Role of ABCB7 in RARS Table 1. Descriptive statistics of ABCB7 expression levels in CD34+ cells according to FAB group, in CD34+ cells according to percentage of bone marrow ring sideroblasts, and in cultured erythroblasts at day 7. CD34+ CELLS - FAB Controls (n = 16) RA (n = 35) RAEB (n = 54) RARS (n = 33) % SIDEROBLASTS 0–14 (n = 57) 15–40 (n = 26) 41+ (n = 18) DAY 7 ERYTHROBLASTS Controls (n = 8) RA (n = 9) RARS (n = 8) doi:10.1371/journal.pone.0001970.t001 MEAN STD DEV Kruskal-Wallis p,0.0001 0.98 0.88 0.94 0.49 1.03 0.62 0.42 1.05 0.73 0.34 0.36 0.34 0.44 0.19 0.39 0.26 0.07 0.11 0.24 0.08 MEAN STD DEV Kruskal-Wallis p,0.0001 MEAN STD DEV Kruskal-Wallis p = 0.0001 RA RAEB RARS 15–40 41+ RA RARS Controls 0.3610 0.5476 ,0.0001 0–14 ,0.0001 ,0.0001 Controls 0.0071 0.0008 RA — 0.7211 ,0.0001 15–40 — 0.0022 RA — 0.0021 RAEB — — ,0.0001 ABCB7 gene sequencing and promoter methylation Direct sequencing of ABCB7, including the promoter region, was performed on DNA from 13 RARS patients and did not show any mutations in any of the patients. We have investigated the methylation status of the ABCB7 promoter region in 6 patients with RARS and 5 healthy controls, and the results showed .80% methylation in all samples, with no significant difference between RARS patients and healthy controls. ABCB7 gene correlation No genomic abnormality in the ABCB7 gene was identified in our cases. Therefore, we examined our microarray dataset for genes with expression levels correlated either strongly positively ($0.8) or inversely (#20.8) with ABCB7 gene expression levels. The expression of two genes showed a positive correlation with ABCB7 expression: ELP2 (0.82) and RTF1 (0.80). No genes were found whose expression correlated inversely with ABCB7. Figure 1. ABCB7 expression levels. (A) ABCB7 expression levels in the CD34+ cells from healthy controls and MDS patients with RA, RAEB and RARS. (B) ABCB7 expression levels and percentage of ring sideroblasts in the bone marrow. (C) ABCB7 expression levels in cultured erythroblasts from healthy controls and MDS patients with RA and RARS. The boxes represent the 25th, 50th and 75th percentiles, the bars correspond to the 10th and 90th percentiles. doi:10.1371/journal.pone.0001970.g001 PLoS ONE | www.plosone.org 3 April 2008 | Volume 3 | Issue 4 | e1970