To assess the frequency of TP53 alterations and their correlation with other genetic changes and outcome in acute myeloid leukemia with complex karyotype (CK-AML), we performed integrative analysis using TP53 mutational screening and array-based genomic profiling in 234 CKAMLs. TP53 mutations were found in 141 of 234 (60%) and TP53 losses were identified in 94 of 234 (40%) CK-AMLs; in total, 164 of 234 (70%) cases had TP53 alterations. TP53-altered CK-AML were characterized by a higher degree of genomic complexity (aberrations per case, 14.30 vs 6.16; P < .0001) and by a higher frequency of specific copy number alterations, such as ؊5/5q؊, ؊7/7q؊, ؊16/ 16q؊, ؊18/18q؊, ؉1/؉1p, and ؉11/؉11q/ amp11q13ϳ25; among CK-AMLs, TP53-altered more frequently exhibited a monosomal karyotype (MK). Patients with TP53 alterations were older and had significantly lower complete remission rates, inferior event-free, relapse-free, and overall survival. In multivariable analysis for overall survival, TP53 alterations, white blood cell counts, and age were the only significant factors. In conclusion, TP53 is the most frequently known altered gene in CK-AML. TP53 alterations are associated with older age, genomic complexity, specific DNA copy number alterations, MK, and dismal outcome. In multivariable analysis, TP53 alteration is the most important prognostic factor in CK-AML, outweighing all other variables, including the MK category. (Blood. 2012;119(9):2114-2121)

Amyotrophic lateral sclerosis (ALS) is the most frequent motor neuron disease. Cytoplasmic fused in sarcoma (FUS) aggregates are pathological hallmarks of FUS-ALS. Proper shuttling between the nucleus and cytoplasm is essential for physiological cell function. However, the initial event in the pathophysiology of FUS-ALS remains enigmatic. Using human induced pluripotent stem cell (hiPSCs)-derived motor neurons (MNs), we show that impairment of poly(ADP-ribose) polymerase (PARP)-dependent DNA damage response (DDR) signaling due to mutations in the FUS nuclear localization sequence (NLS) induces additional cytoplasmic FUS mislocalization which in turn results in neurodegeneration and FUS aggregate formation. Our work suggests that a key pathophysiologic event in ALS is upstream of aggregate formation. Targeting DDR signaling could lead to novel therapeutic routes for ameliorating ALS.

Congenital dyserythropoietic anemias (CDAs) are phenotypically and genotypically heterogeneous diseases. CDA type II (CDAII) is the most frequent CDA. It is characterized by ineffective erythropoiesis and by the presence of bi- and multinucleated erythroblasts in bone marrow, with nuclei of equal size and DNA content, suggesting a cytokinesis disturbance. Other features of the peripheral red blood cells are protein and lipid dysglycosylation and endoplasmic reticulum double-membrane remnants. Development of other hematopoietic lineages is normal. Individuals with CDAII show progressive splenomegaly, gallstones and iron overload potentially with liver cirrhosis or cardiac failure. Here we show that the gene encoding the secretory COPII component SEC23B is mutated in CDAII. Short hairpin RNA (shRNA)-mediated suppression of SEC23B expression recapitulates the cytokinesis defect. Knockdown of zebrafish sec23b also leads to aberrant erythrocyte development. Our results provide in vivo evidence for SEC23B selectivity in erythroid differentiation and show that SEC23A and SEC23B, although highly related paralogous secretory COPII components, are nonredundant in erythrocyte maturation.

Key Points• Relapsed AML with NPM1 mutation is genetically related to the primary leukemia and characterized by an increase in high-risk aberrations.• DNMT3A mutations show the highest stability and thus may precede NPM1 mutations.Mutations in the nucleophosmin 1 (NPM1) gene are considered a founder event in the pathogenesis of acute myeloid leukemia (AML). To address the role of clonal evolution in relapsed NPM1-mutated (NPM1 mut ) AML, we applied high-resolution, genome-wide, single-nucleotide polymorphism array profiling to detect copy number alterations (CNAs) and uniparental disomies (UPDs) and performed comprehensive gene mutation screening in 53 paired bone marrow/peripheral blood samples obtained at diagnosis and relapse. At diagnosis, 15 aberrations (CNAs, n 5 10; UPDs, n 5 5) were identified in 13 patients (25%), whereas at relapse, 56 genomic alterations (CNAs, n 5 46; UPDs, n 5 10) were detected in 29 patients (55%) indicating an increase in genomic complexity. Recurrent aberrations acquired at relapse included deletions affecting tumor suppressor genes (

SUMMARY In Burkitt lymphoma (BL), a germinal center B-cell-derived tumor, the pro-apoptotic properties of c-MYC must be counterbalanced. Predicting that survival signals would be delivered by phosphoinositide-3-kinase (PI3K), a major survival determinant in mature B cells, we indeed found that combining constitutive c-MYC expression and PI3K activity in germinal center B cells of the mouse led to BL-like tumors, which fully phenocopy human BL with regard to histology, surface and other markers, and gene expression profile. The tumors also accumulate tertiary mutational events, some of which are recurrent in the human disease. These results and our finding of recurrent PI3K pathway activation in human BL indicate that deregulated c-MYC and PI3K activity cooperate in BL pathogenesis.

To identify genomic alterations in chronic lymphocytic leukemia (CLL), we performed single-nucleotide polymorphismarray analysis using Affymetrix Version 6.0 on 353 samples from untreated patients entered in the CLL8 treatment trial. Based on paired-sample analysis (n ‫؍‬ 144), a mean of 1.8 copy number alterations per patient were identified; approximately 60% of patients carried no copy number alterations other than those detected by fluorescence in situ hybridization analysis. Copy-neutral loss-ofheterozygosity was detected in 6% of CLL patients and was found most frequently on 13q, 17p, and 11q. Minimally deleted regions were refined on 13q14 (deleted in 61% of patients) to the DLEU1 and DLEU2 genes, on 11q22.3 (27% of patients) to ATM, on 2p16.1-2p15 (gained in 7% of patients) to a 1.9-Mb fragment containing 9 genes, and on 8q24.

Human severe combined immunodeficiencies (SCID) are phenotypically and genotypically heterogeneous diseases. Reticular dysgenesis is the most severe form of inborn SCID. It is characterized by absence of granulocytes and almost complete deficiency of lymphocytes in peripheral blood, hypoplasia of the thymus and secondary lymphoid organs, and lack of innate and adaptive humoral and cellular immune functions, leading to fatal septicemia within days after birth. In bone marrow of individuals with reticular dysgenesis, myeloid differentiation is blocked at the promyelocytic stage, whereas erythro- and megakaryocytic maturation is generally normal. These features exclude a defect in hematopoietic stem cells but point to a unique aberration of the myelo-lymphoid lineages. The dramatic clinical course of reticular dysgenesis and its unique hematological phenotype have spurred interest in the unknown genetic basis of this syndrome. Here we show that the gene encoding the mitochondrial energy metabolism enzyme adenylate kinase 2 (AK2) is mutated in individuals with reticular dysgenesis. Knockdown of zebrafish ak2 also leads to aberrant leukocyte development, stressing the evolutionarily conserved role of AK2. Our results provide in vivo evidence for AK2 selectivity in leukocyte differentiation. These observations suggest that reticular dysgenesis is the first example of a human immunodeficiency syndrome that is causally linked to energy metabolism and that can therefore be classified as a mitochondriopathy.

3558 Acute myeloid leukemia with complex karyotype (CK-AML, CK+) is defined as ≥3 acquired chromosome abnormalities in the absence of recurrent genetic abnormalities (WHO 2008). CK-AML account for 10–15% of all AML and are characterized by a dismal outcome. To delineate prognostic markers in this unfavorable subgroup, we performed integrative analysis using genomic profiling (array-comparative genomic hybridization [CGH] and/or single-nucleotide polymorphism [SNP] analysis), as well as TP53 mutation screening in 234 CK-AML. TP53 mutations were found in 141/234 (60%) CK-AML comprising 130 missense, 21 insertion/deletion, nine nonsense, and eight splice site mutations; genomic losses of TP53 were identified in 94/234 (40%). Combining these data, TP53 alterations were detected in 70% of patients, and at least 66% of these exhibited biallelic alterations. TP53 alterations (loss and/or mutation in TP53) were characterized by a higher degree of genomic complexity, as measured by total number of copy number alterations per case (mean±SD 14.30±9.41 versus 6.16±5.53, P <.0001), and by the association with specific genomic alterations, that is, monosomy 3 or losses of 3q (-3/3q-) (P=.002), -5/5q- (P<.0001), -7/7q- (P=.001), -16/16q- (P<.0001), -18/18q- (P=.001), and -20/20q- (P=.004); gains of chromosome 1 or 1p (+1/+1p) (P=.001), +11/+11q (P=.0002), +13/+13q (P =.02), and +19/+19p (P =.04); and amplifications in 11q13∼25 [amp(11)(q13∼25)]. The recently described cytogenetic category “monosomal karyotype” (MK), defined as two or more autosomal monosomies or one single autosomal monosomy in the presence of structural abnormalities, for which a prognostic impact could be demonstrated even in CK-AML, was correlated with TP53 alterations (P <.0001). Clinically, TP53altered CK-AML patients were older (median age, 61 versus 54 years, P =.002), had lower bone marrow (BM) blast counts (median 65% versus 78%, P=. 04), and had lower complete remission (CR) rates (28% versus 50%, P =.01). For multivariable analysis, a conditional model was used with an age cut point at 60 years to address the different treatment intensities applied in the different age cohorts. In this model the only significant factors for CR achievement were TP53altered (OR, 0.55; 95%-CI, 0.30 to 1.00; P =.05) and age (OR for a 10 years difference, 0.67; 95%-CI, 0.52 to 0.87; P =.003). TP53 altered predicted for inferior survival; the 3-year estimated survival rates for CK+/TP53altered and CK+/TP53unaltered patients were as follows: event-free survival (EFS), 1% versus 13% (log-rank, P =.0007); relapse-free survival (RFS), 7% versus 30% (P =.01); and overall survival (OS), 3% versus 28% (P <.0001), respectively. Other variables predicting for inferior OS in univariable analyses were age and MK. Among the cohort of CK+/MK+ AML, TP53altered patients had a significantly worse OS (P =.0004). Multivariable analysis (stratified for age at cut point of 60 years) revealed TP53altered (HR, 2.43; 95%-CI, 1.56 to 3.77; P =.0001), logarithm of WBC (HR, 1.62; 95%-CI 1.17 to 2.26; P =.004), and age (HR for 10 years difference, 1.26; 95%-CI, 1.01 to 1.56, P =.04), but not MK as significant variables for OS. In addition, explorative subset analysis suggested that allogeneic hematopoietic stem-cell transplantation in first CR which was performed in 30 CK-AML did not impact outcome in TP53altered CK-AML. In summary, TP53 is the most frequently known altered gene in CK-AML. TP53 alterations are associated with older age, genomic complexity, specific DNA copy number alterations, MK, and dismal outcome. In multivariable analysis, TP53 alteration is the most important prognostic factor in CK-AML, outweighing all other variables, including the MK category. TP53 mutational status should be assessed in clinical trials investigating novel agents in order to identify compounds that may be effective in this subset of patients. Disclosures: No relevant conflicts of interest to declare.