22 research outputs found
Two-dimensional topological superconductivity in Pb/Co/Si(111)
Just like insulators can host topological Dirac states at their edges,
superconductors can also exhibit topological phases characterized by Majorana
edge states. Remarkable zero-energy states have been recently observed at the
two ends of proximity induced superconducting wires, and were interpreted as
localized Majorana end states in one-dimensional (1D) topological
superconductor. By contrast, propagating Majorana states should exist at the 1D
edges of two-dimensional (2D) topological superconductors. Here we report the
direct observation of dispersive in-gap states surrounding topological
superconducting domains made of a single atomic layer of Pb covering magnetic
islands of Co/Si(111). We interpret the observed continuous dispersion across
the superconducting gap in terms of a spatial topological transition
accompanied by a chiral edge mode and residual gaped helical edge states. Our
experimental approach enables the engineering and control of a large variety of
novel quantum phases. This opens new horizons in the field of quantum materials
and quantum electronics where the magnetization of the domains could be used as
a control parameter for the manipulation of topological states.Comment: 12 pages, 3 figure
Long range coherent magnetic bound states in superconductors
The quantum coherent coupling of completely different degrees of freedom is a
challenging path towards creating new functionalities for quantum electronics.
Usually the antagonistic coupling between spins of magnetic impurities and
superconductivity leads to the destruction of the superconducting order. Here
we show that a localized classical spin of an iron atom immersed in a
superconducting condensate can give rise to new kind of long range coherent
magnetic quantum state. In addition to the well-known Shiba bound state present
on top of an impurity we reveal the existence of a star shaped pattern which
extends as far as 12 nm from the impurity location. This large spatial
dispersion turns out to be related, in a non-trivial way, to the
superconducting coherence length. Inside star branches we observed short scale
interference fringes with a particle-hole asymmetry. Our theoretical approach
captures these features and relates them to the electronic band structure and
the Fermi wave length of the superconductor. The discovery of a directional
long range effect implies that distant magnetic atoms could coherently interact
leading to new topological superconducting phases with fascinating properties
WS21.2 Non-invasive prenatal diagnosis (NIPD) of cystic fibrosis by quantitative real time mutant enrichment with 3′-modified oligonucleotides (MEMO) PCR
Autosomal dominant SPG9: intrafamilial variability and onset during pregnancy
International audienceINTRODUCTION: The ALDH18A1 gene, encoding delta-1-pyrroline-5-carboxylate synthase (P5CS), is responsible for an autosomal recessive disease with severe developmental delay; more recently, ALDH18A1 was found to be responsible for SPG9, an autosomal dominant (AD) spastic paraplegia.CASE REPORT: We report a three-generation family with AD SPG9, initially suspected because of low citrulline on fasting plasma amino acid chromatography (AAC). Interestingly, in two patients, the spastic paraplegia appeared during pregnancy. One subject presented a severe childhood-onset form while another subject had a mild late-onset disease.CONCLUSION: The description of this family is of particular interest: it highlights the possibility of transient or permanent aggravation of spastic paraplegia due to SPG9 during pregnancy, suggesting a direct link between neurological symptoms and amino acid defect in a period of higher requirements and the potential benefit of amino acid supplementation; it underscores the value of plasma citrulline on fasting plasma AAC as a biomarker for this disease; it shows the variable expression of the disease
Successful treatment of a genetic childhood ataxia due to riboflavin transporter deficiency
Expanding the spectrum of PEX10-related peroxisomal biogenesis disorders: slowly progressive recessive ataxia
International audiencePeroxisomal biogenesis disorders (PBDs) consist of a heterogeneous group of autosomal recessive diseases, in which peroxisome assembly and proliferation are impaired leading to severe multisystem disease and early death. PBDs include Zellweger spectrum disorders (ZSDs) with a relatively mild clinical phenotype caused by PEX1, (MIM# 602136), PEX2 (MIM# 170993), PEX6 (MIM# 601498), PEX10 (MIM# 602859), PEX12 (MIM# 601758), and PEX16 (MIM# 603360) mutations. Three adult patients are reported belonging to a non-consanguineous French family affected with slowly progressive cerebellar ataxia, axonal neuropathy, and pyramidal signs. Mental retardation and diabetes mellitus were optional. The age at onset was in childhood or in adolescence (3-15 years). Brain MRI showed marked cerebellar atrophy. Biochemical blood analyses suggested a mild peroxisomal defect. With whole exome sequencing, two mutations in PEX10 were found in the three patients: c.827G\textgreaterT (novel) causing the missense change p.Cys276Phe and c.932G\textgreaterA causing the missense change p.Arg311Gln. The phenotypic spectrum related to PEX10 mutations includes slowly progressive, syndromic recessive ataxia
Mutation of SLC9A1, encoding the major Na+/H+ exchanger, causes ataxia-deafness Lichtenstein-Knorr syndrome
International audienceLichtenstein-Knorr syndrome is an autosomal recessive condition that associates sensorineural hearing loss and cerebellar ataxia. Here, we report the first identification of a gene involved in Lichtenstein-Knorr syndrome. By using a combination of homozygosity mapping and whole-exome sequencing, we identified the homozygous p.Gly305Arg missense mutation in SLC9A1 that segregates with the disease in a large consanguineous family. Mutant glycine 305 is a highly conserved amino acid present in the eighth transmembrane segment of all metazoan orthologues of NHE1, the Na(+)/H(+) exchanger 1, encoded by SLC9A1. We demonstrate that the p.Gly305Arg mutation causes the near complete de-glycosylation, mis-targeting and loss of proton pumping activity of NHE1. The comparison of our family with the phenotypes of spontaneous and knockout Slc9a1 murine models demonstrates that the association between ataxia and hearing loss is caused by complete or near complete loss of function of NHE1 and altered regulation of pHi in the central nervous system
Turning unreactive copper acetylides into remarkably powerful and mild alkyne transfert reagents by oxidative umpolung
International audienceThis is not breaking news: copper acetylides, readily available polymeric rock-stable solids, have been known for more than a century to be unreactive species and piteous nucleophiles. This lack of reactivity actually makes them ideal alkyne transfer reagents that can be easily activated under mild oxidizing conditions. When treated with molecular oxygen in the presence of simple chelating nitrogen ligands such as TMEDA, phenanthroline or imidazole derivatives, they are smoothly oxidized to highly electrophilic species that formally behave like acetylenic carbocations and can therefore be used for the mild and practical alkynylation of a wide range of nitrogen, phosphorus and carbon nucleophiles
Noninvasive prenatal diagnosis of genetic diseases induced by triplet repeat expansion by linked read haplotyping and Bayesian approach
International audienceAbstract The field of noninvasive prenatal diagnosis (NIPD) has undergone significant progress over the last decade. Direct haplotyping has been successfully applied for NIPD of few single-gene disorders. However, technical issues remain for triplet-repeat expansions. The objective of this study was to develop an NIPD approach for couples at risk of transmitting dynamic mutations. This method includes targeted enrichment for linked-read libraries and targeted maternal plasma DNA sequencing. We also developed an innovative Bayesian procedure to integrate the Hoobari fetal genotyping model for inferring the fetal haplotype and the targeted gene variant status. Our method of directly resolving parental haplotypes through targeted linked-read sequencing was smoothly performed using blood samples from families with Huntington’s disease or myotonic dystrophy type 1. The Bayesian analysis of transmission of parental haplotypes allowed defining the genotype of five fetuses. The predicted variant status of four of these fetuses was in agreement with the invasive prenatal diagnosis findings. Conversely, no conclusive result was obtained for the NIPD of fragile X syndrome. Although improvements should be made to achieve clinically acceptable accuracy, our study shows that linked-read sequencing and parental haplotype phasing can be successfully used for NIPD of triplet-repeat expansion diseases. Trial registration: NCT04698551_date of first registration: 07/01/2021