Cytogenetic, Molecular and FISH Analysis of an Isodicentric Chromosome 21 idic(21)(q22.3) in a Mildly-Affected Patient with Down Syndrome

Abstract Abstract 2561 We present the results of a study demonstrating that the genome profile of RUNX1 in MDS/AML is characterised by hitherto unreported partial deletions and absence of amplifications. This is in stark contrast to reports of chromosome 21 amplifications in ALL. We speculate that the absence of RUNX1 deletions results from them being well below a size detectable by commercial FISH probes. Extra chromosome 21 is the second most common acquired trisomy after (+) 8 in adult myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). It is rarely observed as sole abnormality but seen as part of complex karyotype in some 3–7% of the AML (Atlas of Genetics and Cytogenetics in Oncology and Haematology, http://atlasgeneticsoncology.org). Although the gene(s) in trisomy 21 associated with leukemia are unknown, the 21q22 region appears to be critical since it houses the RUNX1 gene. Multiple amplified copies of the RUNX1 carried by marker chromosomes, such as iAML21, are described in both acute lymphoblastic leukemia (ALL) and AML. A common 5.1 Mb amplification containing the RUNX1, miR-802 and genes mapping to the Down syndrome critical region identified in 91 children with iAML21, was shown to be the likely initiating event in this rare form of childhood B-cell ALL (Rand et al., Blood, 2011). In contrast, recent studies of AML in a Down syndrome and a constitutionally normal individual showed lack of RUNX1, ETS2 and ERG involvement (Canzonetta et al., BJH, 2012). Here we present 16 MDS/AML cases with imbalances of chromosome 21 identified by genomic array screening from a cohort of 83 cases. Whole genome screening (aCGH) was performed on presentation samples of MDS /AML and de novo AML cases using an oligonucleotide array platform (Agilent) at 60K, 244K, 400K and 1M density. G banding and FISH analysis were also successfully performed. Gain of an extra copy (trisomy) of chromosome 21 (+21) was found in 9 patients, all but one with complex karyotypes. In 2 AMLs high level amplifications were detected at 21q22, which involved the ETS2 and ERG but not the RUNX1 sequences. While several commercially available RUNX1 FISH probes showed gene multiple signals, custom FISH probes covering the relevant regions confirmed that the amplifications excluded the RUNX1 but affected both EST2 and ERG thus rendering the commercial probes unfit to assess CNA in this genome area. In another two cases with trisomy 12, cryptic loss of 43Kb and 98Kb resp. within the RUNX1 sequences was detected and confirmed by FISH. Furthermore, similar deletions within the 21q22.12 were also found in another 7 cases all of which had diploid set of chromosome 21 but had multiple changes at G banding level and high TGA score. These RUNX1 deletions were variable in size, ranging from 98Kb to 2.7Mb. Although our observations excluded clinical correlations it is note worthy that most of the patients with RUNX1 loss have not achieved complete cytogenetic remission. These findings suggest role for the RUNX1 loss as indicator of progressive disease and provide a novel insight into pathogenesis of MDS/AML. Disclosures: No relevant conflicts of interest to declare.

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The Effectiveness of Perampanel for Myoclonic Seizures in Down Syndrome with Isodicentric Chromosome 21

Case Reports in Neurology ◽

10.1159/000508357 ◽

2020 ◽

Vol 12 (3) ◽

pp. 270-275

Author(s):

Koji Obara ◽

Tsuyoshi Imota ◽

Shigeo Mamiya ◽

Itaru Toyoshima

Keyword(s):

Down Syndrome ◽

Epileptic Seizures ◽

The Elderly ◽

Sudden Onset ◽

Chromosome 21 ◽

Upper Body ◽

First Line Therapy ◽

Eeg Recordings ◽

Video Eeg ◽

Isodicentric Chromosome

Epileptic seizures are common in the elderly Down syndrome population. We encountered a patient with Down syndrome in whom karyotyping showed the rare isodicentric chromosome 21 and who suffered from myoclonic seizures. A 52-year-old woman with Down syndrome experienced sudden onset of drowsiness and frequent myoclonic jerks in the upper body. Video-EEG recordings demonstrated generalized polyspike-wave discharges consistent with myoclonic jerks, which were exacerbated by photo-stimulation. Her myoclonus completely resolved with perampanel administration. Perampanel was effective for myoclonic seizures in our patient. We suggest that perampanel is an option as first-line therapy for epilepsy and myoclonus in elderly Down syndrome patients.

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Beyond Down syndrome phenotype: Paternally derived isodicentric chromosome 21 with partial monosomy 21q22.3

American Journal of Medical Genetics Part A ◽

10.1002/ajmg.a.38497 ◽

2017 ◽

Vol 173 (12) ◽

pp. 3153-3157

Author(s):

Manesha Putra ◽

Urvashi Surti ◽

Jie Hu ◽

Deana Steele ◽

Michele Clemens ◽

...

Keyword(s):

Down Syndrome ◽

Chromosome 21 ◽

Partial Monosomy ◽

Down Syndrome Phenotype ◽

Isodicentric Chromosome

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A Contiguous 3-Mb Sequence-Ready Map in the S3–MX Region on 21q22.2 Based on High- Throughput Nonisotopic Library Screenings

Genome Research ◽

10.1101/gr.9.4.360 ◽

1999 ◽

Vol 9 (4) ◽

pp. 360-372

Author(s):

Thomas Hildmann ◽

Xianging Kong ◽

John O’Brien ◽

Lisa Riesselman ◽

Hoang-My Christensen ◽

...

Keyword(s):

Down Syndrome ◽

High Throughput ◽

Genomic Sequence ◽

Chromosome 21 ◽

Candidate Gene Approach ◽

Genomic Sequencing ◽

Sequence Information ◽

Fish Analysis ◽

Potential Candidate ◽

Positional Candidate

Progress in complete genomic sequencing of human chromosome 21 relies on the construction of high-quality bacterial clone maps spanning large chromosomal regions. To achieve this goal, we have applied a strategy based on nonradioactive hybridizations to contig building. A contiguous sequence-ready map was constructed in the Down syndrome congenital heart disease (DS-CHD) region in 21q22.2, as a framework for large-scale genomic sequencing and positional candidate gene approach. Contig assembly was performed essentially by high throughput nonisotopic screenings of genomic libraries, prior to clone validation by (1) restriction digest fingerprinting, (2) STS analysis, (3) Southern hybridizations, and (4) FISH analysis. The contig contains a total of 50 STSs, of which 13 were newly isolated. A minimum tiling path (MTP) was subsequently defined that consists of 20 PACs, 2 BACs, and 5 cosmids covering 3 Mb between D21S3 and MX1. Gene distribution in the region includes 9 known genes (c21–LRP, WRB, SH3BGR, HMG14, PCP4, DSCAM, MX2, MX1, and TMPRSS2) and 14 new additional gene signatures consisting of cDNA selection products and ESTs. Forthcoming genomic sequence information will unravel the structural organization of potential candidate genes involved in specific features of Down syndrome pathogenesis.

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Exploring the Pathogenesis of Down Syndrome-Related Myeloproliferative Disorders Using iPSCs

Blood ◽

10.1182/blood.v124.21.868.868 ◽

2014 ◽

Vol 124 (21) ◽

pp. 868-868

Author(s):

Nishinaka Yoko ◽

Akira Niwa ◽

Mitsujiro Osawa ◽

Akira Watanabe ◽

Tatsutoshi Nakahata ◽

...

Keyword(s):

Down Syndrome ◽

B Lymphocytes ◽

Trisomy 21 ◽

Morphological Difference ◽

Chromosome 21 ◽

Fish Analysis ◽

Transcription Activator ◽

Differentiation Potential ◽

Exon 2 ◽

Gata1 Mutation

Abstract Down syndrome (DS) is a congenital syndrome due to the trisomy of chromosome 21. Transient myeloproliferative disorder (TMD) is its hematopoietic complication, affecting approximately 10% of DS-neonates. TMD is characterized by transient abnormal proliferation of blastic cells, and importantly, all TMD blasts bear mutations in GATA1 gene. Although TMD usually resolves spontaneously within 3 months after birth, twenty to thirty percent of TMD patients develop acute megakaryoblastic leukemia (AMKL) within several years afterward. This leukemogenic transition is considered as a good model for multi-step tumorigenesis. According to this putative multi-step model, the first hit should be additional chromosome 21, the second one is mutations on GATA1 gene which is requisite to the onset of TMD, and the “unknown” third hits are required for the progression into AMKL. However, it is still unclear that 1) how GATA1 mutation promotes TMD development, 2) what kinds of third hit are required for the onset of AMKL, and 3) why GATA1-mutated progenitors prevails during embryonic hematopoiesis only in trisomy 21 patients? In order to address these issues, a strictly controlled isogenic cell panels that can reproduce human emboryonic hematopoietic development is needed. Human induced pluripotent stem cells (iPSCs) derived from DS patients are a promising platform for this, but so far there is no report regarding GATA1-mutated TMD-associated iPSCs. Therefore, we set out to establish an iPSC panel that covers each genomic status of chromosome 21 and GATA1 gene. For this, we established both GATA1 mutant and wildtype clones from both trisomy 21 and disomy 21 clones. And we also established TMD patient derived iPSCs. First, we established isogenic iPSCs derived from EB virus immortalized B-lymphocytes of 2 mosaic DS patients. Frequency of trisomy 21 cells evaluated by FISH analysis and G-banding were 93% and 94% for each patient. We reprogrammed these cells by introducing 5 episomal vectors, pCE-hOCT3/4, pCE-hSK, pCE-hUL, pCE-mp53DD and pCXB-EBNA1, under feeder free condition. We genotyped each iPSC clones by digital-PCR analysis and found that the frequency of trisomy iPSC clones were comparable to that of trisomy cells in original EBV immortalized B-lymphocytes. There is no morphological difference between disomy and trisomy iPSC clones in both patients. We next introduced disease-associated GATA1 mutation into established isogenic trisomy and disomy iPS clones using transcription activator-like effector nuclease (TALEN) technology. We introduced a frameshift mutation in exon 2, which causes premature termination of the full-length transcript originated from 1st ATG and exclusively produces the shorter isoform of GATA1 (GATA1s) transcribed from 2nd ATG. Next, we obtained peripheral blood mononuclear cells (PBMCs) from a TMD patient in order to establish TMD-blast-derived iPSCs. Eighty-nine percent of nuclear cells in the PBMC fraction was CD117+CD45+ blastic cells, whereas only 5.6% were non-blast cells including CD3 positive T-lymphocytes, CD11b positive myeloid lineage cells and CD19 positive B-lymphocytes. The CD117+ cells showed TMD/AMKL blast-like appearance such as coarse choromatin pattern with nucleolus and bleb-like structures. We sorted out CD45+CD117+ blastic cells and CD45+CD117- non-blastic cells and successfully established iPSC clones from both populations. In conclusion, we successfully established a comprehensive panel of iPSC clones for evaluating the hematopoietic consequence associated with the GATA1 genotype and the ploidy of chromosome 21. We are currently evaluating hematopoietic differentiation potential of each clone and exploring the underlying pathophysiology of TMD/AMKL by using this platform. We believe that comprehensive understanding of TMD and AMKL pathogenesis provides a fruitful insight into our understanding of human leukemogenesis. Disclosures No relevant conflicts of interest to declare.

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