[WT1 gene expression and its isoform ratio in different cell subsets of normal human bone marrow]

The Wilms' tumor gene (WT1) is a transcription factor involved in tumorigenesis, especially in leukemogenesis. However, the role of WT1 expression in nonmalignant hematopoietic cells remains unclear. Furthermore, due to alternative splicing at two sites: 17 amino acid residues of exon 5 (+17AA) and 3 amino acid residues (+KTS) between exons 9 and 10, WT1 gene has four main isoforms (17AA+/KTS+, 17AA+/KTS-, 17AA-/KTS+, 17AA-/KTS-, abbreviation: +/+, +/-, -/+, -/-). The isoforms probably existed in hematopoietic cells, which make the research more complex. The aim of study was to elucidate the expression and its isoforms of WT1 gene in different cell subsets of healthy bone marrow donors. The fluorescence RT-PCR detection system was established to measure the expressions of full-length WT1, WT1 (+17AA) and WT1 (+KTS) in CD34(+)CD38(-) (stem cell), CD34(+)CD38(+) (progenitor cell), CD15(+)CD11b(+) (granulocyte), CD33(+)CD14(+) (monocyte), CD20(+)CD5(-) (B-lymphocyte) and CD20(-)CD5(+) (T-lymphocyte) subsets from 18 normal human bone marrow samples. The results showed that WT1 expressed in CD34(+)CD38(-), CD34(+)CD38(+), CD15(+)CD11b(+) and CD33(+)CD14(+), but not in CD20(+)CD5(-) and CD20(-)CD5(+) subsets. The highest expression was in CD34(+)CD38(-), but decreased gradually in CD15(+)CD11b(+) and CD33(+)CD14(+) subsets. WT1 (+17AA), WT1 (+KTS) and WT1 (+/+) isoforms were predominant in CD34(+)CD38(-) and CD34(+)CD38(+) primitive subsets, while in CD15(+)CD11b(+) and CD33(+)CD14(+) the dominant isoforms were WT1 (-17AA), WT1 (-KTS) and WT1 (-/-). It is concluded that the expression of WT1 in normal bone marrow decreases gradually with cell differentiation. Hematopoietic cells may adjust the ratios of WT1 isoforms to inhibit or promote cell differentiation.