The article "Receptor Specificity of the Fibroblast Growth Factor Family" by David M. Ornitz et al. investigates the ligand-receptor interactions of fibroblast growth factors (FGFs) and their receptors. FGFs are essential for mammalian development, and their activity is regulated by ligand binding specificity, heparan sulfate proteoglycans, and the differential signaling capacity of individual FGF receptors. The authors engineered mitogenically responsive cell lines expressing major splice variants of all known FGF receptors and assayed the mitogenic activity of nine FGF ligands on these cell lines. They found that FGF 1 is the only FGF that can activate all FGF receptor splice variants. Using FGF 1 as an internal standard, they determined the relative activity of all other FGFs. The study provides a biochemical foundation for understanding developmental, physiological, and pathophysiological processes involving FGF signaling pathways. The results highlight the importance of ligand-receptor pairs in FGF signaling and suggest that FGF 1 may functionally define a core FGF-binding domain.The article "Receptor Specificity of the Fibroblast Growth Factor Family" by David M. Ornitz et al. investigates the ligand-receptor interactions of fibroblast growth factors (FGFs) and their receptors. FGFs are essential for mammalian development, and their activity is regulated by ligand binding specificity, heparan sulfate proteoglycans, and the differential signaling capacity of individual FGF receptors. The authors engineered mitogenically responsive cell lines expressing major splice variants of all known FGF receptors and assayed the mitogenic activity of nine FGF ligands on these cell lines. They found that FGF 1 is the only FGF that can activate all FGF receptor splice variants. Using FGF 1 as an internal standard, they determined the relative activity of all other FGFs. The study provides a biochemical foundation for understanding developmental, physiological, and pathophysiological processes involving FGF signaling pathways. The results highlight the importance of ligand-receptor pairs in FGF signaling and suggest that FGF 1 may functionally define a core FGF-binding domain.