The neurodevelopmental gene MSANTD2 belongs to a gene family formed by recurrent molecular domestication of Harbinger transposons at the base of vertebrates.

The formation of new genes is a major source of organism evolutionary innovation. Beyond their mutational effects, transposable elements can be co-opted by host genomes to form different types of sequences including novel genes, through a mechanism named molecular domestication.We report the formation of four genes through molecular domestication of Harbinger transposons, three in a common ancestor of jawed vertebrates about 500 million years ago and one in sarcopterygians approx. 430 million years ago. Additionally, one processed pseudogene arose approx. 60 million years ago in simians. In zebrafish, Harbinger-derived genes are expressed during early development but also in adult tissues, and predominantly co-expressed in male brain. In human, expression was detected in multiple organs, with major expression in the brain particularly during fetal development. We used CRISPR/Cas9 with direct gene knock-out in the F0 generation and the morpholino antisense oligonucleotide knock-down technique to study in zebrafish the function of one of these genes called MSANTD2, which has been suggested to be associated to neuro-developmental diseases such as autism spectrum disorders and schizophrenia in human. MSANTD2 inactivation led to developmental delays including tail and nervous system malformation at one day post fertilization. Affected embryos showed dead cell accumulation, major anatomical defects characterized by impaired brain ventricle formation and alterations in expression of some characteristic genes involved in vertebrate nervous system development. Hence, the characterization of MSANTD2 and other Harbinger-derived genes might contribute to a better understanding of the genetic innovations having driven the early evolution of the vertebrate nervous system.

Interplay of RFX transcription factors 1, 2 and 3 in motile ciliogenesis.

Cilia assembly is under strict transcriptional control during animal development. In vertebrates, a hierarchy of transcription factors (TFs) are involved in controlling the specification, differentiation and function of multiciliated epithelia. RFX TFs play key functions in the control of ciliogenesis in animals. Whereas only one RFX factor regulates ciliogenesis in C. elegans, several distinct RFX factors have been implicated in this process in vertebrates. However, a clear understanding of the specific and redundant functions of different RFX factors in ciliated cells remains lacking. Using RNA-seq and ChIP-seq approaches we identified genes regulated directly and indirectly by RFX1, RFX2 and RFX3 in mouse ependymal cells. We show that these three TFs have both redundant and specific functions in ependymal cells. Whereas RFX1, RFX2 and RFX3 occupy many shared genomic loci, only RFX2 and RFX3 play a prominent and redundant function in the control of motile ciliogenesis in mice. Our results provide a valuable list of candidate ciliary genes. They also reveal stunning differences between compensatory processes operating in vivo and ex vivo.

Altered GLI3 and FGF8 signaling underlies acrocallosal syndrome phenotypes in Kif7 depleted mice.

Acrocallosal syndrome (ACLS) is a rare genetic disorder characterized by agenesis or hypoplasia of corpus callosum (CC), polydactyly, craniofacial dysmorphism and severe intellectual deficiency. We previously identified KIF7, a key ciliary component of the Sonic hedgehog (SHH) pathway, as being a causative gene for this syndrome, thus including ACLS in the group of ciliopathies. In both humans and mice, KIF7 depletion leads to abnormal GLI3 processing and over-activation of SHH target genes. To understand the pathological mechanisms involved in CC defects in this syndrome, we took advantage of a previously described Kif7-/- mouse model to demonstrate that in addition to polydactyly and neural tube closure defects, these mice present CC agenesis with characteristic Probst bundles, thus recapitulating major ACLS features. We show that CC agenesis in these mice is associated with specific patterning defects of the cortical septum boundary leading to altered distribution of guidepost cells required to guide the callosal axons through the midline. Furthermore, by crossing Kif7-/- mice with Gli3Δ699 mice exclusively producing the repressive isoform of GLI3 (GLI3R), we demonstrate that decreased GLI3R signaling is fully responsible for the ACLS features in these mice, as all phenotypes are rescued by increasing GLI3R activity. Moreover, we show that increased FGF8 signaling is responsible in part for CC defects associated to KIF7 depletion, as modulating FGF8 signaling rescued CC formation anteriorly in Kif7-/- mice. Taken together our data demonstrate that ACLS features rely on defective GLI3R and FGF8 signaling.

Adherence to Adalimumab Was Not Improved by a Reminder-Based Intervention with an Electronic Needle Container.

BACKGROUND: Adherence to adalimumab in inflammatory bowel disease (IBD) patients is reported to be below par. Non-adherence may result in loss-of-response and increased hospitalization. We analyzed the effect of an electronic needle container (ENC) on adherence to adalimumab. METHODS: In this multicenter, 12-months observational study, we included adalimumab treated IBD patients. All patients were invited to receive an ENC. Patients who declined or did not complete the registration for an ENC served as controls. Primary endpoint was whether an ENC increased adherence, calculated from pharmacy refills as proportion of days covered (PDC). Secondary endpoints were clinical outcomes, including loss-of-response, identification of predictors of adherence and correlation between different modalities for measuring adherence. Loss-of-response was defined as a disease flare, dose-escalation or IBD-related hospitalization or surgery. RESULTS: The pharmacies' records identified 198 eligible patients, of whom 32 were excluded. The ENC was supplied to 69 patients, the remaining 97 patient formed the control group. Median baseline PDC (98.4% vs. 96.1%, p = 0.047) and the proportion of adherent (PDC ≥ 86%) patients (87.0% vs. 74.2%, p = 0.045) was higher for the ENC group. The ENC did not improve the adherence of patients during follow-up (odds ratio 1.26, 95% CI 0.55-2.86). During follow-up, five (7.2%) patients in the ENC group and 13 (13.4%) in the control group discontinued adalimumab (log-rank p = 0.22). Loss-of-response occurred in 12 (17.4%) and 14 (14.4%) patients, respectively (log-rank p = 0.66). CONCLUSIONS: Our results show no beneficial effect of a reminder-based intervention on adherence or treatment outcomes.

RFX2 Is a Major Transcriptional Regulator of Spermiogenesis.

Spermatogenesis consists broadly of three phases: proliferation of diploid germ cells, meiosis, and finally extensive differentiation of the haploid cells into effective delivery vehicles for the paternal genome. Despite detailed characterization of many haploid developmental steps leading to sperm, only fragmentary information exists on the control of gene expression underlying these processes. Here we report that the RFX2 transcription factor is a master regulator of genes required for the haploid phase. A targeted mutation of Rfx2 was created in mice. Rfx2-/- mice are perfectly viable but show complete male sterility. Spermatogenesis appears to progress unperturbed through meiosis. However, haploid cells undergo a complete arrest in spermatid development just prior to spermatid elongation. Arrested cells show altered Golgi apparatus organization, leading to a deficit in the generation of a spreading acrosomal cap from proacrosomal vesicles. Arrested cells ultimately merge to form giant multinucleated cells released to the epididymis. Spermatids also completely fail to form the flagellar axoneme. RNA-Seq analysis and ChIP-Seq analysis identified 139 genes directly controlled by RFX2 during spermiogenesis. Gene ontology analysis revealed that genes required for cilium function are specifically enriched in down- and upregulated genes showing that RFX2 allows precise temporal expression of ciliary genes. Several genes required for cell adhesion and cytoskeleton remodeling are also downregulated. Comparison of RFX2-regulated genes with those controlled by other major transcriptional regulators of spermiogenesis showed that each controls independent gene sets. Altogether, these observations show that RFX2 plays a major and specific function in spermiogenesis.

The role of primary cilia in corpus callosum formation is mediated by production of the Gli3 repressor.

Agenesis of the corpus callosum (AgCC) is a frequent brain disorder found in over 80 human congenital syndromes including ciliopathies. Here, we report a severe AgCC in Ftm/Rpgrip1l knockout mouse, which provides a valuable model for Meckel-Grüber syndrome. Rpgrip1l encodes a protein of the ciliary transition zone, which is essential for ciliogenesis in several cell types in mouse including neuroepithelial cells in the developing forebrain. We show that AgCC in Rpgrip1l(-/-) mouse is associated with a disturbed location of guidepost cells in the dorsomedial telencephalon. This mislocalization results from early patterning defects and abnormal cortico-septal boundary (CSB) formation in the medial telencephalon. We demonstrate that all these defects primarily result from altered GLI3 processing. Indeed, AgCC, together with patterning defects and mispositioning of guidepost cells, is rescued by overexpressing in Rpgrip1l(-/-) embryos, the short repressor form of the GLI3 transcription factor (GLI3R), provided by the Gli3(Δ699) allele. Furthermore, Gli3(Δ699) also rescues AgCC in Rfx3(-/-) embryos deficient for the ciliogenic RFX3 transcription factor that regulates the expression of several ciliary genes. These data demonstrate that GLI3 processing is a major outcome of primary cilia function in dorsal telencephalon morphogenesis. Rescuing CC formation in two independent ciliary mutants by GLI3(Δ699) highlights the crucial role of primary cilia in maintaining the proper level of GLI3R required for morphogenesis of the CC.

mTOR inactivation in myocardium from infant mice rapidly leads to dilated cardiomyopathy due to translation defects and p53/JNK-mediated apoptosis.

Mechanistic target of rapamycin (mTOR) is a central regulator of cell growth, proliferation, survival and metabolism, as part of mTOR complex 1 (mTORC1) and mTORC2. While partial inhibition of mTORC1 using rapamycin was shown to be cardioprotective, genetic studies in mouse models revealed that mTOR is essential for embryonic heart development and cardiac function in adults. However, the physiological role of mTOR during postnatal cardiac maturation is not fully elucidated. We have therefore generated a mouse model in which cardiac mTOR was inactivated at an early postnatal stage. Mutant mTORcmKO mice rapidly developed a dilated cardiomyopathy associated with cardiomyocyte growth defects, apoptosis and fibrosis, and died during their third week. Here, we show that reduced cardiomyocyte growth results from impaired protein translation efficiency through both 4E-BP1-dependent and -independent mechanisms. In addition, infant mTORcmKO hearts displayed markedly increased apoptosis linked to stretch-induced ANKRD1 (Ankyrin repeat-domain containing protein 1) up-regulation, JNK kinase activation and p53 accumulation. Pharmacological inhibition of p53 with pifithrin-α attenuated caspase-3 activation. Cardiomyocyte death did not result from activation of the MST1/Hippo pro-apoptotic pathway as reported in adult rictor/mTORC2 KO hearts. As well, mTORcmKO hearts showed a strong downregulation of myoglobin content, thereby leading to a hypoxic environment. Nevertheless, they lacked a HIF1α-mediated adaptive response, as mTOR is required for hypoxia-induced HIF-1α activation. Altogether, our results demonstrate that mTOR is critically required for cardiomyocyte growth, viability and oxygen supply in early postnatal myocardium and provide insight into the molecular mechanisms involved in apoptosis of mTOR-depleted cardiomyocytes.

The coiled-coil domain containing protein CCDC151 is required for the function of IFT-dependent motile cilia in animals.

Cilia are evolutionarily conserved organelles endowed with essential physiological and developmental functions. In humans, disruption of cilia motility or signaling leads to complex pleiotropic genetic disorders called ciliopathies. Cilia motility requires the assembly of multi-subunit motile components such as dynein arms, but mechanisms underlying their assembly pathway and transport into the axoneme are still largely unknown. We identified a previously uncharacterized coiled-coil domain containing protein CCDC151, which is evolutionarily conserved in motile ciliated species and shares ancient features with the outer dynein arm-docking complex 2 of Chlamydomonas. In Drosophila, we show that CG14127/CCDC151 is associated with motile intraflagellar transport (IFT)-dependent cilia and required for geotaxis behavior of adult flies. In zebrafish, Ccdc151 is expressed in tissues with motile cilia, and morpholino-induced depletion of Ccdc151 leads to left-right asymmetry defects and kidney cysts. We demonstrate that Ccdc151 is required for proper motile function of cilia in the Kupffer's vesicle and in the pronephros by controlling dynein arm assembly, showing that Ccdc151 is a novel player in the control of IFT-dependent dynein arm assembly in animals. However, we observed that CCDC151 is also implicated in other cellular functions in vertebrates. In zebrafish, ccdc151 is involved in proper orientation of cell divisions in the pronephros and genetically interacts with prickle1 in this process. Furthermore, knockdown experiments in mammalian cells demonstrate that CCDC151 is implicated in the regulation of primary cilium length. Hence, CCDC151 is required for motile cilia function in animals but has acquired additional non-motile functions in vertebrates.

Underdiagnosis of foodborne hepatitis A, The Netherlands, 2008-2010(1.).

Outbreaks of foodborne hepatitis A are rarely recognized as such. Detection of these infections is challenging because of the infection's long incubation period and patients' recall bias. Nevertheless, the complex food market might lead to reemergence of hepatitis A virus outside of disease-endemic areas. To assess the role of food as a source of infection, we combined routine surveillance with real-time strain sequencing in the Netherlands during 2008-2010. Virus RNA from serum of 248 (59%) of 421 reported case-patients could be sequenced. Without typing, foodborne transmission was suspected for only 4% of reported case-patients. With typing, foodborne transmission increased to being the most probable source of infection for 16%. We recommend routine implementation of an enhanced surveillance system that includes prompt forwarding and typing of hepatitis A virus RNA isolated from serum, standard use of questionnaires, data sharing, and centralized interpretation of data.

DHPR alpha1S subunit controls skeletal muscle mass and morphogenesis.

The alpha1S subunit has a dual function in skeletal muscle: it forms the L-type Ca(2+) channel in T-tubules and is the voltage sensor of excitation-contraction coupling at the level of triads. It has been proposed that L-type Ca(2+) channels might also be voltage-gated sensors linked to transcriptional activity controlling differentiation. By using the U7-exon skipping strategy, we have achieved long-lasting downregulation of alpha1S in adult skeletal muscle. Treated muscles underwent massive atrophy while still displaying significant amounts of alpha1S in the tubular system and being not paralysed. This atrophy implicated the autophagy pathway, which was triggered by neuronal nitric oxide synthase redistribution, activation of FoxO3A, upregulation of autophagy-related genes and autophagosome formation. Subcellular investigations showed that this atrophy was correlated with the disappearance of a minor fraction of alpha1S located throughout the sarcolemma. Our results reveal for the first time that this sarcolemmal fraction could have a role in a signalling pathway determining muscle anabolic or catabolic state and might act as a molecular sensor of muscle activity.

CKIP-1 regulates mammalian and zebrafish myoblast fusion.

Multinucleated muscle fibres arise by fusion of precursor cells called myoblasts. We previously showed that CKIP-1 ectopic expression in C2C12 myoblasts increased cell fusion. In this work, we report that CKIP-1 depletion drastically impairs C2C12 myoblast fusion in vitro and in vivo during zebrafish muscle development. Within developing fast-twich myotome, Ckip-1 localises at the periphery of fast precursor cells, closed to the plasma membrane. Unlike wild-type myoblasts that form spatially arrayed multinucleated fast myofibres, Ckip-1-deficient myoblasts show a drastic reduction in fusion capacity. A search for CKIP-1 binding partners identified the ARPC1 subunit of Arp2/3 actin nucleation complex essential for myoblast fusion. We demonstrate that CKIP-1, through binding to plasma membrane phosphoinositides via its PH domain, regulates cell morphology and lamellipodia formation by recruiting the Arp2/3 complex at the plasma membrane. These results establish CKIP-1 as a regulator of cortical actin that recruits the Arp2/3 complex at the plasma membrane essential for muscle precursor elongation and fusion.

Detection of influenza A virus homo- and heterosubtype-specific memory B-cells using a novel protein microarray-based analysis tool.

The emergence of the A(H1N1) 2009 pandemic influenza virus was initially seen as a major world-wide health concern since a low degree of immunity to this virus strain was anticipated. However, age-specific infection attack rates and age-specific differences in seroresponse indicate that pre-existing immunity may have played a significant role in protection especially in older age groups. This study describes the use of a protein microarray as a multiplex analysis tool for detection of influenza virus H1 strain-specific memory B-cells before and after infection with A(H1N1)pdm09. The discrimination was based on detection of specific antibodies in culture supernatants from polyclonally stimulated B-cells against recombinant influenza virus HA1 proteins representing influenza virus subtypes H1 through H9. The protein microarray proved sensitive and specific for antibody detection in culture supernatants of B-cells, and with the potential to deduce a person's history of infection with particular influenza virus variants, including A(H1N1)pdm09. Blood samples obtained from different age groups prior to the pandemic in 2009 partly showed the presence of B-cells producing antibodies binding to the closely related A(H1N1) 1918 pandemic influenza virus, and of which the magnitude increased with age. These cross-reactive antibodies were produced by single memory B-cells present in these donors, and either bind to epitopes on HA1 which are shared within different H1 strains (homosubtypic response) or shared between different subtypes (heterosubtypic response).

Biophysical ordering transitions underlie genome 3D re-organization during cricket spermiogenesis.

Spermiogenesis is a radical process of differentiation whereby sperm cells acquire a compact and specialized morphology to cope with the constraints of sexual reproduction while preserving their main cargo, an intact copy of the paternal genome. In animals, this often involves the replacement of most histones by sperm-specific nuclear basic proteins (SNBPs). Yet, how the SNBP-structured genome achieves compaction and accommodates shaping remain largely unknown. Here, we exploit confocal, electron and super-resolution microscopy, coupled with polymer modeling to identify the higher-order architecture of sperm chromatin in the needle-shaped nucleus of the emerging model cricket Gryllus bimaculatus. Accompanying spermatid differentiation, the SNBP-based genome is strikingly reorganized as ~25nm-thick fibers orderly coiled along the elongated nucleus axis. This chromatin spool is further found to achieve large-scale helical twisting in the final stages of spermiogenesis, favoring its ultracompaction. We reveal that these dramatic transitions may be recapitulated by a surprisingly simple biophysical principle based on a nucleated rigidification of chromatin linked to the histone-to-SNBP transition within a confined nuclear space. Our work highlights a unique, liquid crystal-like mode of higher-order genome organization in ultracompact cricket sperm, and establishes a multidisciplinary methodological framework to explore the diversity of non-canonical modes of DNA organization.

Multicenter cohort association study of SLC2A1 single nucleotide polymorphisms and age-related macular degeneration.

PURPOSE: Age-related macular degeneration (AMD) is a major cause of blindness in older adults and has a genetically complex background. This study examines the potential association between single nucleotide polymorphisms (SNPs) in the glucose transporter 1 (SLC2A1) gene and AMD. SLC2A1 regulates the bioavailability of glucose in the retinal pigment epithelium (RPE), which might influence oxidative stress-mediated AMD pathology. METHODS: Twenty-two SNPs spanning the SLC2A1 gene were genotyped in 375 cases and 199 controls from an initial discovery cohort (the Amsterdam-Rotterdam-Netherlands study). Replication testing was performed in The Rotterdam Study (the Netherlands) and study populations from Würzburg (Germany), the Age Related Eye Disease Study (AREDS; United States), Columbia University (United States), and Iowa University (United States). Subsequently, a meta-analysis of SNP association was performed. RESULTS: In the discovery cohort, significant genotypic association between three SNPs (rs3754219, rs4660687, and rs841853) and AMD was found. Replication in five large independent (Caucasian) cohorts (4,860 cases and 4,004 controls) did not yield consistent association results. The genotype frequencies for these SNPs were significantly different for the controls and/or cases among the six individual populations. Meta-analysis revealed significant heterogeneity of effect between the studies. CONCLUSIONS: No overall association between SLC2A1 SNPs and AMD was demonstrated. Since the genotype frequencies for the three SLC2A1 SNPs were significantly different for the controls and/or cases between the six cohorts, this study corroborates previous evidence that population dependent genetic risk heterogeneity in AMD exists.

Decision aids can decrease decisional conflict in patients with hip or knee osteoarthritis: Randomized controlled trial.

BACKGROUND: The interest in shared decision making has increased considerably over the last couple of decades. Decision aids (DAs) can help in shared decision making. Especially when there is more than one reasonable option and outcomes between treatments are comparable. AIM: To investigate if the use of DAs decreases decisional conflict in patients when choosing treatment for knee or hip osteoarthritis (OA). METHODS: In this multi-center unblinded randomized controlled trial of patients with knee or hip OA were included from four secondary and tertiary referral centers. One-hundred-thirty-one patients who consulted an orthopedic surgeon for the first time with knee or hip OA were included between December 2014 and January 2016. After the first consultation, patients were randomly assigned by a computer to the control group which was treated according to standard care, or to the intervention group which was treated with standard care and provided with a DA. After the first consultation, patients were asked to complete questionnaires about decisional conflict (DCS), satisfaction, anxiety (PASS-20), gained knowledge, stage of decision making and preferred treatment. Follow-up was carried out after 26 wk and evaluated decisional conflict, satisfaction, anxiety, health outcomes (HOOS/KOOS), quality of life (EQ5D) and chosen treatment. RESULTS: After the first consultation, patients in the intervention group (mean DCS: 25 out of 100, SD: 13) had significantly (P value: 0.00) less decisional conflict compared to patients in the control group (mean DCS: 39 out of 100, SD 11). The mean satisfaction score for the given information (7.6 out of 10, SD: 1.8 vs 8.6 out of 10, SD: 1.1) (P value: 0.00), mean satisfaction score with the physician (8.3 out of 10, SD: 1.7 vs 8.9 out of 10, SD: 0.9) (P value: 0.01) and the mean knowledge score (3.3 out of 4, SD: 0.9 vs 3.7 out of, SD: 0.6) (P value: 0.01) were all significantly higher in the intervention group. At 26-wk follow-up, only 75 of 131 patients (57%) were available for analysis. This sample is too small for meaningful analysis. CONCLUSION: Providing patients with an additional DA may have a positive effect on decisional conflict after the first consultation. Due to loss to follow-up we are unsure if this effect remains over time.

The complement component 5 gene and age-related macular degeneration.

OBJECTIVE: To investigate the association between variants in the complement component 5 (C5) gene and age-related macular degeneration (AMD). DESIGN: Separate and combined data from 3 large AMD case-control studies and a prospective population-based study (The Rotterdam Study). PARTICIPANTS: A total of 2599 AMD cases and 3458 ethnically matched controls. METHODS: Fifteen single nucleotide polymorphisms (SNPs) spanning the C5 gene were initially genotyped in 375 cases and 199 controls from The Netherlands (The Amsterdam/Rotterdam-Netherlands [AMRO-NL] study population). Replication testing of selected SNPs was performed in the Rotterdam Study (NL) and study populations from Southampton, United Kingdom (UK), and New York, United States (US). MAIN OUTCOME MEASURES: Early and late stages of prevalent and incident AMD, graded according to (a modification of) the international grading and classification system of AMD. RESULTS: Significant allelic or genotypic associations between 8 C5 SNPs and AMD were found in the AMRO-NL study and this risk seemed to be independent of CFH Y402H, LOC387715 A69S, age, and gender. None of these findings could be confirmed consistently in 3 replication populations. CONCLUSIONS: Although the complement pathway, including C5, plays a crucial role in AMD, and the C5 protein is present in drusen, no consistent significant associations between C5 SNPs and AMD were found in any of these studies. The implications for genetic screening of AMD are discussed.

Wound complications after total hip arthroplasty: a prospective, randomised controlled trial comparing staples with sutures.

OBJECTIVE: Does the use of staples or sutures for wound closure have a lower surgical site infection rate in patients receiving primary total hip arthroplasty (THA)? DESIGN: Prospective, randomised controlled multicentre trial. METHODS: 535 patients undergoing THA were included and randomised into 2 groups: 268 wounds were closed with staples, and 267 with sutures. Primary outcome was surgical site infection (SSI). Secondary outcomes were prosthetic joint infection (PJI), other wound complications (dehiscence, necrosis and prolonged drainage) and duration of admittance. Follow-up occurred at 2, 6, and 12 weeks, and at 1 year. RESULTS: There were no significant demographic differences between the 2 groups. SSI occurred more frequently when wounds were closed with staples (4% compared to 1% with sutures; OR 2.8; CI, 0.885-0.952; p = 0.057). SSI was treated with oral antibiotics. The staples group showed significantly more wound complications (17% compared to 5%; OR 3.943, CI 2.073-7.498; p = 0.000). Wound discharge was significantly prolonged in the staples group (n = 40, compared to n = 12 in the sutures group; OR 3.728; CI, 1.909-7.281; p = 0.000). There was no significant difference in PJI (p = 0.364). CONCLUSIONS: In this large RCT comparing staples with sutures after THA, the use of staples is associated with a nearly 3 times greater risk of SSI (OR 2.8; p = 0.057). Staples significantly prolong wound discharge. The use of sutures for wound closure after THA is advised. Trial registration: Staples Or Sutures trial (S.O.S. trial) http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=3946 , NTR3946.

Mouse neuroblastoma cells release prion infectivity associated with exosomal vesicles.

BACKGROUND INFORMATION: TSEs (transmissible spongiform encephalopathies) are neurodegenerative disorders affecting humans and animals. PrP(Sc), a conformationally altered isoform of the normal prion protein (PrP(C)), is thought to be the pathogenic agent. However, the biochemical composition of the prion agent is still matter of debate. The potential transmission risk of the prion agent through biological fluids has been shown, but the development of competitive diagnostic tests and treatment for TSEs requires a more comprehensive knowledge of the agent and the cellular mechanisms by which it is disseminated. With this aim, we initiated characterization of the prion agent and the pathways by which it can be propagated using the cellular model system neuroblastoma (N2a). RESULTS: The present study shows that N2a cells infected with scrapie release the prion agent into the cell culture medium in association with exosome-like structures and viral particles of endogenous origin. We found that both prion proteins and scrapie infectivity are mainly associated with exosome-like structures that contain viral envelope glycoprotein and nucleic acids, such as RNAs. CONCLUSIONS: The dissemination of prions in N2a cell culture is mediated through the exosomal pathway.

Morpholino knockdown of lysyl oxidase impairs zebrafish development, and reflects some aspects of copper metabolism disorders.

Lysyl oxidase (LOX), a copper-dependent amine oxidase known in mammals to catalyze the cross-linking of collagen and elastin in the extracellular matrix, is a member of a multigenic family. Eight genes encoding lysyl oxidase isoforms have been identified in zebrafish. Recent studies have revealed a critical role for two zebrafish lysyl oxidases-like in the formation of the notochord. We now present the role of Lox in zebrafish development. lox morpholino-mediated knockdown results in a mildly undulated notochord, truncated anterior-posterior axis, tail bending and smaller head. Analyses of morphants show a complete disorganization of muscle somites and neural defects, in accordance with the lox expression pattern. Lox inhibition also induces pigment defects and pharyngeal arch deformities consistent with neural crest dysfunction. Taken together, these data reveal a role for Lox in early morphogenesis, especially in muscle development and neurogenesis, and resume some aspects of physiopathology of copper metabolism.

Novel function of the ciliogenic transcription factor RFX3 in development of the endocrine pancreas.

The transcription factor regulatory factor X (RFX)-3 regulates the expression of genes required for the growth and function of cilia. We show here that mouse RFX3 is expressed in developing and mature pancreatic endocrine cells during embryogenesis and in adults. RFX3 expression already is evident in early Ngn3-positive progenitors and is maintained in all major pancreatic endocrine cell lineages throughout their development. Primary cilia of hitherto unknown function present on these cells consequently are reduced in number and severely stunted in Rfx3(-/-) mice. This ciliary abnormality is associated with a developmental defect leading to a uniquely altered cellular composition of the islets of Langerhans. Just before birth, Rfx3(-/-) islets contain considerably less insulin-, glucagon-, and ghrelin-producing cells, whereas pancreatic polypeptide-positive cells are markedly increased in number. In adult mice, the defect leads to small and disorganized islets, reduced insulin production, and impaired glucose tolerance. These findings suggest that RFX3 participates in the mechanisms that govern pancreatic endocrine cell differentiation and that the presence of primary cilia on islet cells may play a key role in this process.