THE CHICKEN HOMEOBOX GENE HOXD-11 ENCODES 2 ALTERNATIVELY SPLICED RNASPECIES

Two forms of cDNA clones corresponding to Hoxd-11 were obtained by scr eening a chicken limb bud cDNA library. Comparison of the two cDNA seq uences with the mouse cDNA and genomic sequence, shows that the shorte r cDNA is missing 3 nucleotides, which encode an alanine residue, at t he junction between exons 1 and 2. Analysis of the chicken genomic seq uence shows two tandem CAG repeats at the intron 1-exon 2 junction, bo th of which could serve as splice acceptor sequences. Thus we hypothes ize that the two spliced forms result from alternative use of two tand em splice acceptor sequences. Using reverse transcription polymerase c hain reaction we examined expression of the two forms in 3 to 14-day c hick embryos. All samples showed both species of RNA with approximatel y 2 times more of the larger form compared with the smaller form.