Ina Hainmann

High incidence of t(7;12)(q36;p13) in infant AML but not in infant ALL, with a dismal outcome and ectopic expression of HLXB9.

The t(7;12)(q36;p13) is a recurrent translocation involving the ETV6/TEL gene (12p13) and a heterogeneous breakpoint at 7q36. A fusion transcript between HLXB9 and ETV6 in AML with t(7;12) is occasionally found. To study the incidence of t(7;12) in infant and childhood acute leukemia, we screened 320 cases <36 months using FISH. Additionally, 28 pediatric cases >36 months with cytogenetic breakpoints at 12p and 7q were investigated. We studied the presence of an HXLB9‐ETV6 fusion transcript and quantified the expression of various genes located in the 7q36 breakpoint region. In total, six AML patients carried the t(7;12) of which five were infants and one child of 18 months. Only one out of 99 infant ALL patients harbored the t(7;12). No t(7;12) was found in older children with AML or ALL. AML patients carrying a t(7;12) had a poor outcome with a 3‐year EFS of 0%. A fusion of HLXB9 to ETV6 was found in four AML cases with t(7;12). The 7q36 genes NOM1, LMBR1, RNF32, and SHH were equally expressed among t(7;12)‐positive AML versus t(7;12)‐negative AML, t(7;12)‐negative ALL, or normal bone marrow. However, the HLXB9 expression was highly increased in t(7;12)‐positive cases, including those with an HLXB9‐ETV6 fusion. We conclude that the t(7;12) is almost exclusively present in infant AML and covers 30% of infant AML, while it is extremely rare in infant ALL and older children. The t(7;12) is associated with a poor outcome and an ectopic expression of HLXB9 is commonly involved in this genetic subtype of leukemia.

The novel human platelet septin SEPT8 is an interaction partner of SEPT4

Septins are a family of GTP-binding proteins, which are essential for active membrane movement such as cytokinesis and vesicle trafficking. In non-dividing cells (such as platelets and neurons) septins are implicated in exocytosis. Platelets from a SEPT5 knockout mouse showed an altered serotonin secretion and platelet aggregation, suggesting that SEPT5 is involved in secretion in platelets. Septins form complexes consisting of multiple septin polypeptides. Using the yeast two-hybrid system we had demonstrated that SEPT5 partners with SEPT8. The aim of this study was to identify other interaction partners of the human platelet septin SEPT8. Using the yeast two-hybrid system with SEPT8 as bait protein we identified the human septin SEPT4 as an interaction partner of SEPT8. The interaction between SEPT4 and SEPT8 was confirmed by immunoprecipitation. Expression analysis revealed that SEPT4 is also expressed in human platelets. Thus, SEPT4 is the third described platelet septin besides SEPT5 and SEPT8. Transmission electron microscopy of platelets revealed that SEPT8 and SEPT4 are localized surrounding alpha-granules (as it had been shown for the septin SEPT5) suggesting that the three septins may be components of the septin complex in platelets and contribute in such a way to platelet biology. Activation of platelets by agonists resulted in the translocation of SEPT4 and SEPT8 to the platelet surface indicating a possible functional role of these proteins in platelet granular secretion.

Human septin-septin interaction: CDCrel-1 partners with KIAA0202.

Septins are evolutionary conserved cytoskeletal GTPases forming heteropolymer complexes involved in cytokinesis and other cellular processes. CDCrel‐1 (cell division cycle related‐1) is a recently cloned and characterized human septin which is highly expressed in non‐dividing cells, such as neurons. Using a yeast two‐hybrid system we demonstrate that CDCrel‐1 partners with another uncharacterized human septin, KIAA0202. The interaction of CDCrel‐1 and KIAA0202 was confirmed in the human leukemia cell line K‐562 using pull‐down assays with a KIAA0202–glutathione S‐transferase fusion protein and by immunoprecipitation of the CDCrel‐1–KIAA0202 complex with an anti‐KIAA0202 antibody. Expression studies of the two human septins revealed a concomitant expression of both proteins in certain cells.

Novel findings in two patients with late-diagnosed afibrinogenaemia: intraosseous haemorrhage and fingertip necrosis.

M. ERLACHER,* J. HEISS,* I. HAINMANN,* M. UHL, U. BUDDE, J. OLDENBURG,§ V. IVASKEVICIUS,§ J. AL-JAMALI,– H. ZAJONC,– A. SUPERTI-FURGA* and B. ZIEGER* *Center for Pediatrics and Adolescent Medicine; Department of Diagnostic Radiology, University Medical Center Freiburg, Germany; Coagulation Laboratory, AescuLabor, Hamburg, Germany; §Institute of Experimental Haematology and Transfusion Medicine, University Clinic Bonn, Bonn, Germany; and –Department of Plastic and Hand Surgery, University Medical Center Freiburg, Germany

Recurring mutations in RPL15 are linked to hydrops fetalis and treatment independence in Diamond-Blackfan anemia

Diamond-Blackfan anemia (DBA) is a rare inherited bone marrow failure disorder linked predominantly to ribosomal protein gene mutations. Here the European DBA consortium reports novel mutations identified in the RPL15 gene in 6 unrelated individuals diagnosed with DBA. Although point mutations have not been previously reported for RPL15, we identified 4 individuals with truncating mutations p.Tyr81* (in 3 of 4) and p.Gln29*, and 2 with missense variants p.Leu10Pro and p.Lys153Thr. Notably, 75% (3 of 4) of truncating mutation carriers manifested with severe hydrops fetalis and required intrauterine transfusions. Even more remarkable is the observation that the 3 carriers of p.Tyr81* mutation became treatment-independent between four and 16 months of life and maintained normal blood counts until their last follow up. Genetic reversion at the DNA level as a potential mechanism of remission was not observed in our patients. In vitro studies revealed that cells carrying RPL15 mutations have pre-rRNA processing defects, reduced 60S ribosomal subunit formation, and severe proliferation defects. Red cell culture assays of RPL15-mutated primary erythroblast cells also showed a severe reduction in cell proliferation, delayed erythroid differentiation, elevated TP53 activity, and increased apoptosis. This study identifies a novel subgroup of DBA with mutations in the RPL15 gene with an unexpected high rate of hydrops fetalis and spontaneous, long-lasting remission.

Progressive thrombosis in a 13-year-old girl with trisomy 21 under therapy with low molecular weight heparin.

Introduction ▼ Antiphospholipid syndrome (APS) is a rare and serious autoimmune condition in childhood [2] . APS is defi ned by arterial and / or venous thromboses in the presence of antiphospholipid antibodies (APAs) detected on 2 or more conditions at least 12 weeks apart [5] . Recognition of APS remains challenging, especially because the clinical features are often discrete [10] and the laboratory tests applied are heterogenous [3] . In contrast to adulthood, increased APA titers may occur in a variety of diseases in children and adolescents [1] . However, the frequency of APA-related symptoms is low [4] and children with APAs generally do not experience a high rate of thrombotic events [6] except in cases with predisposing anatomic anomalies [8] . The syndrome is underrecognised and underdiagnosed and can have severe consequences if untreated, mainly because of progressive thrombosis and embolism [2] .

Compound heterozygosity of the protein S-gene as a cause of severe cerebral sinovenous thrombosis in a 7-year-old child.

The genotype-phenotype relationship of compound heterozygous protein S-deficiency in a 7-year-old girl with reduced protein S-levels and a severe cerebral sinovenous thrombosis is illustrated. In this patient we identified a novel deletion in the protein S-gene causing a compound heterozygous state and subsequently a symptomatic protein S-deficiency. In case of thrombosis analysis of protein S is recommended. Low levels of protein S should be further investigated by molecular diagnostics.