FAIR sharing of Chromatin Tracing datasets using the newly developed 4DN FISH Omics Format

Abstract: A key output of the NIH Common Fund 4D Nucleome (4DN) project is the open publication of datasets on the structure of the human cell nucleus and genome. In recent years, multiplexed Fluorescence In Situ Hybridization (FISH) and FISH-omics methods have rapidly expanded, enabling quantification of chromatin organization in single cells, sometimes alongside RNA and protein measurements. These approaches have deepened our understanding of how 3D chromosome architecture relates to transcriptional activity and cell development in health and disease. However, results from Chromatin Tracing FISH-omics experiments remain difficult to share, reuse, and analyze due to the absence of standardized data-exchange specifications. Building on the recent release of microscopy metadata standards, we introduce the 4DN FISH Omics Format-Chromatin Tracing (FOF-CT), a community-developed standard for processed results from diverse imaging techniques. Current studies generally use one of two representations: ball-and-stick, where genomic segments appear as individual fluorescence spots, or volumetric, representing them as clouds of single-molecule localizations. This manuscript focuses on ball-and-stick methods, including those from the pioneering study of Wang et al. (2016) and related techniques. We describe the FOF-CT structure and present newly deposited datasets in the 4DN Data Portal and the OME Image Data Resource (IDR), highlighting their potential for reuse, integration, and modeling. We also outline example analysis pipelines and illustrate biological insights enabled by standardized, FAIR-compliant Chromatin Tracing datasets.