Publications by authors named "Pierre Antoine Rollat Farnier"

Article Synopsis
  • Chromoanagenesis is a cellular process causing complex chromosomal rearrangements during a significant event, potentially leading to genetic material loss or gain and various traits, typically occurring sporadically but can also be inherited.
  • In a study involving six families, researchers investigated how asymptomatic parents passed on these rearrangements to their children, using karyotyping, fluorescent in situ hybridization, chromosomal microarray, and whole genome sequencing to analyze the chromosomal changes.
  • The findings suggest that chromoanagenesis can occur without affecting the parent's health or fertility, and prenatal testing using chromosomal microarray is recommended to identify any genetic imbalances in offspring from these families.
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Genetic diagnosis of familial hypercholesterolemia (FH) remains unexplained in 30 to 70% of patients after exclusion of monogenic disease. There is now a growing evidence that a polygenic burden significantly modulates LDL-cholesterol (LDL-c) concentrations. Several LDL-c polygenic risk scores (PRS) have been set up.

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  • The TCF4 gene is linked to neurodevelopment and can lead to Pitt-Hopkins syndrome when altered, which causes severe intellectual disability and facial abnormalities.
  • Researchers identified structural variations in the TCF4 gene in three patients with a milder phenotype than typical for Pitt-Hopkins syndrome.
  • These variations resulted in decreased expression of long TCF4 isoforms and an increase in shorter isoforms, indicating a potential correlation between the extent of TCF4 disruption and the severity of symptoms.
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  • F8 duplications, found on the X chromosome, can lead to various clinical outcomes, ranging from benign conditions to severe hemophilia A symptoms, depending on their location.
  • The study aimed to analyze two significant duplications found in patients with severe intellectual disabilities but no bleeding disorders, using whole genome sequencing for detailed characterization.
  • Results revealed complex genomic rearrangements in both patients, preserving an intact F8 gene, emphasizing the importance of using advanced genomic analysis to understand their genetic variations and improve genetic counseling.
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  • Human centromeres consist largely of alpha satellite DNA, organized into higher-order repeats (HORs), which can undergo dynamic changes, such as sequence homogenization and relocation during centromere maturation.
  • A notable instance of this was identified through prenatal diagnosis, where a new insertion of alpha satellite DNA from chromosome 18 was found at a non-centromeric location but failed to function as a centromere despite certain protein bindings.
  • This case introduces a rare type of structural variation termed "alpha satellite insertion," enhancing our understanding of alpha satellite dynamics and their potential relocation to ancient centromeric regions.
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  • Dilated cardiomyopathy (DCM) is a common heart problem that can lead to heart failure, often caused by certain genetic mutations.
  • The study looked for hidden genetic mistakes in specific genes to see if they could be causing DCM in some patients.
  • They found that these hidden mutations likely don't cause a lot of DCM cases, meaning that testing for them might not help doctors find new reasons for heart problems in DCM patients.
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Objective: Primary hypobetalipoproteinemia is characterized by LDL-C (low-density lipoprotein cholesterol) concentrations below the fifth percentile. Primary hypobetalipoproteinemia mostly results from heterozygous mutations in the (apolipoprotein B) and genes, and a polygenic origin is hypothesized in the remaining cases. Hypobetalipoproteinemia patients present an increased risk of nonalcoholic fatty liver disease and steatohepatitis.

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The aim of this study was to provide an efficient tool: reliable, able to increase the molecular diagnosis performance, to facilitate the detection of copy number variants (CNV), to assess genetic risk scores (wGRS) and to offer the opportunity to explore candidate genes. Custom SeqCap EZ libraries, NextSeq500 sequencing and a homemade pipeline enable the analysis of 311 dyslipidemia-related genes. In the training group (48 DNA from patients with a well-established molecular diagnosis), this next-generation sequencing (NGS) workflow showed an analytical sensitivity >99% (n = 532 variants) without any false negative including a partial deletion of one exon.

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Background: Systemic lupus erythematosus (SLE) is a rare immunological disorder and genetic factors are considered important in its causation. Monogenic lupus has been associated with around 30 genotypes in humans and 60 in mice, while genome-wide association studies have identified more than 90 risk loci. We aimed to analyse the contribution of rare and predicted pathogenic gene variants in a population of unselected cases of childhood-onset SLE.

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  • Structural variants (SVs), like copy number variants (CNVs) and balanced chromosome rearrangements (ABCRs), are often difficult to detect using traditional short-read sequencing methods due to repetitive sequences, which makes long-read technologies like 10X Genomics' Chromium an interesting alternative.* -
  • In a study involving 13 patients, short-read sequencing successfully identified known SVs in 10 of them, while the linked-read technology also detected 10 SVs, including one additional variant missed by the short-read method.* -
  • Ultimately, the study concluded that the 10X Genomics linked-read strategy did not significantly enhance the detection or characterization of SVs compared to the short-read sequencing approach.*
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  • Hypertrophic cardiomyopathy (HCM) is a heart problem that can be passed down through families, affecting about 1 in 500 people.
  • Researchers wanted to find new ways to diagnose HCM by looking for hidden mutations in a gene called MYBPC3, especially in patients who didn't have clear problems found before.
  • In their study, they found important new mutations in 6.5% of patients, showing that looking for these hidden changes is really important for figuring out HCM better.
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  • Balanced chromosomal rearrangements often have no noticeable effects on individuals, but they can sometimes lead to abnormal traits, as seen in a case study of a 4-year-old boy with supravalvular aortic stenosis (SVAS).
  • The boy's karyotype revealed a balanced paracentric inversion on chromosome 7, and advanced sequencing techniques identified a disruption in a specific gene that caused his condition.
  • This case emphasizes the limitations of common diagnostic tests like array CGH, suggesting that future use of whole-genome sequencing (WGS) should involve analyzing structural variations to better detect rare genetic disruptions.
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  • * Rare genetic abnormalities like duplications and rearrangements of HOXD genes can lead to mesomelic dysplasia, a condition affecting upper and lower limb formation.
  • * In two families with upper limb dysplasia, researchers discovered microduplications affecting HOXD genes, which likely disrupt gene regulation and contribute to the disease phenotype by misplacing a regulatory influence on specific HOXD genes.
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  • Chromoanagenesis involves complex genomic rearrangements with multiple breaks in one or more chromosomes, leading to serious genetic disorders.
  • In a case study, a girl exhibited various developmental issues and a karyotype showed structural abnormalities on chromosome 14, suggesting chromoanagenesis occurred.
  • Genome sequencing helped identify 50 breakpoints interrupting 10 genes, including the YY1 gene, which is associated with the girl's symptoms, improving understanding of genotype-phenotype relationships.
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  • Human retrocopies, which are RNA transcripts that use specific genetic machinery for retrotransposition, can impact genomic testing accuracy due to potential misinterpretation by next-generation sequencing (NGS) techniques.
  • In a study, eight cases of retrocopies were identified during diagnostic NGS analyses, revealing discrepancies in how read alignments indicated copy number gains and intron-exon junctions were affected.
  • The authors stress the importance of recognizing retrocopies during genetic testing to improve detection strategies and avoid common misunderstandings in genomic analysis.
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  • - Williams Beuren syndrome (WBS) is a genetic condition characterized by intellectual disabilities and a social disposition that contrasts with Autism Spectrum Disorder (ASD), yet WBS patients have a higher prevalence of ASD than the general population.
  • - A study analyzed genetic data from six WBS patients with ASD, revealing that the conditions couldn’t be attributed to significant chromosomal deletions, pathogenic gene variants, or clear genetic diagnoses linked to known ID/ASD conditions.
  • - The findings suggest that social behaviors in WBS are more complex than simply being "overfriendly"; they often overlap with ASD traits, indicating a need for further research on the diverse causes of ASD in WBS patients.
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Article Synopsis
  • A study investigated balanced chromosomal rearrangements in patients with intellectual disabilities and congenital anomalies using next-generation sequencing to identify breakpoints at a molecular level.
  • The research characterized breakpoints in 55 patients, revealing that 89% of chromosomal rearrangements were detected, with non-homologous end-joining identified as the primary repair mechanism.
  • The study found that a diagnosis could be established in about 44.8% of patients, revealing disruptions in genes and suggesting that paired-end whole genome sequencing is effective for clinical applications in structural variation analysis.
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Background: Sarcoidosis (OMIM 181000) is a multi-systemic granulomatous disorder of unknown origin. Despite multiple genome-wide association (GWAS) studies, no major pathogenic pathways have been identified to date. To find out relevant sarcoidosis predisposing genes, we searched for de novo and recessive mutations in 3 young probands with sarcoidosis and their healthy parents using a whole-exome sequencing (WES) methodology.

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Background: The whitefly Bemisia tabaci is an important agricultural pest with global distribution. This phloem-sap feeder harbors a primary symbiont, "Candidatus Portiera aleyrodidarum", which compensates for the deficient nutritional composition of its food sources, and a variety of secondary symbionts. Interestingly, all of these secondary symbionts are found in co-localization with the primary symbiont within the same bacteriocytes, which should favor the evolution of strong interactions between symbionts.

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Bacterial endosymbiosis is an important evolutionary process in insects, which can harbor both obligate and facultative symbionts. The evolution of these symbionts is driven by evolutionary convergence, and they exhibit among the tiniest genomes in prokaryotes. The large host spectrum of facultative symbionts and the high diversity of strategies they use to infect new hosts probably impact the evolution of their genome and explain why they undergo less severe genomic erosion than obligate symbionts.

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Many insects harbor inherited bacterial endosymbionts. Although some of them are not strictly essential and are considered facultative, they can be a key to host survival under specific environmental conditions, such as parasitoid attacks, climate changes, or insecticide pressures. The whitefly Bemisia tabaci is at the top of the list of organisms inflicting agricultural damage and outbreaks, and changes in its distribution may be associated to global warming.

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