Getting a-head of the organizer: anterior-posterior patterning of the forebrain

The molecular mechanisms that drive the development of embryonic tissues ar e being uncovered rapidly. One such fascinating example is the development of the forebrain, the most anterior part of the nervous system. In this rev iew, we will discuss the mechanisms that induce the formation of the forebr ain in multiple vertebrate systems, placing emphasis on a recent article pu blished by Grinblat et al.((1)). Using zebrafish as a model system, these a uthors combine elegant embryological manipulations with the use of early ma rkers of the presumptive forebrain, to show that initial induction and patt erning of this tissue occurs near the onset of gastrulation. In addition, t heir results confirm observations made in other systems that planar signals , those traveling in the plane of the ectoderm, are involved in forebrain i nduction and patterning. BioEssays 21 :631-636, 1999. (C) 1999 John Wiley & Sons, Inc.