Cloning and characterization of KPL2, a novel gene induced during ciliogenesis of tracheal epithelial cells

To identify genes upregulated during the process of ciliated cell different iation of airway epithelial cells, differential display was used to compare RNA from rat tracheal epithelial (RTE) cells cultured under conditions tha t inhibit/promote ciliated cell differentiation. Several partial complement ary DNAs (cDNAs) were identified whose expression was regulated coordinatel y with ciliated cell differentiation. One of these, KPL2, detected a messen ger RNA transcript of similar to 6 kb when used as a probe on Northern blot s of RNA from ciliated cultures but was undetectable in RNA from nonciliate d cultures. Sequencing of overlapping clones obtained by a modified rapid a mplification of cDNA ends procedure generated a complete cDNA sequence that exhibited no significant homology to sequences in GenBank, indicating that KPL2 is a novel gene. Southern analysis demonstrated that KPL2 exists as a single-copy gene. KPL2 contains a long open reading frame predicted to cod e for a protein of > 200 kD. Several putative functional motifs are present in the protein, including a calponin homology domain, three nuclear locali zation signals, a consensus P-loop, and a proline-rich region, suggesting t hat KPL2 has a unique function. KPL2 was undetectable in heart and liver sa mples, but was expressed in brain and testis, tissues that contain axonemal structures. In seminiferous tubules of the testis, KPL2 expression was sta ge-specific and appeared to be highest in spermatocytes and round spermatid s. During differentiation of RTE cells, the expression of KPL2 closely para lleled that of an axonemal dynein heavy chain. These results suggest that K PL2 plays an important role in the differentiation or function of ciliated cells in the airway.