Practice question

Morphogens are secreted or diffusible molecules that specify multiple fates in dose-dependent manner, including Sonic hedgehog, FGF8 and BMP4 which pattern neural tube, limb buds and mesoderm via graded Smad or Gli activation. Myosin is intracellular actin-based motor protein generating contractility during cytokinesis, adhesion and cell migration, not secreted signaling ligand forming extracellular gradient. While myosin activity influences morphogenetic movements and tissue folding, it does not encode positional information via concentration thresholds or activate specific target enhancers in neighboring cells. Hence Myosin lacks defining morphogen properties of long-range diffusion, graded distribution and concentration-dependent transcriptional response.