title: The evolution of early neurogenesis.
abstract: The foundation of the diverse metazoan nervous systems is laid by embryonic patterning mechanisms, involving the generation and movement of neural progenitors and their progeny. Here we divide early neurogenesis into discrete elements, including origin, pattern, proliferation, and movement of neuronal progenitors, which are controlled by conserved gene cassettes. We review these neurogenetic mechanisms in representatives of the different metazoan clades, with the goal to build a conceptual framework in which one can ask specific questions, such as which of these mechanisms potentially formed part of the developmental "toolkit" of the bilaterian ancestor and which evolved later.
authors.affiliation: Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA 90095, USA. Electronic address: volkerh@mcdb.ucla.edu.
authors.forename: Volker
authors.initials: V
authors.lastname: Hartenstein
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK. Electronic address: a.stollewerk@qmul.ac.uk.
authors.forename: Angelika
authors.initials: A
authors.lastname: Stollewerk
mesh_terms: D000818:Animals; D005075:Biological Evolution; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006801:Humans; D009420:Nervous System / Q000166:cytology*; D009424:Nervous System Physiological Phenomena; D055495:Neurogenesis / Q000502:physiology*