Functions of BarH transcription factors during embryonic development

Byline: German Reig, Maria E. Cabrejos, Miguel L. Concha Keywords: Homeodomain; BarH; Barhl; FIL domains; Central nervous system; Eye; Development; Vertebrates; Drosophila Abstract: This paper reviews the developmental role of a group of homeobox-containing genes firstly described in the early nineties as critical factors regulating eye development in Drosophila. These genes received the name of BarH due to the Drosophila 'Bar' mutant phenotype and, since then, vertebrate homologues (named BarH-like or Barhl) have been described in a number of species of fish, amphibians and mammals. During embryonic development, BarH/Barhl are expressed primarily in the central nervous system where they play essential roles in decisions of cell fate, migration and survival. Transcriptional regulation mediated by these proteins involves either repression or activation mechanisms. In Drosophila, BarH is involved in morphogenesis and fate determination of the eye and external sensory organs, in regional prepatterning of the notum, and in formation and specification of distal leg segments. Vertebrate Barhl shares some functional properties with the fly counterparts, such as the ability to interact with basic helix-loop-helix (bHLH) proneural proteins, and plays crucial roles during cell type specification within the retina, acquisition of commissural neuron identity in the spinal cord, migration of cerebellar cells, and in cell survival within the neural plate, cochlea and cerebellum. Author Affiliation: Anatomy and Developmental Biology Program, Institute of Biomedical Sciences (ICBM), Faculty of Medicine, Universidad de Chile, Independencia 1027, Santiago, Chile Article History: Received 5 July 2006; Revised 6 September 2006; Accepted 5 October 2006