The molecular basis of lymphatic vessel development
In both the venous and the lymphatic sections the embryonic veins form the basis for vessel formation.
In an initial differentiation step in the young embryo a portion of the endothelial cells in certain regions of the cardinal vein system begins to produce special receptor molecules (Prox-1). This is the first step in the direction of lymphatic vessel determimation. Now follow further expressions of receptor patterns that are characteristic for either blood or lymhatic vessels and which are preserved even into adulthood.
Whether an embryonic vessel differentiates into a vein or a lymphatic vessel depends initially on a gene, the Prox1 Homebox gene. Depending on the direction other receptors are formed during the course of development.
The embryonic lymphatic vessels stem originally from blood vessels. In certain regions of the cardinal vein system of the young embryo endothelial cells express special receptor molecules (Prox-1). This is the first step in the formation in the direction of lymphatic vessel formation. What this stimulation triggers in the Prox-1 Homebox gene that forms the basis for the vessel formation is not yet known. (interactive diagram)