NOVEL GENES EXPRESSED IN THE CHICK OTOCYST DURING DEVELOPMENT - IDENTIFICATION USING DIFFERENTIAL DISPLAY OF RNA

Differential display of mRNA is a technique that enables the researche r to compare genes expressed in two or more different tissues or in th e same tissue or cell under different conditions. The method is based on polymerase chain reaction amplification and comparison of specific subsets of mRNA. We have used this method to clone partial complementa ry DNAs (cDNAs; amplicons) for genes expressed in the otocyst in order to identify genes that may be involved in development of the inner ea r. A full length cDNA was isolated from an embryonic quail head librar y with an amplicon (KH121) obtained from the otocyst. This avian cDNA encoded a novel, 172-amino acid acidic protein and detected a major tr anscript of ca 0.8 kb in RNA from chick embryos and several neonatal c hick tissues. The full length avian cDNA had high sequence identity to several human cDNAs (expressed sequence tags) from human fetal tissue s, including cochlea, brain, liver/spleen and lung, and from placenta. The human homologue of the avian gene encoded a protein that was 183 amino acids long and had 75.6% amino acid sequence identity to the avi an protein. These results identified both the avian and human homologu es of an evolutionarily conserved gene encoding a small acidic protein of unknown function; however, expression of this gene was not restric ted to otocysts. (C) 1997 ISDN.