Orientational lineage memory and mechanical ordering during diffusion-limited growth

TL;DR

This study models how nutrient-driven growth, mechanical forces, and cellular orientation inheritance influence collective organization and shape formation in multicellular assemblies, revealing a transition in nematic order and the role of lineage memory.

Contribution

It introduces a particle-based model that captures nutrient fields, cellular orientations, and inheritance, uncovering a transition in orientational order controlled by front morphology and mechanical interactions.

Findings

Nematic order transition depends on front morphology.

Strong inheritance leads to non-monotonic orientational order.

Mechanical interactions can override lineage memory in alignment.

Abstract

Growth and shape formation in crowded multicellular assemblies arise from the interplay of chemical gradients, single-cell expansion and mechanical interactions, making it essential to understand how these processes jointly shape collective organization. Using a particle-based model that resolves nutrient fields as well as cellular orientations and their inheritance, we investigate how orientational order emerges within expanding fronts whose morphology is set by nutrient limitation. We identify a transition in nematic order controlled by front morphology, with orientational memory influencing alignment only on one side of this transition. Under strong inheritance, orientational order varies non-monotonically: both thin active layers (fingering morphologies) and thick active layers (flat fronts) produce strong alignment, whereas intermediate cases are less ordered. Analysis of velocities, reorientation statistics, and stress anisotropies shows that this behavior reflects a shift from inheritance-dominated to mechanically driven alignment that overrides lineage memory. The resulting differences in front speed produce a fitness advantage of orientational memory only in the diffusion-limited, memory-dominated regime. These findings elucidate how nutrient supply, mechanical interactions, and single-cell expansion together shape self-organization during growth.