EXPRESSION OF MURINE LHX5 SUGGESTS A ROLE IN SPECIFYING THE FOREBRAIN

A LIM homeobox gene, Lim5, is known to be expressed in the forebrain o f Xenopus and zebrafish (Toyama et al. [1995] Dev. Biol. 170:583-593). Results from developmental and comparative studies of its mouse ortho log, Lhx5, indicate that this gene may play important roles in forebra in development. Lhx5 expression is detected in the most anterior porti on of the neural tube at the headfold stage, overlapping partially wit h Otx2 expression domain, After neural tube closure, Lhx5 is expressed as a transverse stripe, covering most of the diencephalic primordium. This expression recedes to restricted areas as Dlx gene expression oc curs; By midgestation, both genes, Lhx5 and Dlx5, are expressed in the diencephalon and ventral telencephalon in an alternating complementar y pattern. It may be that Dlx inhibits Lhx5, and this may represent a step of early regionalization of the forebrain. Lhx5 is also expressed in midbrain, hindbrain, and spinal cord, overlapping extensively with Lhx1 starting from day E10.5 of gestation. The early, persistent, and dynamic expression of Lhx5 suggests a regulatory function in forebrai n formation. (C) 1997 Wiley-Liss, Inc.