Structural integrity and expression of the L3MBTL gene in normal and malignant hematopoietic cells.
The human L3MBTL gene is located in 20q12, a region that is commonly deleted in myeloproliferative disorders (MPD), myelodysplastic syndromes (MDS), and acute myeloid leukemia (AML). L3MBTL is highly homologous to the D-lethal(3) malignant brain tumor [D-l(3)mbt] gene, which is a putative tumor-suppressor gene (TSG) identified in Drosophila and which is closely related to the Drosophila sex combs on midleg (SCM) protein, a member of the Polycomb group (PcG) family of transcriptional repressors. To examine whether L3MBTL functions as a "classic" TSG in human hematologic malignancies, we screened a panel of 17 myeloid leukemia cell lines and peripheral blood or bone marrow samples from 29 MDS and 13 MPD patients for mutations in the entire L3MBTL coding sequence, including intron/exon splice junctions. No mutations were identified, although two single nucleotide differences were found (in intron 14 and in exon 15), which were interpreted as polymorphic changes. We used real-time RT-PCR to quantify the level of L3MBTL mRNA in various normal myeloid and lymphoid cell populations. L3MBTL is expressed in normal CD34+ bone marrow cells, and we found that the pattern of L3MBTL expression was similar to that of BMI1, a well-studied PcG gene with oncogenic activity, suggesting that L3MBTL and BMI1 may be co-regulated during hematopoiesis. The expression of L3MBTL mRNA in 30 of 35 cell lines and 13 of 15 AML samples was comparable to the level of L3MBTL expression in the normal cell populations. However, five leukemia cell lines showed no L3MBTL expression, and two of the AML samples showed aberrant L3MBTL expression. These data suggest that L3MBTL is not mutated in MDS or MPD. However, given the known dosage effects of PcG proteins in regulating gene expression, reduced or absent L3MBTL expression may be relevant in some cases of myeloid leukemia.
MacGrogan
Donal
D
Laboratory of Molecular Aspects of Hematopoiesis, Sloan Kettering Institute, New York, New York 10021, USA.
Kalakonda
Nagesh
N
Alvarez
Sara
S
Scandura
Joseph M
JM
Boccuni
Piernicola
P
Johansson
Bertil
B
Nimer
Stephen D
SD
D018952:Antigens, CD34 / Q000096:biosynthesis; D001854:Bone Marrow Cells / Q000378:metabolism; D045744:Cell Line, Tumor; D002868:Chromosomal Proteins, Non-Histone; D004247:DNA / Q000378:metabolism; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D005091:Exons; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D006801:Humans; D007951:Leukemia, Myeloid / Q000235:genetics; D019656:Loss of Heterozygosity; D009154:Mutation; D009190:Myelodysplastic Syndromes / Q000235:genetics; D009196:Myeloproliferative Disorders / Q000235:genetics; D009363:Neoplasm Proteins / Q000096:biosynthesis* / Q000235:genetics*; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012313:RNA / Q000737:chemistry; D012097:Repressor Proteins; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D025521:Tumor Suppressor Proteins
D018952:Antigens, CD34; D002868:Chromosomal Proteins, Non-Histone; D017931:DNA Primers; D018076:DNA, Complementary; C120887:L3MBTL1 protein, human; D009363:Neoplasm Proteins; D012097:Repressor Proteins; D025521:Tumor Suppressor Proteins; D012313:RNA; D004247:DNA