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Development of the cerebellum is characterized by rapid proliferation of cerebellar granule cell precursors (GCPs) induced by paracrine stimulation of Sonic hedgehog (Shh) signaling from Purkinje cells, in the external granular layer (EGL). Then, granule cell precursors differentiate and migrate into the inner granular layer (IGL) of the cerebellum to form a terminally differentiated cell compartment. Aberrant activation of Sonic hedgehog signaling leads to granule cell precursors hyperproliferation and the onset of Sonic hedgehog medulloblastoma (MB), the most common embryonal brain tumor. β-arrestin1 (ARRB1) protein plays an important role downstream of Smoothened, a component of the Sonic hedgehog pathway. In the medulloblastoma context, β-arrestin1 is involved in a regulatory axis in association with the acetyltransferase P300, leading to the acetylated form of the transcription factor E2F1 (E2F1-ac) and redirecting its activity toward pro-apoptotic gene targets. This axis in the granule cell precursors physiological context has not been investigated yet. In this study, we demonstrate that β-arrestin1 has antiproliferative and pro-apoptotic functions in cerebellar development. β-arrestin1 silencing increases proliferation of Sonic hedgehog treated-cerebellar precursor cells while decreases the transcription of E2F1-ac pro-apoptotic targets genes, thus impairing apoptosis. Indeed, chromatin immunoprecipitation experiments show a direct interaction between β-arrestin1 and the promoter regions of the pro-apoptotic E2F1 target gene and P27, indicating the double role of β-arrestin1 in controlling apoptosis and cell cycle exit in a physiological context. Our data elucidate the role of β-arrestin1 in the early postnatal stages of cerebellar development, in those cell compartments that give rise to medulloblastoma. This series of experiments suggests that the physiological function of β-arrestin1 in neuronal progenitors is to directly control, cooperating with E2F1 acetylated form, transcription of pro-apoptotic genes.

Aims.In recent years several warnings have been issued by regulatory authorities on the risk of electrocardiogram abnormalities in individuals exposed to psychotropic drugs. As a consequence of these warnings, monitoring of the QT interval corrected for heart rate (QTc) has become increasingly common. This study was conducted to measure the frequency of QTc prolongation in unselected psychiatric patients, and to document the associated factors using a cross-sectional approach.Method.The study was carried out in 35 Italian psychiatric services that are part of the STAR (Servizi Territoriali Associati per la Ricerca) Network, a research group established to produce scientific knowledge by collecting data under ordinary circumstances. During a three-month period, a consecutive unselected series of both in- and out-patients were enrolled if they performed an ECG during the recruitment period and were receiving psychotropic drugs on the day ECG was recorded.Results.During the recruitment period a total of 2411 patients were included in the study. The prevalence of QTc prolongation ranged from 14.7% (men) and 18.6% (women) for the cut-off of 450 ms, to 1.26% (men) and 1.01% (women) for the cut-off of 500 ms. In the multivariate model conducted in the whole sample of patients exposed to psychotropic drugs, female sex, age, heart rate, alcohol and/or substance abuse, cardiovascular diseases and cardiovascular drug treatment, and drug overdose were significantly associated with QTc prolongation. In patients exposed to antipsychotic drugs, polypharmacy was positively associated with QTc prolongation, whereas use of aripiprazole decreased the risk. In patients exposed to antidepressant drugs, use of citalopram, citalopram dose and use of haloperidol in addition to antidepressant drugs, were all positively associated with QTc prolongation.Conclusions.The confirmation of a link between antipsychotic polypharmacy and QTc prolongation supports the current guidelines that recommend avoiding the concurrent use of two or more antipsychotic drugs, and the confirmation of a link between citalopram and QTc prolongation supports the need for routine QTc monitoring. The relatively low proportion of patients with QTc prolongation not only suggests compliance with current safety warnings issued by regulatory authorities, but also casts some doubts on the clinical relevance of QTc prolongation related to some psychotropic drugs.

Antipsychotic (AP) drugs have the potential to cause prolongation of the QT interval corrected for heart rate (QTc). As this risk is dose-dependent, it may be associated with the number of AP drugs concurrently prescribed, which is known to be associated with increased cumulative equivalent AP dosage. This study analysed whether AP dose mediates the relationship between polypharmacy and QTc interval. We used data from a cross-sectional survey that investigated the prevalence of QTc lengthening among people with psychiatric illnesses in Italy. AP polypharmacy was tested for evidence of association with AP dose and QTc interval using the Baron and Kenny mediational model. A total of 725 patients were included in this analysis. Of these, 186 (26%) were treated with two or more AP drugs (AP polypharmacy). The mean cumulative AP dose was significantly higher in those receiving AP polypharmacy (prescribed daily dose/defined daily dose = 2.93, standard deviation 1.31) than monotherapy (prescribed daily dose/defined daily dose = 0.82, standard deviation 0.77) (z = -12.62, p < 0.001). Similarly, the mean QTc interval was significantly longer in those receiving AP polypharmacy (mean = 420.86 milliseconds, standard deviation 27.16) than monotherapy (mean = 413.42 milliseconds, standard deviation 31.54) (z = -2.70, p = 0.006). The Baron and Kenny mediational analysis showed that, after adjustment for confounding variables, AP dose mediates the association between polypharmacy and QTc interval. The present study found that AP polypharmacy is associated with QTc interval, and this effect is mediated by AP dose. Given the high prevalence of AP polypharmacy in real-world clinical practice, clinicians should consider not only the myriad risk factors for QTc prolongation in their patients, but also that adding a second AP drug may further increase risk as compared with monotherapy.

Objective: Corrected QT (QTc) interval prolongation is often associated with use of first-generation antipsychotics (FGAs). However, other factors require appropriate consideration, including age and gender, the role of other known medications associated with QTc prolongation, and severe comorbid conditions, such as co-occurring alcohol abuse/dependence. We aimed to study potential mediating roles of different, related, candidate variables on QTc. Methods: We capitalized on data from a large (N = 2366), cross-sectional, national survey, the STAR Network QTc study, using a representative sample of people taking FGAs, and recruited from mental health services across Italy. Results: About one-third of the sample was treated with FGAs, and almost one-tenth of the subjects took a different, additional, drug known to cause QTc prolongation. Our findings confirmed that there is an impact from FGAs, age, gender, alcohol misuse, and concurrent risky drugs on QTc. However, comorbid alcohol abuse/dependence and concurrent risky drugs did not mediate the effect of FGAs on QTc. Conclusions: Our findings showed that FGAs, concurrent risky drugs, and alcohol use disorders prolonged QTc. FGAs had a direct effect on QTc, confirming the need for clinicians to monitor a risk that could lead to sudden unexplained death. Copyright © 2016 John Wiley & Sons, Ltd.

The polymerization of serpins is at the root of a large class of diseases; the molecular structure of serpin polymers has been recently debated. In this work, we study the polymerization kinetics of human neuroserpin by Fourier Transform Infra Red spectroscopy and by time-lapse Size Exclusion Chromatography. First, we show that two distinct neuroserpin polymers, formed at 45 and 85 °C, display the same isosbestic points in the Amide I band, and therefore share common secondary structure features. We also find a concentration independent polymerization rate at 45 °C suggesting that the polymerization rate limiting step is the formation of an activated monomeric species. The polymer structures are consistent with a model that predicts the bare insertion of portions of the reactive center loop into the A b-sheet of neighboring serpin molecule, although with different extents at 45 and 85 °C. Further studies are currently addressing the structure of monomeric neuroserpin conformers.

Neuroserpin is an inhibitory enzyme, belonging to the family of serpins and involved in several pathologies, such as ischemia, Alzheimer disease, and FENIB (Familial Encephalopathy with Neuroserpin Inclusion Body). Here, we study the mechanism of neuroserpin inactivation and polymerization by different experimental techniques (static and dynamic light scattering, liquid chromatography, Fourier transform infrared spectroscopy, emission spectroscopy). Our results show that at intermediate temperatures (45-55 °C) neuroserpin forms flexible polymers with a size from a few tens to a few hundreds of nanometers. At high temperatures, above 80 °C, our results reveal a different polymeric form, reached through an analogous loop-sheet mechanism, with considerably larger size and higher chemical stability. Our observations highlight the role of the different processes involved in serpin self-assembly, namely inactivating conformational changes, oligomer formation, polymer elongation and fragmentation.

Serpins are a wide class of proteins with high structural similarity, characterized by a unique substrate-like inhibitory mechanism that resembles a "molecular mousetrap". The active serpin is characterized by a main 5-stranded β-sheet and an exposed Reactive Centre Loop, which acts as a bait for the target protease. The cleavage of the loop by the protease triggers the insertion of the loop into the β-sheet as a strand and the disruptive translocation of the protease. This peculiar conformational mobility is achievable since serpins fold into a metastable native conformation. This feature gives a selective advantage to the serpin family to develop inhibitory activities, but leaves these proteins labile to misfolding and dysfunctional mutations, which cause a class of diseases known as serpinopathies. Indeed, the thermodynamically stable non-functional conformation can be reached without cleavage by intramolecular loop insertion (latent state) or by intermolecular insertion, leading to polymerization. Neuroserpin is a an inhibitor of tissue-type plasminogen activator that has a role in many pathologies, such as ischemia, Alzheimer disease, and FENIB (Familial Encephalopathy with Neuroserpin Inclusion Body). It is particularly suited to study the molecular basis of serpin inactivation and polymerization, since it may form latent conformers and polymers by thermal activation even in the wild type form. Here, we study the mechanism of neuroserpin unfolding and polymerization by different experimental techniques (static and dynamic light scattering, liquid chromatography, Fourier transform infrared spectroscopy) and by the support of Molecular Dynamics simulations. Our results show that at intermediate temperatures (45-55 °C) neuroserpin forms flexible polymers with a size from a few tens to a few hundreds of nanometers. At high temperatures, above 80 °C, our results reveal a different polymeric form, reached through an analogous loop-sheet mechanism, with considerably larger size and higher chemical stability. These observations highlight the fact that serpin polymerization is context-dependent, and that polymers accumulated in serpinopathies under physiological conditions may be different for different serpin and even for different pathological mutants of the same serpin.

PURPOSE: The authors sought to identify radiological criteria assisting in the diagnosis of craniofacial fibrous dysplasia and differential diagnosis of fibro-osseous lesions by comparing computed tomography (CT) and magnetic resonance imaging (MRI) findings and histological results in 23 patients with presumed fibrous dysplasia. MATERIALS AND METHODS: From February 2000 to March 2005, 23 patients (17 women and six men, aged 9-66 years) with facial bone disease underwent CT and MRI studies. Imaging findings were compared with the results of histological examination performed within 1 month of the radiological diagnosis. RESULTS: The combination of CT and MRI led to a presumptive diagnosis of fibrous dysplasia in all cases, but histology confirmed the diagnosis in 18 cases only. In two cases that had initially been considered cyst-like variants of fibrous dysplasia and were associated with irregular enhancement at MRI, histology characterised the lesions as single locations of multiple myeloma. In one case, targeted biopsy of areas showing intense enhancement led to a diagnosis of low-grade fibrosarcoma; in the remaining two cases, the definitive diagnoses were ossifying fibroma and myeloproliferative disease. CONCLUSIONS: MRI proved useful in differentiating fibrous dysplasia from other bone diseases, defining clinical behaviour, identifying neoplastic foci within dysplastic tissue and distinguishing benign from malignant bone lesions. The authors suggest a broader use of contrast-enhanced MRI for the diagnosis and follow-up of dysplastic lesions of the facial bones and for planning appropriate surgical treatment. Purpose: The authors sought to identify radiological criteria assisting in the diagnosis of craniofacial fibrous dysplasia and differential diagnosis of fibro-osseous lesions by comparing computed tomography (CT) and magnetic resonance imaging (MRI) findings and histological results in 23 patients with presumed fibrous dysplasia. Materials and methods: From February 2000 to March 2005, 23 patients (17 women and six men, aged 9-66 years) with facial bone disease underwent CT and MRI studies. Imaging findings were compared with the results of histological examination performed within 1 month of the radiological diagnosis. Results: The combination of CT and MRI led to a presumptive diagnosis of fibrous dysplasia in all cases, but histology confirmed the diagnosis in 18 cases only. In two cases that had initially been considered cyst-like variants of fibrous dysplasia and were associated with irregular enhancement at MRI, histology characterised the lesions as single locations of multiple myeloma. In one case, targeted biopsy of areas showing intense enhancement led to a diagnosis of low-grade fibrosarcoma; in the remaining two cases, the definitive diagnoses were ossifying fibroma and myeloproliferative disease. Conclusions: MRI proved useful in differentiating fibrous dysplasia from other bone diseases, defining clinical behaviour, identifying neoplastic foci within dysplastic tissue and distinguishing benign from malignant bone lesions. The authors suggest a broader use of contrast-enhanced MRI for the diagnosis and follow-up of dysplastic lesions of the facial bones and for planning appropriate surgical treatment. © 2008 Springer-Verlag.