Characterization of an axonemal dynein heavy chain expressed early in airway epithelial ciliogenesis

The most conspicuous evidence of airway epithelial maturation and vitality is the presence of motile cilia. In an effort to generate genetic and antig enic markers of airway maturation, injury, and repair, we characterized air way epithelial expression of a gene identified by two human expressed seque nce tags that encoded peptides with sequence similarity to an invertebrate ciliary dynein heavy chain (DHC). Molecular analyses showed that the gene h as a very large RNA transcript that encodes a very high molecular weight po lypeptide with biochemical properties that are characteristic of a dynein h eavy chain. Expression of the gene transcript correlated with the presence of ciliated cells in tissues, and immunohistochemical localization of the g ene product confirmed its presence in the cilia of mature airway epithelium . In epithelium undergoing ciliogenesis ex vivo, expression of the gene tra nscript preceded ciliation of the epithelium and the gene product was prese nt in the cytoplasm and at the apical border of nonciliated cells. These da ta suggested that the gene encodes an axonemal DHC that is expressed early during ciliogenesis, before the appearance of cilia.