X chromosome insertion in the MLL gene in a case of childhood acute myeloblastic leukemia

Band 11q23 is known to be involved in translocations and insertions with a variety of partner chromosomes. These lead to MLL rearrangement, resulting in a fusion with numerous genes. We report here the case of a 5-month-old boy presenting with hemianopsia and severe diffuse intravascular coagulopathy in whom a diagnosis of acute myeloblastic leukemia (AML) French-American-British M4 classification was made. Conventional cytogenetic techniques showed an ins(11;X) (q23;q28q12). Fluorescent in situ hybridization (FISH) with whole chromosome paints confirmed this finding. Using a specific probe, the MLL gene was found to be disrupted, a portion of the X chromosome being inserted between the 5' and 3' regions of the MLL gene. Although some cases of insertion involving chromosomes X and 11 have been reported in AML, this appears to be the first case involving band Xq28. We postulate that this chromosomal rearrangement led to the fusion of the 5' region of the MLL gene with a yet unidentified gene located in band Xq28.     

Cryptic ins(4;11)(q21;q23q23) detected by fluorescence in situ hybridization: a variant of t(4;11)(q21;q23) in an infant with a precursor B-cell acute lymphoblastic leukemia report of a second case

We report the chromosomal findings in a 4-year-old female with precursor B-cell acute lymphoblastic leukemia (ALL). The diagnostic karyotype showed an isochromosome 7q, i(7)(q10), as well as questionable rearrangements on 9p and 11q. Fluorescence in situ hybridization (FISH) studies on both interphase and metaphase cells using the MLL "break-apart" and the centromeric chromosome 4 probes were instrumental in the characterization of an MLL gene rearrangement, which was cryptic by conventional cytogenetic analysis. Specifically, the FISH pattern was consistent with an insertion of the 5' region of the MLL gene into chromosome 4 at band q21, most likely a variant t(4;11)(q21;q23). This is the second case of FISH detection of an ins(4;11) in ALL. Our case exemplifies the importance of FISH in the further characterization of precursor B-cell ALL cases without any apparent prognostically significant chromosomal abnormalities.     

A case of acute myelogenous leukemia with MLL-AF10 fusion caused by insertion of 5' MLL into 10p12, with concurrent 3' MLL deletion

Structural abnormalities involving the mixed-lineage leukemia (MLL) gene on 11q23 have been associated with hematological malignancies. The rearrangement of MLL occurs during translocations and insertions involving a variety of genes on the partner chromosome. We report a rare case of acute myelogenous leukemia (AML-M2) with 11q23 abnormalities. Fluorescence in situ hybridization (FISH) using a commercial dual-color MLL probe detected an atypical signal pattern: one fusion signal, two green signals smaller than those usually detected, and no orange signals. Spectral karyotyping (SKY) analysis indicated that one green signal was detected on the short arm of derivative chromosome 10, and the other green signal on the long arm of a derivative chromosome 11, on which no orange signal was detected. A long-distance inverse polymerase chain reaction (LDI-PCR) identified the fusion partner gene, in which intron 6 of MLL was fused with intron 8 of AF10 on 10p12 in the 5' to 3' direction. Our observations indicated that the MLL-AF10 fusion gene resulted from the insertion of part of the region that included the 5' MLL insertion into 10p12; this was concurrent with the deletion of 3' MLL.     

Complex chromosome 9, 20, and 22 rearrangements in acute lymphoblastic leukemia with duplication of BCR and ABL sequences

Cytogenetic analysis was performed on bone marrow cells from a 28-year-old woman who was diagnosed with acute lymphoblastic leukemia (ALL). Her karyotype was: 46,XX,t(9;22)(q34;q11)[6]/47, XX,+8,t(9;22)(q34;q11)[4]/47,XX,+8,t(9;22)(q34;q11),del(20)(q11)[2]/46, XX,t(9;22)(q34;q11),del[20](q11)[7]/45,XX,der(9)t(9;22)(q34;q11),-20,-22 , +mar1[8]/45,XX,der(9)t(9;22)(q34;q11),-20,-22,+mar2[3]. Both marker chromosomes are dicentric and have the same size and banding pattern but different primary constrictions. Fluorescence in situ hybridization (FISH) demonstrated that both markers were derived from chromosomes 9, 20, and 22. FISH with the bcr/abl probe showed fusion of the BCR gene with the ABL gene; however, this fusion signal was present in duplicate on both marker chromosomes. To our knowledge, duplication of the BCR/ABL fusion signal on a single chromosome arm has not been reported before, except for the extensive amplification of BCR/ABL fusion signals in the leukemic cell line K-562. These data demonstrate that the marker chromosomes are the result of complex genomic rearrangements. At the molecular level, the BCR/ABL fusion gene encodes the p190 fusion protein. Similar findings have never been observed in any case of ALL.     

联合间期和中期荧光原位杂交检测发现11q23异常伴D13S319缺失急性髓系白血病一例

目的对1例出现11q23异常伴D13S319缺失的罕见急性髓系白血病(acute myeloid leukemia,AML)患者进行多途径细胞遗传学分析,为诊断、治疗及预后分层提供依据。方法应用G+R显带技术对患者24 h培养后的中期分裂相进行染色体核型分析,联合分裂间期和中期荧光原位杂交(fluorescence in situ hybridization,FISH)技术对患者染色体的特定位点进行检测,明确复杂易位和微小缺失片段。结果患者存在混合系白血病基因(mixed lineage leukemia,MLL)重排,形成了MLL-AF10融合基因,并伴有13号染色体D13S319位点的缺失。结论MLL基因重排合并D13S319位点缺失在急性白血病中是否具有双重打击效应应引起临床的重视。在AML患者核型中发现13q-、del(13)(q14)、-13或der(13)任意一种克隆性异常时,应行FISH检测论证及明确缺失片段的大小,以便进行靶向治疗。     

急性单核系白血病M4/M5中MLL基因重排的间期荧光原位杂交研究

目的　探讨间期荧光原位杂交 ( fluorescence in situ hybridization,FISH)技术对混合谱系白血病 ( mixed lineage leukemia,ML L)基因重排检测的价值 ;评估 ML L 重排在急性单核系白血病 M4 / M5中的发生率和预后意义。方法　采用骨髓直接法或短期培养法制备染色体 ,应用 R显带技术进行核型分析。采用地高辛标记的跨越 11q2 3断裂位点的单色 ML L探针和间期 FISH技术对 2 3例急性单核系白血病M4 / M5病例进行 ML L重排检测。结果　 R显带揭示 2 3例中 7例有涉及 11q2 3的易位 ,5例有其他核型异常 ,10例核型正常 ,1例核型分析失败。 FISH研究显示 12例有 ML L重排 ,包括 R显带检出 11q2 3异常的7例。结论 FISH技术检测 ML L重排的敏感性明显高于常规细胞遗传学技术 ;ML L重排与急性单核系白血病 M4 / M5高度相关 ,是预后不良的指标     

Aneurysmal bone cyst with chromosomal changes involving 7q and 16p

A 6-month-old girl was diagnosed with acute lymphoblastic leukemia (ALL). Chromosome analysis of bone marrow aspirate showed 46,XX,t(4;11)(q21;q23) with an atypical appearance of the 11p on the der(11) chromosome. FISH studies to fully characterize the translocation utilised 8 probes: whole chromosome painting probes for chromosome 11 and chromosome 4; separate chromosome 11 short arm and long arm paints; specific subtelomere probes from 11p, 11q, and 4q; MLL gene probe. Taken together, the results indicated a two-step abnormality: an initial standard t(4;11)(q21;q23), followed by another t(4;11)--this time, between the two derivative chromosomes. The MLL gene was split by the first translocation and its position altered by the second.     

Insertion of MLL sequences into chromosome band 5q31 results in an MLL-AF5Q31 fusion and is a rare but recurrent abnormality associated with infant leukemia

MLL gene rearrangements leading to production of MLL fusion proteins are commonly detected in infant leukemia patients; the most common MLL fusion associated with infant leukemia is the MLL-AF4 fusion. A single case of chromosomal rearrangement leading to production of an MLL fusion with AF5Q31, a gene structurally similar to AF4, has been detected recently in the malignant cells of an infant leukemia patient. We have identified a second case of MLL-AF5Q31 fusion, arising from an insertion of MLL sequences into chromosome 5, also in an infant leukemia patient. Because MLL and AF5Q31 are transcribed in opposite orientations, a simple balanced chromosomal translocation cannot produce a fusion protein, and complex chromosomal rearrangements such as insertions and inversions are required to produce an MLL-AF5Q31 fusion protein. This report demonstrates that chromosomal insertion of MLL sequences is a rare but recurrent abnormality associated with infant leukemia.     

Molecular and fluorescence in situ hybridization analysis of a 10;11 rearrangement in a case of infant acute monocytic leukemia

Fluorescence in situ hybridization (FISH) analysis in a case of infant acute monocytic leukemia M5 revealed a complex rearrangement between chromosomes 10 and 11, leading to the disruption of the MLL gene. Using two painting probes for chromosomes 10 and 11 and a specific probe for the MLL gene localized on 11q23, we observed a paracentric inversion of the 11q13-q23 fragment translocated to 10p12. Molecular analysis showed that AF10 localized on 10p12 was the fusion partner gene of MLL in this rearrangement (10;11). This report underlined the usefulness of FISH and molecular techniques in identifying complex rearrangements.     

Molecular characterization of der(15)t(11;15) as a secondary cytogenetic abnormality in acute promyelocytic leukemia with cryptic PML-RAR alpha fusion on 17q

A case of acute promyelocytic leukemia (APL) with cryptic PML-RAR alpha fusion on 17q and add(15p) as a secondary abnormality was characterized using molecular cytogenetic techniques. Spectral karyotyping (SKY) showed that chromosome 11 material was added to 15p, forming a der(15)t(11;15), which was refined to der(15)t(11;15)(q13.2;p13) with information obtained by comparative genomic hybridization (CGH). Interstitial insertion of chromosome 15 material into chromosome 17q was found by fluorescence in situ hybridization (FISH) with whole chromosome painting (WCP) probes. This study illustrates the necessity of a combination of molecular cytogenetics to decipher complex karyotypic abnormalities and cryptic translocations in leukemia.     

Pediatric T-cell acute lymphoblastic leukemia with aberrations of both MLL loci

Translocations involving the MLL gene at 11q23 have been implicated in acute lymphoblastic leukemia (ALL), as well as acute myeloid leukemia (AML). Such translocations result in gain of function fusion proteins that drive cell proliferation. Except in cases of T-cell ALL, MLL rearrangement is typically associated with a poor prognosis. We report a case of T-cell ALL with a t(11;19)(q23;p13.3) and deletion of the other chromosome 11 homolog at band q23. Fluorescence in situ hybridization (FISH) analyses confirmed involvement of the MLL loci in both the translocation and deletion. This case is unique in that deletions of 11q23 reported in ALL generally do not involve MLL. We are unaware of a previous report showing rearrangement of the MLL loci on both chromosome 11 homologues.     

Prenatal diagnosis of a familial interchromosomal insertion of Y chromosome heterochromatin

An apparently unbalanced karyotype containing an abnormal chromosome 11 was identified in a 16-week female fetus by analysis of cultured amniocytes. Fluorescence in situ hybridization (FISH) with a chromosome 11 paint identified the presence of an insertion in band 11q24. Parental karyotyping documented an unbalanced karyotype with the same der(11) chromosome in the phenotypically normal father. CBG-banding and FISH identified the insertion to be Yq12 heterochromatin: 46,XY, der(11)ins(11;Y)(q24;q12q12)ish der(11) (wcp11+,DYZ1+). The same der(11) chromosome was also found in the phenotypically normal paternal grandmother, demonstrating this additional Y chromosomal material did not affect normal female sexual development or fertility. The parents elected to continue the pregnancy and a normal girl was born at term, further confirming that this rare familial variant has no clinical significance. This case illustrates the importance of family studies, appropriate banding, and FISH analyses to accurately characterize apparent chromosomal abnormalities. Am. J. Med. Genet. 73:470–473, 1997. © 1997 Wiley-Liss, Inc.     

A fluorescence in situ hybridization study of complex t(9;22) in two chronic myelocytic leukemia cases with a masked Philadelphia chromosome

The t(9;22)(q34;q11) is evident in more than 90% of patients with chronic myelocytic leukemia (CML) and gives rise to the Philadelphia chromosome (Ph). Approximately 5%-10% of CML patients show variant translocations involving other chromosomes in addition to chromosomes 9 and 22. In some variant translocations, additional material is transferred on der(22), resulting in a masked Ph chromosome. In this paper, we report two apparently Ph-negative (Ph-) CML cases showing a t(7;9;22)(q22;q34;q11) and a t(8;9;22)(q12;q34;q11), respectively. A detailed molecular cytogenetic characterization was performed by fluorescence in situ hybridization (FISH), which disclosed the presence of the 5'BCR/3'ABL fusion gene on the der(7) and der(8) chromosomes, respectively. Derivative (22) appeared as a masked Ph chromosome in both cases. FISH analysis with appropriate BAC/PAC clones allowed us to precisely characterize the complex chromosomal rearrangements that were not detected by conventional cytogenetic analysis.