P1: GDL May 1, 2001 10:35 Annual Reviews AR121-28 Annu. Rev. Neurosci. 2001. 24:869–96 Copyright c 2001 by Annual Reviews. All rights reserved EARLY ANTERIOR/POSTERIOR PATTERNING OF THE MIDBRAIN AND CEREBELLUM Aimin Liu1 and Alexandra L Joyner1,2 Howard Hughes Medical Institute and Developmental Genetics Program, Skirball Institute of Biomolecular Medicine, Departments of 1Cell Biology and 2Physiology & Neuroscience, New York University School of Medicine, New York, NY10016; e-mail:
[email protected],
[email protected] Key Words midbrain/hindbrain organizer, Fibroblast growth factor, Otx2, Gbx2, Engrailed ■ Abstract Transplantation studies performed in chicken embryos indicated that early anterior/posterior patterning of the vertebrate midbrain and cerebellum might be regulated by an organizing center at the junction between the midbrain and hindbrain. More than a decade of molecular and genetic studies have shown that such an organizer is indeed central to development of the midbrain and anterior hindbrain. Furthermore, a complicated molecular network that includes multiple positive and negative feedback loops underlies the establishment and refinement of a mid/hindbrain organizer, as well as the subsequent function of the organizer. In this review, we first introduce the expression patterns of the genes known to be involved in this patterning process and the quail-chick transplantation experiments that have provided the foundation for understanding the genetic pathways regulating mid/hindbrain patterning. Subsequently, we discuss the molecular genetic studies that have revealed the roles for many genes in normal early patterning of this region. Finally, some of the remaining questions and future directions are discussed.