As discussed in Chapter 11, the regulation of gene expression plays a key role in the early development of organisms as diverse as flies and mammals. In many cases, such regulation involves transcription factors whose synthesis is regulated so that they are only produced at a particular time during development or in a particular region of the embryo. For example, the Oct4 factor is synthesized specifically in pluripotent cells of the early embryo and is important in maintaining their pluripotent nature (see Chapter 11, Section 11.1). Similarly, in both Drosophila and mammals, homeodomain-containing transcription factors are synthesized in particular regions of the embryo and control the production of different embryonic structures (see Chapter 11, Sections 11.2 and 11.3).<\/p>\n\n\n\n