HOMEOBOX GENE-EXPRESSION DURING DEVELOPMENT OF THE VERTEBRATE BRAIN

The study of gene-expression patterns in the embryonic forebrain provides insights into the underlying organization of this structure. The conventional interpretation of forebrain organization is based on the columnar model, developed by His, Herrick, Kuhlenbeck, and several other neuroembryologists. This model has become increasingly discordant with experimental evidence because it is based on an obsolete conception of the longitudinal axis in the forebrain that requires a discontinuity of the forebrain longitudinal axis, with more caudal parts of the neural tube, and because of its dependence on unreliable morphological landmarks (ventricular sulci) for the boundaries of forebrain subdivisions. This chapter describes homeodomain and its structure and discusses the homeobox genes expressed in the rhombencephalon, midbrain, forebrain, isthmus, and cerebellum. Homeobox genes are expressed in complex patterns of the brain, generally in multiple tissues during embryogenesis. © 1994 Academic Press Inc.