Truncated RUNX1 protein generated by a novel t(1;21)(p32;q22) chromosomal translocation impairs the proliferation and differentiation of human hematopoietic progenitors

MAML3-fusions modulate vascular and immune tumour microenvironment and confer high metastatic risk in pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas are rare neuroendocrine tumours. Around 20-25 % of patients develop metastases, for which there is an urgent need of prognostic markers and therapeutic stratification strategies. The presence of a MAML3-fusion is associated with increased metastatic risk, but neither the processes underlying disease progression, nor targetable vulnerabilities have been addressed. We have compiled a cohort of 850 patients, which has shown a 3.65 % fusion prevalence and represents the largest MAML3-positive series reported to date. While MAML3-fusions mainly cause single pheochromocytomas, we also observed somatic post-zygotic events, resulting in multiple tumours in the same patient. MAML3-tumours show increased expression of neuroendocrine-to-mesenchymal transition markers, MYC-targets, and angiogenesis-related genes, leading to a distinct tumour microenvironment with unique vascular and immune profiles. Importantly, our findings have identified MAML3-tumours specific vulnerabilities beyond Wnt-pathway dysregulation, such as a rich vascular network, and overexpression of PD-L1 and CD40, suggesting potential therapeutic targets.

RUNX1::MIR99AHG Chimera in Acute Myeloid Leukemia

RUNX1 fuses with over 70 different partner genes in hematological neoplasms. While common RUNX1 chimeras have been extensively studied and their prognosis is well established, our current understanding of less common RUNX1 chimeras is limited. Here, we present a case of acute myeloid leukemia (AML) with a rare RUNX1 chimera. Bone marrow cells obtained at diagnosis from a 71-year-old patient diagnosed with AML-M5 were studied using G-banding, fluorescence in situ hybridization, array comparative genomic hybridization, RNA sequencing, PCR, and Sanger sequencing. Combined findings from the abovementioned assays suggested three cytogenetic clones: one with a normal karyotype, one with inv(21)(q21q22), and one with two inv(21)(q21q22). The molecular analysis revealed the fusion of RUNX1 with MIR99AHG (at 21q21.1), further supporting the presence of an inv(21)(q21q22). The present case is the third reported AML harboring a RUNX1::MIR99AHG chimera. Similar to the two previously described AML patients, our case also had an FLT3 aberration.

MTAP-ANRIL gene fusion promotes melanoma epithelial-mesenchymal transition-like process by activating the JNK and p38 signaling pathways

Gene fusions caused by cytogenetic aberrations play important roles in the initiation and progression of cancers. The recurrent MTAP-ANRIL fusion gene was reported to have a frequency of greater than 7% in melanoma in our previous study. However, its functions remain unclear. Truncated MTAP proteins resulting from point mutations in the last three exons of MTAP can physically interact with the wild-type MTAP protein, a tumor suppressor in several human cancers. Similarly, MTAP-ANRIL, which is translated into a truncated MTAP protein, would influence wild-type MTAP to act as an oncogene. Here, we found that MTAP-ANRIL gene fusion downregulated the expression of wild-type MTAP and promoted epithelial-mesenchymal transition-like process through the activation of JNK and p38 MAPKs in vitro and in vivo. Our results suggest that MTAP-ANRIL is a potential molecular prognostic biomarker and therapeutic target for melanoma.

The TINCR ubiquitin-like microprotein is a tumor suppressor in squamous cell carcinoma

The TINCR (Terminal differentiation-Induced Non-Coding RNA) gene is selectively expressed in epithelium tissues and is involved in the control of human epidermal differentiation and wound healing. Despite its initial report as a long non-coding RNA, the TINCR locus codes for a highly conserved ubiquitin-like microprotein associated with keratinocyte differentiation. Here we report the identification of TINCR as a tumor suppressor in squamous cell carcinoma (SCC). TINCR is upregulated by UV-induced DNA damage in a TP53-dependent manner in human keratinocytes. Decreased TINCR protein expression is prevalently found in skin and head and neck squamous cell tumors and TINCR expression suppresses the growth of SCC cells in vitro and in vivo. Consistently, Tincr knockout mice show accelerated tumor development following UVB skin carcinogenesis and increased penetrance of invasive SCCs. Finally, genetic analyses identify loss-of-function mutations and deletions encompassing the TINCR gene in SCC clinical samples supporting a tumor suppressor role in human cancer. Altogether, these results demonstrate a role for TINCR as protein coding tumor suppressor gene recurrently lost in squamous cell carcinomas.

Neoplasia-associated Chromosome Translocations Resulting in Gene Truncation

Chromosomal translocations in cancer as well as benign neoplasias typically lead to the formation of fusion genes. Such genes may encode chimeric proteins when two protein-coding regions fuse in-frame, or they may result in deregulation of genes via promoter swapping or translocation of the gene into the vicinity of a highly active regulatory element. A less studied consequence of chromosomal translocations is the fusion of two breakpoint genes resulting in an out-of-frame chimera. The breaks then occur in one or both protein-coding regions forming a stop codon in the chimeric transcript shortly after the fusion point. Though the latter genetic events and mechanisms at first awoke little research interest, careful investigations have established them as neither rare nor inconsequential. In the present work, we review and discuss the truncation of genes in neoplastic cells resulting from chromosomal rearrangements, especially from seemingly balanced translocations.

Comprehensive molecular analysis of immortalization hallmarks in thyroid cancer reveals new prognostic markers

BACKGROUND

Comprehensive molecular studies on tumours are needed to delineate immortalization process steps and identify sensitive prognostic biomarkers in thyroid cancer.

METHODS AND RESULTS

In this study, we extensively characterize telomere-related alterations in a series of 106 thyroid tumours with heterogeneous clinical outcomes. Using a custom-designed RNA-seq panel, we identified five telomerase holoenzyme-complex genes upregulated in clinically aggressive tumours compared to tumours from long-term disease-free patients, being TERT and TERC denoted as independent prognostic markers by multivariate regression model analysis. Characterization of alterations related to TERT re-expression revealed that promoter mutations, methylation and/or copy gains exclusively co-occurred in clinically aggressive tumours. Quantitative-FISH (fluorescence in situ hybridization) analysis of telomere lengths showed a significant shortening in these carcinomas, which matched with a high proliferative rate measured by Ki-67 immunohistochemistry. RNA-seq data analysis indicated that short-telomere tumours exhibit an increased transcriptional activity in the 5-Mb-subtelomeric regions, site of several telomerase-complex genes. Gene upregulation enrichment was significant for specific chromosome-ends such as the 5p, where TERT is located. Co-FISH analysis of 5p-end and TERT loci showed a more relaxed chromatin configuration in short telomere-length tumours compared to normal telomere-length tumours.

CONCLUSIONS

Overall, our findings support that telomere shortening leads to a 5p subtelomeric region reorganization, facilitating the transcription and accumulation of alterations at TERT-locus.

A novel and efficient tandem CD19- and CD22-directed CAR for B cell ALL

CD19-directed chimeric antigen receptor (CAR) T cells have yielded impressive response rates in refractory/relapse B cell acute lymphoblastic leukemia (B-ALL); however, most patients ultimately relapse due to poor CAR T cell persistence or resistance of either CD19⁺ or CD19^- B-ALL clones. CD22 is a pan-B marker whose expression is maintained in both CD19⁺ and CD19^- relapses. CD22-CAR T cells have been clinically used in B-ALL patients, although relapse also occurs. T cells engineered with a tandem CAR (Tan-CAR) containing in a single construct both CD19 and CD22 scFvs may be advantageous in achieving higher remission rates and/or preventing antigen loss. We have generated and functionally validated using cutting-edge assays a 4-1BB-based CD22/CD19 Tan-CAR using in-house-developed novel CD19 and CD22 scFvs. Tan-CAR-expressing T cells showed similar in vitro expansion to CD19-CAR T cells with no increase in tonic signaling. CRISPR-Cas9-edited B-ALL cells confirmed the bispecificity of the Tan-CAR. Tan-CAR was as efficient as CD19-CAR in vitro and in vivo using B-ALL cell lines, patient samples, and patient-derived xenografts (PDXs). Strikingly, the robust antileukemic activity of the Tan-CAR was slightly more effective in controlling the disease in long-term follow-up PDX models. This Tan-CAR construct warrants a clinical appraisal to test whether simultaneous targeting of CD19 and CD22 enhances leukemia eradication and reduces/delays relapse rates and antigen loss.

PD-L1 expression in peripheral T-cell lymphomas is not related to either PD-L1 gene amplification or rearrangements

Nodal peripheral T-cell lymphomas (n-PTCL) are aggressive lymphomas with no specific treatment. Programmed death 1 (PD-1) inhibits T-cell activation and proliferation, and the expression of its ligand PD-L1 has been associated with worse prognosis in some tumors. We performed immunohistochemistry for PD-1, p-STAT3, and PD-L1 (Clones SP142/263/22C3/28.8) and FISH studies for PD-L1/2 genes in chromosome 9p in a series of 168 formalin-fixed, paraffin-embedded n-PTCL samples. PD-L1 (clone 263) was the most frequently detected in both tumor cells (especially in the ALCL subgroup) and the microenvironment (especially in the AITL subgroup). In five ALCL cases, 3-4 copies of the two loci of chromosome 9 were found, suggestive of polyploidy. PD-L1 correlated with p-STAT3 on tumor cells. PD-1 expression in tumor cells was related to expression of PD-L1 in microenvironment. The expression of PD-L1 on tumor cells or microenvironment suggests that some n-PTCL cases might benefit from immune check-point modulation therapy.

In vivo CRISPR/Cas9 targeting of fusion oncogenes for selective elimination of cancer cells

Fusion oncogenes (FOs) are common in many cancer types and are powerful drivers of tumor development. Because their expression is exclusive to cancer cells and their elimination induces cell apoptosis in FO-driven cancers, FOs are attractive therapeutic targets. However, specifically targeting the resulting chimeric products is challenging. Based on CRISPR/Cas9 technology, here we devise a simple, efficient and non-patient-specific gene-editing strategy through targeting of two introns of the genes involved in the rearrangement, allowing for robust disruption of the FO specifically in cancer cells. As a proof-of-concept of its potential, we demonstrate the efficacy of intron-based targeting of transcription factors or tyrosine kinase FOs in reducing tumor burden/mortality in in vivo models. The FO targeting approach presented here might open new horizons for the selective elimination of cancer cells.

In vivo CRISPR/Cas9 targeting of fusion oncogenes for selective elimination of cancer cells

Fusion oncogenes (FOs) are common in many cancer types and are powerful drivers of tumor development. Because their expression is exclusive to cancer cells and their elimination induces cell apoptosis in FO-driven cancers, FOs are attractive therapeutic targets. However, specifically targeting the resulting chimeric products is challenging. Based on CRISPR/Cas9 technology, here we devise a simple, efficient and non-patient-specific gene-editing strategy through targeting of two introns of the genes involved in the rearrangement, allowing for robust disruption of the FO specifically in cancer cells. As a proof-of-concept of its potential, we demonstrate the efficacy of intron-based targeting of transcription factors or tyrosine kinase FOs in reducing tumor burden/mortality in in vivo models. The FO targeting approach presented here might open new horizons for the selective elimination of cancer cells.

NHEJ-Mediated Repair of CRISPR-Cas9-Induced DNA Breaks Efficiently Corrects Mutations in HSPCs from Patients with Fanconi Anemia

Non-homologous end-joining (NHEJ) is the preferred mechanism used by hematopoietic stem cells (HSCs) to repair double-stranded DNA breaks and is particularly increased in cells deficient in the Fanconi anemia (FA) pathway. Here, we show feasible correction of compromised functional phenotypes in hematopoietic cells from multiple FA complementation groups, including FA-A, FA-C, FA-D1, and FA-D2. NHEJ-mediated repair of targeted CRISPR-Cas9-induced DNA breaks generated compensatory insertions and deletions that restore the coding frame of the mutated gene. NHEJ-mediated editing efficacy was initially verified in FA lymphoblastic cell lines and then in primary FA patient-derived CD34⁺ cells, which showed marked proliferative advantage and phenotypic correction both in vitro and after transplantation. Importantly, and in contrast to homologous directed repair, NHEJ efficiently targeted primitive human HSCs, indicating that NHEJ editing approaches may constitute a sound alternative for editing self-renewing human HSCs and consequently for treatment of FA and other monogenic diseases affecting the hematopoietic system.

Functional characterization of two enhancers located downstream FOXP2

BACKGROUND

Mutations in the coding region of FOXP2 are known to cause speech and language impairment. However, it is not clear how dysregulation of the gene contributes to language deficit. Interestingly, microdeletions of the region downstream the gene have been associated with cognitive deficits.

METHODS

Here, we investigate changes in FOXP2 expression in the SK-N-MC neuroblastoma human cell line after deletion by CRISPR-Cas9 of two enhancers located downstream of the gene.

RESULTS

Deletion of any of these two functional enhancers downregulates FOXP2, but also upregulates the closest 3' gene MDFIC. Because this effect is not statistically significant in a HEK 293 cell line, derived from the human kidney, both enhancers might confer a tissue specific regulation to both genes. We have also found that the deletion of any of these enhancers downregulates six well-known FOXP2 target genes in the SK-N-MC cell line.

CONCLUSIONS

We expect these findings contribute to a deeper understanding of how FOXP2 and MDFIC are regulated to pace neuronal development supporting cognition, speech and language.

Immune Profiling and Quantitative Analysis Decipher the Clinical Role of Immune-Checkpoint Expression in the Tumor Immune Microenvironment of DLBCL

PD-1/L1 and CTLA-4 blockade immunotherapies have been approved for 13 types of cancers and are being studied in diffuse large B-cell lymphoma (DLBCL), the most common aggressive B-cell lymphoma. However, whether both PD-1 and CTLA-4 checkpoints are active and clinically significant in DLBCL is unknown. Whether PD-1 ligands expressed by tumor cells or by the microenvironment of DLBCL are critical for the PD-1 immune checkpoint is unclear. We performed immunophenotypic profiling for 405 patients with de novo DLBCL using a MultiOmyx immunofluorescence platform and simultaneously quantitated expression/coexpression of 13 immune markers to identify prognostic determinants. In both training and validation cohorts, results demonstrated a central role of the tumor immune microenvironment, and when its functionality was impaired by deficiency in tumor-infiltrating T cells and/or natural killer cells, high PD-1 expression (but not CTLA-4) on CD8+ T cells, or PD-L1 expression on T cells and macrophages, patients had significantly poorer survival after rituximab-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) immunochemotherapy. In contrast, tumor-cell PD-L2 expression was associated with superior survival, as well as PD-L1+CD20+ cells proximal (indicates interaction) to PD-1 + CD8+ T cells in patients with low PD-1 + percentage of CD8+ T cells. Gene-expression profiling results suggested the reversibility of T-cell exhaustion in PD-1+/PD-L1+ patients with unfavorable prognosis and implication of LILRA/B, IDO1, CHI3L1, and SOD2 upregulation in the microenvironment dysfunction with PD-L1 expression. This study comprehensively characterized the DLBCL immune landscape, deciphered the differential roles of various checkpoint components in rituximab-CHOP resistance in DLBCL patients, and suggests targets for PD-1/PD-L1 blockade and combination immunotherapies.

Teneurins: An Integrative Molecular, Functional, and Biomedical Overview of Their Role in Cancer

Teneurins are large transmembrane proteins originally identified in Drosophila. Their essential role in development of the central nervous system is conserved throughout species, and evidence supports their involvement in organogenesis of additional tissues. Homophilic and heterophilic interactions between Teneurin paralogues mediate cellular adhesion in crucial processes such as neuronal pathfinding and synaptic organization. At the molecular level, Teneurins are proteolytically processed into distinct subdomains that have been implicated in extracellular and intracellular signaling, and in transcriptional regulation. Phylogenetic studies have shown a high degree of intra- and interspecies conservation of Teneurin genes. Accordingly, the occurrence of genetic variants has been associated with functional and phenotypic alterations in experimental systems, and with some inherited or sporadic conditions. Recently, tumor-related variations in Teneurin gene expression have been associated with patient survival in different cancers. Although these findings were incidental and molecular mechanisms were not addressed, they suggested a potential utility of Teneurin transcript levels as biomarkers for disease prognosis. Mutations and chromosomal alterations affecting Teneurin genes have been found occasionally in tumors, but literature remains scarce. The analysis of open-access molecular and clinical datasets derived from large oncologic cohorts provides an invaluable resource for the identification of additional somatic mutations. However, Teneurin variants have not been classified in terms of pathogenic risk and their phenotypic impact remains unknown. On this basis, is it plausible to hypothesize that Teneurins play a role in carcinogenesis? Does current evidence support a tumor suppressive or rather oncogenic function for these proteins? Here, we comprehensively discuss available literature with integration of molecular evidence retrieved from open-access databases. We show that Teneurins undergo somatic changes comparable to those of well-established cancer genes, and discuss their involvement in cancer-related signaling pathways. Current data strongly suggest a functional contribution of Teneurins to human carcinogenesis.

Inducible overexpression of RUNX1b/c in human embryonic stem cells blocks early hematopoiesis from mesoderm

RUNX1 is absolutely required for definitive hematopoiesis, but the function of RUNX1b/c, two isoforms of human RUNX1, is unclear. We established inducible RUNX1b/c-overexpressing human embryonic stem cell (hESC) lines, in which RUNX1b/c overexpression prevented the emergence of CD34+ cells from early stage, thereby drastically reducing the production of hematopoietic stem/progenitor cells. Simultaneously, the expression of hematopoiesis-related factors was downregulated. However, such blockage effect disappeared from day 6 in hESC/AGM-S3 cell co-cultures, proving that the blockage occurred before the generation of hemogenic endothelial cells. This blockage was partially rescued by RepSox, an inhibitor of the transforming growth factor (TGF)-β signaling pathway, indicating a close relationship between RUNX1b/c and TGF-β pathway. Our results suggest a unique inhibitory function of RUNX1b/c in the development of early hematopoiesis and may aid further understanding of its biological function in normal and diseased models.

Somatic genome editing with the RCAS-TVA-CRISPR-Cas9 system for precision tumor modeling

To accurately recapitulate the heterogeneity of human diseases, animal models require to recreate multiple complex genetic alterations. Here, we combine the RCAS-TVA system with the CRISPR-Cas9 genome editing tools for precise modeling of human tumors. We show that somatic deletion in neural stem cells of a variety of known tumor suppressor genes (Trp53, Cdkn2a, and Pten) leads to high-grade glioma formation. Moreover, by simultaneous delivery of pairs of guide RNAs we generate different gene fusions with oncogenic potential, either by chromosomal deletion (Bcan-Ntrk1) or by chromosomal translocation (Myb-Qk). Lastly, using homology-directed-repair, we also produce tumors carrying the homologous mutation to human BRAF V600E, frequently identified in a variety of tumors, including different types of gliomas. In summary, we have developed an extremely versatile mouse model for in vivo somatic genome editing, that will elicit the generation of more accurate cancer models particularly appropriate for pre-clinical testing.

PAN3-PSMA2 fusion resulting from a novel t(7;13)(p14;q12) chromosome translocation in a myelodysplastic syndrome that evolved into acute myeloid leukemia

Background

Acquired primary chromosomal changes in cancer are sometimes found as sole karyotypic abnormalities. They are specifically associated with particular types of neoplasia, essential in establishing the neoplasm, and they often lead to the generation of chimeric genes of pathogenetic, diagnostic, and prognostic importance. Thus, the report of new primary cancer-specific chromosomal aberrations is not only of scientific but also potentially of clinical interest, as is the detection of their gene-level consequences.

Case presentation

RNA-sequencing was performed on a bone marrow sample from a patient with myelodysplastic syndrome (MDS). The karyotype was 46,XX,t(7;13)(p14;q12)[2]/46,XX[23]. The MDS later evolved into acute myeloid leukemia (AML) at which point the bone marrow cells also contained additional, secondary aberrations. The 7;13-translocation resulted in fusion of the gene PAN3 from 13q12 with PSMA2 from 7p14 to generate an out-of-frame PAN3–PSMA2 fusion transcript whose presence was verified by RT-PCR together with Sanger sequencing. Interphase fluorescence in situ hybridization analysis confirmed the existence of the chimeric gene.

Conclusions

The novel t(7;13)(p14;q12)/PAN3–PSMA2 in the neoplastic bone marrow cells could affect two key protein complex: (a) the PAN2/PAN3 complex (PAN3 rearrangement) which is responsible for deadenylation, the process of removing the poly(A) tail from RNA, and (b) the proteasome (PSMA2 rearrangement) which is responsible for degradation of intracellular proteins. The patient showed a favorable response to decitabine after treatment with 5-azacitidine and conventional intensive chemotherapy had failed. Whether this might represent a consistent feature of MDS/AML with this particular gene fusion, remains unknown.

Efficient Recreation of t(11;22) EWSR1-FLI1+ in Human Stem Cells Using CRISPR/Cas9

Efficient methodologies for recreating cancer-associated chromosome translocations are in high demand as tools for investigating how such events initiate cancer. The CRISPR/Cas9 system has been used to reconstruct the genetics of these complex rearrangements at native loci while maintaining the architecture and regulatory elements. However, the CRISPR system remains inefficient in human stem cells. Here, we compared three strategies aimed at enhancing the efficiency of the CRISPR-mediated t(11;22) translocation in human stem cells, including mesenchymal and induced pluripotent stem cells: (1) using end-joining DNA processing factors involved in repair mechanisms, or (2) ssODNs to guide the ligation of the double-strand break ends generated by CRISPR/Cas9; and (3) all-in-one plasmid or ribonucleoprotein complex-based approaches. We report that the generation of targeted t(11;22) is significantly increased by using a combination of ribonucleoprotein complexes and ssODNs. The CRISPR/Cas9-mediated generation of targeted t(11;22) in human stem cells opens up new avenues in modeling Ewing sarcoma.

mTORC1 Inactivation Promotes Colitis-Induced Colorectal Cancer but Protects from APC Loss-Dependent Tumorigenesis

Dietary habits that can induce inflammatory bowel disease (IBD) are major colorectal cancer (CRC) risk factors, but mechanisms linking nutrients, IBD, and CRC are unknown. Using human data and mouse models, we show that mTORC1 inactivation-induced chromosomal instability impairs intestinal crypt proliferation and regeneration, CDK4/6 dependently. This triggers interleukin (IL)-6-associated reparative inflammation, inducing crypt hyper-proliferation, wound healing, and CRC. Blocking IL-6 signaling or reactivating mTORC1 reduces inflammation-induced CRC, so mTORC1 activation suppresses tumorigenesis in IBD. Conversely, mTORC1 inactivation is beneficial in APC loss-dependent CRC. Thus, IL-6 blockers or protein-rich-diet-linked mTORC1 activation may prevent IBD-associated CRC. However, abolishing mTORC1 can mitigate CRC in predisposed patients with APC mutations. Our work reveals mTORC1 oncogenic and tumor-suppressive roles in intestinal epithelium and avenues to optimized and personalized therapeutic regimens for CRC.

FAM53B truncation caused by t(10;19)(q26;q13) chromosome translocation in acute lymphoblastic leukemia

RNA-sequencing of the patient's bone marrow detected fusion transcripts in which the coding sequence of the FAM53B gene (from 10q26) was fused to a genomic sequence (from 19q13) that mapped upstream of the SLC7A10 locus. Reverse transcription-polymerase chain reaction together with Sanger sequencing verified the presence of this fusion transcript. The FAM53B fusion transcript is not expected to produce any chimeric protein. However, it may code for a truncated FAM53B protein consisting of the first 302 amino acids of FAM53B together with amino acids from the 19q13 sequence. Functionally, the truncated FAM53B would be similar to the protein encoded by the FAM53B sequence with accession no. BC031654.1 (FAM53B protein accession no. AAH31654.1). Furthermore, the truncated protein contains the entire conserved domain of the FAM53 protein family. The chromosome aberration t(10;19)(q26;q13) detected in this study was previously reported in a single case of ALL, in which it was also the sole karyotypic change. Both patients entered complete hematological and cytogenetic remission following treatment.

RUNX1 truncation resulting from a cryptic and novel t(6;21)(q25;q22) chromosome translocation in acute myeloid leukemia: A case report

Fluorescence in situ hybridization examination of a pediatric AML patient whose bone marrow cells carried trisomy 4 and FLT3-ITD mutation, demonstrated that part of the RUNX1 probe had unexpectedly moved to chromosome band 6q25 indicating a cryptic t(6;21)(q25;q22) translocation. RNA sequencing showed fusion of exon 7 of RUNX1 with an intergenic sequence of 6q25 close to the MIR1202 locus, something that was verified by RT-PCR together with Sanger sequencing. The RUNX1 fusion transcript encodes a truncated protein containing the Runt homology domain responsible for both heterodimerization with CBFB and DNA binding, but lacking the proline-, serine-, and threonine-rich (PST) region which is the transcription activation domain at the C terminal end. Which genetic event (+4, FLT3-ITD, t(6;21)-RUNX1 truncation or other, undetected acquired changes) was more pathogenetically important in the present case of AML, remains unknown. The case illustrates that submicroscopic chromosomal rearrangements may accompany visible numerical changes and perhaps should be actively looked for whenever a single trisomy is found. An active search for them may provide both pathogenetic and prognostic novel information.

Induction of site-specific chromosomal translocations in embryonic stem cells by CRISPR/Cas9

Chromosomal translocation is the most common form of chromosomal abnormality and is often associated with congenital genetic disorders, infertility, and cancers. The lack of cellular and animal models for chromosomal translocations, however, has hampered our ability to understand the underlying disease mechanisms and to develop new therapies. Here, we show that site-specific chromosomal translocations can be generated in mouse embryonic stem cells (mESCs) via CRISPR/Cas9. Mouse ESCs carrying translocated chromosomes can be isolated and expanded to establish stable cell lines. Furthermore, chimeric mice can be generated by injecting these mESCs into host blastocysts. The establishment of ESC-based cellular and animal models of chromosomal translocation by CRISPR/Cas9 provides a powerful platform for understanding the effect of chromosomal translocation and for the development of new therapeutic strategies.