Unusual complications after bone marrow transplantation for dyskeratosis congenita

Dyskeratosis congenita (DC) is a rare inherited disorder often associated with aplastic anaemia. We report the cases of five boys transplanted with an HLA-identical related donor for severe aplastic anaemia (SAA) associated to DC; in all cases successful engraftment was observed. Three patients died 2–8 years after bone marrow transplantation (BMT) with signs of endothelial cell damage syndrome (kidney microangiopathy and liver veno-occlusive disease). Another boy died 1 year after BMT from Evans syndrome and invasive aspergillosis. One boy currently presents anaemia, polyarthritis of unknown origin, pulmonary fibrosis and gut malabsorption 7.5 years after BMT. SAA associated with DC can be successfully treated by allogeneic BMT. However, these early and late complications observed are very unusual after BMT and probably reflect the association of transplanted-related factors, evolution of the underlying disease, and increased sensitivity of endothelial cells. Modified conditioning approaches, advances in supportive care and surveillance of these unusual complications offer the possibility of improved outcome for these patients.     

Acute autoimmune sensorineural hearing loss associated with Crohn's disease

We report the sudden onset of bilateral hearing loss in a patient with Crohn's disease while the intestinal disease was quiescent. Antibodies directed against collagen type II were detected in the serum. Dramatic improvement of his hearing was observed under corticosteroid therapy. Diagnosis of autoimmune sensorineural hearing loss was established. This condition could be considered as an extraintestinal manifestation of Crohn's disease. Early diagnosis is mandated, as prompt and intensive treatment with corticosteroids and/or immunosuppressive drugs is effective and could prevent irreversible hearing loss.     

Single-stranded DNA oligonucleotides inhibit TLR3-mediated responses in human monocyte-derived dendritic cells and in vivo in cynomolgus macaques

TLR3 is a key receptor for recognition of double-stranded RNA and initiation of immune responses against viral infections. However, hyperactive responses can have adverse effects, such as virus-induced asthma. Strategies to prevent TLR3-mediated pathology are therefore desired. We investigated the effect of single-stranded DNA oligonucleotides (ssDNA-ODNs) on TLR3 activation. Human monocyte-derived dendritic cells up-regulate maturation markers and secrete proinflammatory cytokines on treatment with the synthetic TLR3 ligand polyinosine-polycytidylic acid (poly I:C). These events were inhibited in cultures with ssDNA-ODNs. Poly I:C activation of nonhematopoietic cells was also inhibited by ssDNA-ODNs. The uptake of poly I:C into cells was reduced in the presence of ssDNA-ODNs, preventing TLR3 engagement from occurring. To confirm this inhibition in vivo, we administered ssDNA-ODNs and poly I:C, alone or in combination, via the intranasal route in cynomolgus macaques. Proinflammatory cytokines were detected in nasal secretions in the poly I:C group, while the levels were reduced in the groups receiving ssDNA-ODNs or both substances. Our results demonstrate that TLR3-triggered immune activation can be modulated by ssDNA-ODNs and provide evidence of dampening proinflammatory cytokine release in the airways of cynomolgus macaques. These findings may open novel perspectives for clinical strategies to prevent or treat inflammatory conditions exacerbated by TLR3 signaling.     

Basal peroxisome proliferator activated receptor gamma coactivator 1α expression is independent of calcineurin in skeletal muscle

Both calcineurin-A and peroxisome proliferator activated receptor gamma coactivator 1α (PGC-1α) are key players in the acquisition and maintenance of slow-oxidative skeletal muscle phenotype. Whether calcineurin can control PGC-1α expression has been proposed but is still controversial. Our aim was to examine the relationship between calcineurin activation and PGC-1α expression in nonexercising skeletal muscles of rats. We first examined PGC-1α and modulatory calcineurin-interacting protein-1 messenger RNA (mRNA) (a marker of calcineurin activity) expression patterns within rat single myofibers, classified according to their phenotype (type I, IIa, IIx, and IIb). Secondly, we measured PGC-1α mRNA and protein in soleus and plantaris muscles of rats treated or not by cyclosporin A or FK506, 2 pharmacological inhibitors of calcineurin activity. In single myofibers, no differences were found in PGC-1α mRNA levels, whereas modulatory calcineurin-interacting protein-1 mRNA was substantially higher in type I and IIa compared with type IIx and IIb fibers. In cyclosporin A- and FK506-treated animals, no decrease in PGC-1α mRNA and protein was found, despite an efficient blockade of calcineurin activity. Taken together, our results show that, in weight-bearing skeletal muscles, basal PGC-1α expression, necessary to maintain slow-oxidative phenotype, is independent of calcineurin activity.     

High prevalence of hemoglobin disorders and glucose-6-phosphate dehydrogenase (G6PD) deficiency in the Republic of Guinea (West Africa)

Reliable and accurate epidemiological data is a prerequisite for a cost effective screening program for inherited disorders, which however, is lacking in a number of developing countries. Here we report the first detailed population study in the Republic of Guinea, a sub-Saharan West African country, designed to assess the frequency of glucose-6-phosphate dehydrogenase (G6PD) deficiency and hemoglobinopathies, including screening for thalassemia. Peripheral blood samples from 187 Guinean adults were screened for hemoglobin (Hb) variants by standard hematological methods. One hundred and ten samples from males were screened for G6PD deficiency by the fluorescent spot test. Molecular analysis was performed for the most common α-thalassemia (α-thal) deletions, β-globin gene mutations, G6PD variants B (376A), A (376G), A- (376G/202A) and Betica (376G/968C), using polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP) or sequencing. Of the 187 subjects screened, 36 were heterozygous for Hb S [β6(A3)Glu→Val, GAG>GTG] (allele frequency 9.62%). Sixty-four subjects were heterozygous and seven were homozygous for the -α(3.7) kb deletion (allele frequency 20.85%). β-Thalassemia alleles were detected in five subjects, four with the -29 (A>G) mutation (allele frequency 1.07%) and one with codon 15 (TGG>TAG) (allele frequency 0.96%). The G6PD A- and G6PD Betica deficient variants were highly prevalent with a frequency of 5.7 and 3.3%, respectively. While we did not test for ferritin levels or α(0)-thal, four females (5.2%) had red cell indices strongly suggestive of iron deficient anemia: Hb <9.7 g/dL; MCH <19.3 pg; MCV <68.2; MCHC <31.6 g/dl; RDW >19.8%. Our results are consistent with high frequency of alleles such as Hb S, α-thal and G6PD deficient alleles associated with malaria resistance. Finding a 9.6% Hb S allele frequency supports the notion for a proficient neonatal screening to identify the sickle cell patients, who might benefit from early prophylactic treatment for infections. The incidence of significant iron deficient anemia in women is lower than expected in an under developed country.     

SAMBA, a plant-specific anaphase-promoting complex/cyclosome regulator is involved in early development and A-type cyclin stabilization

The anaphase-promoting complex/cyclosome (APC/C) is a large multiprotein E3 ubiquitin ligase involved in ubiquitin-dependent proteolysis of key cell cycle regulatory proteins, including the destruction of mitotic cyclins at the metaphase-to-anaphase transition. Despite its importance, the role of the APC/C in plant cells and the regulation of its activity during cell division remain poorly understood. Here, we describe the identification of a plant-specific negative regulator of the APC/C complex, designated SAMBA. In Arabidopsis thaliana, SAMBA is expressed during embryogenesis and early plant development and plays a key role in organ size control. Samba mutants produced larger seeds, leaves, and roots, which resulted from enlarged root and shoot apical meristems, and, additionally, they had a reduced fertility attributable to a hampered male gametogenesis. Inactivation of SAMBA stabilized A2-type cyclins during early development. Our data suggest that SAMBA regulates cell proliferation during early development by targeting CYCLIN A2 for APC/C-mediated proteolysis.     

Structure-function analysis of pneumococcal DprA protein reveals that dimerization is crucial for loading RecA recombinase onto DNA during transformation

Transformation promotes genome plasticity in bacteria via RecA-driven homologous recombination. In the Gram-positive human pathogen Streptococcus pneumoniae, the transformasome a multiprotein complex, internalizes, protects, and processes transforming DNA to generate chromosomal recombinants. Double-stranded DNA is internalized as single strands, onto which the transformation-dedicated DNA processing protein A (DprA) ensures the loading of RecA to form presynaptic filaments. We report that the structure of DprA consists of the association of a sterile alpha motif domain and a Rossmann fold and that DprA forms tail-to-tail dimers. The isolation of DprA self-interaction mutants revealed that dimerization is crucial for the formation of nucleocomplexes in vitro and for genetic transformation. Residues important for DprA-RecA interaction also were identified and mutated, establishing this interaction as equally important for transformation. Positioning of key interaction residues on the DprA structure revealed an overlap of DprA-DprA and DprA-RecA interaction surfaces. We propose a model in which RecA interaction promotes rearrangement or disruption of the DprA dimer, enabling the subsequent nucleation of RecA and its polymerization onto ssDNA.     

Myostatin inhibits proliferation but not differentiation of trout myoblasts

The muscle growth in mammals is regulated by several growth factors including myostatin (MSTN), a member of the transforming growth factor-beta (TGF-beta) superfamily. To date, it is unknown in fish whether MSTN could have any effect on proliferation or differentiation of myogenic cells. Using culture of trout satellite cells, we showed that mstn1a and mstn1b mRNA are expressed in myoblasts and that their expression decreased in differentiating myoblasts. We also demonstrated that a treatment with huMSTN decreased the proliferation of IGF1-stimulated myoblasts in a dose-dependent manner. By contrast, treatment of myoblasts with 100 nM of huMSTN for three days, did not affect the percentage of positive cells for myogenin neither the percentage of nuclei in myosin positive cells. Moreover, our results clearly indicated that huMSTN treatment had no effect on MyoD and myogenin protein levels, which suggests that huMSTN did not strongly affect MyoD activity. In conclusion, we showed that huMSTN inhibited proliferation but not differentiation of trout myoblasts, probably resulting from a lack of huMSTN effect on MyoD activity. Altogether, these results show high interspecies differences in the function of MSTN.     

Macrophage LRP1 contributes to the clearance of von Willebrand factor

The relationship between low-density lipoprotein receptor-related protein-1 (LRP1) and von Willebrand factor (VWF) has remained elusive for years. Indeed, despite a reported absence of interaction between both proteins, liver-specific deletion of LRP1 results in increased VWF levels. To investigate this discrepancy, we used mice with a macrophage-specific deficiency of LRP1 (macLRP1(-)) because we previously found that macrophages dominate VWF clearance. Basal VWF levels were increased in macLRP1(-) mice compared with control mice (1.6 ± 0.4 vs 1.0 ± 0.4 U/mL). Clearance experiments revealed that half-life of human VWF was significantly increased in macLRP1(-) mice. Ubiquitous blocking of LRP1 or additional lipoprotein receptors by overexpressing receptor-associated protein in macLRP1(-) mice did not result in further rise of VWF levels (0.1 ± 0.2 U/mL), in contrast to macLRP1(+) mice (rise in VWF, 0.8 ± 0.4 U/mL). This points to macLRP1 being the only lipoprotein receptor regulating VWF levels. When testing the mechanism(s) involved, we observed that VWF-coated beads adhered efficiently to LRP1 but only when exposed to shear forces exceeding 2.5 dyne/cm(2), implying the existence of shear stress-dependent interactions. Furthermore, a mechanism involving β2-integrins that binds both VWF and LRP1 also is implicated because inhibition of β2-integrins led to increased VWF levels in control (rise, 0.19 ± 0.16 U/mL) but not in macLRP1(-) mice (0.08 ± 0.15 U/mL).