extensible, bending chain. Its root shares forces with the soma or its parent process. Actomyosin recovery shortens the mechanical rest target, while lasting growth adds structural rest length from a finite transported supply. Tip fingers sweep, elongate, catastrophize, bind, load, and release. Each is covered by the same continuous cell mask.
Microtubules do not stick through the plasma membrane. The fingers represent actin-rich membrane protrusions with a coarse internal microtubule-invasion fraction. Gold lines visualize the flexible coarse scaffold, not resolved microtubules.
Each scaffold interval has an excitable activator and a slower recovery variable. Asymmetric nearest-neighbor coupling gives anterograde propagation. Ignition is stochastic and locally refractory; a user pulse is an explicit experimental intervention. Width, microtubule support, cargo flow, and growth respond locally to the computed field.
These are phenomenological excitable equations, not identified actin biochemistry. The soma-initiated bias is a modeling assumption. The coefficients were not estimated from the paper.
New primary processes require a persistent cortical hotspot. Lateral branches require retained exploratory protrusions, internal support, and a stochastic stabilization step. No neuron shape is pre-drawn. A spatial hash restricts contact searches. Neurite crossings remain separate graph edges; this 2.5-D implementation does not resolve physical 3-D overpasses, full membrane collisions, synapses, axon identity, or electrical activity.
Winans et al. (2016) supports coupled actin waves, transient shaft widening, microtubule polymerization, transport, and intermittent early neurite extension. Flynn et al. (2009) reports growth-cone-like waves and branch-associated shaft protrusions. Bard et al. (2008) and Nichol et al. (2016) support adhesion–actin coupling and traction. Li et al. (2015) provides a non-neuronal mechanical spreading reference; it is not a neuronal calibration.
A contrasting 2017 study found wave-associated retraction and exploration without increased net elongation in its cultures. This engine therefore tests a wave-coupled growth hypothesis, not a universal rule that every actin wave must lengthen a neurite.
Verification is not biological validation. Neither individual microtubules, membrane chemistry, realistic material constants, molecular cargo species, nor developmental cell identity are resolved. Whole-cell crawling remains weak; tip growth is not proof of soma locomotion. See the model and deployment notes.