Zebrafish BarH-like genes define discrete neural domains in the early embryo

BarH (Barhl) genes encode for highly conserved homeodomain-containing transcription factors involved in critical functions during development, including cell fate specification, migration and survival. Here, we report the dynamic and restricted expression of three zebrafish barhl within the developing central nervous system. barhl2 becomes expressed in the late gastrula as a transverse diencephalic domain located immediately caudal to the prospective eyes. At early somitogenesis, barhl1.1 and barhl1.2 are expressed in the diencephalon in domains that partially overlap with the ventral and dorsal aspects of barhl2 expression, respectively. At later stages, expression of all zebrafish barhl shows large extent of overlap in the pretectum, tectum and dorsal hindbrain. The presence of a unique territory of barhl2 expression in the dorsal telencephalon and the high levels of expression in the retina are both consistent with expression reports of other Barhl2 orthologues, and support the subdivision of vertebrate Barhl into two paralogue groups based on the phylogenetic analysis of nucleotide and amino acid sequences.