Ensemble heterogeneity mimics ageing for endosomal dynamics within eukaryotic cells

Area of Science:

• Cellular and Molecular Biology
• Biophysics
• Statistical Mechanics

Background:

• Transport processes within living cells, such as endosome movement in eukaryotic cells, often exhibit anomalous diffusion.
• This cellular transport is characterized by significant heterogeneity in both space and time.
• Analyzing large datasets of single-particle trajectories is crucial for quantifying these heterogeneities and developing accurate mathematical models.

Purpose of the Study:

• To investigate the complex dynamics of endosomal transport in eukaryotic cells.
• To address central questions in anomalous dynamics, specifically ergodicity and statistical ageing, and their implications for mathematical modeling.
• To challenge the prevailing belief that non-ergodicity and ageing occur concurrently in anomalous diffusion.

Main Methods:

• Analysis of large ensembles of single-particle trajectories to quantify spatial and temporal heterogeneities.
• Application of concepts of ergodicity and statistical ageing to characterize the anomalous diffusion of endosomes.
• Development of novel analytical and modeling approaches for heterogeneous dynamics.

Main Results:

• Endosomal dynamics were found to be ergodic, contradicting typical assumptions for ageing systems.
• Despite being ergodic, endosomal motion exhibits statistical ageing, a paradoxical observation.
• This paradoxical behavior is attributed to ensemble heterogeneity, in addition to intra-trajectory space-time heterogeneity.

Conclusions:

• Endosomal motion presents a novel case of ergodic ageing, driven by ensemble heterogeneity.
• The findings necessitate revised mathematical models for anomalous diffusion, accounting for multiple layers of heterogeneity.
• This research introduces new methodologies for analyzing and modeling complex heterogeneous dynamics in biological systems, with potential applications in drug delivery.