Cloning of responsible genes causing myelodysplasia in myelodysplastic syndrome

使用FISH和13个cosmid探针（tel- FB12-CA5-G7-FD2- CB1 - ed8 - fd9 - g32 - ae3 - g50 - ad8 - gg4 - pebp2_c -cen），我们确定了4例骨髓增生异常综合征（MDS）患者和1例成人型CML患者的t(1; 3)（p36; q21）易位的1p36断点：4例MDS患者的断点在CA5和G7 （1p36.3）之间，CML患者的断点在GG4-PEBP2αC （1p36.1）之间。这表明不同疾病之间的1p36断点是不同的。下一步，我们使用33个BAC克隆建立了CA5和G7之间的contig图。3例MDS患者的断点在PAC163G9克隆中发现，其余MDS患者的断点在BAC737N8中发现，说明MDS中1p36的断点可能最多分散在340 kb的区域，因为BAC克隆一般覆盖约170kb。目前，我们正在通过DNA测序对两个克隆中包含的所有基因进行搜索，以找出MDS的致病基因。另一方面，Mochizuki等人报道，他们发现了t(1; 3)（p36; q21）易位的相关基因(Mochizuki N， et al：一个定位于1p36.3的新基因MEL1与MDS/EVI1基因高度同源，并在t(1; 3)（p36; q21）阳性白血病细胞中被转录激活。Blood 96: 3209,2000)：位于1p36断点附近的MEL1基因仅在t(1; 3)（p36; q21）阳性白血病细胞中被位于3q21断点附近的Evi1基因启动子转录激活。我们还研究了MEL1基因是否在我们系列的两名MDS患者中表达。我们发现，PRDM16基因在其他细胞系（准备中）未表达，而MEL1基因没有表达，与MEL1具有高度同源性，仅在3'端有差异。

Using FISH with 13 cosmid probes (tel--FB12-CA5-G7-FD2- CB1 -ED8-FD9-G32-AE3-G50-AD8-GG4-PEBP2_C--cen), we have determined the 1p36 breakpoint of t(1 ; 3)(p36 ; q21) translocation in four myelodysplastic syndrome (MDS) patients and one adult-type CML patient : the breakpoint was between CA5 and G7 (1p36.3) in four MDS patients and between GG4-PEBP2αC (1p36.1) in the CML patient. This indicated that the 1p36 breakpoint was different between different disorders. As a next step, we made a contig map between CA5 and G7 using a total of 33 BAC clones. The breakpoints of three MDS patients were found in PAC163G9 clone, and that of the remaining MDS patient was found in BAC737N8, suggesting that the 1p36 breakpoint in MDS may be scattered in 340 kb region at most, since BAC clone generally cover ca 170kb. Now, we are searching all the genes contained in the two clones through DNA sequencing to find out the responsible gene for MDS.On the other hand, Mochizuki, et al. reported that they found out responsible genes for t(1 ; 3)(p36 ; q21) translocation (Mochizuki N, et al : A novel gene, MEL1, mapped to 1p36.3 is highly homologous to the MDS/EVI1 gene and is transcriptionally activated in t(1 ; 3)(p36 ; q21)-positive leukemia cells. Blood 96 : 3209, 2000) : MEL1 gene located adjacent to the 1p36 breakpoint was transcriptionally activated by the promoter of Evi1 gene located adjacent to the 3q21 breakpoint only in t(1 ; 3)(p36 ; q21)-positive leukemia cells. We also studied whether the MEL1 gene was expressed in two MDS patients of our series. We found that PRDM16 gene, not MEL1, which shows highly homology to MEL1 with only difference in 3' end was highly expressed although this gene was not expressed in any other cell lines (in preparation).