Otx and Emx homeobox genes in brain development

Over the last few years great progress has been made in the understanding o f the formation and regionalisation of the mouse brain. In this review we w ill focus our attention on two families of homeobox-containing genes essent ially coding for four transcription factors involved in brain and forebrain development: the two Emx and the two Otx genes. Here we describe the expre ssion pattern of these genes in the developing mouse, as well as the charac terisation of the corresponding knockout mice with special emphasis on Emx2 . Whereas Otx genes are clearly involved in the formation and regionalisati on of the whole rostral brain, comprised of forebrain and midbrain, our dat a suggest a role for Emx2 in the specification of the cytoarchitecture of t he cerebral cortex, achieved through the control of proliferation of neuron al precursors and of migration of newly-formed neurons to their final desti nation.