Developing roles for Hox proteins in hindbrain gene regulatory networks

Hox proteins have long been known to function as transcriptional regulators during development of the vertebrate hindbrain. In particular, these factors are thought to play key roles in assigning distinct fates to the rhombomere segments arising in the embryonic hindbrain. However, it remains uncertain exactly how the Hox proteins fit into the regulatory networks controlling hindbrain formation. For instance, it is unclear if Hox proteins fulfill similar roles in different rhombomeres and if they are absolutely required for all aspects of each rhombomere fate. Recent advances in the discovery, characterization and functional analysis of hindbrain gene regulatory networks is now allowing us to revisit these types of questions. In this review we focus on recent data on the formation of caudal rhombomeres in vertebrates, with a specific focus on zebrafish, to derive an up-to-date view of the role for Hox proteins in the regulation of hindbrain development.