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.
Li
Chuan-Ming
CM
Department of Ophthalmology, University of Alabama at Birmingham School of Medicine, 700, South 18th Street, USA.
Yan
Run-Tao
RT
Wang
Shu-Zhen
SZ
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