In this study, we examined a large number of patients to clarify FLT3 gene has some structural similarities including the the distribution and frequency of a recently described FLT3 tannumber of exons, size of exons and exon/intron boundaries dem duplication among hematopoietic malignancies, including with genes RTKs, FMS, KIT, and platelet-derived growth-factor of 24 showed internal tandem duplication with or withoutWe recently demonstrated internal tandem duplication insertion of nucleotides. In one AML, insertion and deletion within JM/TK-I domains as a somatic mutation of FLT3 found without duplication was determined. All 24 lengthened in 17% of patients with acute myelogenous leukemia (AML). 14 sequences were in-frame. Duplication takes place in the Since this mutation was not found in any patients with acute sequence coding for the JM domain and leaves the TK domain lymphocytic leukemia, we described that this mutation could intact. In conclusion, we emphasize that the length mutation of FLT3 at JM/TK-I domains were restricted to AML and MDS.be specific in myeloid malignancies. To clarify the incidence Since all these mutations resulted in in-frame, this abnormality and distribution of the FLT3 mutation among hematological might function for the proliferation of leukemic cells.malignancies, we examined a large number of patients with

Precise analysis of human CD34-negative (CD34 ؊ ) hematopoietic stem cells (HSCs) has been hindered by the lack of a simple and reliable assay system of these rare cells. Here, we successfully identify human cord blood-derived CD34 ؊ severe combined immunodeficiency (SCID)-repopulating cells (SRCs) with extensive lymphoid and myeloid repopulating ability using the intra-bone marrow injection (IBMI) technique. Lineage-negative (Lin ؊ ) CD34 ؊ cells did not show SRC activity by conventional tail-vein injection, possibly due to their low levels of homing receptor expression and poor SDF-1/CXCR4-mediated homing abilities, while they clearly showed a high SRC activity by IBMI. They generated CD34 ؉ progenies not only in the injected left tibia but also in other bones following migration. Moreover, they showed slower differentiating and reconstituting kinetics than CD34 ؉ cells in vivo. These in vivo-generated CD34 ؉ cells showed a distinct SRC activity after secondary transplantation, clearly indicating the long-term human cell repopulating capacity of our identified CD34 ؊ SRCs in nonobese diabetic (

scribed in frame, and coded mutant FLT3 with a long JM

We recently reported an internal tandem duplication of the receptor-type tyrosine kinases (RTKs), 8,9 ses were also performed to reveal the time when the mutation duplication transformed to overt leukemia within a few months.emerged. Together with the FLT3 mutation, chromosome fin-

We analyzed tandem duplication in the juxtamembrane (JM) domain of the FLT3 (FMS-like tyrosine kinase 3/FLK2, CD135) gene in 94 children with acute myeloid leukemia (AML) and evaluated its correlation with clinical features. Longer polymerase chain reaction (PCR) products were observed in five patients; 1/3 of M0, 1/9 of M1, 1/39 of M2, 1/9 of M3 and 1/12 of M5. The sequence analyses of abnormal PCR products showed that all the abnormal products were derived from tandem duplications involving the JM domain and that all the lengthened sequences were in-frame as we previously reported. Statistical analyses revealed a significantly lower incidence of the tandem duplication in childhood AML patients than in adult patients (P Ͻ 0.05), and significantly shorter disease-free survival in patients with mutant FLT3 than in patients with wild-type FLT3 (P Ͻ 0.05). Our results suggest that the tandem duplication in the JM domain of the FLT3 gene is not a frequent phenomenon but might be a factor of poor prognosis in childhood patients with AML.