Variabilité du nombre de copies

Résumé

La variabilité du nombre de copies d'un gène (en anglais copy number variation, CNV) désigne en génétique une forme particulière de polymorphisme dans lequel le nombre de copies d'un même gène ou d'un segment chromosomique dans le génome est variable entre les individus de la même espèce. Origine du polymorphisme du nombre de copies La présence de plusieurs copies de même gènes dans le génome est due à des événements de duplication de gènes, qui peuvent affecter un gène, quelques gènes, ou l'intégralité du génome. La variabilité du nombre de copies d'un gène au sein d'une même espèce est en général due à des évènements de duplication (regroupement dans une même génération chromosomique de gènes dupliqués en tandem) et délétion locales (c'est-à-dire d'un ou de quelques gènes), souvent à la suite d'un enjambement inégal. Importance quantitative Cette forme de polymorphisme, découverte récemment, constitue une part importante de la variabilité individuelle au s

Source officielle

https://fr.wikipedia.org/wiki/Variabilit%C3%A9_du_nombre_de_copies

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This course covers the main applications of micro devices for life science and biomedical applications. The course is organized by application topic. It is also covering the basic physical, biological, chemical, technological concepts, which are presented as transversal introductory section

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Effects of eight neuropsychiatric copy number variants on human brain structure

Bogdan Draganski, Kuldeep Kumar, Lester Melie Garcia, Claudia Modenato, Borja Rodriguez Herreros

Many copy number variants (CNVs) confer risk for the same range of neurodevelopmental symptoms and psychiatric conditions including autism and schizophrenia. Yet, to date neuroimaging studies have typically been carried out one mutation at a time, showing that CNVs have large effects on brain anatomy. Here, we aimed to characterize and quantify the distinct brain morphometry effects and latent dimensions across 8 neuropsychiatric CNVs. We analyzed T1-weighted MRI data from clinically and non-clinically ascertained CNV carriers (deletion/duplication) at the 1q21.1 (n = 39/28), 16p11.2 (n = 87/78), 22q11.2 (n = 75/30), and 15q11.2 (n = 72/76) loci as well as 1296 non-carriers (controls). Case-control contrasts of all examined genomic loci demonstrated effects on brain anatomy, with deletions and duplications showing mirror effects at the global and regional levels. Although CNVs mainly showed distinct brain patterns, principal component analysis (PCA) loaded subsets of CNVs on two latent brain dimensions, which explained 32 and 29% of the variance of the 8 Cohen's d maps. The cingulate gyrus, insula, supplementary motor cortex, and cerebellum were identified by PCA and multi-view pattern learning as top regions contributing to latent dimension shared across subsets of CNVs. The large proportion of distinct CNV effects on brain morphology may explain the small neuroimaging effect sizes reported in polygenic psychiatric conditions. Nevertheless, latent gene brain morphology dimensions will help subgroup the rapidly expanding landscape of neuropsychiatric variants and dissect the heterogeneity of idiopathic conditions.

SPRINGERNATURE2021

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A genome-wide association study of resistance to HIV infection in highly exposed uninfected individuals with hemophilia A

Jacques Fellay, Amalio Telenti

Human genetic variation contributes to differences in susceptibility to HIV-1 infection. To search for novel host resistance factors, we performed a genome-wide association study (GWAS) in hemophilia patients highly exposed to potentially contaminated factor VIII infusions. Individuals with hemophilia A and a documented history of factor VIII infusions before the introduction of viral inactivation procedures (1979-1984) were recruited from 36 hemophilia treatment centers (HTCs), and their genome-wide genetic variants were compared with those from matched HIV-infected individuals. Homozygous carriers of known CCR5 resistance mutations were excluded. Single nucleotide polymorphisms (SNPs) and inferred copy number variants (CNVs) were tested using logistic regression. In addition, we performed a pathway enrichment analysis, a heritability analysis, and a search for epistatic interactions with CCR5 D32 heterozygosity. A total of 560 HIV-uninfected cases were recruited: 36 (6.4) were homozygous for CCR5 32 or m303. After quality control and SNP imputation, we tested 1 081 435 SNPs and 3686 CNVs for association with HIV-1 serostatus in 431 cases and 765 HIV-infected controls. No SNP or CNV reached genome-wide significance. The additional analyses did not reveal any strong genetic effect. Highly exposed, yet uninfected hemophiliacs form an ideal study group to investigate host resistance factors. Using a genome-wide approach, we did not detect any significant associations between SNPs and HIV-1 susceptibility, indicating that common genetic variants of major effect are unlikely to explain the observed resistance phenotype in this population.

Oxford University Press2013

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Single-Shot Imaging with Higher-Dimensional Encoding Using Magnetic Field Monitoring and Concomitant Field Correction

Daniel Gallichan

PurposePatLoc (Parallel Imaging Technique using Localized Gradients) accelerates imaging and introduces a resolution variation across the field-of-view. Higher-dimensional encoding employs more spatial encoding magnetic fields (SEMs) than the corresponding image dimensionality requires, e.g. by applying two quadratic and two linear spatial encoding magnetic fields to reconstruct a 2D image. Images acquired with higher-dimensional single-shot trajectories can exhibit strong artifacts and geometric distortions. In this work, the source of these artifacts is analyzed and a reliable correction strategy is derived. MethodsA dynamic field camera was built for encoding field calibration. Concomitant fields of linear and nonlinear spatial encoding magnetic fields were analyzed. A combined basis consisting of spherical harmonics and concomitant terms was proposed and used for encoding field calibration and image reconstruction. ResultsA good agreement between the analytical solution for the concomitant fields and the magnetic field simulations of the custom-built PatLoc SEM coil was observed. Substantial image quality improvements were obtained using a dynamic field camera for encoding field calibration combined with the proposed combined basis. ConclusionThe importance of trajectory calibration for single-shot higher-dimensional encoding is demonstrated using the combined basis including spherical harmonics and concomitant terms, which treats the concomitant fields as an integral part of the encoding. Magn Reson Med 73:1340-1357, 2015. (c) 2014 Wiley Periodicals, Inc.

Wiley-Blackwell2015

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