TileScope quantifies spatial gene expression relationships beyond colocalization

Gene expression patterns within the same tissue region can exhibit similar correlation or enrichment, but still differ in their organization within regions and at their boundaries. We present TileScope, a framework for analysing genes and transcriptional programs within predefined tissue regions, their components and their contacts with neighbouring regions. TileScope combines regional enrichment, within-region correlation, cross-correlation over distance and expression differences near specific boundaries. Repeated spatial partitions and consensus aggregation show how these measurements depend on the grouping of spots or cells. Across 30 controlled constructions derived from glioblastoma and hepatocellular carcinoma data representing ten spatial expression scenarios, combined measurements separated arrangements that individual statistics left ambiguous, including coincident patches, gradients and expression localised at region boundaries. In 30 human glioblastoma sections, TileScope distinguished shared regional enrichment from internal covariation and identified hypoxia-associated expression localised at region boundary despite negligible within-region correlation. In newly acquired Visium profiles of control and myeloid-targeted MCT1-knockout (KO) orthotopic GL261 mouse gliomas, proliferation and myeloid programs were enriched in tumour peripheries but showed opposite within-periphery-region correlations. Proliferation was higher near the tumour-facing boundary in both samples, whereas myeloid expression was higher near the tumour-facing boundary in the control and farther within periphery in the KO condition. Xenium applications on glioblastoma and breast cancer samples demonstrated feasibility with irregularly spaced individual cells and different regional annotations. TileScope provides spatially explicit descriptions of gene and program relationships, linking their organization within tissue compartments to their sensitivity to aggregation.