ARTICLE Bi-allelic loss-of-function variants in PPFIBP1 cause a neurodevelopmental disorder with microcephaly, epilepsy, and periventricular calcifications

PPFIBP1 encodes for the liprin-β1 protein, which has been shown to play a role in neuronal outgrowth and synapse formation in Drosophila melanogaster. By exome and genome sequencing, we detected nine ultra-rare homozygous loss-of-function variants in 16 individuals from 12 unrelated families. The individuals presented with moderate to profound developmental delay, often refractory early-onset epilepsy, and progressive microcephaly. Further common clinical findings included muscular hyper- and hypotonia, spasticity, failure to thrive and short stature, feeding difficulties, impaired vision, and congenital heart defects. Neuroimaging revealed abnormalities of brain morphology with leukoencephalopathy, ventriculomegaly, cortical abnormalities, and intracranial periventricular calcifications as major features. In a fetus with intracranial calcifications, we identified a rare homozygous missense variant that by structural analysis was predicted to disturb the topology of the SAM domain region that is essential for protein-protein interaction. For further insight into the effects of PPFIBP1 loss of function, we performed automated behavioral phenotyping of a Caenorhabditis elegans PPFIBP1/hlb-1 knockout model, which revealed defects in spontaneous and light-induced behavior and confirmed resistance to the acetylcholinesterase inhibitor aldicarb, suggesting a defect in the neuronal presynaptic zone. In conclusion, we establish bi-allelic loss-of-function variants in PPFIBP1 as a cause of an autosomal recessive severe neurodevelopmental disorder with early-onset epilepsy, microcephaly, and periventricular calcifications

Widening of the genetic and clinical spectrum of Lamb-Shaffer syndrome, a neurodevelopmental disorder due to SOX5 haploinsufficiency

Purpose Lamb-Shaffer syndrome (LAMSHF) is a neurodevelopmental disorder described in just over two dozen patients with heterozygous genetic alterations involving SOX5, a gene encoding a transcription factor regulating cell fate and differentiation in neurogenesis and other discrete developmental processes. The genetic alterations described so far are mainly microdeletions. The present study was aimed at increasing our understanding of LAMSHF, its clinical and genetic spectrum, and the pathophysiological mechanisms involved. Methods Clinical and genetic data were collected through GeneMatcher and clinical or genetic networks for 41 novel patients harboring various types ofSOX5 alterations. Functional consequences of selected substitutions were investigated. Results Microdeletions and truncating variants occurred throughout SOX5. In contrast, most missense variants clustered in the pivotal SOX-specific high-mobility-group domain. The latter variants prevented SOX5 from binding DNA and promoting transactivation in vitro, whereas missense variants located outside the high-mobility-group domain did not. Clinical manifestations and severity varied among patients. No clear genotype-phenotype correlations were found, except that missense variants outside the high-mobility-group domain were generally better tolerated. Conclusions This study extends the clinical and genetic spectrum associated with LAMSHF and consolidates evidence that SOX5 haploinsufficiency leads to variable degrees of intellectual disability, language delay, and other clinical features

The "extreme phenotype approach" applied to male breast cancer allows the identification of rare variants of ATR as potential breast cancer susceptibility alleles

In oncogenetics, some patients could be considered as "extreme phenotypes", such as those with very early onset presentation or multiple primary malignancies, unusually high numbers of cancers of the same spectrum or rare cancer types in the same parental branch. For these cases, a genetic predisposition is very likely, but classical candidate gene panel analyses often and frustratingly remains negative. In the framework of the EX2TRICAN project, exploring unresolved extreme cancer phenotypes, we applied exome sequencing on rare familial cases with male breast cancer, identifying a novel pathogenic variant of ATR (p.Leu1808*). ATR has already been suspected as being a predisposing gene to breast cancer in women. We next identified 3 additional ATR variants in a cohort of both male and female with early onset and familial breast cancers (c.7762-2A>C; c.2078+1G>A; c.1A>G). Further molecular and cellular investigations showed impacts on transcripts for variants affecting splicing sites and reduction of ATR expression and phosphorylation of the ATR substrate CHEK1. This work further demonstrates the interest of an extended genetic analysis such as exome sequencing to identify very rare variants that can play a role in cancer predisposition in extreme phenotype cancer cases unexplained by classical cancer gene panels testing

Clinical practice guidelines for BRCA1 and BRCA2 genetic testing

BRCA1 and BRCA2 gene pathogenic variants account for most hereditary breast cancer and are increasingly used to determine eligibility for PARP inhibitor (PARPi) therapy of BRCA-related cancer. Because issues of BRCA testing in clinical practice now overlap with both preventive and therapeutic management, updated and comprehensive practice guidelines for BRCA genotyping are needed. The integrative recommendations for BRCA testing presented here aim to (1) identify individuals who may benefit from genetic counselling and risk-reducing strategies; (2) update germline and tumour-testing indications for PARPi-approved therapies; (3) provide testing recommendations for personalised management of early and metastatic breast cancer; and (4) address the issues of rapid process and tumour analysis. An international group of experts, including geneticists, medical and surgical oncologists, pathologists, ethicists and patient representatives, was commissioned by the French Society of Predictive and Personalised Medicine (SFMPP). The group followed a methodology based on specific formal guidelines development, including (1) evaluating the likelihood of BRCAm from a combined systematic review of the literature, risk assessment models and expert quotations, and (2) therapeutic values of BRCAm status for PARPi therapy in BRCA-related cancer and for management of early and advanced breast cancer. These international guidelines may help clinicians comprehensively update and standardise BRCA testing practices

De novo TBR1 variants cause a neurocognitive phenotype with ID and autistic traits:report of 25 new individuals and review of the literature

TBR1, a T-box transcription factor expressed in the cerebral cortex, regulates the expression of several candidate genes for autism spectrum disorders (ASD). Although TBR1 has been reported as a high-confidence risk gene for ASD and intellectual disability (ID) in functional and clinical reports since 2011, TBR1 has only recently been recorded as a human disease gene in the OMIM database. Currently, the neurodevelopmental disorders and structural brain anomalies associated with TBR1 variants are not well characterized. Through international data sharing, we collected data from 25 unreported individuals and compared them with data from the literature. We evaluated structural brain anomalies in seven individuals by analysis of MRI images, and compared these with anomalies observed in TBR1 mutant mice. The phenotype included ID in all individuals, associated to autistic traits in 76% of them. No recognizable facial phenotype could be identified. MRI analysis revealed a reduction of the anterior commissure and suggested new features including dysplastic hippocampus and subtle neocortical dysgenesis. This report supports the role of TBR1 in ID associated with autistic traits and suggests new structural brain malformations in humans. We hope this work will help geneticists to interpret TBR1 variants and diagnose ASD probands

Copy number variants as modifiers of breast cancer risk for BRCA1/BRCA2 pathogenic variant carriers

The risk of germline copy number variants (CNVs) in BRCA1 and BRCA2 pathogenic variant carriers in breast cancer is assessed, with CNVs overlapping SULT1A1 decreasing breast cancer risk in BRCA1 carriers.The contribution of germline copy number variants (CNVs) to risk of developing cancer in individuals with pathogenic BRCA1 or BRCA2 variants remains relatively unknown. We conducted the largest genome-wide analysis of CNVs in 15,342 BRCA1 and 10,740 BRCA2 pathogenic variant carriers. We used these results to prioritise a candidate breast cancer risk-modifier gene for laboratory analysis and biological validation. Notably, the HR for deletions in BRCA1 suggested an elevated breast cancer risk estimate (hazard ratio (HR) = 1.21), 95% confidence interval (95% CI = 1.09-1.35) compared with non-CNV pathogenic variants. In contrast, deletions overlapping SULT1A1 suggested a decreased breast cancer risk (HR = 0.73, 95% CI 0.59-0.91) in BRCA1 pathogenic variant carriers. Functional analyses of SULT1A1 showed that reduced mRNA expression in pathogenic BRCA1 variant cells was associated with reduced cellular proliferation and reduced DNA damage after treatment with DNA damaging agents. These data provide evidence that deleterious variants in BRCA1 plus SULT1A1 deletions contribute to variable breast cancer risk in BRCA1 carriers.Peer reviewe

A Solve-RD ClinVar-based reanalysis of 1522 index cases from ERN-ITHACA reveals common pitfalls and misinterpretations in exome sequencing

Purpose Within the Solve-RD project (https://solve-rd.eu/), the European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies aimed to investigate whether a reanalysis of exomes from unsolved cases based on ClinVar annotations could establish additional diagnoses. We present the results of the “ClinVar low-hanging fruit” reanalysis, reasons for the failure of previous analyses, and lessons learned. Methods Data from the first 3576 exomes (1522 probands and 2054 relatives) collected from European Reference Network for Intellectual disability, TeleHealth, Autism and Congenital Anomalies was reanalyzed by the Solve-RD consortium by evaluating for the presence of single-nucleotide variant, and small insertions and deletions already reported as (likely) pathogenic in ClinVar. Variants were filtered according to frequency, genotype, and mode of inheritance and reinterpreted. Results We identified causal variants in 59 cases (3.9%), 50 of them also raised by other approaches and 9 leading to new diagnoses, highlighting interpretation challenges: variants in genes not known to be involved in human disease at the time of the first analysis, misleading genotypes, or variants undetected by local pipelines (variants in off-target regions, low quality filters, low allelic balance, or high frequency). Conclusion The “ClinVar low-hanging fruit” analysis represents an effective, fast, and easy approach to recover causal variants from exome sequencing data, herewith contributing to the reduction of the diagnostic deadlock

Genome-wide exploration of congenital anomalies of rare origin

Titre : Exploration pangénomique des anomalies du développement de causes raresMots clés : anomalies du développement, séquençage d’exome, paratage de données, phénotypage inverseLes anomalies du développement sont un groupe de maladies hétérogènes, tant sur le plan clinique que moléculaire. Elles comprennent plus de 3.000 maladies monogéniques, mais seulement un tiers d’entre elles ont actuellement une cause moléculaire connue. Bien que les progrès des techniques de séquençage aient permis d’identifier des centaines de nouveaux gènes ces dernières années, de nombreux patients restent encore sans diagnostic. La grande hétérogénéité génétique de ces pathologies met à l’épreuve la démarche diagnostique classique comprenant une expertise clinique, une étude pan-génomique par puce à ADN et/ou l’analyse ciblée de gènes connus et, depuis peu, le séquençage haut débit d’exome ciblé sur les gènes associés à une pathologie humaine. En attendant que le séquençage du génome soit économiquement plus accessible et l’interprétaion des ses données mieux appréhendée pour une utilisation diagnostique, nous avons choisi d’explorer de nouvelles stratégies afin d’optimiser le séquençage d’exome dans l’identification de nouvelles bases moléculaires.Le premier article a pour objectif de démontrer la faisabilité et l’efficacité de la réanalyse annuelle des données de séquençage d’exome négatif dans un cadre diagnostique. Les patients éligibles à l’étude présentaient une anomalie du développement sans cause moléculaire établie après une démarche diagnostique classique incluant une analyse chromosomique sur puce à ADN et une analyse d’exome diagnostique. Cette première étude a permis de réaliser un nombre significatif de diagnostics supplémentaires, mais aussi d’identifier des variations candidates pour lesquelles nous avons utilisé le partage international de données et l’approche de phénotypage inverse pour établir des corrélations phénotype-génotype et des cohortes de réplication génotypique et/ou phénotypique. Ces stratégies nous ont permis de remplir les critères ACMG nécessaires pour établir la pathogénicité de ces variations.Fort de cette expérience et souhaitant aller plus loin dans l’identification de nouvelles bases moléculaires pour nos patients, nous avons poursuivi cet effort de réanalyse dans un cadre de recherche. Ce travail fait l’objet du second article de cette thèse et a conduit à l’identification de 17 nouveaux gènes d’anomalies du développement. Le partage de données a conduit à l’élaboration de nombreuses collaborations internationales et de plusieurs études fonctionnelles par des équipes spécialisées.L’application de ces outils dans une forme syndromique de déficience intellectuelle ultra-rare est illustrée à travers le troisieme article. Suite à un effort collaboratif important, nous avons pu décrire de manière précise le phénotype de 25 patients jamais rapportés dans la littérature porteurs de variations pathogènes au sein du gène TBR1, gène candidat dans les troubles du spectre autistique associés à une déficience intellectuelle.Ces différents travaux démontrent l’efficacité de stratégies innovantes dans l’identification de nouvelles bases moléculaires chez les patients atteints d’anomalies du développement, à savoir la réanalyse des données d’exome, le phénotypage inverse et le partage international de données. Pour les patients et leur famille, cela permet de comprendre l’origine de leur pathologie, de mettre fin à l’errance diagnostique, de préciser le pronostic et l’évolution développementale probable, et la mise en place d’une prise en charge adaptés. Il est aussi indispensable pour fournir un conseil génétique fiable, et éventuellement proposer un diagnostic prénatal voire pré-implantatoire. Pour les généticiens, cela permet la compréhension de nouveaux processus physiopathologiques, l’élaboration de nouveaux tests diagnostiques et la découverte de nouvelles cibles thérapeutiques.Title : Genome-wide exploration of congenital anomalies of rare causesKey words : congenital anomalies, exome sequencing, data-sharing, reverse phenotypingCongenital anomalies are a group of diseases that are both clinically and molecularly heterogeneous. They include more than 3,000 monogenic diseases, but only a third of them have a known molecular cause. Although advances in sequencing techniques have identified hundreds of new genes in recent years, many patients remain undiagnosed. The vast genetic heterogeneity of these conditions challenges the conventional diagnostic approach that typically includes clinical expertise, a pan-genomic microarray study and/or targeted analysis of known genes and, recently, exome sequencing targeting the genes already associated with human disease. Until genome sequencing becomes more affordable and the interpretation of its data for diagnostic use is better perceived, we have chosen to explore new strategies to optimize the identification of new molecular bases through exome sequencing.The first article aimed to demonstrate the feasibility and effectiveness of annual reanalysis of negative exome sequencing data in a diagnostic setting. Patients eligible for the study had developmental anomalies, but no molecular cause was established after a standard diagnostic procedure including DNA chromosome analysis and diagnostic exome analysis. This first study yielded a significant number of additional diagnoses, but also identified candidate variants for which we used international data-sharing and reverse phenotyping to establish cohorts of genotypic and/or phenotypic replication and genotype-phenotype correlations. These strategies allowed us to meet the ACMG criteria necessary to establish the pathogenicity of these variants.With this experience, and because we wished to go further in identifying new molecular bases for our patients, we continued the reanalysis project within a research framework. This was the focus of the second article of this thesis. The reanalysis project led to the identification of 17 new genes associated with congenital anomalies. Data-sharing has led to the development of numerous international collaborations and functional studies carried out by specialized teams.The third article illustrated the application of these tools in a syndromic form of ultra-rare intellectual disability. Following a considerable collaborative effort, we were able to accurately describe the phenotype of 25 unreported patients in the literature with pathogenic variants in the TBR1 gene, a candidate gene in autism spectrum disorders associated to intellectual disability.These various studies demonstrate how innovative strategies can be effective for identifying new molecular bases in patients with congenital anomalies. These strategies include exome data reanalysis, reverse phenotyping, and international data-sharing. For patients and their families, knowing the molecular basis of the disease makes it possible to understand the origin of the condition and to put an end to diagnostic wandering. In addition, they are able to learn more about the prognosis and developmental progression, and they can obtain appropriate care management. This information is also essential for reliable genetic counseling, and may offer the possibility of prenatal or even pre-implantation diagnosis. These new diagnoses also give geneticists a chance to understand new physiopathological processes, to develop new diagnostic tests and even to discover new therapeutic targets