Chick homeobox gene cbx and its role in retinal development.
Homeobox genes play important roles in animal development. We isolated a chick homeobox gene, cbx, and studied its function during embryonic development. The deduced Cbx protein contained 376 amino acid residues. Its homeodomain was related (with 65-71% sequence identity) to that of human Crx, human Cart-1, and chick Alx-4. On searching the human genome sequence, a human homologue was found, which had 78% overall sequence identity and a 100% identical homeodomain. In the developing chick retina, cbx was expressed in a small fraction of post-mitotic cells residing at anatomical locations typical of bipolar cells. These cells were Goalpha(+) and protein kinase C(-), suggesting that they were probably cone bipolar cells. cbx mRNA was also detected outside the retina, particularly in the tectum and Rathke's pouch. Replication-competent retrovirus was used to drive misexpression of cbx and of an Engrailed repression construct. Engrailed-mediated repression of Cbx was embryonic lethal, while misexpression of cbx itself was tolerated. In the retina, misexpression of cbx resulted in fewer PKC(+) bipolar cells. Our data suggest that cbx is essential for embryonic survival and may participate in the development of bipolar, probably cone bipolar, cells in the retina.
Department of Ophthalmology, University of Alabama at Birmingham School of Medicine, 700, South 18th Street, USA.
Chuan-Ming
CM
Li
Run-Tao
RT
Yan
Shu-Zhen
SZ
Wang
D000595:Amino Acid Sequence; D000818:Animals; D019677:Artificial Gene Fusion; D002642:Chick Embryo; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000196:embryology* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D018398:Homeodomain Proteins; D012333:RNA, Messenger