n The genes of homeobox gene superfamily encode

n The genes of homeobox gene superfamily encode homeodomain proteins that act as transcription factors at critical points in development. The homeodomain region is a conserved 60 a. a. domain that recognizes and binds to regulatory region of the target gene. During the evolution, the homeobox gene superfamily is highly conserved in different species. The heart is the first organ that forms and functions within mammalian embryo. Heart development begins during gastrulation and its process is very complex and may involve within many regulatory factors. Today, there about 8 in a 1000 for live borns with cardiac structure abnormalities in human. In this study, we cloned the novel heart expressing homeobox gene Dux-3 and analyzed the expression pattern of Dux-3. A nested PCR and electronic screening of the mouse ESTs c. DNA library were used to clone murine heart expressing homeobox genes. A 663 -bp c. DNA fragment of Dux-3 was cloned and encoded 221 amino acids with two paired-type homeodomains. A 1. 35 kb transcript was found mostly in heart by the mouse multiple tissue northern blot analysis. Dux-3 m. RNA was further detected in E 15. 5 heart and outer ventricle region of the adult heart by whole mount in situ and section in situ hybridization analyses. FSHD is an autosomal dominant neuromuscular disorder and D 4 Z 4 is FSHD associated 3. 3 kb tandem repeats with two homeodomains. Sequence comparison indicated that the sequence of Dux-3 homeodomain 1, 2 was highly homology to the two homeodomain of D 4 Z 4/FSHD locus. Based on these data, it has been shown that Dux-3 is a novel heart expressing homeobox gene and may be involved in the heart development. Sequence similarity implies that Dux-3 may also related to neuromuscular disorder.