Quox-1, a quail homeobox gene expressed in the embryonic central nervous system, including the forebrain

This paper reports the cloning and sequencing of a quail homeobox-containing gene, Quox-1, and its expression pattern in embryos from 3 to 6 days (E3 to E6) of development as determined by in situ hybridization. The opening reading frame in cDNA clone g11 corresponds to a predicted protein of 242 amino acids. Quox-1 protein displays high sequence similarity to the Antennapedia family, especially to the mouse homeodomain-containing protein Hox-1.1 (100% identity in the homeobox region, 77% at the 5' end beyond the homeobox). However, the carboxyl-terminal domain of the postulated protein has no significant homology with other known homeoproteins, including Hox-1.1. In situ hybridization experiments showed that Quox-1 is widely expressed in the developing central nervous system including the entire brain and the spinal cord. Outside the central nervous system, transcription of Quox-1 was mainly detected in the endoderm-derived epithelium of esophagus, trachea, and other digestive organs, as well as in the sensory epithelium of the olfactory region and perichondrium of the vertebrae. Thus, Quox-1 transcripts have a remarkably wide distribution that, unlike the other vertebrate homeobox genes examined to date, encompasses the rostral part of the developing nervous system, including the forebrain.