Identification of two novel human genes, DIPLA1 and DIPAS, expressed in placenta tissue.

Here we report the identification and expression analysis of two novel human genes--DIPLA1 (Differentially expressed in placenta 1) and DIPAS (DIPLA1 Antisense). These genes are located at chromosomal region 9q33.1, in opposite orientations, and are flanked by the pregnancy-associated plasma protein-A (PAPP-A) and astrotactin 2 (ASTN2) genes. The mRNA sequences of both genes contain several upstream AUGs (uAUG) and various potential open reading frames (ORFs). DIPLA1 mRNA is 1.8 kb long and contains a 285 nt ORF coding for a polypeptide designated as replicative senescence up-regulated (RSU) protein. Antisense DIPAS mRNA is 2.7 kb long and contains a 309 nt ORF coding for a protein with partial similitude to the gamma isoform variant of the human Ca(2+)/calmodulin (CaM)-dependent protein kinase II. Both genes are conserved in placental-species and are presumably transcribed from initiator (Inr) promoter elements located at opposite strands. In 20 human normal tissues tested, DIPLA1 mRNA expression was placenta-specific, whereas DIPAS mRNA expression was higher in placenta, brain, kidney and testis. In addition, DIPAS mRNA hybridizes with the 3'UTR region from PAPP-A mRNA, which spans over 4 kb more than previously reported, forming a potential sense-antisense double stranded RNA (dsRNA) duplex. Our results are of interest for placenta gene expression regulation and for the identification of novel genes in the human genome.