A new non-aggregative splicing isoform of human Tau is decreased in Alzheimer's disease

Tauopathies, including Alzheimer's disease (AD) and frontotemporal lobar degeneration with Tau pathology (FTLD-tau), are a group of neurodegenerative disorders characterized by Tau hyperphosphorylation. Post-translational modifications of Tau such as phosphorylation and truncation have been demonstrated to be an essential step in the molecular pathogenesis of these tauopathies. In this work, we demonstrate the existence of a new, human-specific truncated form of Tau generated by intron 12 retention in human neuroblastoma cells and, to a higher extent, in human RNA brain samples, using qPCR and further confirming the results on a larger database of human RNA-seq samples. Diminished protein levels of this new Tau isoform are found by Westernblotting in Alzheimer's patients' brains (Braak I n = 3; Braak II n = 6, Braak III n = 3, Braak IV n = 1, and Braak V n = 10, Braak VI n = 8) with respect to non-demented control subjects (n = 9), suggesting that the lack of this truncated isoform may play an important role in the pathology. This new Tau isoform exhibits similar post-transcriptional modifications by phosphorylation and affinity for microtubule binding, but more interestingly, is less prone to aggregate than other Tau isoforms. Finally, we present evidence suggesting this new Tau isoform could be linked to the inhibition of GSK3β, which would mediate intron 12 retention by modulating the serine/arginine rich splicing factor 2 (SRSF2). Our results show the existence of an important new isoform of Tau and suggest that further research on this less aggregation-prone Tau may help to develop future therapies for Alzheimer's disease and other tauopathies.

Huntington's disease-specific mis-splicing unveils key effector genes and altered splicing factors

Correction of mis-splicing events is a growing therapeutic approach for neurological diseases such as spinal muscular atrophy or neuronal ceroid lipofuscinosis 7, which are caused by splicing-affecting mutations. Mis-spliced effector genes that do not harbour mutations are also good candidate therapeutic targets in diseases with more complex aetiologies such as cancer, autism, muscular dystrophies or neurodegenerative diseases. Next-generation RNA sequencing (RNA-seq) has boosted investigation of global mis-splicing in diseased tissue to identify such key pathogenic mis-spliced genes. Nevertheless, while analysis of tumour or dystrophic muscle biopsies can be informative on early stage pathogenic mis-splicing, for neurodegenerative diseases, these analyses are intrinsically hampered by neuronal loss and neuroinflammation in post-mortem brains. To infer splicing alterations relevant to Huntington’s disease pathogenesis, here we performed intersect-RNA-seq analyses of human post-mortem striatal tissue and of an early symptomatic mouse model in which neuronal loss and gliosis are not yet present. Together with a human/mouse parallel motif scan analysis, this approach allowed us to identify the shared mis-splicing signature triggered by the Huntington’s disease-causing mutation in both species and to infer upstream deregulated splicing factors. Moreover, we identified a plethora of downstream neurodegeneration-linked mis-spliced effector genes that—together with the deregulated splicing factors—become new possible therapeutic targets. In summary, here we report pathogenic global mis-splicing in Huntington’s disease striatum captured by our new intersect-RNA-seq approach that can be readily applied to other neurodegenerative diseases for which bona fide animal models are available.

Pathogenic SREK1 decrease in Huntington's disease lowers TAF1 mimicking X-linked dystonia parkinsonism

Huntington’s disease and X-linked dystonia parkinsonism are two monogenic basal ganglia model diseases. Huntington’s disease is caused by a polyglutamine-encoding CAG repeat expansion in the Huntingtin (HTT) gene leading to several toxic interactions of both the expanded CAG-containing mRNA and the polyglutamine-containing protein, while X-linked dystonia parkinsonism is caused by a retrotransposon insertion in the TAF1 gene, which decreases expression of this core scaffold of the basal transcription factor complex TFIID. SRSF6 is an RNA-binding protein of the serine and arginine-rich (SR) protein family that interacts with expanded CAG mRNA and is sequestered into the characteristic polyglutamine-containing inclusion bodies of Huntington’s disease brains. Here we report decreased levels of the SRSF6 interactor and regulator SREK1—another SR protein involved in RNA processing—which includes TAF1 as one of its targets. This led us to hypothesize that Huntington’s disease and X-linked dystonia parkinsonism pathogeneses converge in TAF1 alteration. We show that diminishing SRSF6 through RNA interference in human neuroblastoma cells leads to a decrease in SREK1 levels, which, in turn, suffices to cause diminished TAF1 levels. We also observed decreased SREK1 and TAF1 levels in striatum of Huntington’s disease patients and transgenic model mice. We then generated mice with neuronal transgenic expression of SREK1 (TgSREK1 mice) that, interestingly, showed transcriptomic alterations complementary to those in Huntington’s disease mice. Most importantly, by combining Huntington’s disease and TgSREK1 mice we verify that SREK1 overexpression corrects TAF1 deficiency and attenuates striatal atrophy and motor phenotype of Huntington’s disease mice. Our results therefore demonstrate that altered RNA processing upon SREK1 dysregulation plays a key role in Huntington’s disease pathogenesis and pinpoint TAF1 as a likely general determinant of selective vulnerability of the striatum in multiple neurological disorders.

Correction to: Isolation, Purification, and Culture of Primary Murine Sensory Neurons

In chapter 15, section 2.3, the unit "180 μg/ml mouse laminin in HBSS. Prepare 150 μl per coverslip" is corrected to "18 μg/ml mouse laminin in HBSS. Prepare 150 μl per coverslip."

Faulty splicing and cytoskeleton abnormalities in Huntington's disease

Huntington's disease (HD) is caused by a CAG-repeat encoding a polyglutamine (polyQ) tract in the huntingtin protein. There is plenty of evidence of polyQ-driven toxicity. However, CAG repeat RNA-driven alteration of splicing has recently been proposed in analogy to CUG-repeat diseases. Here we review the reported alteration of the CAG-repeat associated splicing factor SRSF6 in brains of HD patients and mouse models and how this correlates with altered splicing of, at least, two microtubule-associated proteins in HD, namely MAPT (tau) and MAP2. Regarding tau, altered splicing of exon 10 has been reported, along with increased levels and 4R/3R-tau ratio and detection of tau in a new nuclear rod-shaped histopathological hallmark termed tau nuclear rod (TNR) or tau nuclear indentation (TNI). These findings, together with an attenuation of HD phenotype in R6/1 mice with tau deficiency and subsequent studies showing increased phosphorylation in mouse models and increased levels in CSF of patients, has led to proposing HD as a tauopathy. Regarding MAP2, an increase in its juvenile form and a decrease in total MAP2 together with redistribution from dendrites to soma is observed in HD patients, which may contribute to the dendritic atrophy in HD. Furthermore, MAP2 positive structures filling nuclear indentations have occasionally been found and co-localized with tau. Therefore, altered MAP function with imbalance in tau/MAP2 content could contribute to HD striatal atrophy and dysfunction. Besides, TNIs might be indicative of such MAP abnormalities. TNIs are also found in early pathology Alzheimer's disease and in tauopathy mice over-expressing mutant 4R-tau. This indicates that tau alteration is sufficient for TNI detection, which becomes a marker of increased total tau and/or altered 4R/3R-tau ratio and reporter of pathology-associated nuclear indentations. Altogether, these recent studies suggest that correcting the SRSF6-driven missplicing and/or microtubule-associated imbalance might be of therapeutic value in HD.

Growth differentiation factor 11 (GDF11) - a promising anti-ageing factor - is highly concentrated in platelets

Recent research suggests that growth differentiation factor 11 (GDF11) could reverse age-related diseases and that its blood concentration decreases with age. This poses plasma from young donors as a therapeutic GDF11 source to treat age-related diseases. In addition, the tissue source of circulating GDF11 remains unknown. We analysed GDF11 levels in paired samples of serum, plasma and platelet lysate (PL) from 23 volunteers. Plasma and PL were collected by plateletpheresis. Here, we show that GDF11 is highly concentrated in platelets and that the circulating levels reported in previous studies could be biased as a result of serum sample manipulation.

Severe infections after single umbilical cord blood transplantation in adults with or without the co-infusion of CD34+ cells from a third-party donor: results of a multicenter study from the Grupo Español de Trasplante Hematopoyético (GETH)

BACKGROUND

Umbilical cord blood transplantation (CBT) is an established alternative source of stem cells in the setting of unrelated transplantation. When compared with other sources, single-unit CBT (sCBT) is associated with a delayed hematologic recovery, which may lead to a higher infection-related mortality (IRM). Co-infusion with the sCBT of CD34+ peripheral blood stem cells from a third-party donor (TPD) (sCBT + TPDCD34+) has been shown to markedly accelerate leukocyte recovery, potentially reducing the IRM. However, to our knowledge, no comparative studies have focused on severe infections and IRM with these 2 sCBT strategies.

METHODS

A total of 148 consecutive sCBT (2000-2010, median follow-up 4.5 years) were included in a multicenter retrospective study to analyze the incidence and risk factors of IRM and severe viral and invasive fungal infections (IFIs). Neutrophil engraftment occurred in 90% of sCBT (n = 77) and 94% sCBT + TPDCD34+ (n = 71) recipients at a median of 23 and 12 days post transplantation, respectively (P < 0.01).

RESULTS

The 4-year IRM was 24% and 20%, respectively (P = 0.7), with no differences at day +30 (5% and 4%, respectively) and day +100 (10% and 8%, respectively). In multivariate analysis early status of the underlying malignancy, cytomegalovirus (CMV)-seronegative recipient and high CD34+ cell content in the cord blood unit before cryostorage (≥1.4 × 10(5) /kg) were protective of IRM. Among the causes of IRM, bacterial infections and IFIs were more common in sCBT (15% vs. 4%), while CMV disease and parasitic infections were more common in the sCBT + TPDCD34+ cohort (5% vs. 16%).

CONCLUSION

These data show that sCBT supported with TPDCD34(+) cells results in much shorter periods of post-transplant leukopenia, but the short- and long-term rates of IRM were comparable to those of sCBT, presumably because immune recovery is equally delayed in both graft types.

RET modulates cell adhesion via its cleavage by caspase in sympathetic neurons

RET is a tyrosine kinase receptor involved in numerous cellular mechanisms including proliferation, neuronal navigation, migration, and differentiation upon binding with glial cell derived neurotrophic factor family ligands. RET is an atypical tyrosine kinase receptor containing four cadherin domains in its extracellular part. Furthermore, it has been shown to act as a dependence receptor. Such a receptor is active in the absence of ligand, triggering apoptosis through a mechanism that requires receptor intracellular caspase cleavage. However, different data suggest that RET is not always associated with the cell death/survival balance but rather provides positional information. We demonstrate here that caspase cleavage of RET is involved in the regulation of adhesion in sympathetic neurons. The cleavage of RET generates an N-terminal truncated fragment that functions as a cadherin accessory protein, modifying cadherin environment and potentiating cadherin-mediated cell aggregation. Thus, the caspase cleavage of RET generates two RET fragments: one intracellular domain that can trigger cell death in apoptotic permissive settings, and one membrane-anchored ectodomain with cadherin accessory activity. We propose that this latter function may notably be important for the adequate development of the superior cervical ganglion.

[Umbilical cord blood cell transplantation from an unrelated donor: dual transplantation]

Our team conducted an original procedure of hematopoietic transplantation of umbilical cord blood (UCB) from an unrelated donor. The procedure consists of co-infusing hematopoietic stem cells selected from the blood of a third-party donor; it is conceived as a tool to shorten the engraftment period without preventing the engraftment of the UCB, even when using units with relatively low cell content and a low HLA compatibility. Between 1999 and 2008 we performed 64 transplantations in 60 adult patients (35 men and 25 women) with a median age of 34 years (range: 76-60) and a median weight of 70 kg (range: 43-95), all of whom were diagnosed with a high risk hematologic neoplasm (leukemia in most cases). Fludarabine, cyclophosphamide, ATG, and whole body irradiation or busulfan were used as conditioners. UCB was infused at medians of 2.4 x 107 CNT/kg (range: 1.14-4.30 x 107), 0.11 x 106 CD34+/kg (range: 0.035-0.37 x 106). Then, hematopoietic stem cells selected from the third-party donor were infused (2.43 x 106/kg [range: 1.05-3.34 x 106], with 0.3 x 104 CD3+/kg [range: 0.05-1.56 x 104]). Granulocyte engraftment occurred (ANC > 0.5 x 109/L) at a median of 10 days (range: 9-34 days), and the granulocyte engraftment of the UCB occurred in 21 days (range: 13-57 days). Complete UCB chimerism was observed in 37 days (range: 11-186 days) (previously double complete chimerism, presence of third-party donor and of cord) and platelet engraftment > 20 x 109/L in 33 days (range: 13 98 days) and > 50 x 109/L in 58 days (range: 14-106 days). Overall 3-year survival reached 51%, and 5 10 year-survival was 47% (plateau). Disease-free survival was 48% at three years, and 45% at 5 to 10 years; the mean follow-up of survivors was 48 months (range: 13-123 months). (Kaplan-Meier). In conclusion, early granulocyte recovery occurred thanks to a foster engraftment of hematopoietic stem from the third-party donor, which are not HLA-restricted; this is associated with a lower morbidity and mortality from infections secondary to neutropenia. There was also a high rate of engraftment and final full UCB chimerism, even with non-histocompatible UCB units (2/6 HLA mismatches) and with relatively low cell counts. In most cases, a single unit of UCB was sufficient. The incidence of severe GVHD and the percentage of relapses have been low. Opportunistic infections have occurred over a long period of time. This procedures makes allogeneic hematopoietic transplantation accessible to almost all patients.

Cord blood transplants supported by co-infusion of mobilized hematopoietic stem cells from a third-party donor

This open label clinical study provides updated evaluation of the strategy of single unit cord blood transplants (CBTs) with co-infusion of third-party donor (TPD) mobilized hematopoietic stem cells (MHSC). Fifty-five adults with high-risk hematological malignancies, median age 34 years (16-60 years) and weight 70 kg (43-95 kg), received CBTs (median 2.39 x 10(7) total nucleated cell (TNC) per kg and 0.11 x 10(6) CD34+ per kg) and TPD-MHSC (median 2.4 x 10(6) CD34+ per kg and 3.2 x 10(3) CD3+ per kg). Median time to ANC and to CB-ANC >0.5 x 10(9)/l as well as to full CB-chimerism was 10, 21 and 44 days, with maximum cumulative incidences (MCI) of 0.96, 0.95 and 0.91. Median time to unsupported platelets >20 x 10(9)/l was 32 days (MCI 0.78). MCI for grades I-IV and III-IV acute GVHD (aGVHD) were 0.62 and 0.11; 12 of 41 patients (29%) who are at risk developed chronic GVHD, becoming severely extensive in three patients. Relapses occurred in seven patients (MCI=0.17). The main causes of morbi-mortality were post-engraftment infections. CMV reactivations were the most frequent, their incidence declining after the fourth month. Five-year overall survival and disease-free survival (Kaplan-Meier) were 56 % and 47% (63% and 54% for patients <or=40 years). In conclusion, CBT with single units of relatively low cell content and 0-3 HLA mismatches is feasible as a first choice option for adult patients who lack a readily available adequate adult donor.

Idiopathic dilated cardiomyopathy. Elastic parallel element dysfunction as a physiopathological hypothesis for ventricular failure

BACKGROUND

Idiopathic dilated cardiomyopathy is a disease of unknown etiology, although the viral-immunologic pathogenesis has recently emerged as an important hypothesis. Its distinctive anatomopathologic features are: macroscopically, a great ventricular dilation with little hypertrophy, and microscopically marked diffuse interstitial fibrosis not observed in other pathologic entities with dilation. Hemodynamically, its main characteristic is a progressive loss of the systolic function, although the diastolic function is also impaired. To date it is accepted that in dilated states ventricular remodeling occurs due to sliding of fiber with a maximal sarcomere distention; it is also assumed that the ventricular dysfunction is due to a primary deficit in contractility caused by the injury and loss of myocites.

HYPOTHESIS

The aggressive agent mainly attacks the interstitial tissue, thus damaging the elastic parallel element structures. This results in a loss of absorbing power during diastole, starting a progressive dilation which results in maximum sarcomere distention, and compromises the ventricular function. The organ response is to create a new parallel element, which results in an increased fibrosis which also compromises this function.

Donor leukocyte infusions for treatment of relapsed acute myeloid leukemia after allogeneic bone marrow transplantation

A 24-year-old man with acute myelomonocytic leukemia (AML-M4) who relapsed 6 months after an allogeneic BMT was treated with chemotherapy followed by donor leukocyte infusions (4.19 x 10(8) mononuclear cells/kg). The patient developed grade II acute GVHD that responded to therapy with CsA and prednisone. Chimerism was assessed by PCR amplification of the MCT 118 hypervariable region. Fourteen months after donor leukocyte infusions the patient remains in complete remission, without any morphologic and cytogenetic evidence of leukemia, and with a complete donor chimerism. This case shows that donor leukocyte infusions are an effective therapy for some acute myeloid leukemia patients who relapse after allogeneic BMT.

[Treatment with fludarabine of chronic refractory lymphoid leukemia]

PURPOSE

New antimetabolic drugs, purine-analogous, have been introduced in the treatment of advanced or refractory cases of chronic lymphocytic leukaemia (CLL), fludarabine (FLU) being one of such drugs. The results attained with FLU in 6 cases of refractory CLL are reported.

PATIENTS AND METHODS

The efficacy and toxicity of FLU was evaluated in 6 patients (median age 63 years) between March 1993 and March 1994. Five patients were in stage III-IV and one in stage II of the Rai's system, and they were refractory to the usual treatment. The dosis used here was 30 mg/sq m/day, for 5 days every 4 weeks, up to a total of 6 therapeutic courses. The response was assessed after 3 and 6 courses. Anti-infectious prophylaxis was made with co-trimoxazole, monthly benzathine penicillin G and isoniazid in Mantoux-positive patients. The response criteria were those given by the NIC Working Group for CLL.

RESULTS

The patients received 2 to 6 courses. None of them attained complete remission: 1 had nodular remission, 2 had partial remission, 2 responded partially although not reaching criteria for partial remission (1 died of pancytopenia), and 1 had disease progression and died after the second course. Fast and important reduction of the lymphocyte count as well as the CD4 lymphocytes was present in all cases. Bone-marrow infiltration decreased strikingly in 2 cases and the platelet count improved in 3 cases and worsened in 2 others. The following toxicity was recorded: 2 patients had nausea, 5 had neutropenia (below 500 x 10(9)/L in 3 instances) and 4 had thrombocytopenia (lower than 40 x 10(9)/L in one case). In 26 therapeutic courses there were 10 febrile episodes (1 for pneumonia, 1 for gastroenteritis and 8 without any septic foci); 1 patient developed pulmonary tuberculosis after completing the treatment and one patient died of posttransfusion graft versus host disease after splenectomy once she had completes six courses.

CONCLUSION

This experience confirms the efficacy of FLU in the treatment of refractory B-CLL patients and is in agreement with previous reports as no response is initiated after the 3rd course. The lymphocyte count decreases quickly and strikingly. Depletion of CD4 lymphocytes along with neutropenia and hypogammaglobulinaemia make these patients highly sensitive to all types of infection, chiefly by opportunistic germs, so adequate anti-infectious prophylaxis is of great importance. The two patients with pre-treatment haemoglobin and platelet values lower than 10 g/dL and 40 x 10(9)/L, respectively, were the only ones in need of transfusion. No cumulative myelosuppression was appreciated.

Gastric Castleman's disease with a lupus-like circulating anticoagulant

We report the case of a 13-yr-old patient with retarded growth and a 2-yr background of asthenia, anorexia, and fever, whose laboratory data revealed anemia, thrombocytosis, an elevated erythrocyte sedimentation rate, ferropenia, hyperglobulinemia, hyperfibrinogenemia, and presence of a lupus-like circulating anticoagulant. Clinical studies revealed a tumor-like overgrowth in the gastric wall, and surgery confirmed its subserosal localization in the gastric fundus. After total removal of the mass, the systemic manifestations disappeared. The pathological study revealed the existence of the hyaline-vascular variety of Castleman's disease. Having reviewed the medical literature, we have not found a single unquestionable case of gastric Castleman's disease, although three other cases have been described as gastric pseudolymphoma which, when analyzed, could correspond to typical cases of Castleman's disease. Likewise, this is the second case associated with a circulating anticoagulant of lupoid characteristics. We conclude that Castleman's disease should be included in the differential diagnosis of gastric lesions of lymphoid nature and in the series of processes associated with lupus anticoagulant.

Defective neutrophil mobility in the May-Hegglin anomaly

A case of May-Hegglin anomaly is reported in which functional studies of PMN cells showed abnormalities consisting of impairment of chemotactic and chemokinetic responses, random mobility being otherwise normal. These abnormalities seem unrelated to microtubule system dysfunction or to abnormal cell deformability, since no defect was observed in the concanavalin A (Con A) surface receptors and no improvement of directional movement resulted when filters of larger pore size were used in the assays. Other possible mechanisms of the functional defect, such as abnormal membrane receptors to kinetic signals or metabolic abnormalities cannot be excluded. PMN function should be studied in additional cases in order to ascertain if these findings are a constant feature in the May-Hegglin anomaly, a syndrome in which undue susceptibility to infection has not been reported.