DENN, a novel human gene differentially expressed in normal and neoplastic cells

A novel 5843 bp human cDNA sequence was isolated from fetal liver cDNA using the RACE procedure. Within this cDNA was characterised an uninterrupted ORF of 3861 nt encoding a predicted hydrophilic protein of 1287 aa with a calculated molecular mass of 141790 Da and an isoelectric point of 5.41. An RGD cellular adhesion motif was identified within the putative serine- and leucine-rich protein. Northern blot hybridisation with a specific cDNA probe revealed differential levels of expression of 6.5 kb transcripts in 35 human tissues and cancer cell lines, with strongest signals observed in fetal brain and kidney; adult testis, ovary, brain and heart; and in the SW480, K-562, HeLa S3 and HL-60 cell lines. To reflect this feature, the novel gene was designated DENN for differentially expressed in normal and neoplastic cells. Furthermore, an alternative splicing event within DENN involving a 129 nt alternative exon encoding 43 aa was found in fetal liver and in several human cancer cell lines. Based on the predicted aa sequence, two peptides were designed and synthesised to raise rabbit polyclonal antisera which detected a distinct protein band of 140-145 kDa in Western blots of human cell lines. Immunofluorescent labelling of human cells with the same antibodies indicated predominant cell membrane localisation with some cytoplasmic staining.