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Fragile X-associated tremor and ataxia syndrome (FXTAS) is a late-onset, progressive neurodegenerative disorder characterized by tremors, ataxia and neuropsychological problems. This disease is quite common in the general population with approximately 20 million carriers worldwide. The risk of developing FXTAS increases dramatically with age, with about 45% of male carriers over the age of 50 being affected. FXTAS is caused by a CGG-repeat expansion (CGGexp) in the fragile X mental retardation 1 (FMR1) gene. CGGexp RNA is translated into the FMRpolyG protein by a mechanism called RAN translation. Although both gene and pathogenic trigger are known, no therapeutic interventions are available at this moment. Here, we present, for the first time, primary hippocampal neurons derived from the ubiquitous inducible mouse model which is used as a screening tool for targeted interventions. A promising candidate is the repeat binding, RAN translation blocking, small molecule 1a. Small molecule 1a shields the disease-causing CGGexp from being translated into the toxic FMRpolyG protein. Primary hippocampal neurons formed FMRpolyG-positive inclusions, and upon treatment with 1a, the numbers of FMRpolyG-positive inclusions are reduced. We also describe for the first time the formation of FMRpolyG-positive inclusions in the liver of this mouse model. Treatment with 1a reduced the insoluble FMRpolyG protein fraction in the liver but not the number of inclusions. Moreover, 1a treatment had a reducing effect on the number of Rad23b-positive inclusions and insoluble Rad23b protein levels. These data suggest that targeted small molecule therapy is effective in an FXTAS mouse model and has the potential to treat CGGexp-mediated diseases, including FXTAS.

Fragile X syndrome (FXS) is the most common monogenetic cause of intellectual disability and autism spectrum disorders. Mostly, FXS is caused by transcriptional silencing of the FMR1 gene due to a repeat expansion in the 5′ UTR, and consequently lack of the protein product FMRP. However, in rare cases FXS is caused by other types of variants in the FMR1 gene. We describe a missense variant in the FMR1 gene, identified through whole-exome sequencing, in a boy with intellectual disability and behavioral problems. The variant is located in the FMRP's nuclear export signal (NES). We performed expression and localization studies of the variant in hair roots and HEK293 cells. Our results show normal expression but significant retention of the FMRP in the cells’ nucleus. This finding suggests a possible FMRP reduction at its essential functional sites in the dendrites and the synaptic compartments and possible interference of other cellular processes in the nucleus. Together, this might lead to a FXS phenotype in the boy.

Human homologue of yeast UV excision repair protein Rad23b (HR23B) inclusions are found in a number of neurodegenerative diseases, including frontotemporal dementia (FTD), Huntington’s disease (HD), spinocerebellar ataxia type 3 and 7 (SCA3/7), fragile X associated tremor/ataxia syndrome (FXTAS) and Parkinson’s disease (PD). Here, we describe HR23B pathology in C9ORF72 linked FTD and amyotrophic lateral sclerosis (ALS) cases. HR23B presented in neuropils, intranuclear inclusions and cytoplasmic and perinuclear inclusions and was predominantly found in cortices (frontal, temporal and motor), spinal cord and hippocampal dentate gyrus. HR23B co-localized with poly-GA-, pTDP-43- and p62-positive inclusions in frontal cortex and in hippocampal dentate gyrus, the latter showing higher co-localization percentages. HR23B binding partners XPC, 20S and ataxin-3, which are involved in nucleotide excision repair (NER) and the ubiquitin-proteasome system (UPS), did not show an aberrant distribution. However, C9ORF72 fibroblasts were more sensitive for UV-C damage than healthy control fibroblasts, even though all factors involved in NER localized normally to DNA damage and the efficiency of DNA repair was not reduced. HR23Bs other binding partner NGly1/PNGase, involved in ER-associated degradation (ERAD) of misfolded proteins, was not expressed in the majority of neurons in C9FTD/ALS brain sections compared to non-demented controls. Our results suggest a difference in HR23B aggregation and co-localization pattern with DPRs, pTDP-43 and p62 between different brain areas from C9FTD/ALS cases. We hypothesize that HR23B may play a role in C9ORF72 pathogenesis, possibly by aberrant ERAD functioning. Electronic supplementary material The online version of this article (10.1186/s40478-019-0694-6) contains supplementary material, which is available to authorized users.

Figure S6 Validation of HR23B pathology by a second independent antibody. HR23B staining using Abcam antibody in C9ORF72 FTD cases (n = 5) and non-demented control (n = 3) post-mortem brain sections. Staining pattern is consistent with HR23B GeneTex antibody (see Figs. 1 and 2). All scale bars are 20 μm (PDF 1543 kb)

Figure S4 Pur-alpha staining in C9FTD cases and non-demented controls. Pur-alpha staining reveals abundant stress granules in both C9ORF72 FTD cases (n = 5) and non-demented controls (n = 3) post-mortem brain sections. All scale bars are 20 μm. (PDF 1826 kb)

Table S1. Neuropathological scores of C9ORF72 FTD patients. Neuronal loss score was based on hematoxylin and eosin (HE) staining and pathological report and scored as absent (0), mild (1), moderate (2) or severe (3). Pathological scores were based on the degree of pathology as absent (0), rare (1), occasional (2), moderate (3), or numerous (4). Brain areas: F = frontal cortex, T = temporal cortex, M = motor cortex, H = hippocampus dentate gyrus, C = cerebellum. NCI = neuronal cytoplasmic inclusion, NII = neuronal intranuclear inclusion, DNs = dystrophic neurites. (DOCX 23 kb)

Figure S3. FMRP staining in C9FTD cases and non-demented controls. FMRP staining does not reveal any differences between C9ORF72 FTD cases (n = 5) and non-demented control (n = 3) post-mortem brain sections. Occasional inclusions are found in the hippocampus dentate gyrus in both C9FTD cases and controls. All scale bars are 20 μm. (PDF 1883 kb)

Figure S2. ADARB2 staining in C9FTD cases and non-demented controls. A) Staining of ADARB2 in C9ORF72 FTD cases (n = 5) and non-demented control (n = 3) post-mortem brain sections shows some intranuclear inclusions in hippocampus CA and DG. All scale bars are 20 μm B) Immunofluorescence staining of ADARB2 (red) and p62 (green) in hippocampal dentate gyrus reveals ADARB2 punctuated staining and some intranuclear inclusions in both C9ORF72 FTD cases (n = 5) and non-demented controls (n = 3). Scale bars in fluorescent pictures are 10 μm. (PDF 2721 kb)

Figure S5. HR23B pathology in different brain areas of C9FTD cases. Staining of HR23B in several brain areas of C9FTD cases and non-demented controls. Pathology burden was highest in cortices (frontal, temporal and motor) and was mostly cytoplasmic (inclusions and neuropils) and intranuclear (cateye). Hippocampus dentate gyrus (DG) harbors perinuclear inclusions, and hippocampus cornu ammonis (CA) had some cells with strong nuclear staining. Pathology was low in cerebellum granular layer with only some nuclear and perinuclear inclusions and almost absent in cerebellum molecular layer. Our C9FTD cases did not show HR23B pathology in spinal cord neurons. All scale bars are 20â Îźm (PDF 2260 kb)

Figure S1. Ran-GAP staining in C9FTD cases and non-demented controls. Ran-GAP is predominantly localized to the nucleus and nuclear membrane. Unevenly shaped nuclear membranes occur in both C9ORF72 FTD cases (n = 5) and non-demented controls (n = 3). All scale bars are 20 μm. (PDF 2202 kb)

Figure S7. Nucleotide excision repair is not affected in C9ORF72 human fibroblasts. A) Dose-response curve for 4 healthy control human fibroblast lines (81E253, 86E1375, 06E0717 and 99E0774) and 4 C9ORF72 human fibroblast lines (13E634, 13E659, 17E0225, 17E0278) and the NER deficient XP25RO human fibroblast line treated with increasing dose of UV-C light (0–12 J/m2). B) Immunofluorescence staining showing the recruitment of NER factors XPC, XPB, XPA, XPF and XPG to local DNA damage (visualized by CPD antibody), induced by 60 J/m2 UV-C irradiation through a microporous filter. Fibroblast lines used for pictures: 13E634, 13E659 and 81E253 C) Human fibroblasts lines were treated with 16 J/m2 UV-C light and incubated with EdU for 1 h to measure unscheduled DNA synthesis (UDS) as measure of DNA repair. The NER-deficient XPC25RO cell line is shown as negative control. Ctrl 1–4 are lines 81E253, 86E1375, 06E0717 and 99E0774 in this order. C9 1–4 are lines 13E634, 13E659, 17E0225, 17E0278 in this order. (PDF 934 kb)

The fragile X premutation is a CGG trinucleotide repeat expansion between 55 and 200 repeats in the 5′-untranslated region of the fragile X mental retardation 1 (FMR1) gene. Human carriers of the premutation allele are at risk of developing the late-onset neurodegenerative disorder, fragile X-associated tremor/ataxia syndrome (FXTAS). Characteristic neuropathology associated with FXTAS includes intranuclear inclusions in neurons and astroglia. Previous studies recapitulated these histopathological features in neurons in a knock-in mouse model, but without significant astroglial pathology. To determine the role of astroglia in FXTAS, we generated a transgenic mouse line (Gfa2-CGG99-eGFP) that selectively expresses a 99-CGG repeat expansion linked to an enhanced green fluorescent protein (eGFP) reporter in astroglia throughout the brain, including cerebellar Bergmann glia. Behaviorally these mice displayed impaired motor performance on the ladder-rung test, but paradoxically better performance on the rotarod. Immunocytochemical analysis revealed that CGG99-eGFP co-localized with GFAP and S-100ß, but not with NeuN, Iba1, or MBP, indicating that CGG99-eGFP expression is specific to astroglia. Ubiquitin-positive intranuclear inclusions were found in eGFP-expressing glia throughout the brain. In addition, intracytoplasmic ubiquitin-positive inclusions were found outside the nucleus in distal astrocyte processes. Intriguingly, intranuclear inclusions, in the absence of eGFP mRNA and eGFP fluorescence, were present in neurons of the hypothalamus and neocortex. Furthermore, intranuclear inclusions in both neurons and astrocytes displayed immunofluorescent labeling for the polyglycine peptide FMRpolyG, implicating FMRpolyG in the pathology found in Gfa2-CGG99 mice. Considered together, these results show that Gfa2-CGG99 expression in mice is sufficient to induce key features of FXTAS pathology, including formation of intranuclear inclusions, translation of FMRpolyG, and deficits in motor function. Electronic supplementary material The online version of this article (10.1186/s40478-019-0677-7) contains supplementary material, which is available to authorized users.

Table S2. Co-localization of HR23B with DPRs/pTDP-43/p62 differs between brain areas. The percentage is the amount of HR23B inclusions also positive for other pathological hallmarks (not the other way around). For example 11/153 for poly-GA in C9FTD patient 1 means that out of 153 HR23B inclusions, 11 were also positive forpoly- GA, which is 7%. F = frontal cortex. H = hippocampus dentate gyrus. *1 = All co-localizations are fibrils of poly-GP and HR23B in frontal cortex. Perinuclear inclusions of poly-GP did not stain positive for HR23B. *2 = In total 2 poly-PA inclusions have been found in frontal cortex of 5 C9FTD patients, too less to quantify. We therefore state N/A = non-applicable in this table. *3 = Non-demented cases had some p62 and some HR23B inclusions per person per section, which sometimes overlapped. No pTDP-43 inclusions were found so no co-localization of pTDP-43 with HR23B in non-demented cases. (DOCX 19 kb)

Ribonucleoprotein (RNP) granules are dense aggregations composed of RNA-binding proteins (RBPs) and a part of the transcriptome that is still uncharacterized. We performed a large-scale study of interaction networks and discovered that RBPs phase-separating in RNP granules share specific RNA partners with high structural content, long untranslated regions (UTRs) and nucleotide repeat expansions. Our analysis suggests that RNAs can promote formation of RNP granules by acting as scaffolds for protein assembly. To experimentally validate our findings, we investigated the scaffolding ability of CGG repeats contained in the 5’ UTR of FMR1 transcript implicated in Fragile X-associated Tremor / Ataxia Syndrome (FXTAS). Using a novel high-throughput approach we identified RBPs recruited by FMR1 5’ UTRs of different lengths. We employed human primary tissues as well as primate and mouse models of FXTAS to characterize protein sequestration in FMR1 aggregates and focused on a previously unreported partner, TRA2A, which induces impairment of splicing in genes linked to mental retardation and intellectual disability. SIGNIFICANCE Proteins and RNAs phase-separate into granules under physiological (ribosome assembly and shuttling through neurons) and pathological (Amyotrophic Lateral Sclerosis and Fragile X Tremor/Ataxia Syndrome) conditions. We report here that granule-forming proteins share more RNA targets than other proteins and form a dense network of interactions. RNAs interacting with granule-forming proteins have longer UTRs, are more structured and contain nucleotide repeats. Our study suggests that specific RNAs can act as the ‘glue’ of ribonucleoprotein assemblies. To experimentally validate the results of our analysis, we investigated how nucleotide repeats contained in the 5’ UTR of FMR1 are able to sequester proteins in intranuclear inclusions. We predicted protein interactions in silico, confirmed them in vitro and further characterized the ribonucleoprotein aggregates in vivo.

Intellectual disability (ID) comprises a large group of heterogeneous disorders, often without a known molecular cause. X-linked ID accounts for 5–10% of male ID cases. We investigated a large, three-generation family with mild ID and behavior problems in five males and one female, with a segregation suggestive for X-linked inheritance. Linkage analysis mapped a disease locus to a 7.6 Mb candidate region on the X-chromosome (LOD score 3.3). Whole-genome sequencing identified a 2 bp insertion in exon 2 of the chromosome X open reading frame 56 gene (CXorf56), resulting in a premature stop codon. This insertion was present in all intellectually impaired individuals and carrier females. Additionally, X-inactivation status showed skewed methylation patterns favoring the inactivation of the mutated allele in the unaffected carrier females. We demonstrate that the insertion leads to nonsense-mediated decay and that CXorf56 mRNA expression is reduced in the impaired males and female. In murine brain slices and primary hippocampal neuronal cultures, CXorf56 protein was present and localized in the nucleus, cell soma, dendrites, and dendritic spines. Although no other families have been identified with pathogenic variants in CXorf56, these results suggest that CXorf56 is the causative gene in this family, and thus a novel candidate gene for X-linked ID with behavior problems.

A CGG-repeat expansion in the premutation range in the Fragile X mental retardation 1 gene (FMR1) has been identified as the genetic cause of Fragile X-associated tremor/ataxia syndrome (FXTAS), a late-onset neurodegenerative disorder that manifests with action tremor, gait ataxia and cognitive impairments. In this study, we used a bigenic mouse model, in which expression of a 90CGG premutation tract is activated in neural cells upon doxycycline administration-P90CGG mouse model. We, here, demonstrate the behavioural manifestation of clinically relevant features of FXTAS patients and premutation carrier individuals in this inducible mouse model. P90CGG mice display heightened anxiety, deficits in motor coordination and impaired gait and represent the first FXTAS model that exhibits an ataxia phenotype as observed in patients. The behavioural phenotype is accompanied by the formation of ubiquitin/FMRpolyglycine-positive intranuclear inclusions, as another hallmark of FXTAS, in the cerebellum, hippocampus and amygdala. Strikingly, upon cessation of transgene induction the anxiety phenotype of mice recovers along with a reduction of intranuclear inclusions in dentate gyrus and amygdala. In contrast, motor function deteriorates further and no reduction in intranuclear inclusions can be observed in the cerebellum. Our data thus demonstrate that expression of a 90CGG premutation expansion outside of the FMR1 context is sufficient to evoke an FXTAS-like behavioural phenotype. Brain region-specific neuropathology and (partial) behavioural reversibility make the inducible P90CGG a valuable mouse model for testing pathogenic mechanisms and therapeutic intervention methods.

Primary open-angle glaucoma (POAG) is a hereditary neurodegenerative disease, characterized by optic nerve changes including increased excavation, notching and optic disc hemorrhages. The excavation can be described by the vertical cup-disc ratio (VCDR). Previously, genome-wide significant evidence for the association of rs10483727 in SIX1-SIX6 locus with VCDR and subsequent POAG was found. Using 1000 genomes-based imputation of four independent population-based cohorts in the Netherlands, we identified a missense variant rs33912345 (His141Asn) in SIX6 associated with VCDR (P-meta = 7.74 x 10(-7), n = 11 473) and POAG (Pmeta = 6.09 x 10(-3), n = 292). Exome sequencing analysis revealed another missense variant rs146737847 (Glu129Lys) also in SIX6 associated with VCDR (P = 5.09 x 10(-3), n = 1208). These two findings point to SIX6 as the responsible gene for the previously reported association signal. Functional characterization of SIX6 in zebrafish revealed that knockdown of six6b led to a small eye phenotype. Histological analysis showed retinal lamination, implying an apparent normal development of the eye, but an underdeveloped lens, and reduced optic nerve diameter. Expression analysis of morphants at 3 dpf showed a 5.5-fold up-regulation of cdkn2b, a cyclin-dependent kinase inhibitor, involved in cell cycle regulation and previously associated with VCDR and POAG in genome-wide association studies (GWASs). Since both six6b and cdkn2b play a key role in cell proliferation, we assessed the proliferative activity in the eye of morphants and found an alteration in the proliferative pattern of retinal cells. Our findings in humans and zebrafish suggest a functional involvement of six6b in early eye development, and open new insights into the genetic architecture of POAG.

Neuronal intranuclear inclusion disease (NIID) is a rare heterogeneous progressive neurodegenerative disease characterized by the presence of eosinophilic hyaline intranuclear inclusions in neuronal and glial cells of the CNS, peripheral cells of the autonomic nervous system, visceral organs and skin. The clinical presentation is broadly heterogeneous and includes limb weakness, dementia, seizures, ataxia, and parkinsonism. High-intensity signal in the corticomedullary junction on brain MRI is a characteristic finding in NIID. We describe a 65-year-old patient presenting with mild cognitive impairment, evolving in dementia with behavioral disturbances and parkinsonism. Brain MRI showed mild global cortical atrophy, more pronounced in the cingulate and temporal cortex and mild leukoaraiosis, but no high-intensity signal in corticomedullary junction on diffusion weighted imaging. Neuropathological examination showed p62- and optineurin-positive neuronal intranuclear inclusions in the hippocampus and in some subcortical structures. Glial cells did not present any intranuclear inclusions, and no spongiotic changes proximal to the U-fibers or diffuse myelin pallor were disclosed in the white matter. We report on a case with pathological features of NIID showing different neuroimaging and pathological findings. We noted an absence of typical MRI abnormalities, lack of intranuclear inclusions in glial cells, and prominent involvement of hippocampal neurons, refining the clinico-pathological spectrum of the disease.

Mutations in the gene encoding the F-box only protein 7 (FBXO7) cause PARK15, an autosomal recessive form of juvenile parkinsonism. Although the brain pathology in PARK15 patients remains unexplored, in vivo imaging displays severe loss of nigrostriatal dopaminergic terminals. Understanding the pathogenesis of PARK15 might therefore illuminate the mechanisms of the selective dopaminergic neuronal degeneration, which could also be important for understanding idiopathic Parkinson disease (PD). The expression of FBXO7 in the human brain remains poorly characterized, and its expression in idiopathic PD and different neurodegenerative diseases has not been investigated. Here, we studied FBXO7 protein expression in brain samples of normal controls (n = 9) and from patients with PD (n = 13), multiple system atrophy (MSA) (n = 5), Alzheimer disease (AD) (n = 5), and progressive supranuclear palsy (PSP) (n = 5) using immunohistochemistry with 2 anti-FBXO7 antibodies. We detected widespread brain FBXO7 immunoreactivity, with the highest levels in neurons of the cerebral cortex, putamen, and cerebellum. There were no major differences between normal and PD brains overall, but FBXO7 immunoreactivity was detected in large proportions of α-synuclein-positive inclusions (Lewy bodies, Lewy neurites, glial cytoplasmic inclusions), where it colocalized with α-synuclein in PD and MSA cases. By contrast, weak FBXO7 immunoreactivity was occasionally detected in tau-positive inclusions in AD and PSP. These findings suggest a role for FBXO7 in the pathogenesis of the synucleinopathies. Copyright

Item does not contain fulltext Manganese is essential for several metabolic pathways but becomes toxic in excessive amounts. Manganese levels in the body are therefore tightly regulated, but the responsible protein(s) remain incompletely known. We studied two consanguineous families with neurologic disorders including juvenile-onset dystonia, adult-onset parkinsonism, severe hypermanganesemia, polycythemia, and chronic hepatic disease, including steatosis and cirrhosis. We localized the genetic defect by homozygosity mapping and then identified two different homozygous frameshift SLC30A10 mutations, segregating with disease. SLC30A10 is highly expressed in the liver and brain, including in the basal ganglia. Its encoded protein belongs to a large family of membrane transporters, mediating the efflux of divalent cations from the cytosol. We show the localization of SLC30A10 in normal human liver and nervous system, and its depletion in liver from one affected individual. Our in silico analyses suggest that SLC30A10 possesses substrate specificity different from its closest (zinc-transporting) homologs. We also show that the expression of SLC30A10 and the levels of the encoded protein are markedly induced by manganese in vitro. The phenotype associated with SLC30A10 mutations is broad, including neurologic, hepatic, and hematologic disturbances. Intrafamilial phenotypic variability is also present. Chelation therapy can normalize the manganesemia, leading to marked clinical improvements. In conclusion, we show that SLC30A10 mutations cause a treatable recessive disease with pleomorphic phenotype, and provide compelling evidence that SLC30A10 plays a pivotal role in manganese transport. This work has broad implications for understanding of the manganese biology and pathophysiology in multiple human organs.

Item does not contain fulltext Fragile X-associated tremor/ataxia syndrome (FXTAS) is an adult-onset neurodegenerative disorder generally presenting with intention tremor and gait ataxia, but with a growing list of co-morbid medical conditions including hypothyroidism, hypertension, peripheral neuropathy, and cognitive decline. The pathological hallmark of FXTAS is the presence of intranuclear inclusions in both neurons and astroglia. However, it is unknown to what extent such inclusions are present outside the central nervous system (CNS). To address this issue, we surveyed non-CNS organs in ten human cases with FXTAS and in a CGG repeat knock-in (CGG KI) mouse model known to possess neuronal and astroglial inclusions. We find inclusions in multiple tissues from FXTAS cases and CGG KI mice, including pancreas, thyroid, adrenal gland, gastrointestinal, pituitary gland, pineal gland, heart, and mitral valve, as well as throughout the associated autonomic ganglia. Inclusions were observed in the testes, epididymis, and kidney of FXTAS cases, but were not observed in mice. These observations demonstrate extensive involvement of the peripheral nervous system and systemic organs. The finding of intranuclear inclusions in non-CNS somatic organ systems, throughout the PNS, and in the enteric nervous system of both FXTAS cases as well as CGG KI mice suggests that these tissues may serve as potential sites to evaluate early intervention strategies or be used as diagnostic factors.

Summary Recent evidence indicates that specific RNAs promote the formation of ribonucleoprotein condensates by acting as scaffolds for RNA-binding proteins (RBPs). We systematically investigated RNA-RBP interaction networks to understand ribonucleoprotein assembly. We found that highly contacted RNAs are structured, have long UTRs, and contain nucleotide repeat expansions. Among the RNAs with such properties, we identified the FMR1 3′ UTR that harbors CGG expansions implicated in fragile X-associated tremor/ataxia syndrome (FXTAS). We studied FMR1 binding partners in silico and in vitro and prioritized the splicing regulator TRA2A for further characterization. In a FXTAS cellular model, we validated the TRA2A-FMR1 interaction and investigated implications of its sequestration at both transcriptomic and post-transcriptomic levels. We found that TRA2A co-aggregates with FMR1 in a FXTAS mouse model and in post-mortem human samples. Our integrative study identifies key components of ribonucleoprotein aggregates, providing links to neurodegenerative disease and allowing the discovery of therapeutic targets., Graphical Abstract, Highlights • Highly contacted granule RNAs are structured and contain long, repetitive UTRs • Mutations related with FXTAS increase FMR1 scaffolding propensity • TRA2A co-aggregates with FMR1 in FXTAS mouse model and in post-mortem human samples • TRA2 sequestration has both transcriptomic and post-transcriptomic implications, Cid-Samper et al. analyze protein-RNA networks and identify properties of RNA scaffolds within biological condensates. They find that CGG repeats in the 3′ UTR of FMR1 attract several proteins, including the splicing factor TRA2A that co-aggregates in fragile X-associated tremor/ataxia syndrome (FXTAS).

Tau mutations in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) are associated with changes in alternative splicing of exon 10. The DeltaK280 mutation in exon 10 is exceptional because in vitro observations suggest a dramatic effect on microtubule binding, enhanced self-aggregation, as well as a decrease of the 4R/3R ratio by the ablation of an exon splicing enhancer element. Using immunohistochemistry, Western blotting, and electron microscopy on brain material with the DeltaK280 mutation, we investigated which of these effects is most dominant in vivo. The brain showed abundant Pick bodies in several brain regions, which stained positive with 3-repeat-specific but not with 4-repeat-specific tau antibodies. Western blots of sarkosyl-insoluble tau showed exclusively three repeat (3R0N and 3R1N) tau in most regions, although some 4R1N could be detected in the frontal cortex. In addition, the sarkosyl-soluble tau fraction showed a significantly higher amount of 3-repeat tau. Because quantitative analysis of 4R and 3R mRNA transcripts showed a 4R/3R ratio of only 0.3, association between increased transcription and protein expression was observed. These observations confirm the postulated hypothesis that the DeltaK280 mutation abolishes a splice enhancer element, which overrules the decreased microtubule binding and enhanced self-aggregation.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder affecting carriers of the fragile X-premutation, who have an expanded CGG repeat in the 5'-UTR of the FMR1 gene. FXTAS is characterized by progressive development of intention tremor, ataxia, parkinsonism and neuropsychological problems. The disease is thought to be caused by a toxic RNA gain-of-function mechanism, and the major hallmark of the disease is ubiquitin-positive intranuclear inclusions in neurons and astrocytes. We have developed a new transgenic mouse model in which we can induce expression of an expanded repeat in the brain upon doxycycline (dox) exposure (i.e. Tet-On mice). This Tet-On model makes use of the PrP-rtTA driver and allows us to study disease progression and possibilities of reversibility. In these mice, 8 weeks of dox exposure was sufficient to induce the formation of ubiquitin-positive intranuclear inclusions, which also stain positive for the RAN translation product FMRpolyG. Formation of these inclusions is reversible after stopping expression of the expanded CGG RNA at an early developmental stage. Furthermore, we observed a deficit in the compensatory eye movements of mice with inclusions, a functional phenotype that could be reduced by stopping expression of the expanded CGG RNA early in the disease development. Taken together, this study shows, for the first time, the potential of disease reversibility and suggests that early intervention might be beneficial for FXTAS patients.

It is still unclear why absence of the fragile X protein (FMRP) leads to mental retardation and specific behavioral problems. In neurons, the protein transports specific mRNAs towards the actively translating ribosomes near the synapses. To unravel the mechanism leading to the disorder, we performed global gene expression analysis by means of the differential display method using the fragile X mouse model. To verify differential expression, we used microarray technology and real-time PCR. Three differentially expressed cDNAs showed consistent underexpression in the fragile X knockout mouse, including a GABAA receptor subunit δ, a Rho guanine exchange factor 12 and an EST BU563433. In addition, we identified 5 genes that showed differential expression dependent on the sample of RNA analysis. We consider their differential expression as provisional. It is possible that these differentially expressed genes play an important role in the cognitive and behavioral problems observed in the fragile X syndrome.

The Fxr gene family is composed of three members, FMR1, FXR1 and FXR2. The FMR1 gene is involved in the fragile X syndrome, whereas for the other two members, no human disorder has been identified yet. An appropriate animal model to study in vivo gene function is essential to unravel the cellular function of the gene products FMRP, FXR1P and FXR2P, respectively. In Xenopus tropicalis both Fmr1 and Fxr1 were identified; however, unexpectedly Fxr2 was not. Here we describe the characterization of both Fmrp and Fxr1p in Xenopus tropicalis. Fmrp is expressed ubiquitously throughout the embryo during embryonic development, whereas Fxr1p shows a more tissue-specific expression particularly during late embryonic development. In adult frogs both proteins are highly expressed in most neurons of the central nervous system and in all spermatogenic cells in the testis. In addition, Fxr1p is also highly expressed in striated muscle tissue. Western blotting experiments revealed only one prominent isoform for both proteins using different tissue homogenates from adult frogs. Thus, for in vivo gene function studies, this relative simple animal model may serve as a highly advantageous and complementary model.

Frontotemporal dementia and parkinsonism linked to chromosome 17 have been associated with mutations in the microtubule associated protein tau (MAPT or tau) gene. This disorder is characterized by a large spectrum of neuronal and glial tau lesions in different brain regions. Pick bodies were found in a family with hereditary Pick’s disease with the G272V mutation and in several families with other tau mutations in exons 9 and 11–13. The biochemical composition of Pick bodies varies between these mutations. Until recently, no detailed biochemical characterization of G272V brain material was done owing to unavailability of fresh frozen brain material. We now report a detailed study using the immunohistochemistry, western blots and electron microscopy of two brains with the G272V mutation that recently became available. Both brains showed severe neuronal loss in the temporal cortex, whereas in the frontal cortex the loss was less; and abundant Pick bodies in the dentate gyrus of the hippocampus, and caudate nucleus. The Pick bodies consisted exclusively of threerepeat (3R) isoforms, as was demonstrated by isoform-specific antibodies and supported by western blot analysis of sarkosyl-insoluble tau. These observations confirm that this family diagnosed with hereditary Pick disease meets all the criteria for this condition, including the presence of Pick bodies that are unphosphorylated at Ser 262 and contain twisted filaments with long periodicity consisting only of 3R tau.

textabstractRecent studies have reported that alleles in the premutation range in the FMR1 gene in males result in increased FMR1 mRNA levels and at the same time mildly reduced FMR1 protein levels. Some elderly males with premutations exhibit an unique neurodegenerative syndrome characterized by progressive intention tremor and ataxia. We describe neurohistological, biochemical and molecular studies of the brains of mice with an expanded CGG repeat and report elevated Fmr1 mRNA levels and intranuclear inclusions with ubiquitin, Hsp40 and the 20S catalytic core complex of the proteasome as constituents. An increase was observed of both the number and the size of the inclusions during the course of life, which correlates with the progressive character of the cerebellar tremor/ataxia syndrome in humans. The observations in expanded-repeat mice support a direct role of the Fmr1 gene, by either CGG expansion per se or by mRNA level, in the formation of the inclusions and suggest a correlation between the presence of intranuclear inclusions in distinct regions of the brain and the clinical features in symptomatic premutation carriers. This mouse model will facilitate the possibilities to perform studies at the molecular level from onset of symptoms until the final stage of the disease.

Lack of fragile X mental retardation protein (FMRP) causes fragile X syndrome, a common form of inherited mental retardation. FMRP is an RNA binding protein thought to be involved in translation efficiency and/or trafficking of certain mRNAs. Recently, a subset of mRNAs to which FMRP binds with high affinity has been identified. These FMRP-associated mRNAs contain an intramolecular G-quartet structure. In neurons, dendritic mRNAs are involved in local synthesis of proteins in response to synaptic activity, and this represents a mechanism for synaptic plasticity. To determine the role of FMRP in dendritic mRNA transport, we have generated a stably FMR1-enhanced green fluorescent protein (EGFP)-transfected PC12 cell line with an inducible expression system (Tet-On) for regulated expression of the FMRP-GFP fusion protein. After doxycycline induction, FMRP-GFP was localized in granules in the neurites of PC12 cells. By using time-lapse microscopy, the trafficking of FMRP-GFP granules into the neurites of living PC12 cells was demonstrated. Motile FMRP-GFP granules displayed two types of movements: oscillatory (bidirectional) and unidirectional anterograde. The average velocity of the granules was 0.19 micro m/s with a maximum speed of 0.71 micro m/s. In addition, we showed that the movement of FMRP-GFP labeled granules into the neurites was microtubule dependent. Colocalization studies further showed that the FMRP-GFP labeled granules also contained RNA, ribosomal subunits, kinesin heavy chain, and FXR1P molecules. This report is the first example of trafficking of RNA-containing granules with FMRP as a core constituent in living PC12 cells.

Fragile X syndrome is caused by the expansion of the CGG repeat in the 5' untranslated region of the FMR1 gene. This expansion leads to methylation of the FMR1 promoter region thereby blocking FMR1 protein (FMRP) expression. Prenatal diagnosis can be performed on chorionic villi samples (CVS) by Southern blot analysis. Alternatively, for males, an immunohistochemical method has been introduced for CVS. In this study, we have used this immunocytochemical method for CVS in full mutation male fetuses at different times of gestational age, varying from 10.0-12.5 weeks, and in two cases of full mutation female fetuses (>13 weeks). FMRP expression studies in CVS from full mutation male fetuses (10.0-12.5 weeks) illustrate the timing of the disappearance of FMRP expression in these CVS. Until approximately 10 weeks of gestation, FMRP is expressed normally in full mutation male CVS, whereas FMRP is completely absent at 12.5 weeks of gestation. FMRP expression in full mutation female CVS (>13 weeks) is completely absent in a number of villi, whereas other villi show normal FMRP expression. Unlabelled villi can only be present in the absence of the expression of the full mutation FMR1 gene on one X-chromosome together with the X-inactivation of the normal X allele. FMRP positive villi can be explained by an active normal X allele. The presence of both positive and negative villi indicates that X-inactivation in human CVS is a random process. No villi are found with a mixture of both FMRP-expressing and non-FMRP-expressing cells. This indicates that X-inactivation occurs very early in development, before the villi start to proliferate, and that X-inactivation in villi is a clonal process. In addition, our results indicate that the timing of both X-inactivation and full mutation FMR1 allele inactivation is different, i.e. X-inactivation occurs earlier in development than inactivation of the full mutation.

Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are two neurodegenerative disorders that share clinical, genetic and pathological overlap. In 2011, a hexanucleotide repeat (GGGGCC) expansion in the ‘chromosome 9 open reading frame 72’ (C9orf72) gene was identified as a cause of FTD and ALS [1,2]. This mutation has proven to be the most common genetic defect in the neurodegenerative field, especially in FTD and ALS [3]. Patients harboring the C9orf72 repeat expansion can develop FTD, ALS or both and are therefore associated with wide clinical diversity [4]. There have been multiple hypotheses about the underlying mechanisms by which the repeat expansion leads to neuropathology, including loss-of-function caused by haploinsufficiency of the endogenous C9orf72 protein product or gain-of-function induced by either RNA or protein toxicity. Either free RNA molecules containing the repeat expansion or RNA foci that sequester proteins could be toxic for cells. Alternatively, a pathogenic mechanism has been proposed for the production of toxic dipeptide repeat proteins (DPR) by repeat-associated non-AUG translation (RAN) of the repeat [5,6]. Interestingly, to differentiate between repeat “RNA-only” and DPR protein toxicity fruit fly models carrying a range of pure and RNA-only repeats have been generated. These studies demonstrated that the major toxic species were the DPR proteins [7]. Here we report on an “RNA-only” gain-of-function mouse model. To study the intrinsic effect of the repeat without assessing its effect on the C9orf72 gene, we created a spatially and temporally inducible transgenic mouse model. This mouse model has a repeat size of 80 GGGGCC-repeats, without human flanking regions, which may affect repeat translation. This repeat was cloned in the 5′ UTR of a GFP reporter gene and controlled by a tetracycline responsive element (TRE) promoter (Figure 1A). To enable expression of the TRE-construct we created bigenic mice that possess both the TRE-construct and the tetracycline-responsive transcriptional activator (rtTA) under a general heterogeneous nuclear ribonucleoprotein (hnRNP) promoter [8]. Expression of the repeat was turned on after weaning by adding doxycycline (dox) to the drinking water. Expression of the repeat construct can be stopped at any time by withdrawal of dox, allowing for reversibility studies (Figure 1A; more information about the creation of the model can be found in Additional file 1). After generation of transgenic mice, the repeat size remained stable for multiple generations (data not shown). GFP expression was seen in bigenic mice as soon as 4 days after dox treatment started and remained stable over time (assessed by western blot of liver homogenates, data not shown). Next to liver, multiple other tissues showed GFP expression including lung, kidney and brain; with most prominent expression in the striatum (Figure 1B) and the cuneate nucleus in the brainstem. Figure 1 Expression of 80GGGGCC-repeats leads to the formation of ubiquitin-positive inclusions in mouse brain. A) Schematic of the model used to create the inducible mice. Simultaneous expression of rtTA and doxycycline treatment are needed to drive expression ... Both ubiquitin-positive, TDP-43-positive and TDP-43 negative neuronal and cytoplasmic inclusions are pathological hallmarks in post mortem brain tissue from C9orf72 FTD and ALS patients. We used the presence of inclusions as a readout for the effect of expression of the repeat in our “RNA-only” gain-of-function ALS/FTD model [9,10]. We found ubiquitin-positive inclusions in those brain regions that express high levels of GFP, including the striatum (Figure 1C) and the cuneate nucleus of bigenic mice after twelve weeks of dox treatment (n = 7 mice per group). Inclusions were found in the nuclei and the neuropil in striatum and mainly in the nuclei in the cuneate nucleus. The presence of ubiquitin-positive inclusions in our mouse model is a shared phenomenon with non-C9orf72 mouse models of ALS and FTD [11,12]. We did not observe any TDP-43 positive nor p409/410 TDP-43 positive inclusions in our mouse model after twelve weeks of dox treatment, despite the positive staining in a C9orf72 patient hippocampus control (data not shown). TDP-43 inclusions might only appear after prolonged expression of the repeat or additional genetic or environmental factors might be needed to drive TDP-43 dysfunction. Importantly, TDP-43 function could also be affected without the presence of TDP-43 positive aggregates [13]. The absence of DPR pathology was assessed with a poly-GA antibody [6]. We could not detect poly-GA aggregation in brain tissue from bigenic mice, but only revealed GA-positive inclusions in C9orf72 patient hippocampus control material illustrating lack of DPR pathology in this mouse model (Figure 2). The mice did not develop any obvious behavioral phenotype and showed no cell loss. The neurotoxic effect of the C9orf72 hexarepeat expansion has been suggested by both RNA- and protein-mediated pathology [7]. Due to lack of DPR pathology, this mouse is a good model to investigate whether toxicity can be driven by the repeat RNA only. Future studies focusing on molecular changes and behavior deficits in our mouse model can provide additional insight in disease progression, reversibility and create options for therapeutic intervention. In conclusion, we demonstrate that solely expression of the GGGGCC repeat outside the C9orf72 context results in ubiquitin-positive inclusions, which is a pathological hallmark in postmortem brain from ALS and FTD patients. Our data on this first C9orf72 mouse model argues in favor for a gain-of-function pathological mechanism in C9orf72 associated ALS and FTD. Figure 2 Absence of DPR pathology in brain of 80GGGGCC RNA expressing mouse. A) GA positive inclusions in the hippocampus of C9orf72FTD patient. B) the striatum of bigenic mice treated with dox for 12 weeks shows no GA positive inclusions. All animal experiments were conducted with the permission of the local animal welfare committee (DEC). Experiments on human brain material were done under informed consent and approved by the Medical Ethical Test Committee (METC). Human paraffin embedded brain material was provided by the Dutch brain bank (Nederlandse Hersenbank NHB).

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder affecting carriers of premutation forms of the FMR1 gene, resulting in a progressive development of tremor, ataxia and neuropsychological problems. The disease is caused by an expanded CGG repeat in the FMR1 gene, leading to an RNA gain-of-function toxicity mechanism. In order to study the pathogenesis of FXTAS, new inducible transgenic mouse models have been developed that expresses either 11CGGs or 90CGGs at the RNA level under control of a Tet-On promoter. When bred to an hnRNP-rtTA driver line, doxycycline (dox) induced expression of the transgene could be found in almost all tissues. Dox exposure resulted in loss of weight and death within 5 d for the 90CGG RNA expressing mice. Immunohistochemical examination of tissues of these mice revealed steatosis and apoptosis in the liver. Decreased expression of GPX1 and increased expression of cytochrome C is found. These effects were not seen in mice expressing a normal sized 11CGG repeat. In conclusion, we were able to show in vivo that expression of an expanded CGG-repeat rather than overexpression of a normal CGG-repeat causes pathology. In addition, we have shown that expanded CGG RNA expression can cause mitochondrial dysfunction by regulating expression levels of several markers. Although FTXAS patients do not display liver abnormalities, our findings contribute to understanding of the molecular mechanisms underlying toxicity of CGG repeat RNA expression in an animal model. In addition, the dox inducible mouse lines offer new opportunities to study therapeutic interventions for FXTAS.

BACKGROUND: Topical corticosteroid therapy reduces symptoms and nasal mucosal inflammatory cells in patients with allergic rhinitis. Usually patients are advised to start their medication (1 week) before the beginning of the pollen season. The effect of pretreatment with a topical corticosteroid on unchallenged nasal mucosa is not well documented. OBJECTIVES: The purpose of this study was to investigate, in a double-blind, placebo-controlled study, the effect of 6 weeks' pretreatment with 200 microg twice daily fluticasone propionate on nasal symptoms and inflammatory cell numbers after nasal allergen provocation in patients with seasonal allergic rhinitis. METHODS: Nineteen patients with grass pollen-induced allergic rhinitis were treated for a 6-week period out of the grass pollen season. After completing the treatment period, patients were challenged with grass pollen. Nasal mucosal biopsy specimens were taken 5 times in every patient. In nasal mucosa changes in numbers of T cells, B cells, mast cells, eosinophils, macrophages, and Langerhans' cells were investigated. RESULTS: After 4 weeks of treatment but before allergen provocation, significantly fewer epithelial Langerhans' cells, macrophages, mast cells, T cells, and eosinophils were found in the fluticasone propionate group compared with those found in the placebo group. In the lamina propria significantly fewer Langerhans' cells and eosinophils were found in the fluticasone propionate group. Cell influx in nasal mucosa after allergen provocation was significantly inhibited in the fluticasone propionate group compared with that in the placebo group for epithelial Langerhans' cells, mast cells, macrophages, and T cells and for lamina propria eosinophils, mast cells, Langerhans' cells, macrophages, and T cells. CONCLUSIONS: Fluticasone propionate is effective in reducing early- and late-phase nasal symptoms. Topical corticosteroid treatment reduces inflammatory cells in unchallenged nasal mucosa

Little is known about the cellular infiltrates in the nasal mucosa of children. This study was set up to compare the nasal cellular infiltrates in biopsy specimens from allergic children and controls. Atopic children were distinguished from controls on the basis of symptoms of allergic rhinitis and/or asthma, total serum immunoglobulin (Ig)E, family history and specific serum IgE to food and aeroallergens. Fifteen allergic patients (median age 4.3 yrs) and 15 age-matched nonallergic control subjects were evaluated. The number of cells positive for CD1a, CD4, CD8, CD19, CD68, chymase, tryptase, IgE and major basic protein was determined in the mucosa of the inferior turbinate. A significantly higher number of IgE-positive cells and mast cells was found in the epithelia of the allergic group. In the lamina propria, higher numbers of IgE-positive cells and eosinophils were found. Langerhans' cells positive for IgE were only seen in allergic children with specific serum IgE against aeroallergens. These children also had a higher number of IgE-positive mast cells compared to controls and atopic children without specific serum IgE. These results show that the nasal cellular infiltrates of allergic children differ from nonallergic control subjects. Prior to the detection of specific serum immunoglobulin E, cellular changes can be found in the nasal mucosa of atopic children.

Rationale: Congenital heart malformations are a major cause of morbidity and mortality, especially in young children. Failure to establish normal left-right (L-R) asymmetry often results in cardiovascular malformations and other laterality defects of visceral organs. Objective: To identify genetic mutations causing cardiac laterality defects. Methods and Results: We performed a genome-wide linkage analysis in patients with cardiac laterality defects from a consanguineous family. The patients had combinations of defects that included dextrocardia, transposition of great arteries, double-outlet right ventricle, atrioventricular septal defects, and caval vein abnormalities. Sequencing of positional candidate genes identified mutations in NPHP4 . We performed mutation analysis of NPHP4 in 146 unrelated patients with similar cardiac laterality defects. Forty-one percent of these patients also had laterality defects of the abdominal organs. We identified 8 additional missense variants that were absent or very rare in control subjects. To study the role of nphp4 in establishing L-R asymmetry, we used antisense morpholinos to knockdown nphp4 expression in zebrafish. Depletion of nphp4 disrupted L-R patterning as well as cardiac and gut laterality. Cardiac laterality defects were partially rescued by human NPHP4 mRNA, whereas mutant NPHP4 containing genetic variants found in patients failed to rescue. We show that nphp4 is involved in the formation of motile cilia in Kupffer's vesicle, which generate asymmetrical fluid flow necessary for normal L-R asymmetry. Conclusions: NPHP4 mutations are associated with cardiac laterality defects and heterotaxy. In zebrafish, nphp4 is essential for the development and function of Kupffer's vesicle cilia and is required for global L-R patterning.

Mutations in the F-box only protein 7 gene (FBXO7) cause PARK15, an autosomal recessive neurodegenerative disease presenting with severe levodopa-responsive parkinsonism and pyramidal disturbances. Understanding the PARK15 pathogenesis might thus provide clues on the mechanisms of maintenance of brain dopaminergic neurons, the same which are lost in Parkinson's disease. The protein(s) encoded by FBXO7 remain very poorly characterized. Here, we show that two protein isoforms are expressed from the FBXO7 gene in normal human cells. The isoform 1 is more abundant, particularly in primary skin fibroblasts. Both isoforms are undetectable in cell lines from the PARK15 patient of an Italian family; the isoform 1 is undetectable and the isoform 2 is severely decreased in the patients from a Dutch PARK15 family. In human cell lines and mouse primary neurons, the endogenous or over-expressed, wild type FBXO7 isoform 1 displays mostly a diffuse nuclear localization. An intact N-terminus is needed for the nuclear FBXO7 localization, as N-terminal modification by PARK15-linked missense mutation, or N-terminus tag leads to cytoplasmic mislocalization. Furthermore, the N-terminus of wild type FBXO7 (but not of mutant FBXO7) is able to confer nuclear localization to profilin (a cytoplasmic protein). Our data also suggest that overexpressed mutant FBXO7 proteins (T22M, R378G and R498X) have decreased stability compared to their wild type counterpart. In human brain, FBXO7 immunoreactivity was highest in the nuclei of neurons throughout the cerebral cortex, intermediate in the globus pallidum and the substantia nigra, and lowest in the hippocampus and cerebellum. In conclusion, the common cellular abnormality found in the PARK15 patients from the Dutch and Italian families is the depletion of the FBXO7 isoform 1, which normally localizes in the cell nucleus. The activity of FBXO7 in the nucleus appears therefore crucial for the maintenance of brain neurons and the pathogenesis of PARK15.

SUMMARY Lack of the FMR1 gene product causes fragile X syndrome, the commonest inherited cause of mental impairment. We know little of the roles that fragile X related (FXR) gene family members(FMR1, FXR2 and FXR1) play during embryonic development. Although all are expressed in the brain and testis, FXR1is the principal member found in striated and cardiac muscle. The Fxr1 knockout mice display a striated muscle phenotype but it is not known why they die shortly after birth; however, a cardiac cause is possible. The zebrafish is an ideal model to investigate the role of fxr1during development of the heart. We have carried out morpholino knockdown of fxr1 and have demonstrated abnormalities of striated muscle development and abnormal development of the zebrafish heart, including failure of looping and snapping of the atrium from its venous pole. In addition, we have measured cardiac function using high-speed video microscopy and demonstrated a significant reduction in cardiac function. This cardiac phenotype has not been previously described and suggests that fxr1 is essential for normal cardiac form and function.

(2009). Cell proliferation and migration are mutually exclusive cellular phenomena in vivo: Implications for cancer therapeutic strategies. Cell Cycle: Vol. 8, No. 6, pp. 950-951.

The 5′untranslated region (UTR) of the FMR1 gene contains a CGG-repeat, which may become unstable upon transmission to the next generation. When repeat length exceeds 200, the FMR1 gene generally undergoes methylation-mediated transcriptional silencing. The subsequent absence of the gene product Fragile X Mental Retardation Protein (FMRP) causes the mental retardation seen in fragile X patients. A CGG-repeat length between 55 and 200 trinucleotides has been termed the premutation (PM). Predominantly elderly male PM carriers are at risk of developing a progressive neurodegenerative disorder: fragile X-associated tremor/ataxia syndrome (FXTAS). All PM carriers have elevated FMR1 mRNA levels, in spite of slightly decreased FMRP levels. The presence of intranuclear ubiquitin-positive inclusions in many brain regions is a neuropathological hallmark of FXTAS. Studies in humans attempting to correlate neuropathological outcomes with molecular measures are difficult because of the limited availability of tissue. Therefore, we have used the expanded CGG-repeat knock-in mouse model of FXTAS to examine the relationship between the molecular and neuropathological parameters in brain. We present Fmr1 mRNA and Fmrp levels and the presence of intranuclear inclusions at different repeat lengths. Contrary to existing hypotheses, our results suggest that inclusion formation may not depend on the elevation per se of Fmr1 transcript levels in aged CGG mice.

Aims We explored the in vivo effects of knockdown of caldesmon on vascular development in zebrafish. Methods and results We investigated the effects of caldesmon knockdown on the vascular development in a zebrafish model with special attention for the trunk and head vessels including the aortic arches. We examined the developing fishes at various time points. The vascular abnormalities observed in the caldesmon morphants were morphologically and functionally characterized in detail in fixed and living embryos. The knockdown of caldesmon caused serious defects in vasculogenesis and angiogenesis in zebrafish morphants, and the vascular integrity and blood circulation were concomitantly impaired. Conclusion The data provide the first functional assessment of the role of caldesmon in vascular development in vivo, indicating that this molecule plays a crucial role in vasculogenesis and angiogenesis in vivo. Interfering with caldesmon opens new therapeutic avenues for anti-angiogenesis in cancer and ischaemic cardiovascular disease.

The fragile X syndrome is a common cause of familial mental retardation with an estimated prevalence of 1/4000-1/6000 for males in western countries.1–3 This X linked disorder is characterised by mental retardation with additional features like a long face with large protruding ears, macro-orchidism, and eye gaze avoidance.4–6 The causative mutation is an amplification of a trinucleotide (CGG) repeat in the 5′ UTR of the FMR1 gene. Normal people have between six and 54 CGG repeats, carriers of the premutation have between 55 and 200, and affected subjects have more than 200 CGG repeats in their FMR1 gene, the so called full mutation.7,8 The latter expansion is accompanied by hypermethylation of the repeat and its upstream region resulting in a shutdown of transcription and absence of the FMRP.9–11 In fragile X patients, two special subclasses of mosaicism can be distinguished on the basis of size and methylation pattern: (1) subjects with a premutation in a proportion of their cells in addition to a full mutation, often referred to as “size mosaics”; this pattern can be observed in 20–40% of male patients12,13; (2) subjects with intercellular variations in the methylation status of a full mutation, “methylation mosaics”.14 In a large multicentre study, “methylation mosaicism” was observed in 3% of the males with a full mutation.12 ### Key points

The fragile X syndrome, the most common form of hereditary cognitive impairment, with a frequency of 1:4000 males and 1:6000 females, is caused by expansion of a trinucleotide repeat (CGG) within the FMR1 gene.1 In the normal population, the length varies from five to 50 repeats.2 Subjects with the fragile X syndrome have more than 200 CGG repeats (full mutation, FM) and, as a consequence, the FMR1 promoter region, including the CGG repeat, is hypermethylated.3,4 As methylation results in a lack of FMR1 gene transcription, no FMR1 protein (FMRP) is produced. The absence of FMRP in the brain (neurones) is responsible for the cognitive impairment in the fragile X syndrome.5,6 In addition, some subjects have intermediate sized alleles of between 50 and 200 CGG repeats (premutations; PM). The PM alleles are unmethylated with normal FMRP biosynthesis, but are unstable during transmission to the next generation. Male fragile X patients are characterised by mild to severe learning difficulties. Macro-orchidism and facial abnormalities, including a long face with large, prominent ears and behavioural features such as hyperactivity, poor eye contact, and hand flapping, may be part of the fragile X phenotype in males. Generally, there is wide variation in the degree of clinical involvement in female FM carriers. Approximately 60% of females carriers have mild to moderate mental impairment, while the remaining 40% have normal intellectual capacity. The molecular basis for the phenotypic variability in both males and females is believed to be linked to the variable number of neurones in the brain that express FMRP. Mosaic males who are affected show a variable combination of PM and FM alleles, but the usual predominance of FM.7 In female carriers of FM, variation in the X chromosome inactivation ratio may account for the clinical variability in …