Asymmetric expression of a novel homeobox gene in vertebrate sensory organs.

A novel homeobox gene, SOHo-1, was isolated from embryonic chicken retina. On embryonic day 2 (E2), SOHo-1 is expressed in the retina, posterolateral otic pit, and neural tube anterior to the spinal cord. On E4, SOHo-1 is expressed at high levels in anterior retina and low levels in posterior retina, suggestive of a role in patterning the anterior-posterior axis. It is also expressed on E4 in the otocyst, the dorsal root ganglia, some cranial ganglia, and the second branchial arch. SOHo-1 expression in the otic pit and otocyst is restricted to regions that will give rise to the nonsensory tissues of the inner ear. SOHo-1 is not closely related to any identified vertebrate or Drosophila homeobox-containing genes. Since it is expressed in sensory-related structures and does not fit into existing classes of homeobox genes, we propose the name SOHo-1, for sensory organ homeobox-1.