ETSAM: Effectively Segmenting Cell Membranes in cryo-Electron Tomograms

Cryogenic Electron Tomography (cryo-ET) is an emerging experimental technique to visualize cell structures and macromolecules in their native cellular environment. Accurate segmentation of cell structures in cryo-ET tomograms, such as cell membranes, is crucial to advance our understanding of cellular organization and function. However, several inherent limitations in cryo-ET tomograms, including the very low signal-to-noise ratio, missing wedge artifacts from limited tilt angles, and other noise artifacts, collectively hinder the reliable identification and delineation of these structures. In this study, we introduce ETSAM - a two-stage SAM2-based (1) fine-tuned AI model that effectively segments cell membranes in cryo-ET tomograms. It is trained on a diverse dataset comprising 83 experimental tomograms from the CryoET Data Portal (CDP) (2) database and 28 simulated tomograms generated using PolNet (3). ETSAM achieves state-of-the-art performance on an independent test set comprising 10 simulated tomograms and 15 experimental tomograms for which ground-truth annotations are available. It robustly segments cell membranes with high sensitivity and strong precision, achieving a more favorable precision–recall trade-off than other deep-learning methods. The ETSAM source code is freely available at https://github.com/jianlin-cheng/ETSAM .