Mutations in UBQLN2 have been associated with rare cases of X-linked juvenile and adult forms of amyotrophic lateral sclerosis (ALS) and ALS linked to frontotemporal dementia (FTD). Here, we report 1 ...known (c.1489C>T, p.Pro497Ser, P497S) and 3 novel (c.1481C>T, p.Pro494Leu, P494L; c.1498C>T, p.Pro500Ser, P500S; and c.1516C>G, p.Pro506Ala, P506A) missense mutations in the PXX domain of UBQLN2 in familial motor neuron diseases including ALS and spastic paraplegia (SP). A novel missense mutation (c.1462G>A, p.Ala488Thr, A488T) adjacent to this hotspot UBQLN2 domain was identified in a sporadic case of ALS. These mutations are conserved in mammals, are absent from ExAC and gnomAD browsers, and are predicted to be deleterious by SIFT in silico analysis. Patient lymphoblasts carrying a UBQLN2 mutation showed absence of ubiquilin-2 accumulation, disrupted binding with HSP70, and impaired autophagic pathway. Our results confirm the role of PXX repeat in ALS pathogenesis, show that UBQLN2-linked disease can manifest like a SP phenotype, evidence a highly reduced disease penetrance in females carrying UBQLN2 mutations, which is important information for genetic counseling, and underline the pivotal role of ubiquilin-2 in proteolysis regulation pathways.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Valosin-containing protein (VCP) mutations are rare causes of autosomal dominant frontotemporal dementias associated with Paget's disease of bone, inclusion body myopathy, and amyotrophic lateral ...sclerosis. We analyzed the VCP gene in a cohort of 199 patients with frontotemporal dementia and identified 7 heterozygous mutations in unrelated families, including 3 novel mutations segregating with dementia. This expands the VCP mutation spectrum and suggests that although VCP mutations are rare (3.5% in this study), the gene should be analyzed even in absence of the full syndromic complex. Reporting genetic variants with convincing arguments for pathogenicity is important considering the large amount of data generated by next-generation sequencing and the growing difficulties to interpret rare genetic variants identified in isolated cases.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Morphological alterations of the endosomal compartment have been widely described in post-mortem brains from Alzheimer's disease (AD) patients and subjects with Down syndrome (DS) who are at high ...risk for AD. Immunostaining with antibodies against endosomal markers such as Early Endosome Antigen 1 (EEA1) revealed increased size of EEA1-positive puncta. In DS, peripheral cells such as peripheral blood mononuclear cells (PBMCs) and fibroblasts, share similar phenotype even in the absence of AD. We previously found that PBMCs from AD patients have larger EEA1-positive puncta, correlating with brain amyloid load. Here we analysed the endosomal compartment of fibroblasts from a very well characterised cohort of AD patients (IMABio3) who underwent thorough clinical, imaging and biomarkers assessments. Twenty-one subjects were included (7 AD with mild cognitive impairment (AD-MCI), 7 AD with dementia (AD-D) and 7 controls) who had amyloid-PET at baseline (PiB) and neuropsychological tests at baseline and close to skin biopsy. Fibroblasts isolated from skin biopsies were immunostained with anti-EEA1 antibody and imaged using a spinning disk microscope. Endosomal compartment ultrastructure was also analysed by electron microscopy. All fibroblast lines were genotyped and their AD risk factors identified. Our results show a trend to an increased EEA1-positive puncta volume in fibroblasts from AD-D as compared to controls (p.adj = 0.12) and reveal enhanced endosome area in fibroblasts from AD-MCI and AD-AD versus controls. Larger puncta size correlated with PiB retention in different brain areas and with worse cognitive scores at the time of biopsy as well as faster decline from baseline to the time of biopsy. Finally, we identified three genetic risk factors for AD (ABCA1, COX7C and MYO15A) that were associated with larger EEA1 puncta volume. In conclusion, the endosomal compartment in fibroblasts could be used as cellular peripheral biomarker for both amyloid deposition and cognitive decline in AD patients.
Hereditary spastic paraplegias (HSPs) are genetically and phenotypically heterogeneous disorders. Both “uncomplicated” and “complicated” forms have been described with various modes of inheritance. ...Sixteen loci for autosomal-recessive “complicated” HSP have been mapped. The SPG15 locus was first reported to account for a rare form of spastic paraplegia variably associated with mental impairment, pigmented maculopathy, dysarthria, cerebellar signs, and distal amyotrophy, sometimes designated as Kjellin syndrome. Here, we report the refinement of SPG15 to a 2.64 Mb genetic interval on chromosome 14q23.3-q24.2 and the identification of ZFYVE26, which encodes a zinc-finger protein with a FYVE domain that we named spastizin, as the cause of SPG15. Six different truncating mutations were found to segregate with the disease in eight families with a phenotype that included variable clinical features of Kjellin syndrome. ZFYVE26 mRNA was widely distributed in human tissues, as well as in rat embryos, suggesting a possible role of this gene during embryonic development. In the adult rodent brain, its expression profile closely resembled that of SPG11, another gene responsible for complicated HSP. In cultured cells, spastizin colocalized partially with markers of endoplasmic reticulum and endosomes, suggesting a role in intracellular trafficking.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
, and
are unequivocally associated with autosomal dominant Parkinson's disease (PD). We evaluated the prevalence of
, and
mutations and associated clinical features in a large French multi-center ...cohort of PD patients. Demographic and clinical data were collected for 1,805 index cases (592 with autosomal dominant inheritance and 1,213 isolated cases) since 1990. All probands were screened with TaqMan assays for
Gly2019Ser. In the absence of this mutation, the coding sequences of the three genes were analyzed by Sanger sequencing and/or next-generation sequencing. The data for the three genes were analyzed according to age at onset, family history, ethnic origin and clinical features. We identified 160 index cases (8.9%) with known pathogenic variants: 138 with pathogenic
variants (7.6%), including 136 with the Gly2019Ser mutation, 19 with
point mutations or genomic rearrangements (1.1%), and three with the
Asp620Asn mutation (0.16%). Mutation frequencies were higher in familial than isolated cases, consistent with autosomal dominant inheritance (12.0 vs. 7.3%; OR 1.7, 95% CI 1.2-2.4,
= 0.001). PD patients with
variants were more likely to have higher rates of late-onset PD (>50 years; OR 1.5, 95% CI 1.0-2.1,
= 0.03), whereas those with
mutations tended to have earlier age at onset disease (≤ 50 years,
= 0.06). The clinical features of
carriers and those without any pathogenic variants in known PD-associated genes were similar. The likelihood of detecting disease-causing mutations was higher in cases compatible with autosomal dominant inheritance.
Hereditary spastic paraplegias (HSP) constitute a heterogeneous group of neurodegenerative disorders characterized by slowly progressive spasticity of the lower extremities. Only a few different ...mutations in the SPG10 gene, KIF5A, have been described in pure dominant forms of the disease. We sequenced the motor domain of KIF5A in a large panel of 205 European HSP patients with either pure or complicated forms of the disease. We identified eight different heterozygous missense mutations, seven novels, in eight different families of French origin. Residue R280 was a mutational hot spot. Interestingly, the patients in 7/8 families had a complex phenotype, with peripheral neuropathy, severe upper limb amyotrophy (Silver syndrome-like), mental impairment, parkinsonism, deafness and/or retinitis pigmentosa as variably associated features. We report the largest series of SPG10 families described so far, which extends both the mutational spectrum of the disease and its phenotype, which now includes complicated forms of HSP. SPG10 mutations were found in 10% of our complicated forms of HSP, suggesting that mutations in KIF5A represent the major cause of complicated AD-HSP in France.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Early sequential expression of mouse Hox genes is essential for their later function. Analysis of the relationship between early Hox gene expression and the laying down of anterior to posterior ...structures during and after gastrulation is therefore crucial for understanding the ontogenesis of Hox-mediated axial patterning. Using explants from gastrulation stage embryos, we show that the ability to express 3â² and 5â² Hox genes develops sequentially in the primitive streak region, from posterior to anterior as the streak extends, about 12 hours earlier than overt Hox expression. The ability to express autonomously the earliest Hox gene, Hoxb1 , is present in the posterior streak region at the onset of gastrulation, but not in the anterior region at this stage. However, the posterior region can induce Hoxb1 expression in these anterior region cells. We conclude that tissues are primed to express Hox genes early in gastrulation, concomitant with primitive streak formation and extension, and that Hox gene inducibility is transferred by cell to cell signalling. Axial structures that will later express Hox genes are generated in the node region in the period that Hox expression domains arrive there and continue to spread rostrally. However, lineage analysis showed that definitive Hox codes are not fixed at the node, but must be acquired later and anterior to the node in the neurectoderm, and independently in the mesoderm. We conclude that the rostral progression of Hox gene expression must be modulated by gene regulatory influences from early on in the posterior streak, until the time cells have acquired their stable positions along the axis well anterior to the node.
Mouse Cdx and Hox genes presumably evolved from genes on a common ancestor cluster involved in anteroposterior patterning. Drosophila caudal ( cad ) is involved in specifying the posterior end of the ...early embryo, and is essential for patterning tissues derived from the most caudal segment, the analia. Two of the three mouse Cdx paralogues, Cdx 1 and Cdx2 , are expressed early in a Hox-like manner in the three germ layers. In the nascent paraxial mesoderm, both genes are expressed in cells contributing first to the most rostral, and then to progressively more caudal parts of the vertebral column. Later, expression regresses from the anterior sclerotomes, and is only maintained for Cdx1 in the dorsal part of the somites, and for both genes in the tail bud. Cdx1 null mutants show anterior homeosis of upper cervical and thoracic vertebrae. Cdx2 -null embryos die before gastrulation, and Cdx2 heterozygotes display anterior transformations of lower cervical and thoracic vertebrae. We have analysed the genetic interactions between Cdx1 and Cdx2 in compound mutants. Combining mutant alleles for both genes gives rise to anterior homeotic transformations along a more extensive length of the vertebral column than do single mutations. The most severely affected Cdx1 null/ Cdx2 heterozygous mice display a posterior shift of their cranio-cervical, cervico-thoracic, thoraco-lumbar, lumbo-sacral and sacro-caudal transitions. The effects of the mutations in Cdx1 and Cdx2 were co-operative in severity, and a more extensive posterior shift of the expression of three Hox genes was observed in double mutants. The alteration in Hox expression boundaries occurred early. We conclude that both Cdx genes cooperate at early stages in instructing the vertebral progenitors all along the axis, at least in part by setting the rostral expression boundaries of Hox genes. In addition, Cdx mutants transiently exhibit alterations in the extent of Hox expression domains in the spinal cord, reminding of the strong effects of overexpressing Cdx genes on Hox gene expression in the neurectoderm. Phenotypical alterations in the peripheral nervous system were observed at mid-gestation stages. Strikingly, the altered phenotype at caudal levels included a posterior truncation of the tail, mildly affecting Cdx2 heterozygotes, but more severely affecting Cdx1/Cdx2 double heterozygotes and Cdx1 null/ Cdx2 heterozygotes. Mutations in Cdx1 and Cdx2 therefore also interfere with axis elongation in a cooperative way. The function of Cdx genes in morphogenetic processes during gastrulation and tail bud extension, and their relationship with the Hox genes are discussed in the light of available data in Amphioxus , C. elegans , Drosophila and mice.
Reliable and easy to perform functional scales are a prerequisite for future therapeutic trials in cerebellar ataxias. In order to assess the specificity of quantitative functional tests of ...cerebellar dysfunction, we investigated 123 controls, 141 patients with an autosomal dominant cerebellar ataxia (ADCA) and 53 patients with autosomal dominant spastic paraplegia (ADSP). We evaluated four different functional tests (nine-hole pegboard, click, tapping and writing tests), in correlation with the scale for the assessment and rating of cerebellar ataxia (SARA), the scale of functional disability on daily activities (part IV of the Huntington disease rating scale), depression (the Public Health Questionnaire PHQ-9) and the EQ-5D visual analogue scale for self-evaluation of health status. There was a significant correlation between each functional test and a lower limb score. The performance of controls on the functional tests was significantly correlated with age. Subsequent analyses were therefore adjusted for this factor. The performances of ADCA patients on the different tests were significantly worse than that of controls and ADSP patients; there was no difference between ADSP patients and controls. Linear regression analysis showed that only two independent tests, the nine-hole pegboard and the click test on the dominant side (P < 0.0001), accounted for the severity of the cerebellar syndrome as reflected by the SARA scores, and could be represented by a composite cerebellar functional severity (CCFS) score calculated as follows:
CCFS
The CCFS score was significantly higher in ADCA patients compared to controls (1.12 ± 0.18 versus 0.85 ± 0.05, P
c < 0.0001) and ADSP patients (1.12 ± 0.18 versus 0.90 ± 0.08, P
c < 0.0001) and was correlated with disease duration (P < 0.0001) but independent of self-evaluated depressive mood in ADCA. Among genetically homogeneous subgroups of ADCA patients (Spinocerebellar ataxia 1, 2, 3), SCA3 patients had significantly lower (better) CCFS scores than SCA2 (P
c < 0.04) and the same tendency was observed in SCA1. Their CCFS scores remained significantly worse than those of ADSP patients with identified SPG4 mutations (P < 0.0001). The pegboard and click tests are easy to perform and accurately reflect the severity of the disease. The CCFS is a simple and validated method for assessing cerebellar ataxia over a wide range of severity, and will be particularly useful for discriminating paucisymptomatic carriers from affected patients and for evaluating disease progression in future therapeutic trials.
BackgroundGenes involved in Tourette syndrome (TS) remain largely unknown. We aimed to identify genetic factors contributing to TS in a French cohort of 120 individuals using a combination of ...hypothesis-driven and exome-sequencing approaches. MethodsWe first sequenced exons of SLITRK1-6 and HDC in the TS cohort and subsequently sequenced the exome of 12 individuals harboring rare variants in these genes to find additional rare variants contributing to the disorder under the hypothesis of oligogenic inheritance. We further screened three candidate genes (OPRK1, PCDH10, and NTSR2) preferentially expressed in the basal ganglia, and three additional genes involved in neurotensin and opioid signaling (OPRM1, NTS, and NTSR1), and compared variant frequencies in TS patients and 788 matched control individuals. We also investigated the impact of altering the expression of Oprk1 in zebrafish. ResultsThirteen ultrarare missense variants of SLITRK1-6 and HDC were identified in 12 patients. Exome sequencing in these patients revealed rare possibly deleterious variants in 3,041 genes, 54 of which were preferentially expressed in the basal ganglia. Comparison of variant frequencies altering selected candidate genes in TS and control individuals revealed an excess of potentially disrupting variants in OPRK1, encoding the opioid kappa receptor, in TS patients. Accordingly, we show that downregulation of the Oprk1 orthologue in zebrafish induces a hyperkinetic phenotype in early development. DiscussionThese results support a heterogeneous and complex genetic etiology of TS, possibly involving rare variants altering the opioid pathway in some individuals, which could represent a novel therapeutic target in this disorder.
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