Transient abnormal myelopoiesis (TAM) is a myeloid proliferation resembling acute megakaryoblastic leukemia (AMKL), mostly affecting perinatal infants with Down syndrome. Although self-limiting in a majority of cases, TAM may evolve as non-self-limiting AMKL after spontaneous remission (DS-AMKL). Pathogenesis of these Down syndrome-related myeloid disorders is poorly understood, except for GATA1 mutations found in most cases. Here we report genomic profiling of 41 TAM, 49 DS-AMKL and 19 non-DS-AMKL samples, including whole-genome and/or whole-exome sequencing of 15 TAM and 14 DS-AMKL samples. TAM appears to be caused by a single GATA1 mutation and constitutive trisomy 21. Subsequent AMKL evolves from a pre-existing TAM clone through the acquisition of additional mutations, with major mutational targets including multiple cohesin components (53%), CTCF (20%), and EZH2, KANSL1 and other epigenetic regulators (45%), as well as common signaling pathways, such as the JAK family kinases, MPL, SH2B3 (LNK) and multiple RAS pathway genes (47%).

The NF-E2-binding sites or Maf recognition elements (MARE) are essential cis-acting elements in the regulatory regions of erythroid-specific genes recognized by the erythroid transcription factor NF-E2, composed of p45 and MafK. Recently, two p45-related factors Nrf1 and Nrf2 were isolated, and they are now collectively grouped as the Cap'n' collar (CNC) family. CNC factors bind to MARE through heterodimer formation with small Maf proteins. We report here the identification and characterization of a novel CNC factor, Nrf3, encoding a predicted 73-kDa protein with a basic regionleucine zipper domain highly homologous to those of other CNC proteins. In vitro and in vivo analyses showed that Nrf3 can heterodimerize with MafK and that this complex binds to the MARE in the chicken ␤-globin enhancer and can activate transcription. Nrf3 mRNA is highly expressed in human placenta and B cell and monocyte lineage. Chromosomal localization of human Nrf3 is 7p14 -15, which lies near the hoxA gene locus. As the genetic loci of p45, nrf1, and nrf2 have been mapped close to those of hoxC, hoxB, and hoxD, respectively, the present study strongly argues for the idea that a single ancestral gene for the CNC family members may have been localized near the ancestral Hox cluster and have diverged to give rise to four closely related CNC factors through chromosome duplication.

To identify oncogenes in leukemias, we performed largescale resequencing of the leukemia genome using DNA sequence arrays that determine B9 Mbp of sequence corresponding to the exons or exon-intron boundaries of 5648 protein-coding genes. Hybridization of genomic DNA from CD34-positive blasts of acute myeloid leukemia (n ¼ 19) or myeloproliferative disorder (n ¼ 1) with the arrays identified 9148 nonsynonymous nucleotide changes. Subsequent analysis showed that most of these changes were also present in the genomic DNA of the paired controls, with 11 somatic changes identified only in the leukemic blasts. One of these latter changes results in a Met-to-Ile substitution at amino-acid position 511 of Janus kinase 3 (JAK3), and the JAK3(M511I) protein exhibited transforming potential both in vitro and in vivo. Further screening for JAK3 mutations showed novel and known transforming changes in a total of 9 out of 286 cases of leukemia. Our experiments also showed a somatic change responsible for an Arg-to-His substitution at amino-acid position 882 of DNA methyltransferase 3A, which resulted in a loss of DNA methylation activity of 450%. Our data have thus shown a unique profile of gene mutations in human leukemia.

The transcription factor GATA-1 is a fundamental regulator of genes in haematopoietic cell lineages and belongs to a family of factors that bind to the consensus sequence WGATAR. The GATA motif was originally identified in cis-regulatory regions of globin and other erythroid-specific genes, but the range of genes controlled by the GATA factors has since expanded. Members of the GATA transcription factor family share a conserved zinc-finger DNA-binding domain, but the expression profile of each GATA factor is distinct. Here we show that a testis form of murine (m)GATA-1 messenger RNA is transcribed from a promoter located 5' to the erythroid first exon, and the remaining exons (which encode the mGATA-1 protein) are used in common by both testis and erythroid transcripts. We use an anti-mGATA-1 monoclonal antibody to show that the factor expressed in erythroid cells is the same as that found in the seminiferous tubules of murine testis. The GATA-1-expressing cells in 10-week-old testis were found only in contact with the basement membrane of seminiferous tubules, suggesting that GATA-1 regulates genes during the earliest stages of spermatogenesis.

Highlights d Genetic and functional analyses of myeloid preleukemia and leukemia in Down syndrome d Non-GATA1 preleukemic mutations are often not required for preleukemia d Previously undescribed transforming hotspot mutation in CSF2RB identified d Loss of function of 18 genes validated in transformation of preleukemia to leukemia

Chromosomal aneuploidy and specific gene mutations are recognized early hallmarks of many oncogenic processes. However, the net effect of these abnormalities has generally not been explored. We focused on transient myeloproliferative disorder (TMD) in Down syndrome, which is characteristically associated with somatic mutations in GATA1. To better understand functional interplay between trisomy 21 and GATA1 mutations in hematopoiesis, we constructed cellular disease models using human induced pluripotent stem cells (iPSCs) and genome-editing technologies. Comparative analysis of these engineered iPSCs demonstrated that trisomy 21 perturbed hematopoietic development through the enhanced production of early hematopoietic progenitors and the upregulation of mutated GATA1, resulting in the accelerated production of aberrantly differentiated cells. These effects were mediated by dosage alterations of RUNX1, ETS2, and ERG, which are located in a critical 4-Mb region of chromosome 21. Our study provides insight into the genetic synergy that contributes to multi-step leukemogenesis.

Cardio-facio-cutaneous (CFC) syndrome is a multiple congenital anomaly/mental retardation syndrome characterized by heart defects, a distinctive facial appearance, ectodermal abnormalities and mental retardation. Clinically, it overlaps with both Noonan syndrome and Costello syndrome, which are caused by mutations in two genes, PTPN11 and HRAS, respectively. Recently, we identified mutations in KRAS and BRAF in 19 of 43 individuals with CFC syndrome, suggesting that dysregulation of the RAS/RAF/MEK/ERK pathway is a molecular basis for CFC syndrome. The purpose of this study was to perform comprehensive mutation analysis in 56 patients with CFC syndrome and to investigate genotype-phenotype correlation. We analyzed KRAS, BRAF, and MAP2K1/2 (MEK1/2) in 13 new CFC patients and identified five BRAF and one MAP2K1 mutations in nine patients. We detected one MAP2K1 mutation in three patients and four new MAP2K2 mutations in four patients out of 24 patients without KRAS or BRAF mutations in the previous study [Niihori et al., 2006]. No mutations were identified in MAPK3/1 (ERK1/2) in 21 patients without any mutations. In total, 35 of 56 (62.5%) patients with CFC syndrome had mutations (3 in KRAS, 24 in BRAF, and 8 in MAP2K1/2). No significant differences in clinical manifestations were found among 3 KRAS-positive patients, 16 BRAF-positive patients, and 6 MAP2K1/2-positive patients. Wrinkled palms and soles, hyperpigmentation and joint hyperextension, which have been commonly reported in Costello syndrome but not in CFC syndrome, were observed in 30-40% of the mutation-positive CFC patients, suggesting a significant clinical overlap between these two syndromes.

We report here 7 new mutations in the ADAMTS13 gene responsible for UpshawSchulman syndrome (USS), a catastrophic phenotype of congenital thrombotic thrombocytopenic purpura, by analyzing 5 Japanese families. There were 3 mutations that occurred at exon-intron boundaries: 414؉1G>A at intron 4, 686؉1G>A at intron 6, and 1244؉2T>G at intron 10 (numbered from the A of the initiation Met codon), and we confirmed that 2 of these mutations produced aberrantly spliced messenger RNAs (mRNAs). The remaining 4 mutations were missense mutations: R193W, I673F, C908Y, and R1123C. In expression experiments using HeLa cells, all mutants showed no or a marginal secretion of ADAMTS13. Taken together with the findings in our recent report we determined the responsible mutations in a total of 7 Japanese patients with USS with a uniform clinical picture of severe neonatal hyperbilirubinemia, and in their family members, based on ADAMTS13 gene analysis. Of these patients, 2 were homozygotes and 5 were compound heterozygotes. The parents of one homozygote were related (cousins), while those of the other were not. Molecular models of the metalloprotease, fifth domain of thrombospondin 1 (Tsp1-5), and Tsp1-8 domains of ADAMTS13 suggest that the missense mutations could cause structural defects in the mutants. IntroductionThrombotic thrombocytopenic purpura (TTP) is a life-threatening generalized disorder, and its diagnosis is made according to the criteria of Moschcowitz's pentad 1 : thrombocytopenia, microangiopathic hemolytic anemia (MAHA), fluctuating neurologic signs, renal failure, and fever. These criteria, however, are almost undistinguishable from those of hemolytic-uremic syndrome (HUS) with Gasser's triad 2 ; MAHA, thrombocytopenia, and renal insufficiency. Thus, the comprehensive term "TTP/HUS" or "thrombotic microangiopathy" 3 has frequently been used in clinical practice.Recent advances in elucidating the proteolytic processing of plasma von Willebrand factor (VWF) multimers have established assays for the activity of VWF-cleaving protease and its inhibitor (autoantibody). [4][5][6][7] These assays have largely made it possible to distinguish TTP from HUS, because the former has defective VWF-cleaving activity, whereas the latter has VWF-cleaving activity. 6,7 Studies by several groups of investigators have led to the identification of this enzyme as a new metalloprotease belonging to the ADAMTS (a disintegrinlike and metalloprotease with thrombospondin type 1 motif) family, which has been designated ADAMTS13. [8][9][10][11][12] This enzyme is produced in the liver. [10][11][12] The deduced amino acid residue number is 1427, and the gene contains 29 exons and is located on chromosome 9q34. [10][11][12] Upshaw-Schulman syndrome (USS) was originally reported as a disease complex with repeated episodes of thrombocytopenia and hemolytic anemia that quickly respond to infusions of fresh frozen plasma (FFP). [13][14][15][16] Clinical signs often develop in the patients during the newborn period or early infancy. In fact, the ea...