Next, analysis of ligand–receptor genes in the different subpopulations revealed that the strongest interactions in the PCOS-endometrium involved ECM components, including collagen, laminin and fibronectin 1 (FN1) pathways, aligning with DEGs in major subpopulations (Fig. 5a,b, Extended Data Fig. 8a and Supplementary Table 4a–e). The gene discussed is FN1; the disease is polycystic ovary syndrome.