Search

The AML1-ETO ( RUNX1-RUNX1T1) fusion gene created by the chromosome translocation t(8;21) (q21;q22) is one of the essential contributors to leukemogenesis. Only a few studies in the literature have focused on fusion gene-derived circular RNAs (f-circRNAs). Here, we report several AML1-ETO -related fusion circular RNAs (F-CircAEs) in AML1-ETO -positive cell lines and primary patient blasts. Functional studies demonstrate that the over-expression of F-CircAE in NIH3T3 cells promotes cell proliferation in vitro and in vivo. F-CircAE expression enhances the colony formation ability of c-Kit + hematopoietic stem and progenitor cells (HSPCs). Meanwhile, the knockdown of endogenous F-CircAEs can inhibit the proliferation and colony formation ability of AML1-ETO -positive Kasumi-1 cells. Intriguingly, bioinformatic analysis revealed that the glycolysis pathway is down-regulated in F-CircAE-knockdown Kasumi-1 cells and up-regulated in F-CircAE over-expressed NIH3T3 cells. Further studies show that F-CircAE binds to the glycolytic protein ENO-1, up-regulates the expression level of glycolytic enzymes, and enhances lactate production. In summary, our study demonstrates that F-CircAE may exert biological activities on the growth of AML1-ETO leukemia cells by regulating the glycolysis pathway. Determining the role of F-CircAEs in AML1-ETO leukemia can lead to great strides in understanding its pathogenesis, thus providing new diagnostic markers and therapeutic targets.

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) is a serine/threonine kinase that belongs to the DYRK family of proteins, a subgroup of the evolutionarily conserved CMGC protein kinase superfamily. Due to its localization on chromosome 21, the biological significance of DYRK1A was initially characterized in the pathogenesis of Down syndrome (DS) and related neurodegenerative diseases. However, increasing evidence has demonstrated a prominent role in cancer through its ability to regulate biologic processes including cell cycle progression, DNA damage repair, transcription, ubiquitination, tyrosine kinase activity, and cancer stem cell maintenance. DYRK1A has been identified as both an oncogene and tumor suppressor in different models, underscoring the importance of cellular context in its function. Here, we review mechanistic contributions of DYRK1A to cancer biology and its role as a potential therapeutic target., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

Research Question: Can cumulus cells be used as a non-invasive target for the study of determinants of preimplantation embryo quality?, Design: Cumulus cells were collected from monosomy 21, trisomy 21 and euploid embryos and subjected to RNA sequencing analysis and real-time polymerase chain reaction assays. The differential gene expression was analysed for different comparisons., Results: A total of 3122 genes in monosomy 21 cumulus cells and 19 genes in trisomy 21 cumulus cells were differentially expressed compared with euploid cumulus cells. Thirteen of these genes were differentially expressed in both monosomy and trisomy 21, compared with euploid, including disheveled segment polarity protein 2 (DVL2), cellular communication network factor 1 (CCN1/CYR61) and serum response factor (SRF), which have been previously implicated in embryo developmental competence. In addition, ingenuity pathway analysis revealed cell-cell contact function to be affected in both monosomy and trisomy 21 cumulus cells., Conclusions: These findings support the use of cumulus cell gene expression analysis for the development of biomarkers evaluating oocyte quality for patients undergoing fertility preservation of oocytes., (Copyright © 2021 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Children with Down syndrome have a 150-fold increased risk of developing myeloid leukemia, but the mechanism of predisposition is unclear. Because Down syndrome leukemogenesis initiates during fetal development, we characterized the cellular and developmental context of preleukemic initiation and leukemic progression using gene editing in human disomic and trisomic fetal hematopoietic cells and xenotransplantation. GATA binding protein 1 ( GATA1 ) mutations caused transient preleukemia when introduced into trisomy 21 long-term hematopoietic stem cells, where a subset of chromosome 21 microRNAs affected predisposition to preleukemia. By contrast, progression to leukemia was independent of trisomy 21 and originated in various stem and progenitor cells through additional mutations in cohesin genes. CD117 + /KIT proto-oncogene (KIT) cells mediated the propagation of preleukemia and leukemia, and KIT inhibition targeted preleukemic stem cells., (Copyright © 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Acute myeloid leukemia development occurs in a stepwise fashion whereby an original driver mutation is followed by additional mutations. The first type of mutations tends to be in genes encoding members of the epigenetic/transcription regulatory machinery (i.e., RUNX1, DNMT3A, TET2), while the secondary mutations often involve genes encoding members of signaling pathways that cause uncontrolled growth of such cells such as the growth factor receptors c-KIT of FLT3. Patients usually present with both types of mutations, but it is currently unclear how both mutational events shape the epigenome in developing AML cells. To this end we generated an in vitro model of t(8;21) AML by expressing its driver oncoprotein RUNX1-ETO with or without a mutated (N822K) KIT protein. Expression of N822K-c-KIT strongly increases the self-renewal capacity of RUNX1-ETO-expressing cells. Global analysis of gene expression changes and alterations in the epigenome revealed that N822K-c-KIT expression profoundly influences the open chromatin landscape and transcription factor binding. However, our experiments also revealed that double mutant cells still differ from their patient-derived counterparts, highlighting the importance of studying patient cells to obtain a true picture of how gene regulatory networks have been reprogrammed during tumorigenesis., Competing Interests: Conflict of interest disclosure The authors declare no competing financial interests., (Copyright © 2020 ISEH -- Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.)

Introduction: A prototype of good prognosis, t(8;21)-positive AML, has diverse clinical and genetic features which affect its outcome. This study aimed at evaluating the clinico-pathological spectrum of t(8;21)-positive AML and ascertaining prognostic factors influencing its outcome in the Indian subcontinent., Methods: A retrospective analysis of 75 cases of t(8;21)-positive AML diagnosed over a period of six years (2013-2018) was carried out. Detailed clinical and laboratory data of the patients were collected from the electronic medical records and reviewed., Results: Median age was 19.5 years (range 5-75 years) with a M:F of 1.7. Myeloid sarcoma was observed in 9.3% cases. There were 85% FAB AML-M2, 8% AML-M1, and 7% AML-M4 subtypes. Prominent morphological characteristics included dyspoiesis in maturing myeloid cells (83%), long thin tapered Auer rods (58%), cytoplasmic vacuoles (58%), eosinophilia (50%), and mast cells (22%). Auer rods in maturing granulocytes (4% cases) were highly suggestive of the translocation. Additional cytogenetic abnormalities were present in 53% cases. Seventy-one percent (25/35) achieved CR. The overall survival (OS) was 40%, with a median follow-up of 27 months (range 4-57 months). None of the hematological or cytogenetic factors correlated with OS, except for the presence of myeloid sarcoma which had a trend toward poor survival (P = .07)., Conclusion: Outcome of t(8;21) AML is not influenced by any of the clinico-pathological parameters, except for a myeloid sarcoma, which may herald a poor prognosis. Recognition of this distinct subtype of AML would facilitate further molecular screening for risk stratification in resource-constrained settings., (© 2019 John Wiley & Sons Ltd.)

Acute myeloid leukemia (AML) is associated with mutations in transcriptional and epigenetic regulator genes impairing myeloid differentiation. The t(8;21)(q22;q22) translocation generates the RUNX1-ETO fusion protein, which interferes with the hematopoietic master regulator RUNX1. We previously showed that the maintenance of t(8;21) AML is dependent on RUNX1-ETO expression. Its depletion causes extensive changes in transcription factor binding, as well as gene expression, and initiates myeloid differentiation. However, how these processes are connected within a gene regulatory network is unclear. To address this question, we performed Promoter-Capture Hi-C assays, with or without RUNX1-ETO depletion and assigned interacting cis-regulatory elements to their respective genes. To construct a RUNX1-ETO-dependent gene regulatory network maintaining AML, we integrated cis-regulatory element interactions with gene expression and transcription factor binding data. This analysis shows that RUNX1-ETO participates in cis-regulatory element interactions. However, differential interactions following RUNX1-ETO depletion are driven by alterations in the binding of RUNX1-ETO-regulated transcription factors., (Copyright © 2019 The Author(s). Published by Elsevier Inc. All rights reserved.)

The TEL-AML1 fusion gene, generated by the t(12;21) chromosome translocation, arises in a progenitor/stem cell and could induce clonal expansion of a persistent preleukemic B-cell clone which, on acquisition of secondary alterations, may turn into full-blown leukemia. During infections, deregulated cytokine signaling, including transforming growth factor β (TGF-β), can further accelerate this process by creating a protumoral bone marrow (BM) microenvironment. Here, we show that activin A, a member of the TGF-β family induced under inflammatory conditions, inhibits the proliferation of normal progenitor B cells but not that of preleukemic TEL-AML1-positive clones, thereby providing a selective advantage to the latter. Finally, we find that activin A inhibits BM-derived mesenchymal stromal cell-mediated secretion of CXCL12, a major chemoattractant in the BM compartment, thereby contributing to shape a leukemia-promoting environment. Overall, our findings indicate that activin A, in concert with TGF-β, could play an important role in the creation of a pro-oncogenic BM microenvironment and provide novel mechanistic insights into TEL-AML1-associated leukemogenesis., (Copyright © 2019. Published by Elsevier Inc.)

The most frequently occurring genetic abnormality in pediatric B-lymphocyte-lineage acute lymphoblastic leukemia is the t(12;21) chromosomal translocation that results in a ETV6-RUNX1 (also known as TEL-AML1) fusion gene. Expression of ETV6-RUNX1 induces a preleukemic condition leading to acquisition of secondary driver mutations, but the mechanism is poorly understood. SPI-B (encoded by SPIB) is an important transcriptional activator of B-cell development and differentiation. We hypothesized that SPIB is directly transcriptionally repressed by ETV6-RUNX1. Using chromatin immunoprecipitation, we identified a regulatory region in the first intron of SPIB that interacts with ETV6-RUNX1. Mutation of the RUNX1 binding site in SPIB intron 1 prevented transcriptional repression in transient transfection assays. Next, we sought to determine to what extent gene expression in REH cells can be altered by ectopic SPI-B expression. SPI-B expression was forced using CRISPR-mediated gene activation and also using a retroviral vector. Forced expression of SPI-B resulted in altered gene expression and, at high levels, impaired cell proliferation and induced apoptosis. Finally, we identified CARD11 and CDKN1A (encoding p21) as transcriptional targets of SPI-B involved in regulation of proliferation and apoptosis. Taken together, this study identifies SPIB as an important target of ETV6-RUNX1 in regulation of B-cell gene expression in t(12;21) leukemia., (Copyright © 2019 ISEH -- Society for Hematology and Stem Cells. Published by Elsevier Inc. All rights reserved.)

We previously demonstrated that an integrated XIST transgene can broadly repress one chromosome 21 in Down syndrome (DS) pluripotent cells. Here we address whether trisomy-silencing can normalize cell function and development sufficiently to correct cell pathogenesis, tested in an in vitro model of human fetal hematopoiesis, for which DS cellular phenotypes are best known. XIST induction in four transgenic clones reproducibly corrected over-production of megakaryocytes and erythrocytes, key to DS myeloproliferative disorder and leukemia. A contrasting increase in neural stem and iPS cells shows cell-type specificity, supporting this approach successfully rebalances the hematopoietic developmental program. Given this, we next used this system to extend knowledge of hematopoietic pathogenesis on multiple points. Results demonstrate trisomy 21 expression promotes over-production of CD43 + but not earlier CD34 + /CD43 - progenitors and indicates this is associated with increased IGF signaling. This study demonstrates proof-of-principle for this epigenetic-based strategy to investigate, and potentially mitigate, DS developmental pathologies.

Purpose of Review: Acute lymphoblastic leukemias (ALL) are malignant disorders of immature B or T cells that occur characteristically in children, usually under the age of 6 (75%). Approximately 6000 new cases of ALL are diagnosed each year in the USA, 80-85% of which represent B-ALL forms. Most presentations of B-ALL are leukemic, whereas T-ALL presents with a mediastinal mass, with or without leukemic involvement. The revised fourth edition of the World Health Organization (WHO) classification (2017) has introduced some changes in both B and T-ALL. Here, we summarize the categories of lymphoblastic leukemia/lymphomas as defined by the WHO and recent developments in the understanding of this group of hematologic malignancy., Recent Findings: Two provisional categories of B-ALL have now been identified including B-ALL, BCR-ABL1-like, and B-ALL with iAMP21. The Philadelphia chromosome-like B-ALL includes forms of the disease that shares the expression profiling of B-ALL with t(9;22) but lack such rearrangement. The second one shows amplification of part of the chromosome 21. Both entities are associated with worse prognosis. Within the T-ALL group, an early precursor T cell form has now been introduced as a provisional category. Such group demonstrates expression of stem cell and myeloid markers in conjunction with the T cell antigens. The current review summarizes the recent updates to the WHO classification.

The AML1-ETO fusion protein (A/E), which results from the t(8;21) translocation, is considered to be a leukemia-initiating event. Identifying the mechanisms underlying the oncogenic activity of A/E remains a major challenge. In this study, we identified a specific down-regulation of brain acid-soluble protein 1 (BASP1) in t(8;21) acute myeloid leukemia (AML). A/E recognized AML1-binding sites and recruited DNA methyltransferase 3a (DNMT3a) to the BASP1 promoter sequence, which triggered DNA methylation-mediated silencing of BASP1. Ectopic expression of BASP1 inhibited proliferation and the colony-forming ability of A/E-positive AML cell lines and led to apoptosis and cell cycle arrest. The DNMT inhibitor decitabine up-regulated the expression of BASP1 in A/E-positive AML cell lines. In conclusion, our data suggest that BASP1 silencing via promoter methylation may be involved in A/E-mediated leukemogenesis and that BASP1 targeting may be an actionable therapeutic strategy in t(8;21) AML.

Objective: MicroRNA-155 (miRNA-155) resides within the B-cell integration cluster gene on chromosome 21. It can act either as an oncogene or as a tumor-suppressor gene, depending on the cell background in which miRNA-155 is performing its specific target gene controlling function. Therefore, the aim of this study was to investigate miRNA-155 expression in patients with B-cell non-Hodgkin lymphoma (NHL) and its relation to disease prognosis in diffuse large B-cell lymphoma (DLBCL) patients., Materials and Methods: Reverse transcription-polymerase chain reaction assay was performed to evaluate the expression levels of miRNA-155 in 84 patients with newly diagnosed B-cell NHL and 15 normal controls., Results: Compared with normal controls, miRNA-155 expression was significantly upregulated in patients. Moreover, higher levels of miRNA-155 were associated with the presence of B symptoms, involvement of extranodal sites, and high Eastern Cooperative Oncology Group (ECOG) score. Higher levels of miRNA-155 in DLBCL were associated with non-germinal B-cell-like type, the presence of B symptoms, involvement of extranodal sites, and higher International Prognostic Index (IPI) and ECOG scores. Only the high IPI score and high miRNA-155 expression indicated a higher risk of lower event-free survival using multivariate Cox regression analysis. Our data demonstrated that the expression of miRNA-155 was upregulated in newly diagnosed B-cell NHL patients. miRNA-155 is expressed at a lower level in GCB-subtype DLBCL. Low IPI score and miRNA-155 expression were predictors of longer event-free survival., Conclusion: Despite contradicting literature reports, the current findings suggest the potential value of miRNA-155 as a biomarker of prognosis and monitoring in B-cell NHL, and especially that of the DLBCL type.

Gene copy-number changes influence phenotypes through gene-dosage alteration and subsequent changes of protein complex stoichiometry. Human trisomies where gene copy numbers are increased uniformly over entire chromosomes provide generic cases for studying these relationships. In most trisomies, gene and protein level alterations have fatal consequences. We used genome-wide protein-protein interaction data to identify chromosome-specific patterns of protein interactions. We found that some chromosomes encode proteins that interact infrequently with each other, chromosome 21 in particular. We combined the protein interaction data with transcriptome data from human brain tissue to investigate how this pattern of global interactions may affect cellular function. We identified highly connected proteins that also had coordinated gene expression. These proteins were associated with important neurological functions affecting the characteristic phenotypes for Down syndrome and have previously been validated in mouse knockout experiments. Our approach is general and applicable to other gene-dosage changes, such as arm-level amplifications in cancer., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Down syndrome (DS) patients demonstrate the neuropathology of Alzheimer's disease (AD) characterized by the formation of senile plaques and neurofibrillary tangles by age 40-50 years. It has been considered for a number of years that 1.5-fold expression of the gene for the amyloid precursor protein (APP) located on chromosome 21 leading to overproduction of amyloid-β peptide (Aβ) results in the early onset of AD in adults with DS. However, the mean age of onset of familial AD with the Swedish mutation on APP which has high affinity for β-secretase associated with a dramatic increase in Aβ production is about 55 years. This paradox indicates that there is a poor correlation between average ages of AD onset and the theoretical amount of Aβ production and that there are factors exacerbating AD on chromosome 21. We therefore focused on dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A), since overexpressing transgenic mice show AD-like brain pathology. The overexpression of DYRK1A caused suppression of the activity of neprilysin (NEP), which is a major Aβ-degrading enzyme in the brain, and phosphorylation at the NEP cytoplasmic domain. NEP activity was markedly reduced in fibroblasts derived from DS patients compared with that in fibroblasts derived from healthy controls. This impaired activity of NEP was rescued by DYRK1A inhibition. These results show that DYRK1A overexpression causes suppression of NEP activity through its phosphorylation in DS patients. Our results suggest that DYRK1A inhibitors could be effective against AD not only in adults with DS but also in sporadic AD patients.

Trisomy 21 (T21) is the most common chromosome abnormality in humans and is associated with a spectrum of phenotypes, including cognitive impairment, congenital heart defects and immune system defects. In addition, T21 is also associated with abnormalities of fetal membranes including chorioamniotic separation, delayed fusion of the chorioamniotic membranes, defects in syncytiotrophoblast formation, as well as amniocyte senescence. There is evidence indicating miRNAs encoded by sequences on chromosome 21 (Chr-21) are involved in several of the cognitive and neurological phenotypes of T21, but the role of Chr-21 derived miRNAs in fetal membrane abnormalities associated with T21 has not been investigated. In the current study, we determined the expression patterns of three miRNAs derived from a cluster on Chr-21 - hsa-miR-99a, hsa-miR-125b and hsa-let-7c in chorioamniotic membranes obtained from term pregnancies with spontaneous rupture (n = 20). Tissue and location specific expression patterns within the chorioamniotic membranes were identified. The rupture zone in the choriodecidua had distinct expression patterns compared to other fetal membrane locations. Despite the increased gene dosage associated with T21, the expression of all three miRNAs was reduced in cultured T21 amniocytes as compared to cultured euploid amniocytes. In silico analysis of experimentally validated targets of the three miRNAs suggest these Chr-21 derived miRNAs play a potential role in fetal membrane rupture and the fetal membrane defects associated with T21., (Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The t(8;21) translocation is one of the most frequent cytogenetic abnormalities in acute myeloid leukaemia (AML) and results in the RUNX1/RUNX1T1 rearrangement. Despite the causative role of the RUNX1/RUNX1T1 fusion gene in leukaemia initiation, additional genetic lesions are required for disease development. Here we identify recurring ZBTB7A mutations in 23% (13/56) of AML t(8;21) patients, including missense and truncating mutations resulting in alteration or loss of the C-terminal zinc-finger domain of ZBTB7A. The transcription factor ZBTB7A is important for haematopoietic lineage fate decisions and for regulation of glycolysis. On a functional level, we show that ZBTB7A mutations disrupt the transcriptional repressor potential and the anti-proliferative effect of ZBTB7A. The specific association of ZBTB7A mutations with t(8;21) rearranged AML points towards leukaemogenic cooperativity between mutant ZBTB7A and the RUNX1/RUNX1T1 fusion.

Introduction: Trisomy 21 (T21) is the most common aneuploidy affecting humans and is caused by an extra copy of all or part of chromosome 21 (chr21). DNA methylation is an epigenetic event that plays an important role in human diseases via regulation of gene expression. However, the integrative association between DNA methylation and gene expression in T21 fetal placenta has yet to be determined., Methods: We profiled expression of 207 genes on chr21 and their DNA methylation patterns in placenta samples from normal and DS fetuses using microarray analysis and predicted the functions of differentially expressed genes using bioinformatics tools., Results: We found 47 genes with significantly increased expression in the T21 placenta compared to the normal placenta. Hypomethylation of the 47 genes was observed in the T21 placenta. Most of hypomethylated DNA positions were intragenic regions, i.e. regions inside a gene. Moreover, gene expression and hypomethylated DNA position showed significantly positive associations. By analyzing the properties of the gene-disease network, we found that increased genes in the T21 placenta were significantly associated with T21 and T21 complications such as mental retardation, neurobehavioral manifestations, and congenital abnormalities., Discussion: To our knowledge, this is the first study to comprehensively survey the association between gene expression and DNA methylation in chr21 of the T21 fetal placenta. Our findings provide a broad overview of the relationships between gene expression and DNA methylation in the placentas of fetuses with T21 and could contribute to future research efforts concerning genes involvement in disease pathogenesis., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Autism Spectrum Disorder (ASD) is a group of neurodevelopmental disorders with complex genetic etiology. Recent studies have indicated that children with ASD may have altered folate or methionine metabolism, suggesting that the folate-methionine cycle may play a key role in the etiology of ASD. SLC19A1, also referred to as reduced folate carrier 1 (RFC1), is a member of the solute carrier group of transporters and is one of the key enzymes in the folate metabolism pathway. Findings from multiple genomic screens suggest the presence of an autism susceptibility locus on chromosome 21q22.3, which includes SLC19A1. Therefore, we performed a case-control study in a Japanese population. In this study, DNA samples obtained from 147 ASD patients at the Kanazawa University Hospital in Japan and 150 unrelated healthy Japanese volunteers were examined by the sequence-specific primer-polymerase chain reaction method pooled with fluorescence correlation spectroscopy. p < 0.05 was considered to represent a statistically significant outcome. Of 13 single nucleotide polymorphisms (SNPs) examined, a significant p-value was obtained for AA genotype of one SNP (rs1023159, OR = 0.39, 95% CI = 0.16-0.91, p = 0.0394; Fisher's exact test). Despite some conflicting results, our findings supported a role for the polymorphism rs1023159 of the SLC19A1 gene, alone or in combination, as a risk factor for ASD. However, the findings were not consistent after multiple testing corrections. In conclusion, although our results supported a role of the SLC19A1 gene in the etiology of ASD, it was not a significant risk factor for the ASD samples analyzed in this study.

Hirschsprung's disease (HSCR) is a severe congenital anomaly of the enteric nervous system (ENS) characterized by functional intestinal obstruction due to a lack of intrinsic innervation in the distal bowel. Distal innervation deficiency results from incomplete colonization of the bowel by enteric neural crest cells (eNCCs), the ENS precursors. Here, we report the generation of a mouse model for HSCR--named Holstein--that contains an untargeted transgenic insertion upstream of the collagen-6α4 (Col6a4) gene. This insertion induces eNCC-specific upregulation of Col6a4 expression that increases total collagen VI protein levels in the extracellular matrix (ECM) surrounding both the developing and the postnatal ENS. Increased collagen VI levels during development mainly result in slower migration of eNCCs. This appears to be due to the fact that collagen VI is a poor substratum for supporting eNCC migration and can even interfere with the migration-promoting effects of fibronectin. Importantly, for a majority of patients in a HSCR cohort, the myenteric ganglia from the ganglionated region are also specifically surrounded by abundant collagen VI microfibrils, an outcome accentuated by Down syndrome. Collectively, our data thus unveil a clinically relevant pathogenic mechanism for HSCR that involves cell-autonomous changes in ECM composition surrounding eNCCs. Moreover, as COL6A1 and COL6A2 are on human Chr.21q, this mechanism is highly relevant to the predisposition of patients with Down syndrome to HSCR.

Following the observation of increased oxidative DNA damage in nuclear and mitochondrial DNA extracted from post-mortem brain regions of patients affected by neurodegenerative diseases, the last years of the previous century and the first decade of the present one have been largely dedicated to the search of markers of DNA damage in neuronal samples and peripheral tissues of patients in early, intermediate or late stages of neurodegeneration. Those studies allowed to demonstrate that oxidative DNA damage is one of the earliest detectable events in neurodegeneration, but also revealed cytogenetic damage in neurodegenerative conditions, such as for example a tendency towards chromosome 21 malsegregation in Alzheimer's disease. As it happens for many neurodegenerative risk factors the question of whether DNA damage is cause or consequence of the neurodegenerative process is still open, and probably both is true. The research interest in markers of oxidative stress was shifted, in recent years, towards the search of epigenetic biomarkers of neurodegenerative disorders, following the accumulating evidence of a substantial contribution of epigenetic mechanisms to learning, memory processes, behavioural disorders and neurodegeneration. Increasing evidence is however linking DNA damage and repair with epigenetic phenomena, thereby opening the way to a very attractive and timely research topic in neurodegenerative diseases. We will address those issues in the context of Alzheimer's disease, Parkinson's disease, and Amyotrophic Lateral Sclerosis, which represent three of the most common neurodegenerative pathologies in humans., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Introduction: Down syndrome (DS) is the most common aneuploidy, caused by an extra copy of all or part of chromosome 21 (chr21). Differential microRNA (miRNA) expression is involved in many human diseases including DS. However, the genome-wide changes in miRNA expression in DS fetal placentas have yet to be determined, and the function of these changes is also unclear., Methods: We profiled genome-wide miRNA expression in placenta samples from euploid or DS fetuses by using microarray technology and predicted the functions of differentially expressed miRNAs using bioinformatics tools., Results: Thirty-four miRNAs were significantly differentially expressed in the DS placenta compared with the normal placenta (16 up-regulated and 18 down-regulated). However, expression of chr21-derived miRNAs did not change. Predicted target genes included 7434 genes targeted by up-regulated miRNAs and 6071 genes targeted by down-regulated miRNAs. Seventy-six of these target genes were located on chr21 (10 genes controlled by down-regulated miRNAs and 34 genes by up-regulated miRNAs, and 32 genes by both). Target genes on chr21 were significantly associated with DS and DS-related disorders, such as mental retardation, neurobehavioral manifestations, and congenital abnormalities., Discussion: To our knowledge, this is the first genome-wide study to comprehensively survey placental miRNAs in DS fetuses. Our results provide new insight into miRNA expression in placentas of fetuses with DS. Additionally, our findings indicate that the differentially expressed miRNAs in the DS placenta may potentially affect various pathways related to DS pathogenesis., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The aim of the current study was to identify the genes on human chromosome 21 (HC21) that may serve important functions in the pathogenesis of Down syndrome (DS). The microarray data GSE5390 were obtained from the Gene Expression Omnibus database, which contained 7 DS and 8 healthy normal samples. The data were then normalized and the differentially expressed genes (DEGs) were identified using the LIMMA package and Bonferroni correction. Furthermore, the DEGs underwent clustering and gene ontology analysis. Additionally, the locations of the DEGs on HC21 were confirmed using human genome 19 in the University of California, Santa Cruz Interaction Browser. A total of 25 upregulated and 275 downregulated genes were screened between DS and healthy samples with a false discovery rate of <0.05 and |logFC|>1. The expression levels of these genes in the two samples were different. In addition, the up‑ and downregulated genes were markedly enriched in organic substance biological processes (P=4.48x10‑10) and cell‑cell signaling (P=0.000227). Furthermore, 17 overexpressed genes were identified on the 21q21‑22 area, including COL6A2, TTC3 and ABCG1. Together, these observations suggest that 17 upregulated genes on HC21 may be involved in the development of DS and provide the basis for understanding this disability.

The majority of children with Down syndrome (DS) develop Alzheimer's disease (AD) at an early age. Although long-chain n-3 fatty acids (FA) are protective of neurodegeneration, little is known about the FA status in DS. In the present study, we aimed to investigate whether children with DS presented altered plasma and erythrocyte membrane phospholipids (PL) FA composition, when compared with their non-affected siblings. Venous blood samples were analysed for plasma and erythrocyte membrane FA composition by TLC followed by GC techniques. Lipid molecular species were determined by electrospray ionisation/tandem MS (ESI-MS/MS). FA analysis measured by standard GC showed an increased concentration of MUFA and a decreased concentration of plasmalogens in major PL fractions, but there were no differences in the concentrations of arachidonic acid or DHA. However, as identified by ESI-MS/MS, children with DS had increased levels of the following erythrocyte PL molecular species: 16 : 0-16 : 0, 16 : 0-18 : 1 and 16 : 0-18 : 2n-6, with reduced levels of 16 : 0-20 : 4n-6 species. Children with DS presented significantly higher levels of MUFA in both plasma and erythrocyte membrane, as well as higher levels of saturated and monounsaturated molecular species. Of interest was the almost double proportion of 16 : 0-18 : 2n-6 and nearly half the proportion of 16 : 0-20 : 4n-6 of choline phosphoacylglycerol species in children with DS compared with their non-affected siblings. These significant differences were only revealed by ESI-MS/MS and were not observed in the GC analysis. Further investigations are needed to explore molecular mechanisms and to test the association between the pathophysiology of DS and the risk of AD.

Objective: To examine in a general population the performance of cell-free DNA (cfDNA) testing for trisomies 21, 18 and 13 at 10-11 weeks' gestation and compare it to that of the combined test at 11-13 weeks., Methods: In 2905 singleton pregnancies, prospective screening for trisomies was performed by chromosome-selective sequencing of cfDNA in maternal blood at 10-11 weeks' gestation and by the combined test at 11-13 weeks' gestation., Results: Median maternal age of the study population was 36.9 (range, 20.4-51.9) years. Results from cfDNA analysis were provided for 2851 (98.1%) cases and these were available within 14 days from sampling in 2848 (98.0%) cases. The trisomic status of the pregnancies was determined by prenatal or postnatal karyotyping or clinical examination of the neonates. Of the 2785 pregnancies with a cfDNA result and known trisomic status, cfDNA testing correctly identified all 32 cases with trisomy 21, nine of 10 with trisomy 18 and two of five with trisomy 13, with false-positive rates of 0.04%, 0.19% and 0.07%, respectively. In cases with discordant results between cfDNA testing and fetal karyotype, the median fetal fraction was lower than in those with concordant results (6% vs 11%). Using the combined test, the estimated risk for trisomy 21 was ≥ 1/100 in all trisomic cases and in 4.4% of the non-trisomic pregnancies., Conclusion: The performance of first-trimester cfDNA testing for trisomies 21 and 18 in the general population is similar to that in high-risk pregnancies. Most false-positive and false-negative results from cfDNA testing could be avoided if the a priori risk from the combined test is taken into account in the interpretation of individual risk., (Copyright © 2014 ISUOG. Published by John Wiley & Sons Ltd.)

Children with constitutional trisomy 21 (cT21, Down Syndrome, DS) are at a higher risk for both myeloid and B-lymphoid leukaemias. The myeloid leukaemias are often preceded by a transient neonatal pre-leukaemic syndrome, Transient Abnormal Myelopoiesis (TAM). TAM is caused by cooperation between cT21 and acquired somatic N-terminal truncating mutations in the key haematopoietic transcription factor GATA1. These mutations, which are not leukaemogenic in the absence of cT21, are found in almost one-third of neonates with DS. Analysis of primary human fetal liver haematopoietic cells and of human embryonic stem cells demonstrates that cT21 itself substantially alters human fetal haematopoietic development. Consequently, many haematopoietic developmental defects are observed in neonates with DS even in the absence of TAM. Although studies in mouse models have suggested a pathogenic role of deregulated expression of several chromosome 21-encoded genes, their role in human leukaemogenesis remains unclear. As cT21 exists in all embryonic cells, the molecular basis of cT21-associated leukaemias probably reflects a complex interaction between deregulated gene expression in haematopoietic cells and the fetal haematopoietic microenvironment in DS., (© 2014 John Wiley & Sons Ltd.)

Exposure of cells to ultraviolet (UV)-A radiation induces oxidative damage in DNA, such as 8-oxo-7,8-dihydroguanine (8-oxoG), single-strand breaks, a-basic sites, and DNA-protein cross-links, via reactions with reactive oxygen species (ROS). In this study we examine whether the damage other than double-strand breaks (non-DSB damage), which is UV-A-induced oxidative damage, plays a role in the induction of chromosomal instability. We exposed human chromosome 21 to UV-A and transferred the chromosome into non-irradiated mouse recipient cells by microcell-mediated chromosome transfer. The chromosomal instability of both the transferred human chromosome and the recipient mouse chromosomes was examined by whole-chromosome painting and fluorescence in situ hybridization (WCP-FISH). The ploidy of the mouse recipient cells increased, and chromosomal aberrations occurred not only in the UV-A-irradiated human chromosome but also in the non-irradiated mouse chromosomes. The frequencies of these abnormalities increased with the radiation dose received by the transferred human chromosome. In contrast, in the control experiment, in which an non-irradiated human chromosome was transferred, the micro-cell hybrids remained diploid, and the frequency of chromosomal aberrations in both the transferred human chromosome and recipient mouse chromosomes remained low. Thus, the present study indicates that a chromosome harboring non-DSB damage induced by UV-A irradiation is unstable and transmits instability to chromosomes of non-irradiated recipient mouse cells., (Copyright © 2014 Elsevier B.V. All rights reserved.)

One of the most frequent chromosomal translocation found in patients with acute myeloid leukemia (AML) is the t(8;21). This translocation involves the RUNX1 and ETO genes. The breakpoints regions for t(8;21) are located at intron 5 and intron 1 of the RUNX1 and ETO gene respectively. To date, no homologous sequences have been found in these regions to explain their recombination. The breakpoint regions of RUNX1 gene are characterized by the presence of DNasaI hypersensitive sites and topoisomerase II cleavage sites, but no information exists about complementary regions of ETO gene. Here, we report analysis of chromatin structure of ETO breakpoint regions. Chromatin immunoprecipitation (ChIP) were performed with antibodies specific to acetylated histone H3, H4, and total histone H1. Nucleosomal distribution at the ETO locus was evaluated by determining total levels of histone H3. Our data show that in myeloid cells, the breakpoint regions at the ETO gene are enriched in hyperacetylated histone H3 compared to a control region of similar size where no translocations have been described. Moreover, acetylated H4 associates with both the whole ETO breakpoint regions as well as the control intron. Interestingly, we observed no H1 association either at the breakpoint regions or the control region of the ETO gene. Our data indicate that a common chromatin structure enriched in acetylated histones is present in breakpoint regions involved in formation of (8;21) leukemic translocation., (© 2013 Wiley Periodicals, Inc.)

The biochemical properties and subcellular localization of prolyl endopeptidase (PREP) in brain are well characterized and its implications in the realization of cognitive processes and in the pathogenesis of neurodegenerative disorders are a matter of intensive investigation. In contrast, very little is known about its homolog, the PREP-like protein (PREPL). In order to obtain initial hints about the involvement of PREPL in physiological processes, a differential proteomic screen was performed with human skin fibroblasts from controls and patients with PREPL deficiency (hypotonia-cystinuria syndrome). The majority of affected proteins represented cytoskeletal proteins, including caldesmon, tropomyosin α3 chain, lamin A, β-actin, γ-actin, vimentin and zyxin. Therefore, the analysis of PREPL subcellular localization by confocal laser scanning and electron microscopy in mouse neurons was focused on the cytoskeleton. The co-localization of PREPL with cytoskeletal marker proteins such as β-actin and microtubulin-associated protein-2 was observed, in addition to the presence of PREPL within Golgi apparatus and growth cones. In the mouse brain, PREPL is neuronally expressed and highly abundant in neocortex, substantia nigra and locus coeruleus. This mirrors to some extent the distribution pattern of PREP and points toward redundant functions of both proteins. In the human neocortex, PREPL immunostaining was found in the cytoplasm and in neuropil, in particular of layer V pyramidal neurons. This staining was reduced in the neocortex of Alzheimer's disease (AD) patients. Moreover, in AD brains, PREPL immunoreactivity was observed in the nucleus and in varicose neuritic processes. Our data indicate physiological functions of PREPL associated with the cytoskeleton, which may be affected under conditions of cytoskeletal degeneration., (Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.)

Down syndrome (DS) is the most common chromosomal abnormality in humans. DS is characterized by a number of phenotypes, including the development of Alzheimer's disease-like pathology and immunological, hematological and cardiovascular alterations. Apoptosis or programmed cell death is physiologically involved in development and aging, as well as in numerous pathological processes. Altered apoptosis has been proposed as a putative mechanism underlying many DS phenotypes. Evidence from human and animal studies indicates that apoptosis does not have a prominent role in the disturbances found in brain development in trisomy 21. However, alterations in apoptosis have been associated with neurodegeneration in the aging DS brain, with impairments in general growth and with immunological, cardiovascular and oncological alterations. Altered apoptosis in DS is likely to be the result of the interplay between several chromosome 21 (Hsa21) and non-Hsa21 genes. The interplay between these genes may affect physiological programmed cell death either directly, by modifying the activity of the apoptotic pathways, or indirectly, by inducing degeneration and rendering the cell more vulnerable to apoptosis-inducing factors.

At least half of the human genome is derived from repetitive elements, which are often lineage specific and silenced by a variety of genetic and epigenetic mechanisms. Using a transchromosomic mouse strain that transmits an almost complete single copy of human chromosome 21 via the female germline, we show that a heterologous regulatory environment can transcriptionally activate transposon-derived human regulatory regions. In the mouse nucleus, hundreds of locations on human chromosome 21 newly associate with activating histone modifications in both somatic and germline tissues, and influence the gene expression of nearby transcripts. These regions are enriched with primate and human lineage-specific transposable elements, and their activation corresponds to changes in DNA methylation at CpG dinucleotides. This study reveals the latent regulatory potential of the repetitive human genome and illustrates the species specificity of mechanisms that control it., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Down syndrome (DS) is the most common genetic aberration leading to intellectual disability. DS results from an extra copy of the long arm of human chromosome 21 (HSA21) and the increased expression of trisomic genes due to gene dosage. While expression in DS and DS models has been studied extensively at the RNA level, much less is known about expression of trisomic genes at the protein level. We have used quantitative Western blotting with antibodies to 20 proteins encoded by HSA21 to assess trisomic protein expression in lymphoblastoid cell lines (LCLs) from patients with DS and in brains from two mouse models of DS. These antibodies have recently become available and the 20 proteins largely have not been investigated previously for their potential contributions to the phenotypic features of DS. Twelve proteins had detectable expression in LCLs and three, CCT8, MX1 and PWP2, showed elevated levels in LCLs derived from patients with DS compared with controls. Antibodies against 15 proteins detected bands of appropriate sizes in lysates from mouse brain cortex. Genes for 12 of these proteins are trisomic in the Tc1 mouse model of DS, but only SIM2 and ZNF295 showed elevated expression in Tc1 cortex when compared with controls. Genes for eight of the 15 proteins are trisomic in the Ts65Dn mouse model of DS, but only ZNF294 was over expressed in cortex. Comparison of trisomic gene expression at the protein level with previous reports at the mRNA level showed many inconsistencies. These may be caused by natural inter-individual variability, differences in the age of mice analyzed, or post-transcriptional regulation of gene dosage effects. These antibodies provide resources for further investigation of the molecular basis of intellectual disability in DS., (Copyright © 2012 Elsevier B.V. All rights reserved.)

The genetics of acute lymphoblastic leukemia are becoming well understood and the incidence of individual chromosomal abnormalities varies considerably with age. Cytogenetics provide reliable risk stratification for treatment: high hyperdiploidy and ETV6-RUNX1 are good risk, whereas BCR-ABL1, MLL rearrangements, and hypodiploidy are poor risk. Nevertheless, some patients within the good- and intermediate-risk groups will unpredictably relapse. With advancing technologies in array-based approaches (single nucleotide polymorphism arrays) and next-generation sequencing to study the genome, increasing numbers of new genetic changes are being discovered. These include deletions of B-cell differentiation and cell cycle control genes, as well as mutations of genes in key signaling pathways. Their associations and interactions with established cytogenetic subgroups and with each other are becoming elucidated. Whether they have a link to outcome is the most important factor for refinement of risk factors in relation to clinical trials. For several newly identified abnormalities, including intrachromosomal amplification of chromosome 21 (iAMP21), that are associated with a poor prognosis with standard therapy, appropriately modified treatment has significantly improved outcome. After the successful use of tyrosine kinase inhibitors in the treatment of BCR-ABL1-positive acute lymphoblastic leukemia, patients with alternative ABL1 translocations and rearrangements involving PDGFRB may benefit from treatment with tyrosine kinase inhibitors. Other aberrations, for example, CRLF2 overexpression and JAK2 mutations, are also providing potential novel therapeutic targets with the prospect of reduced toxicity.

With 24.3 million people affected in 2005 and an estimated rise to 42.3 million in 2020, dementia is currently a leading unmet medical need and costly burden on public health. Seventy percent of these cases have been attributed to Alzheimer's disease (AD), a neurodegenerative pathology whose most evident symptom is a progressive decline in cognitive functions. Dual specificity tyrosine phosphorylation regulated kinase-1A (DYRK1A) is important in neuronal development and plays a variety of functional roles within the adult central nervous system. The DYRK1A gene is located within the Down syndrome critical region (DSCR) on human chromosome 21 and current research suggests that overexpression of DYRK1A may be a significant factor leading to cognitive deficits in people with Alzheimer's disease (AD) and Down syndrome (DS). Currently, treatment options for cognitive deficiencies associated with Down syndrome, as well as Alzheimer's disease, are extremely limited and represent a major unmet therapeutic need. Small molecule inhibition of DYRK1A activity in the brain may provide an avenue for pharmaceutical intervention of mental impairment associated with AD and other neurodegenerative diseases. We herein review the current state of the art in the development of DYRK1A inhibitors.

The Human Proteome Project has been proposed to create a knowledge-based resource based on a systematical mapping of all human proteins, chromosome by chromosome, in a gene-centric manner. With this background, we here describe the systematic analysis of chromosome 21 using an antibody-based approach for protein profiling using both confocal microscopy and immunohistochemistry, complemented with transcript profiling using next generation sequencing data. We also describe a new approach for protein isoform analysis using a combination of antibody-based probing and isoelectric focusing. The analysis has identified several genes on chromosome 21 with no previous evidence on the protein level, and the isoform analysis indicates that a large fraction of human proteins have multiple isoforms. A chromosome-wide matrix is presented with status for all chromosome 21 genes regarding subcellular localization, tissue distribution, and molecular characterization of the corresponding proteins. The path to generate a chromosome-specific resource, including integrated data from complementary assay platforms, such as mass spectrometry and gene tagging analysis, is discussed.

Haploinsufficiency of part of human chromosome 21 results in a rare condition known as Monosomy 21. This disease displays a variety of clinical phenotypes, including intellectual disability, craniofacial dysmorphology, skeletal and cardiac abnormalities, and respiratory complications. To search for dosage-sensitive genes involved in this disorder, we used chromosome engineering to generate a mouse model carrying a deletion of the Lipi-Usp25 interval, syntenic with 21q11.2-q21.1 in humans. Haploinsufficiency for the 6 genes in this interval resulted in no gross morphological defects and behavioral analysis performed using an open field test, a test of anxiety, and tests for social interaction were normal in monosomic mice. Monosomic mice did, however, display impaired memory retention compared to control animals. Moreover, when fed a high-fat diet (HFD) monosomic mice exhibited a significant increase in fat mass/fat percentage estimate compared with controls, severe fatty changes in their livers, and thickened subcutaneous fat. Thus, genes within the Lipi-Usp25 interval may participate in memory retention and in the regulation of fat deposition.

The presence of an additional copy of HSA21 chromosome in Down syndrome (DS) individuals leads to the overexpression of 30-50% of HSA21 genes. This upregulation can, in turn, trigger a deregulation on the expression of non-HSA21 genes. Moreover, the overdose of HSA21 microRNAs (miRNAs) may result in the downregulation of its target genes. Additional complexity can also arise from epigenetic changes modulating gene expression. Thus, a myriad of transcriptional and posttranscriptional alterations participate to produce abnormal phenotypes in almost all tissues and organs of DS individuals. The study of the physiological roles of genes dysregulated in DS, as well as their characterization in murine models with gene(s) dosage imbalance, pointed out several genes, and functional noncoding elements to be particularly critical in the etiology of DS. Recent findings indicate that gene therapy strategies-based on the introduction of genetic elements by means of delivery vectors-toward the correction of phenotypic abnormalities in DS are also very promising tool to identify HSA21 and non-HSA21 gene candidates, contributing to DS phenotype. In this chapter, we focus on the impact of normalizing the expression levels of up or downregulated genes to rescue particular phenotypes of DS. Attempts toward gene-based treatment approaches in mouse models will be discussed as new opportunities to ameliorate DS alterations., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Two genes on chromosome 21, namely dual specificity tyrosine phosphorylation-regulated kinase 1A (Dyrk1A) and regulator of calcineurin 1 (RCAN1), have been implicated in some of the phenotypic characteristics of Down syndrome, including the early onset of Alzheimer disease. Although a link between Dyrk1A and RCAN1 and the nuclear factor of activated T cells (NFAT) pathway has been reported, it remains unclear whether Dyrk1A directly interacts with RCAN1. In the present study, Dyrk1A is shown to directly interact with and phosphorylate RCAN1 at Ser(112) and Thr(192) residues. Dyrk1A-mediated phosphorylation of RCAN1 at Ser(112) primes the protein for the GSK3β-mediated phosphorylation of Ser(108). Phosphorylation of RCAN1 at Thr(192) by Dyrk1A enhances the ability of RCAN1 to inhibit the phosphatase activity of calcineurin (Caln), leading to reduced NFAT transcriptional activity and enhanced Tau phosphorylation. These effects are mediated by the enhanced binding of RCAN1 to Caln and its extended half-life caused by Dyrk1A-mediated phosphorylation. Furthermore, an increased expression of phospho-Thr(192)-RCAN1 was observed in the brains of transgenic mice overexpressing the Dyrk1A protein. These results suggest a direct link between Dyrk1A and RCAN1 in the Caln-NFAT signaling and Tau hyperphosphorylation pathways, supporting the notion that the synergistic interaction between the chromosome 21 genes RCAN1 and Dyrk1A is associated with a variety of pathological features associated with DS.

This study reports on a cytogenetic finding in a bone marrow examination of a 47-year-old male patient treated in the Hematology and Blood Transfusion Service of the Hospital de Base in São José do Rio Preto, São Paulo State, Brazil. The only alteration found at diagnosis of myelodysplastic syndrome (MDS) subtype refractory anemia with excess blasts (RAEB-2) was clonal monosomy of chromosome 21. The patient evolved to acute myeloid leukemia type M2 and died nine months after diagnosis. Clonal monosomy of chromosome 21, as the only cytogenetic abnormality in MDS, has only been reported three times previously. This uncommon cytogenetic abnormality in MDS has been associated with a poor clinical course, although more data will be needed to determine if this prognosis is invariable.

Background: Bisphenol A (BPA) is a 'weak' endocrine disruptor. The effect of BPA on human reproduction is controversial but has been related to meiotic anomalies, recurrent miscarriages and abnormal karyotypes., Methods: To evaluate the effects of BPA on survival, pairing-synapsis and meiotic recombination of human fetal oocytes, 21 510 oocytes from 12 cultured fetal ovaries were analyzed. Ovaries were cultured for 7, 14 or 21 days in control medium, dimethylsulfoxide-medium, BPA-medium and estradiol (E(2))-medium. Meiotic pairing-synapsis and recombination were studied by immunofluorescence against lateral element protein, central element protein of the synaptonemal complex and chromosome axis cohesin REC8. Mismatch repair protein, MLH1, was used as a crossover (CO) marker. Meiotic progression was analyzed following the number of surviving oocytes at different meiotic stages found in each culture time and condition, and the total number of MLH1 foci found in oocytes from cultured ovaries., Results: Oocyte survival in vitro decreased with the addition of BPA to the medium (1 µM or greater). Oocyte degeneration was up to five times higher when BPA was added to culture medium. Moreover, oocytes exposed to BPA concentrations of 10 µM or higher presented approximately two times more MLH1 foci than unexposed cultured oocytes (P = 0.01). This was also observed in chromosome 21 from BPA-exposed oocytes, which had double the average number of MLH1 foci found in control oocytes (P = 0.001). E(2) was used as a positive control of estrogen receptors activity, and E(2) addition to the medium had similar effects on meiotic progression of oocytes from cultured ovaries., Conclusions: Our findings show that BPA concentrations of 1 µM or higher decrease the survival of human fetal oocytes in vitro, and concentrations of 10 µM or higher increase MLH1 foci number. MLH1 is considered a CO marker, and thus an increase in MLH1 foci could indicate an increase in COs in BPA-exposed oocytes. These data suggest that BPA can act as a toxic substance, which has particular implications for human females and the critical events of meiotic prophase, such as pairing-synapsis and recombination processes, as well as oocyte survival.

The transcription factor RUNX1 is a key regulator of haematopoiesis in vertebrates. In humans, the 260-kb long gene coding for this transcription factor is located on chromosome 21. This gene is transcribed from two alternative promoters that are commonly referred to as the distal and the proximal promoters. In model experiments, these two promoters were found to be active in cells of different lineages, although RUNX1 is preferentially expressed in haematopoietic cells. In the present study, we attempted to identify the regulatory elements that could guide tissue-specific expression of the RUNX1 gene. Two such regulatory elements were found within the RUNX1 gene. One of these elements, located within intron 1, is a haematopoietic-specific enhancer. The second regulatory element, located within intron 5.2, contributes to the formation of an active chromatin hub, which integrates the above-mentioned enhancer and the P1 and P2 promoters., (Copyright © 2011 Wiley-Liss, Inc.)

Individuals with Down syndrome (DS) will inevitably develop Alzheimer disease (AD) neuropathology sometime after middle age, which may be attributable to genes triplicated in individuals with DS. The characteristics of AD neuropathology include neuritic plaques, neurofibrillary tangles, and neuronal loss in various brain regions. The mechanism underlying neurodegeneration in AD and DS remains elusive. Regulator of calcineurin 1 (RCAN1) has been implicated in the pathogenesis of DS. Our data show that RCAN1 expression is elevated in the cortex of DS and AD patients. RCAN1 expression can be activated by the stress hormone dexamethasone. A functional glucocorticoid response element was identified in the RCAN1 isoform 1 (RCAN1-1) promoter region, which is able to mediate the up-regulation of RCAN1 expression. Here we show that overexpression of RCAN1-1 in primary neurons activates caspase-9 and caspase-3 and subsequently induces neuronal apoptosis. Furthermore, we found that the neurotoxicity of RCAN1-1 is inhibited by knock-out of caspase-3 in caspase-3(-/-) neurons. Our study provides a novel mechanism by which RCAN1 functions as a mediator of stress- and Aβ-induced neuronal death, and overexpression of RCAN1 due to an extra copy of the RCAN1 gene on chromosome 21 contributes to AD pathogenesis in DS.

The full-length AML1-ETO (AE) fusion gene resulting from t(8;21)(q22;q22) in human acute myeloid leukemia (AML) is not sufficient to induce leukemia in animals, suggesting that additional mutations are required for leukemogenesis. We and others have identified activating mutations of C-KIT in nearly half of patients with t(8;21) AML. To test the hypothesis that activating C-KIT mutations cooperate with AE to cause overt AML, we generated a murine transduction and transplantation model with both mutated C-KIT and AE. To overcome the intracellular transport block of human C-KIT in murine cells, we engineered hybrid C-KIT (HyC-KIT) by fusing the extracellular and transmembrane domains of the murine c-Kit in-frame to the intracellular signaling domain of human C-KIT. We showed that tyrosine kinase domain mutants HyC-KIT N822K and D816V, as well as juxtamembrane mutants HyC-KIT 571+14 and 557-558Del, could transform murine 32D cells to cytokine-independent growth. The protein tyrosine kinase inhibitor dasatinib inhibited the proliferation of 32D cells expressing these C-KIT mutants, with potency in the low nanomolar range. In mice, HyC-KIT N822K induced a myeloproliferative disease, whereas HyC-KIT 571+14 induces both myeloproliferative disease and lymphocytic leukemia. Interestingly, coexpression of AE and HyC-KIT N822K led to fatal AML. Our data have further enriched the two-hit model that abnormalities of both transcription factor and membrane/cytosolic signaling molecule are required in AML pathogenesis. Furthermore, dasatinib prolonged lifespan of mice bearing AE and HyC-KIT N822K-coexpressing leukemic cells and exerted synergic effects while combined with cytarabine, thus providing a potential therapeutic for t(8;21) leukemia.

Down syndrome (DS) is associated with many neural defects, including reduced brain size and impaired neuronal proliferation, highly contributing to the mental retardation. Those typical characteristics of DS are closely associated with a specific gene group "Down syndrome critical region" (DSCR) on human chromosome 21. Here we investigated the molecular mechanisms underlying impaired neuronal proliferation in DS and, more specifically, a regulatory role for dual-specificity tyrosine-(Y) phosphorylation-regulated kinase 1A (Dyrk1A), a DSCR gene product, in embryonic neuronal cell proliferation. We found that Dyrk1A phosphorylates p53 at Ser-15 in vitro and in immortalized rat embryonic hippocampal progenitor H19-7 cells. In addition, Dyrk1A-induced p53 phosphorylation at Ser-15 led to a robust induction of p53 target genes (e.g. p21(CIP1)) and impaired G(1)/G(0)-S phase transition, resulting in attenuated proliferation of H19-7 cells and human embryonic stem cell-derived neural precursor cells. Moreover, the point mutation of p53-Ser-15 to alanine rescued the inhibitory effect of Dyrk1A on neuronal proliferation. Accordingly, brains from embryonic DYRK1A transgenic mice exhibited elevated levels of Dyrk1A, Ser-15 (mouse Ser-18)-phosphorylated p53, and p21(CIP1) as well as impaired neuronal proliferation. These findings suggest that up-regulation of Dyrk1A contributes to altered neuronal proliferation in DS through specific phosphorylation of p53 at Ser-15 and subsequent p21(CIP1) induction.

The functional analysis of chromosome 21 (Chr21) proteins is of great medical relevance. This refers, in particular, to the trisomy of human Chr21, which results in Down's syndrome, a complex developmental and neurodegenerative disease. In a previous study we analyzed 89 human Chr21 genes for the subcellular localization of their encoded proteins using a transfected-cell array technique. In the present study, the results of the follow-up investigation are presented in which 52 human Chr21 genes were over-expressed in HEK cells using the transfected-cell array platform, and the effect of this protein over-expression on the induction of apoptosis has been analyzed. We found that the over-expression of two Chr21 proteins (claudin-14 and -8) induced cell death independent of the classic caspase-mediated apoptosis. Our results strongly suggest the functional involvement of claudins in the control of the cell cycle and regulation of the cell death induction mechanism.

We monitored the telomere lengths and chromosomal instability characteristics of fibroblasts at different population doubling levels (PDLs) to gain further insight into the role of telomere shortening in chromosomal instability. We used 7 normal diploid human fibroblast strains (TIG-1, 3, 7, 103, 104, 112, and 114) and a quantitative fluorescence in situ hybridization method to measure telomere lengths of the p- and q-arms of individual chromosomes. We also enumerated morphologic signs of chromosomal instability, including fusion or loss of chromosomes, and anaphase bridges. In strains TIG-1, 3, 7, 103, and 114 at the late (phase 3) stage (≧40PDLs), 29 (96.6%) of 30 fusions were associated with one or both of the chromosomal arms that bear significantly shorter telomeres in those populations. In TIG-1 at 62PDL, 6 fusions were associated with Xq (n=3), 21q (n=3), and other (n=6) chromosomes. Xq and 21q had significantly shorter telomeres, and anaphase bridges were often associated with chromosomes X and/or 21 (74.6%). Our results indicate that chromosomes having excessively shortened telomeres at late PDLs begin to show features of instability such as fusions and anaphase bridges., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)

Down syndrome (DS) or Trisomy 21 (Ts21) is caused by the presence of an extra copy of all or part of human chromosome 21 (Hsa21) and is the most frequent survivable congenital chromosomal abnormality. Bioinformatic annotation has established that Hsa21 harbors more than 400 genes, including five microRNA (miRNA) genes (miR-99a, let-7c, miR-125b-2, miR-155, and miR-802). MiRNAs are endogenous, single-stranded, small non-coding RNA molecules that regulate gene expression by interacting with specific recognition elements harbored within the 3'-untranslated region (3'-UTR) of mRNAs and subsequently target these mRNAs for translational repression or destabilization. MiRNA expression profiling, miRNA RT-PCR, and miRNA in situ hybridization experiments have demonstrated that Hsa21-derived miRNAs were over-expressed in fetal brain and heart specimens isolated from individuals with DS. We now propose that Ts21 gene dosage over-expression of Hsa21-derived miRNAs in DS individuals result in the decreased expression of specific target proteins (i.e. haploinsufficiency) that contribute, in part, to the DS phenotype.

Trisomy of human chromosome 21 (Hsa21) results in Down syndrome (DS), a disorder that affects many aspects of physiology, including hematopoiesis. DS children have greatly increased rates of acute lymphoblastic leukemia and acute megakaryoblastic leukemia (AMKL); DS newborns present with transient myeloproliferative disorder (TMD), a preleukemic form of AMKL. TMD and DS-AMKL almost always carry an acquired mutation in GATA1 resulting in exclusive synthesis of a truncated protein (GATA1s), suggesting that both trisomy 21 and GATA1 mutations are required for leukemogenesis. To gain further understanding of how Hsa21 contributes to hematopoietic abnormalities, we examined the Tc1 mouse model of DS, which carries an almost complete freely segregating copy of Hsa21, and is the most complete model of DS available. We show that although Tc1 mice do not develop leukemia, they have macrocytic anemia and increased extramedullary hematopoiesis. Introduction of GATA1s into Tc1 mice resulted in a synergistic increase in megakaryopoiesis, but did not result in leukemia or a TMD-like phenotype, demonstrating that GATA1s and trisomy of approximately 80% of Hsa21 perturb megakaryopoiesis but are insufficient to induce leukemia.