HOX genes in human lung - Altered expression in primary pulmonary hypertension and emphysema

HOX genes belong to the large family of homeodomain genes that function as transcription factors. Animal studies indicate that they play an essential role in lung development. We investigated the expression pattern of HOX gen es in human lung tissue by using microarray and degenerate reverse transcri ptase-polymerase chain reaction survey techniques. HOX genes predominantly from the 3' end of clusters A and B were expressed in normal human adult lu ng and among them HOXA5 was the most abundant, followed by HOXB2 and HOXB6. In fetal (12 weeks old) and diseased lung specimens (emphysema, primary pu lmonary hypertension) additional HOX genes from clusters C and D were expre ssed. Using in situ hybridization, transcripts for HOXA5 were predominantly found in alveolar septal and epithelial cells, both in normal and diseased lungs. A 2.5-fold increase in HOXA5 mRNA expression was demonstrated by qu antitative reverse transcriptase-polymerase chain reaction in primary pulmo nary hypertension lung specimens when compared to normal lung tissue. In co nclusion, we demonstrate that HOX genes are selectively expressed in the hu man lung. Differences in the pattern of HOX gene expression exist among fet al, adult, and diseased lung specimens. The altered pattern of HOX gene exp ression may contribute to the development of pulmonary diseases.