Hereditary spastic paraplegia in Greece: characterisation of a previously unexplored population using next-generation sequencing

Hereditary Spastic Paraplegia (HSP) is a syndrome characterised by lower limb spasticity, occurring alone or in association with other neurological manifestations, such as cognitive impairment, seizures, ataxia or neuropathy. HSP occurs worldwide, with different populations having different frequencies of causative genes. The Greek population has not yet been characterised. The purpose of this study was to describe the clinical presentation and molecular epidemiology of the largest cohort of HSP in Greece, comprising 54 patients from 40 families. We used a targeted next-generation sequencing (NGS) approach to genetically assess a proband from each family. We made a genetic diagnosis in >50% of cases and identified 11 novel variants. Variants in SPAST and KIF5A were the most common causes of autosomal dominant HSP, whereas SPG11 and CYP7B1 were the most common cause of autosomal recessive HSP. We identified a novel variant in SPG11, which led to disease with later onset and may be unique to the Greek population and report the first nonsense mutation in KIF5A. Interestingly, the frequency of HSP mutations in the Greek population, which is relatively isolated, was very similar to other European populations. We confirm that NGS approaches are an efficient diagnostic tool and should be employed early in the assessment of HSP patients

Insights into the morphology of multicomponent organic and inorganic aerosols from molecular dynamics simulations

We explore the morphologies of multicomponent nanoparticles through atomistic molecular dynamics simulations under atmospherically relevant conditions. The particles investigated consist of both organic (cis-pinonic acid – CPA, 3-methyl-1,2,3-butanetricarboxylic acid – MBTCA, n-C20H42, n-C24H50, n-C30H62 or mixtures thereof) and inorganic (sulfate, ammonium and water) compounds. The effects of relative humidity, organic mass content and type of organic compound present in the nanoparticle are investigated. Phase separation is predicted for almost all simulated nanoparticles either between organics and inorganics or between hydrophobic and hydrophilic constituents. For oxygenated organics, our simulations predict an enrichment of the nanoparticle surface in organics, often in the form of islands depending on the level of humidity and organic mass fraction, giving rise to core–shell structures. In several cases the organics separate from the inorganics, especially from the ions. For particles containing water-insoluble linear alkanes, separate hydrophobic and hydrophilic domains are predicted to develop. The surface partitioning of organics is enhanced as the humidity increases. The presence of organics in the interior of the nanoparticle increases as their overall mass fraction in the nanoparticle increases, but this also depends on the humidity conditions. Apart from the organics–inorganics and hydrophobics–hydrophilics separation, our simulations predict a third type of separation (layering) between CPA and MBTCA molecules under certain conditions.</p

Spastic paraplegia preceding PSEN1-related familial Alzheimer's disease.

Introduction: We investigated the frequency, neuropathology, and phenotypic characteristics of spastic paraplegia (SP) that precedes dementia in presenilin 1 (PSEN1) related familial Alzheimer's disease (AD). Methods: We performed whole exome sequencing (WES) in 60 probands with hereditary spastic paraplegia (HSP) phenotype that was negative for variants in known HSP-related genes. Where PSEN1 mutation was identified, brain biopsy was performed. We investigated the link between HSP and AD with PSEN1 in silico pathway analysis and measured in vivo the stability of PSEN1 mutant γ-secretase. Results: We identified a PSEN1 variant (p.Thr291Pro) in an individual presenting with pure SP at 30 years of age. Three years later, SP was associated with severe, fast cognitive decline and amyloid deposition with diffuse cortical plaques on brain biopsy. Biochemical analysis of p.Thr291Pro PSEN1 revealed that although the mutation does not alter active γ-secretase reconstitution, it destabilizes γ-secretase-amyloid precursor protein (APP)/amyloid beta (Aβn) interactions during proteolysis, enhancing the production of longer Aβ peptides. We then extended our analysis to all 226 PSEN1 pathogenic variants reported and show that 7.5% were associated with pure SP onset followed by cognitive decline later in the disease. We found that PSEN1 cases manifesting initially as SP have a later age of onset, are associated with mutations located beyond codon 200, and showed larger diffuse, cored plaques, amyloid-ring arteries, and severe CAA. Discussion: We show that pure SP can precede dementia onset in PSEN1-related familial AD. We recommend PSEN1 genetic testing in patients presenting with SP with no variants in known HSP-related genes, particularly when associated with a family history of cognitive decline

Mosaicism for combined tetrasomy of chromosomes 8 and 18 in a dysmorphic child: A result of failed tetraploidy correction?

<p>Abstract</p> <p>Background</p> <p>Mosaic whole-chromosome tetrasomy has not previously been described as a cause of fetal malformations.</p> <p>Case presentation</p> <p>In a markedly dysmorphic child with heart malformations and developmental delay, CGH analysis of newborn blood DNA suggested a 50% dose increase of chromosomes 8 and 18, despite a normal standard karyotype investigation. Subsequent FISH analysis revealed leukocytes with four chromosomes 8 and four chromosomes 18. The child's phenotype had resemblance to both mosaic trisomy 8 and mosaic trisomy 18. The double tetrasomy was caused by mitotic malsegregation of all four chromatids of both chromosome pairs. A possible origin of such an error is incomplete correction of a tetraploid state resulting from failed cytokinesis or mitotic slippage during early embryonic development.</p> <p>Conclusion</p> <p>This unique case suggests that embryonic cells may have a mechanism for tetraploidy correction that involves mitotic pairing of homologous chromosomes.</p

New mutation of the MPZ gene in a family with the Dejerine-Sottas disease phenotype

Charcot-Marie-Tooth disease type 1B is associated with mutations in the myelin protein zero gene. In the present study a new myelin protein zero gene mutation (c.89T&gt;C,Ile30Thr) was detected in a family with the Dejerine-Sottas disease phenotype. The results support the hypothesis that severe, early-onset neuropathy may be related to either an alteration of a conserved amino acid or a disruption of the tertiary structure of myelin protein zero. © 2006 Wiley Periodicals, Inc

Co-segregation of huntington disease and hereditary spastic paraplegia in 4 generations

INTRODUCTION: Huntington disease (HD) is an autosomal dominant neurodegenerative disease characterized by choreic hyperkinesias, cognitive decline, and psychiatric manifestations, caused by an increased number of CAG repeats in the IT15 gene on chromosome 4p16.3. Silver syndrome is a rare autosomal dominant form of complicated hereditary spastic paraplegia, characterized by lower limb spasticity in addition to amyotrophy of the small muscles of the hands. In addition to the previously identified locus SPG17 on chromosome 11q12-q14, a new locus (SPG38) on chromosome 4p16-p15 has been recently identified, a region that includes the HD gene. REPORT OF THE CASES: We present a Greek family with 5 members diagnosed with HD in 4 generations. All affected members also presented with clinical features of Silver syndrome showing severe spastic paraplegia and prominent atrophy of all small hand muscles bilaterally. None of the other family members showed features of either HD or spastic paraplegia. CONCLUSIONS: The reported coexistence of Silver syndrome with HD in 4 generations is not fortuitous, suggesting that these 2 distinct genetic disorders are in linkage disequilibrium. Although rare, it is reasonable to expect additional similar cases. Clinical neurologists should perhaps investigate this possibility in cases combining features of HD and involvement of the upper and lower motor neurons. Copyright © 2011 by Lippincott Williams &amp;Wilkins