👤 Pierre-Antoine Rollat-Farnier

Obesity is a multifactorial disease with a strong genetic component. It is imperative to enhance the identification of genetic variations in their early and severe manifestations in order to facilitate the development of personalized therapeutic strategies, informed clinical care, and the facilitation of genetic counseling. The objective of the study was to provide a comprehensive description of rare variations identified by next generation sequencing of a panel of genes. From 2018 to 2023, a panel of 22 genes was genotyped in 1066 probands (499 children and 567 adults) with severe early-onset obesity. The genetic study led to a molecular diagnosis in 34 probands (3.2%) and revealed variants of unknown significance (VUS) in 10.3% of cases. In the pediatric cohort, a genetic diagnosis was established in 19 probands (3.8%) and a VUS was identified in 67 (13.4%). A total of 152 rare single-nucleotides variants (SNVs) were identified, of which 34 were classified as pathogenic, predominantly within the Early genetic screening in severe obesity provides valuable diagnostic insights and identifies candidates for personalized treatment. The integration of genetics into clinical practice is imperative for the enhancement of care pathways and the facilitation of targeted therapeutic strategies. Show less

Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiomyopathy, historically believed to affect 1 of 500 people. MYBPC3 pathogenic variations are the most frequent cause of familial HCM and more than 90% of them introduce a premature termination codon. The current study aims to determine the prevalence of deep intronic MYBPC3 pathogenic variations that could lead to splice mutations. To improve molecular diagnosis, a next-generation sequencing (NGS) workflow based on whole MYBPC3 sequencing of a cohort of 93 HCM patients, for whom no putatively causative point mutations were identified after NGS sequencing of a panel of 48 cardiomyopathy-causing genes, was performed. Our approach led us to reconsider the molecular diagnosis of six patients of the cohort (6.5%). These HCM probands were carriers of either a new large MYBPC3 rearrangement or splice intronic variations (five cases). Four pathogenic intronic variations, including three novel ones, were detected. Among them, the prevalence of one of them (NM₀₀₀₂₅₆.3:c.1927+ 600 C>T) was estimated at about 0.35% by the screening of 1,040 unrelated HCM individuals. This study suggests that deep MYBPC3 splice mutations account for a significant proportion of HCM cases (6.5% of this cohort). Consequently, NGS sequencing of MYBPC3 intronic sequences have to be performed systematically. Show less

Balanced chromosomal rearrangements associated with abnormal phenotype are rare events, but may be challenging for genetic counselling, since molecular characterisation of breakpoints is not performed routinely. We used next-generation sequencing to characterise breakpoints of balanced chromosomal rearrangements at the molecular level in patients with intellectual disability and/or congenital anomalies. Breakpoints were characterised by a paired-end low depth whole genome sequencing (WGS) strategy and validated by Sanger sequencing. Expression study of disrupted and neighbouring genes was performed by RT-qPCR from blood or lymphoblastoid cell line RNA. Among the 55 patients included (41 reciprocal translocations, 4 inversions, 2 insertions and 8 complex chromosomal rearrangements), we were able to detect 89% of chromosomal rearrangements (49/55). Molecular signatures at the breakpoints suggested that DNA breaks arose randomly and that there was no major influence of repeated elements. Non-homologous end-joining appeared as the main mechanism of repair (55% of rearrangements). A diagnosis could be established in 22/49 patients (44.8%), 15 by gene disruption ( Paired-end WGS is a valid strategy and may be used for structural variation characterisation in a clinical setting. Show less