Identification of Pathogenetically Important Genes within the Common Deleted Region (CDR) of the 5q- Syndrome.

The 5q- syndrome is characterized by refractory anemia, normal or high platelet count, hypolobulated megakaryocytes, a good prognosis and a low risk of leukemic transformation. Although the CDR has been defined to a 1.5 Mb interval on the long arm on chromosome 5 (5q33.1), the molecular pathogenesis of the disease is still unknown. The CDR contains 39 known-genes of which 33 have been shown to be expressed in hematopoietic stem cells. In order to elucidate the molecular mechanisms behind the 5q- syndrome, we performed real-time quantitative PCR on these 33 genes. Samples from the bone marrow of 12 patients with a sole deletion of 5q and 14 patients with MDS with normal karyotype were initially analyzed. The genes that showed the most pronounced decrease in expression in the 5q- samples were: SLC36A1 (89% down-regulated compared to non 5q-), G3BP (79%), ATOX1 (76%), CSF1R (76%), RPS14 (74%), PDGFRB (73%), TNIP1 (72%), SPARC (71%), ANAX6 (69%), NSDT (66%) and TIGD (60%). SPARC expression was found to be higher in both types of MDS samples compared to normal bone marrow (n=18) as well as compared to seven leukemic cell lines (HL-60, NB4, HEL, KG1, K562, U937 and TP-1). ATOX1 expression was highly over-expressed (20- to 80-fold) in the leukemic cell lines and modestly but significantly higher in normal bone marrow compared to both types of MDS. For G3BP, the expression was similar in normal bone marrow compared to the non-5q- samples but 1- to 10-fold higher in the cell lines. RPS14 was down-regulated in both types of MDS compared to normal bone marrow and leukemic cell lines. Thus, we have identified the most significantly down-regulated genes within the CDR of the 5q- syndrome. Based on our expression data, their known biological functions and on publicly available tissue expression data, genes such as G3BP, ATOX1, TNIP1, RPS14 and CSF1R are interesting targets for further studies. Biological studies are currently being performed on these genes with respect to their role during hematopoiesis with special focus on erythropoiesis.