Isolation and analysis of chick homeobox cDNA clones

Homeobox-containing clones were isolated from a Lambda-ZAP cDNA library derived from somites of 2.5 day old chick embryos. The clones were identified by hybridization to the homeobox-containing Xenopus gene Xhoxl-A (1). Fourteen clones isolated from a screen of 3.3 xlO plaques of an amplified library contain homeobox sequences and some are highly conserved homologues of murine Hox genes. Sequence analysis of these clones has shown three to be highly homologous, within their homeodomains, to the murine genes A. Hoxl .4 (2), B. Hox 2.4 (3) and C. Hox2.7 (Robb Krumlauf, personal communication), and we have named them accordingly A. Choxl.4, B. Chox2.4 and C. Chox2.7 (Fig. 1, homeoboxes boxed and conserved hexapeptide motif underlined). Comparison with the sequences of chick homeobox clones so far isolated by others show that Chox2.4 and Chox2.7 described here are new chick isolates while Choxl.4 has also been isolated recently by Sasaki et al. (4). ACKNOWLEDGEMENTS