How does a cell in your spleen know how to express spleen genes

During growth and development of the embryo, the multipotent cells move to particular regions of the embryo and begin to differentiate - beginning in the gastrulation stage. The cells vary in the silencing of particular genes so that they produce only the appropriate proteins for the specific function of the organs that they develop into. Silencing means particular areas of the genetic material are inaccessible to polymerase enzymes because they are locked up into nucleosomes by histone complexes. Therefore the genes that are turned on in skins cells may differ slightly with those of the spleen cells.