ASYMMETRIC EXPRESSION OF A NOVEL HOMEOBOX GENE IN VERTEBRATE SENSORY ORGANS

A novel homeobox gene, SOHo-1, was isolated from embryonic chicken ret ina. On embryonic day 2 (E2), SOHo-1 is expressed in the retina, poste rolateral 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. SOH o-1 expression in the otic Bit and otocyst is restricted to regions th at will give rise to the nonsensory tissues of the inner ear. SOHo-1 i s not closely related to any identified vertebrate or Drosophila homeo box-containing genes. Since it is expressed in sensory-related structu res and does not fit into existing classes of homeobox genes, we propo se the name SOHo-1, for sensory organ homeobox-1.