Quantitative analysis of peroxisome tracks using a Hidden Markov Model

Area of Science:

• Cell Biology
• Biophysics

Background:

• Molecular diffusion and organelle mobility are crucial for cellular functions, requiring molecules and organelles to interact within the cell.
• Observing and analyzing cellular migration dynamics, especially rare directed movements, is challenging due to resolution and analysis limitations.

Purpose of the Study:

• To accurately quantify and analyze the distinct migration modes of peroxisomes within living cells.
• To investigate the role of the peroxisomal membrane protein PEX14 and microtubule interactions in peroxisome directed migration.

Main Methods:

• Utilized high-resolution 2D spinning disc fluorescence microscopy to capture temporal diffusion tracks of thousands of individual peroxisomes.
• Applied a Hidden Markov Model with two hidden states to automatically identify and quantify directed migration segments.

Main Results:

• Demonstrated that peroxisomes exhibit both random and directed migration, with directed movement linked to microtubule binding.
• Showed that PEX14 knockout reduces directed migration by decreasing microtubule binding probability, but does not eliminate it.
• Nocodazole treatment, which disassembles microtubules, effectively eradicates directed peroxisome movement.

Conclusions:

• The study provides a robust method for analyzing organelle migration modes and switching dynamics.
• Identified PEX14 as a key but not exclusive factor in peroxisome-microtubule binding and directed migration.
• Highlights the critical role of microtubule integrity in directed organelle transport.