Publications by authors named "Carmen Badiu"

4 Publications

  • Page 1 of 1

Heterozygous HTRA1 nonsense or frameshift mutations are pathogenic.

Brain 2021 Jul 16. Epub 2021 Jul 16.

AP-HP, Service de Génétique Moléculaire Neurovasculaire, Hôpital Saint-Louis, France.

Heterozygous missense HTRA1 mutations have been associated with an autosomal dominant cerebral small vessel disease whereas the pathogenicity of heterozygous HTRA1 stop codon variants is unclear. We performed a targeted high throughput sequencing of all known cerebral small vessel disease genes, including HTRA1, in 3,853 unrelated consecutive CSVD patients referred for molecular diagnosis. The frequency of heterozygous HTRA1 mutations leading to a premature stop codon in this patient cohort was compared with their frequency in large control databases. An analysis of HTRA1 messenger RNA was performed in several stop codon carrier patients. Clinical and neuroimaging features were characterized in all probands. Twenty unrelated patients carrying a heterozygous HTRA1 variant leading to a premature stop codon were identified. A highly significant difference was observed when comparing our patient cohort with control databases (gnomAD v3.1.1 (p = 3.12 x 10-17, OR = 21.9), TOPMed freeze 5 (p = 7.6 x 10-18, OR = 27.1) and 1000 Genomes (p = 1.5 x 10-5). Messenger RNA analysis performed in eight patients showed a degradation of the mutated allele strongly suggesting a haploinsufficiency. Clinical and neuroimaging features are similar to those previously reported in heterozygous missense mutation carriers, except for penetrance, which seems lower. Altogether, our findings strongly suggest that heterozygous HTRA1 stop codons are pathogenic through a haploinsufficiency mechanism. Future work will help to estimate their penetrance, an important information for genetic counseling.
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http://dx.doi.org/10.1093/brain/awab271DOI Listing
July 2021

Nucleus-specific abnormalities of GABAergic synaptic transmission in a genetic model of absence seizures.

J Neurophysiol 2006 Dec 13;96(6):3074-81. Epub 2006 Sep 13.

Neurobiologie des Processus Adaptatifs, UMR 7102 CNRS, Université Pierre et Marie Curie-Paris 6, 9 quai St Bernard, 75252 Paris Cedex 05, France.

Human and experimental studies indicate that molecular genetic changes in GABA(A) receptors may underlie the expression of spike-and-waves discharges (SWDs) occurring during absence seizures. However, the full spectrum of the genetic defects underlying these seizures has only been partially elucidated, the expression and functional profiles of putative abnormal protein(s) within the thalamocortical network are undefined, and the pathophysiological mechanism(s) by which these proteins would lead to absence paroxysms are poorly understood. Here we investigated GABA(A) inhibitory postsynaptic currents (IPSCs) in key thalamocortical areas, i.e., the somatosensory cortex, ventrobasal thalamus (VB) and nucleus reticularis thalami (NRT), in preseizure genetic absence epilepsy rats from Strasbourg (GAERS), a well-established genetic model of typical absence seizures that shows no additional neurological abnormalities, and compared their properties to age-matched non-epileptic controls (NECs). Miniature GABA(A) IPSCs of VB and cortical layers II/III neurons were similar in GAERS and NEC, whereas in GAERS NRT neurons they had 25% larger amplitude, 40% faster decay. In addition, baclofen was significantly less effective in decreasing the frequency of NRT mIPSCs in GAERS than in NEC, whereas no difference was observed for cortical and VB mIPSCS between the two strains. Paired-pulse depression was 45% smaller in GAERS NRT, but not in VB, and was insensitive to GABA(B) antagonists. These results point to subtle, nucleus-specific, GABA(A) receptor abnormalities underlying SWDs of typical absence seizures rather than a full block of these receptors across the whole thalamocortical network, and their occurrence prior to seizure onset suggests that they might be of epileptogenic significance.
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http://dx.doi.org/10.1152/jn.00682.2006DOI Listing
December 2006

Heterogeneity of postsynaptic receptor occupancy fluctuations among glycinergic inhibitory synapses in the zebrafish hindbrain.

J Physiol 2003 Dec 18;553(Pt 3):819-32. Epub 2003 Sep 18.

UMR 7102 CNRS, Université Pierre et Marie Curie, Bât B 6ème étage, 7 Quai Saint Bernard, 75252 Paris Cedex 05, France.

The amplitude of glycinergic miniature inhibitory postsynaptic currents (mIPSCs) varies considerably in neurons recorded in the isolated hindbrain of 50-h-old zebrafish larvae. At this age, glycinergic synapses are functionally mature. In order to measure the occupancy level of postsynaptic glycine receptors (GlyRs) and to determine the pre- and/or postsynaptic origin of its variability, we analysed mIPSCs within bursts evoked by alpha-latrotoxin (0.1-1 nM). Two types of burst were observed according to their mIPSC frequencies: 'slow' bursts with clearly spaced mIPSCs and 'fast' bursts characterised by superimposed events. Non-stationary noise analysis of mIPSCs in some 'slow' bursts recorded in the presence or in the absence of Ca2+ denoted that mIPSC amplitude variance did not depend on the quantity of neurotransmitters released (presynaptic origin), but rather on intrinsic stochastic behaviour of the same group of GlyRs (postsynaptic origin). In these bursts, the open probability measured at the peak of the mIPSCs was close to 0.5 while the maximum open probability is close to 0.9 for the synaptic isoform of GlyRs (heteromeric alpha1/beta GlyRs). In 'fast' bursts with superimposed events, a correlation was found between the amplitude of mIPSCs and the basal current level measured at their onset, which could suggest that the same group of GlyRs is activated during such bursts. Altogether, our results indicate that glycine synapses can display different release modes in the presence of alpha-latrotoxin. They also indicate that, in our model, postsynaptic GlyRs cannot be saturated by the release of a single vesicle.
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http://dx.doi.org/10.1113/jphysiol.2003.049577DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2343629PMC
December 2003

Desensitization of homomeric alpha1 glycine receptor increases with receptor density.

Mol Pharmacol 2002 Oct;62(4):817-27

Unité Mixte Recherche Centre National de la Recherche Scientifique 7102, Université Pierre et Marie Curie, Paris, France.

Variations in the number of receptors at glycinergic synapses are now established and are believed to contribute to inhibitory synaptic plasticity. However, the relation between glycine receptor (GlyR) kinetics and density is still unclear. We used outside-out patch-clamp recordings and fast-flow application techniques to resolve fast homomeric GlyRalpha1 kinetics and to determine how the functional properties of these receptors depend on their density and on the presence of the anchoring protein gephyrin. The expression of GlyRs in human embryonic kidney cells increased with time and was correlated with an increase in GlyR desensitization at 2 days after transfection. Cotransfection of homomeric GlyRalpha1 bearing the gephyrin-binding site with gephyrin also increased desensitization but at 1 day after transfection compared with transfections of homomeric GlyRalpha1 without gephyrin. This increase results from the occurrence of a fast desensitization component and short applications of a saturating concentration of glycine suffice to promote a rapidly entered desensitized closed state. The level of desensitization changed neither the EC(50) value nor the Hill coefficient of the glycine dose-response curves because the amplitude of the current was measured at the peak of the responses. These results demonstrate that variations in GlyR density during cluster formation result from a change in GlyR efficiency due to modifications in their desensitization properties.
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http://dx.doi.org/10.1124/mol.62.4.817DOI Listing
October 2002
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