Publications by authors named "Joelle Roume"

43 Publications

Clinical and neuroimaging findings in 33 patients with MCAP syndrome: A survey to evaluate relevant endpoints for future clinical trials.

Clin Genet 2021 May 20;99(5):650-661. Epub 2021 Jan 20.

Centre de Référence Anomalies du Développement et Syndromes Malformatifs, FHU TRANSLAD, Hôpital d'Enfants, CHU Dijon, Dijon, France.

Megalencephaly-CApillary malformation-Polymicrogyria (MCAP) syndrome results from somatic mosaic gain-of-function variants in PIK3CA. Main features are macrocephaly, somatic overgrowth, cutaneous vascular malformations, connective tissue dysplasia, neurodevelopmental delay, and brain anomalies. The objectives of this study were to describe the clinical and radiological features of MCAP, to suggest relevant clinical endpoints applicable in future trials of targeted drug therapy. Based on a French collaboration, we collected clinical features of 33 patients (21 females, 12 males, median age of 9.9 years) with MCAP carrying mosaic PIK3CA pathogenic variants. MRI images were reviewed for 21 patients. The main clinical features reported were macrocephaly at birth (20/31), postnatal macrocephaly (31/32), body/facial asymmetry (21/33), cutaneous capillary malformations (naevus flammeus 28/33, cutis marmorata 17/33). Intellectual disability was present in 15 patients. Among the MRI images reviewed, the neuroimaging findings were megalencephaly (20/21), thickening of corpus callosum (16/21), Chiari malformation (12/21), ventriculomegaly/hydrocephaly (10/21), cerebral asymmetry (6/21) and polymicrogyria (2/21). This study confirms the main known clinical features that defines MCAP syndrome. Taking into account the phenotypic heterogeneity in MCAP patients, in the context of emerging clinical trials, we suggest that patients should be evaluated based on the main neurocognitive expression on each patient.
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http://dx.doi.org/10.1111/cge.13918DOI Listing
May 2021

Growth charts in Kabuki syndrome 1.

Am J Med Genet A 2020 03 26;182(3):446-453. Epub 2019 Dec 26.

Service de Génétique, Hôpital Saint Pierre, GH Sud Réunion, Ile de la Réunion, Saint Pierre, France.

Kabuki syndrome (KS, KS1: OMIM 147920 and KS2: OMIM 300867) is caused by pathogenic variations in KMT2D or KDM6A. KS is characterized by multiple congenital anomalies and neurodevelopmental disorders. Growth restriction is frequently reported. Here we aimed to create specific growth charts for individuals with KS1, identify parameters used for size prognosis and investigate the impact of growth hormone therapy on adult height. Growth parameters and parental size were obtained for 95 KS1 individuals (41 females). Growth charts for height, weight, body mass index (BMI) and occipitofrontal circumference were generated in standard deviation values for the first time in KS1. Statural growth of KS1 individuals was compared to parental target size. According to the charts, height, weight, BMI, and occipitofrontal circumference were lower for KS1 individuals than the normative French population. For males and females, the mean growth of KS1 individuals was -2 and -1.8 SD of their parental target size, respectively. Growth hormone therapy did not increase size beyond the predicted size. This study, from the largest cohort available, proposes growth charts for widespread use in the management of KS1, especially for size prognosis and screening of other diseases responsible for growth impairment beyond a calculated specific target size.
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http://dx.doi.org/10.1002/ajmg.a.61462DOI Listing
March 2020

Mutations in IFT80 cause SRPS Type IV. Report of two families and review.

Am J Med Genet A 2019 04 14;179(4):639-644. Epub 2019 Feb 14.

Reference Center for Skeletal Dysplasia, AP-HP, Necker-Enfants Malades Hospital, Paris, France.

We report novel causative mutations in the IFT80 gene identified in four fetuses from two unrelated families with Beemer-Langer syndrome (BLS) or BLS-like phenotypes. We discuss the implication of the IFT80 gene in ciliopathies, and its diagnostic value for BLS among other SRPS.
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http://dx.doi.org/10.1002/ajmg.a.61050DOI Listing
April 2019

Integrated clinical and omics approach to rare diseases: novel genes and oligogenic inheritance in holoprosencephaly.

Brain 2019 01;142(1):35-49

Univ Rennes, CNRS, IGDR (Institut de génétique et développement de Rennes) - UMR 6290, F-35000 Rennes, France.

Holoprosencephaly is a pathology of forebrain development characterized by high phenotypic heterogeneity. The disease presents with various clinical manifestations at the cerebral or facial levels. Several genes have been implicated in holoprosencephaly but its genetic basis remains unclear: different transmission patterns have been described including autosomal dominant, recessive and digenic inheritance. Conventional molecular testing approaches result in a very low diagnostic yield and most cases remain unsolved. In our study, we address the possibility that genetically unsolved cases of holoprosencephaly present an oligogenic origin and result from combined inherited mutations in several genes. Twenty-six unrelated families, for whom no genetic cause of holoprosencephaly could be identified in clinical settings [whole exome sequencing and comparative genomic hybridization (CGH)-array analyses], were reanalysed under the hypothesis of oligogenic inheritance. Standard variant analysis was improved with a gene prioritization strategy based on clinical ontologies and gene co-expression networks. Clinical phenotyping and exploration of cross-species similarities were further performed on a family-by-family basis. Statistical validation was performed on 248 ancestrally similar control trios provided by the Genome of the Netherlands project and on 574 ancestrally matched controls provided by the French Exome Project. Variants of clinical interest were identified in 180 genes significantly associated with key pathways of forebrain development including sonic hedgehog (SHH) and primary cilia. Oligogenic events were observed in 10 families and involved both known and novel holoprosencephaly genes including recurrently mutated FAT1, NDST1, COL2A1 and SCUBE2. The incidence of oligogenic combinations was significantly higher in holoprosencephaly patients compared to two control populations (P < 10-9). We also show that depending on the affected genes, patients present with particular clinical features. This study reports novel disease genes and supports oligogenicity as clinically relevant model in holoprosencephaly. It also highlights key roles of SHH signalling and primary cilia in forebrain development. We hypothesize that distinction between different clinical manifestations of holoprosencephaly lies in the degree of overall functional impact on SHH signalling. Finally, we underline that integrating clinical phenotyping in genetic studies is a powerful tool to specify the clinical relevance of certain mutations.
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http://dx.doi.org/10.1093/brain/awy290DOI Listing
January 2019

Loss-of-function mutations in KIF14 cause severe microcephaly and kidney development defects in humans and zebrafish.

Hum Mol Genet 2019 03;28(5):778-795

Laboratory of Hereditary Kidney Diseases, INSERM UMR 1163, Imagine Institute, Paris, France.

Mutations in KIF14 have previously been associated with either severe, isolated or syndromic microcephaly with renal hypodysplasia (RHD). Syndromic microcephaly-RHD was strongly reminiscent of clinical ciliopathies, relating to defects of the primary cilium, a signalling organelle present on the surface of many quiescent cells. KIF14 encodes a mitotic kinesin, which plays a key role at the midbody during cytokinesis and has not previously been shown to be involved in cilia-related functions. Here, we analysed four families with fetuses presenting with the syndromic form and harbouring biallelic variants in KIF14. Our functional analyses showed that the identified variants severely impact the activity of KIF14 and likely correspond to loss-of-function mutations. Analysis in human fetal tissues further revealed the accumulation of KIF14-positive midbody remnants in the lumen of ureteric bud tips indicating a shared function of KIF14 during brain and kidney development. Subsequently, analysis of a kif14 mutant zebrafish line showed a conserved role for this mitotic kinesin. Interestingly, ciliopathy-associated phenotypes were also present in mutant embryos, supporting a potential direct or indirect role for KIF14 at cilia. However, our in vitro and in vivo analyses did not provide evidence of a direct role for KIF14 in ciliogenesis and suggested that loss of kif14 causes ciliopathy-like phenotypes through an accumulation of mitotic cells in ciliated tissues. Altogether, our results demonstrate that KIF14 mutations result in a severe syndrome associating microcephaly and RHD through its conserved function in cytokinesis during kidney and brain development.
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http://dx.doi.org/10.1093/hmg/ddy381DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6381319PMC
March 2019

Correction: IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 Aug;21(8):1897-1898

APHP, Service de genetique medicale, Necker- Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

This Article was originally published under Nature Research's License to Publish, but has now been made available under a CC BY 4.0 license. The PDF and HTML versions of the Article have been modified accordingly.
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http://dx.doi.org/10.1038/s41436-018-0327-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608434PMC
August 2019

IQSEC2-related encephalopathy in males and females: a comparative study including 37 novel patients.

Genet Med 2019 04 12;21(4):837-849. Epub 2018 Sep 12.

APHP, Service de genetique medicale, Necker-Enfants Malades Hospital, Imagine Institute, Paris Descartes University, Paris, France.

Purpose: Variants in IQSEC2, escaping X inactivation, cause X-linked intellectual disability with frequent epilepsy in males and females. We aimed to investigate sex-specific differences.

Methods: We collected the data of 37 unpublished patients (18 males and 19 females) with IQSEC2 pathogenic variants and 5 individuals with variants of unknown significance and reviewed published variants. We compared variant types and phenotypes in males and females and performed an analysis of IQSEC2 isoforms.

Results: IQSEC2 pathogenic variants mainly led to premature truncation and were scattered throughout the longest brain-specific isoform, encoding the synaptic IQSEC2/BRAG1 protein. Variants occurred de novo in females but were either de novo (2/3) or inherited (1/3) in males, with missense variants being predominantly inherited. Developmental delay and intellectual disability were overall more severe in males than in females. Likewise, seizures were more frequently observed and intractable, and started earlier in males than in females. No correlation was observed between the age at seizure onset and severity of intellectual disability or resistance to antiepileptic treatments.

Conclusion: This study provides a comprehensive overview of IQSEC2-related encephalopathy in males and females, and suggests that an accurate dosage of IQSEC2 at the synapse is crucial during normal brain development.
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http://dx.doi.org/10.1038/s41436-018-0268-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6752297PMC
April 2019

New GJA8 variants and phenotypes highlight its critical role in a broad spectrum of eye anomalies.

Hum Genet 2019 Sep 20;138(8-9):1027-1042. Epub 2018 Feb 20.

Genetics Service, Instituto de Investigación Sanitaria-Fundación Jiménez Díaz University Hospital, Universidad Autónoma de Madrid (IIS-FJD, UAM), Madrid, Spain.

GJA8 encodes connexin 50 (Cx50), a transmembrane protein involved in the formation of lens gap junctions. GJA8 mutations have been linked to early onset cataracts in humans and animal models. In mice, missense mutations and homozygous Gja8 deletions lead to smaller lenses and microphthalmia in addition to cataract, suggesting that Gja8 may play a role in both lens development and ocular growth. Following screening of GJA8 in a cohort of 426 individuals with severe congenital eye anomalies, primarily anophthalmia, microphthalmia and coloboma, we identified four known [p.(Thr39Arg), p.(Trp45Leu), p.(Asp51Asn), and p.(Gly94Arg)] and two novel [p.(Phe70Leu) and p.(Val97Gly)] likely pathogenic variants in seven families. Five of these co-segregated with cataracts and microphthalmia, whereas the variant p.(Gly94Arg) was identified in an individual with congenital aphakia, sclerocornea, microphthalmia and coloboma. Four missense variants of unknown or unlikely clinical significance were also identified. Furthermore, the screening of GJA8 structural variants in a subgroup of 188 individuals identified heterozygous 1q21 microdeletions in five families with coloboma and other ocular and/or extraocular findings. However, the exact genotype-phenotype correlation of these structural variants remains to be established. Our data expand the spectrum of GJA8 variants and associated phenotypes, confirming the importance of this gene in early eye development.
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http://dx.doi.org/10.1007/s00439-018-1875-2DOI Listing
September 2019

Diagnostic strategy in segmentation defect of the vertebrae: a retrospective study of 73 patients.

J Med Genet 2018 Jun 19;55(6):422-429. Epub 2018 Feb 19.

Service de Génétique, Hôpital de Mulhouse, Mulhouse, France.

Background: Segmentation defects of the vertebrae (SDV) are non-specific features found in various syndromes. The molecular bases of SDV are not fully elucidated due to the wide range of phenotypes and classification issues. The genes involved are in the Notch signalling pathway, which is a key system in somitogenesis. Here we report on mutations identified in a diagnosis cohort of SDV. We focused on spondylocostal dysostosis (SCD) and the phenotype of these patients in order to establish a diagnostic strategy when confronted with SDV.

Patients And Methods: We used DNA samples from a cohort of 73 patients and performed targeted sequencing of the five known SCD-causing genes (, , , and ) in the first 48 patients and whole-exome sequencing (WES) in 28 relevant patients.

Results: Ten diagnoses, including four biallelic variants in , two biallelic variants in and , and one in and , were made with the gene panel, and two diagnoses, including biallelic variants in and one variant in were made by WES. The diagnostic yield of the gene panel was 10/73 (13.7%) in the global cohort but 8/10 (80%) in the subgroup meeting the SCD criteria; the diagnostic yield of WES was 2/28 (8%).

Conclusion: After negative array CGH, targeted sequencing of the five known SCD genes should only be performed in patients who meet the diagnostic criteria of SCD. The low proportion of candidate genes identified by WES in our cohort suggests the need to consider more complex genetic architectures in cases of SDV.
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http://dx.doi.org/10.1136/jmedgenet-2017-104939DOI Listing
June 2018

Mutations in GREB1L Cause Bilateral Kidney Agenesis in Humans and Mice.

Am J Hum Genet 2017 Nov;101(5):803-814

Laboratory of Hereditary Kidney Diseases, INSERM UMR 1163, Imagine Institute, 75015 Paris, France; Paris Descartes-Sorbonne Paris Cité University, Imagine Institute, 75015 Paris, France.

Congenital anomalies of the kidney and urinary tract (CAKUT) constitute a major cause of chronic kidney disease in children and 20% of prenatally detected anomalies. CAKUT encompass a spectrum of developmental kidney defects, including renal agenesis, hypoplasia, and cystic and non-cystic dysplasia. More than 50 genes have been reported as mutated in CAKUT-affected case subjects. However, the pathophysiological mechanisms leading to bilateral kidney agenesis (BKA) remain largely elusive. Whole-exome or targeted exome sequencing of 183 unrelated familial and/or severe CAKUT-affected case subjects, including 54 fetuses with BKA, led to the identification of 16 heterozygous variants in GREB1L (growth regulation by estrogen in breast cancer 1-like), a gene reported as a target of retinoic acid signaling. Four loss-of-function and 12 damaging missense variants, 14 being absent from GnomAD, were identified. Twelve of them were present in familial or simplex BKA-affected case subjects. Female BKA-affected fetuses also displayed uterus agenesis. We demonstrated a significant association between GREB1L variants and BKA. By in situ hybridization, we showed expression of Greb1l in the nephrogenic zone in developing mouse kidney. We generated a Greb1l knock-out mouse model by CRISPR-Cas9. Analysis at E13.5 revealed lack of kidneys and genital tract anomalies in male and female Greb1l embryos and a slight decrease in ureteric bud branching in Greb1l embryos. We showed that Greb1l invalidation in mIMCD3 cells affected tubulomorphogenesis in 3D-collagen culture, a phenotype rescued by expression of the wild-type human protein. This demonstrates that GREB1L plays a major role in early metanephros and genital development in mice and humans.
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http://dx.doi.org/10.1016/j.ajhg.2017.09.026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5673669PMC
November 2017

Targeted Exome Sequencing Identifies as Involved in Monogenic Congenital Anomalies of the Kidney and Urinary Tract.

J Am Soc Nephrol 2017 Oct 31;28(10):2901-2914. Epub 2017 May 31.

Institut National de la Santé et de la Recherche Médicale Unité Mixte de Recherche 1163, Laboratory of Hereditary Kidney Diseases,

Congenital anomalies of the kidney and urinary tract (CAKUT) occur in three to six of 1000 live births, represent about 20% of the prenatally detected anomalies, and constitute the main cause of CKD in children. These disorders are phenotypically and genetically heterogeneous. Monogenic causes of CAKUT in humans and mice have been identified. However, despite high-throughput sequencing studies, the cause of the disease remains unknown in most patients, and several studies support more complex inheritance and the role of environmental factors and/or epigenetics in the pathophysiology of CAKUT. Here, we report the targeted exome sequencing of 330 genes, including genes known to be involved in CAKUT and candidate genes, in a cohort of 204 unrelated patients with CAKUT; 45% of the patients were severe fetal cases. We identified pathogenic mutations in 36 of 204 (17.6%) patients. These mutations included five heterozygous loss of function mutations/deletions in the PBX homeobox 1 gene (), a gene known to have a crucial role in kidney development. In contrast, the frequency of and variants recently reported as pathogenic in CAKUT did not indicate causality. These findings suggest that is involved in monogenic CAKUT in humans and call into question the role of some gene variants recently reported as pathogenic in CAKUT. Targeted exome sequencing also proved to be an efficient and cost-effective strategy to identify pathogenic mutations and deletions in known CAKUT genes.
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http://dx.doi.org/10.1681/ASN.2017010043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619971PMC
October 2017

Genetic and phenotypic dissection of 1q43q44 microdeletion syndrome and neurodevelopmental phenotypes associated with mutations in ZBTB18 and HNRNPU.

Hum Genet 2017 04 10;136(4):463-479. Epub 2017 Mar 10.

Institut de Génétique Médicale, CHRU de Lille, Lille, France.

Subtelomeric 1q43q44 microdeletions cause a syndrome associating intellectual disability, microcephaly, seizures and anomalies of the corpus callosum. Despite several previous studies assessing genotype-phenotype correlations, the contribution of genes located in this region to the specific features of this syndrome remains uncertain. Among those, three genes, AKT3, HNRNPU and ZBTB18 are highly expressed in the brain and point mutations in these genes have been recently identified in children with neurodevelopmental phenotypes. In this study, we report the clinical and molecular data from 17 patients with 1q43q44 microdeletions, four with ZBTB18 mutations and seven with HNRNPU mutations, and review additional data from 37 previously published patients with 1q43q44 microdeletions. We compare clinical data of patients with 1q43q44 microdeletions with those of patients with point mutations in HNRNPU and ZBTB18 to assess the contribution of each gene as well as the possibility of epistasis between genes. Our study demonstrates that AKT3 haploinsufficiency is the main driver for microcephaly, whereas HNRNPU alteration mostly drives epilepsy and determines the degree of intellectual disability. ZBTB18 deletions or mutations are associated with variable corpus callosum anomalies with an incomplete penetrance. ZBTB18 may also contribute to microcephaly and HNRNPU to thin corpus callosum, but with a lower penetrance. Co-deletion of contiguous genes has additive effects. Our results confirm and refine the complex genotype-phenotype correlations existing in the 1qter microdeletion syndrome and define more precisely the neurodevelopmental phenotypes associated with genetic alterations of AKT3, ZBTB18 and HNRNPU in humans.
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http://dx.doi.org/10.1007/s00439-017-1772-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5360844PMC
April 2017

Type 0 Spinal Muscular Atrophy: Further Delineation of Prenatal and Postnatal Features in 16 Patients.

J Neuromuscul Dis 2016 11;3(4):487-495

Department of Genetics, Normandy Center for Medical Genomics and Personalized Medicine, Rouen University Hospital, Rouen, France.

Background: Spinal muscular atrophy (SMA) is caused by homozygous inactivation of the SMN1 gene. The SMN2 copy number modulates the severity of SMA. The 0SMN1/1SMN2 genotype, the most severe genotype compatible with life, is expected to be associated with the most severe form of the disease, called type 0 SMA, defined by prenatal onset.

Objective: The aim of the study was to review clinical features and prenatal manifestations in this rare SMA subtype.

Methods: SMA patients with the 0SMN1/1SMN2 genotype were retrospectively collected using the UMD-SMN1 France database.

Results: Data from 16 patients were reviewed. These 16 patients displayed type 0 SMA. At birth, a vast majority had profound hypotonia, severe muscle weakness, severe respiratory distress, and cranial nerves involvement (inability to suck/swallow, facial muscles weakness). They showed characteristics of fetal akinesia deformation sequence and congenital heart defects. Recurrent episodes of bradycardia were observed. Death occurred within the first month. At prenatal stage, decreased fetal movements were frequently reported, mostly only by mothers, in late stages of pregnancy; increased nuchal translucency was reported in about half of the cases; congenital heart defects, abnormal amniotic fluid volume, or joint contractures were occasionally reported.

Conclusion: Despite a prenatal onset attested by severity at birth and signs of fetal akinesia deformation sequence, prenatal manifestations of type 0 SMA are not specific and not constant. As illustrated by the frequent association with congenital heart defects, type 0 SMA physiopathology is not restricted to motor neuron, highlighting that SMN function is critical for organogenesis.
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http://dx.doi.org/10.3233/JND-160177DOI Listing
November 2016

Phenotype and genotype in 52 patients with Rubinstein-Taybi syndrome caused by EP300 mutations.

Am J Med Genet A 2016 12 20;170(12):3069-3082. Epub 2016 Sep 20.

Department of Molecular Medicine and Surgery, and Center for Molecular Medicine, Karolinska University Hospital, Stockholm, Sweden.

Rubinstein-Taybi syndrome (RSTS) is a developmental disorder characterized by a typical face and distal limbs abnormalities, intellectual disability, and a vast number of other features. Two genes are known to cause RSTS, CREBBP in 60% and EP300 in 8-10% of clinically diagnosed cases. Both paralogs act in chromatin remodeling and encode for transcriptional co-activators interacting with >400 proteins. Up to now 26 individuals with an EP300 mutation have been published. Here, we describe the phenotype and genotype of 42 unpublished RSTS patients carrying EP300 mutations and intragenic deletions and offer an update on another 10 patients. We compare the data to 308 individuals with CREBBP mutations. We demonstrate that EP300 mutations cause a phenotype that typically resembles the classical RSTS phenotype due to CREBBP mutations to a great extent, although most facial signs are less marked with the exception of a low-hanging columella. The limb anomalies are more similar to those in CREBBP mutated individuals except for angulation of thumbs and halluces which is very uncommon in EP300 mutated individuals. The intellectual disability is variable but typically less marked whereas the microcephaly is more common. All types of mutations occur but truncating mutations and small rearrangements are most common (86%). Missense mutations in the HAT domain are associated with a classical RSTS phenotype but otherwise no genotype-phenotype correlation is detected. Pre-eclampsia occurs in 12/52 mothers of EP300 mutated individuals versus in 2/59 mothers of CREBBP mutated individuals, making pregnancy with an EP300 mutated fetus the strongest known predictor for pre-eclampsia. © 2016 Wiley Periodicals, Inc.
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http://dx.doi.org/10.1002/ajmg.a.37940DOI Listing
December 2016

Mutational Spectrum in Holoprosencephaly Shows That FGF is a New Major Signaling Pathway.

Hum Mutat 2016 12 23;37(12):1329-1339. Epub 2016 Aug 23.

Service de Génétique Moléculaire et Génomique, CHU, Rennes, France.

Holoprosencephaly (HPE) is the most common congenital cerebral malformation in humans, characterized by impaired forebrain cleavage and midline facial anomalies. It presents a high heterogeneity, both in clinics and genetics. We have developed a novel targeted next-generation sequencing (NGS) assay and screened a cohort of 257 HPE patients. Mutations with high confidence in their deleterious effect were identified in approximately 24% of the cases and were held for diagnosis, whereas variants of uncertain significance were identified in 10% of cases. This study provides a new classification of genes that are involved in HPE. SHH, ZIC2, and SIX3 remain the top genes in term of frequency with GLI2, and are followed by FGF8 and FGFR1. The three minor HPE genes identified by our study are DLL1, DISP1, and SUFU. Here, we demonstrate that fibroblast growth factor signaling must now be considered a major pathway involved in HPE. Interestingly, several cases of double mutations were found and argue for a polygenic inheritance of HPE. Altogether, it supports that the implementation of NGS in HPE diagnosis is required to improve genetic counseling.
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http://dx.doi.org/10.1002/humu.23038DOI Listing
December 2016

Mutations in RIT1 cause Noonan syndrome with possible juvenile myelomonocytic leukemia but are not involved in acute lymphoblastic leukemia.

Eur J Hum Genet 2016 08 13;24(8):1124-31. Epub 2016 Jan 13.

Department of Genetics, Jeanne de Flandre University Hospital, Lille, France.

Noonan syndrome is a heterogeneous autosomal dominant disorder caused by mutations in at least eight genes involved in the RAS/MAPK signaling pathway. Recently, RIT1 (Ras-like without CAAX 1) has been shown to be involved in the pathogenesis of some patients. We report a series of 44 patients from 30 pedigrees (including nine multiplex families) with mutations in RIT1. These patients display a typical Noonan gestalt and facial phenotype. Among the probands, 8.7% showed postnatal growth retardation, 90% had congenital heart defects, 36% had hypertrophic cardiomyopathy (a lower incidence compared with previous report), 50% displayed speech delay and 52% had learning difficulties, but only 22% required special education. None had major skin anomalies. One child died perinatally of juvenile myelomonocytic leukemia. Compared with the canonical Noonan phenotype linked to PTPN11 mutations, patients with RIT1 mutations appear to be less severely growth retarded and more frequently affected by cardiomyopathy. Based on our experience, we estimate that RIT1 could be the cause of 5% of Noonan syndrome patients. Because mutations found constitutionally in Noonan syndrome are also found in several tumors in adulthood, we evaluated the potential contribution of RIT1 to leukemogenesis in Noonan syndrome. We screened 192 pediatric cases of acute lymphoblastic leukemias (96 B-ALL and 96 T-ALL) and 110 cases of juvenile myelomonocytic leukemias (JMML), but detected no variation in these tumoral samples, suggesting that Noonan patients with germline RIT1 mutations are not at high risk to developing JMML or ALL, and that RIT1 has at most a marginal role in these sporadic malignancies.
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http://dx.doi.org/10.1038/ejhg.2015.273DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4970687PMC
August 2016

Molecular diagnosis of hypophosphatasia and differential diagnosis by targeted Next Generation Sequencing.

Mol Genet Metab 2015 Nov 30;116(3):215-20. Epub 2015 Sep 30.

Unité de Génétique Constitutionnelle, Centre Hospitalier de Versailles, 78150 Le Chesnay, France. Electronic address:

Hypophosphatasia (HPP) is a rare inherited skeletal dysplasia due to loss of function mutations in the ALPL gene. The disease is subject to an extremely high clinical heterogeneity ranging from a perinatal lethal form to odontohypophosphatasia affecting only teeth. Up to now genetic diagnosis of HPP is performed by sequencing the ALPL gene by Sanger methodology. Osteogenesis imperfecta (OI) and campomelic dysplasia (CD) are the main differential diagnoses of severe HPP, so that in case of negative result for ALPL mutations, OI and CD genes had often to be analyzed, lengthening the time before diagnosis. We report here our 18-month experience in testing 46 patients for HPP and differential diagnosis by targeted NGS and show that this strategy is efficient and useful. We used an array including ALPL gene, genes of differential diagnosis COL1A1 and COL1A2 that represent 90% of OI cases, SOX9, responsible for CD, and 8 potentially modifier genes of HPP. Seventeen patients were found to carry a mutation in one of these genes. Among them, only 10 out of 15 cases referred for HPP carried a mutation in ALPL and 5 carried a mutation in COL1A1 or COL1A2. Interestingly, three of these patients were adults with fractures and/or low BMD. Our results indicate that HPP and OI may be easily misdiagnosed in the prenatal stage but also in adults with mild symptoms for these diseases.
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http://dx.doi.org/10.1016/j.ymgme.2015.09.010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5257278PMC
November 2015

A systematic variant screening in familial cases of congenital heart defects demonstrates the usefulness of molecular genetics in this field.

Eur J Hum Genet 2016 Feb 27;24(2):228-36. Epub 2015 May 27.

Laboratoire Cardiogénétique, Hospices Civils de Lyon, Lyon, France.

The etiology of congenital heart defect (CHD) combines environmental and genetic factors. So far, there were studies reporting on the screening of a single gene on unselected CHD or on familial cases selected for specific CHD types. Our goal was to systematically screen a proband of familial cases of CHD on a set of genetic tests to evaluate the prevalence of disease-causing variant identification. A systematic screening of GATA4, NKX2-5, ZIC3 and Multiplex ligation-dependent probe amplification (MLPA) P311 Kit was setup on the proband of 154 families with at least two cases of non-syndromic CHD. Additionally, ELN screening was performed on families with supravalvular arterial stenosis. Twenty-two variants were found, but segregation analysis confirmed unambiguously the causality of 16 variants: GATA4 (1 ×), NKX2-5 (6 ×), ZIC3 (3 ×), MLPA (2 ×) and ELN (4 ×). Therefore, this approach was able to identify the causal variant in 10.4% of familial CHD cases. This study demonstrated the existence of a de novo variant even in familial CHD cases and the impact of CHD variants on adult cardiac condition even in the absence of CHD. This study showed that the systematic screening of genetic factors is useful in familial CHD cases with up to 10.4% elucidated cases. When successful, it drastically improved genetic counseling by discovering unaffected variant carriers who are at risk of transmitting their variant and are also exposed to develop cardiac complications during adulthood thus prompting long-term cardiac follow-up. This study provides an important baseline at dawning of the next-generation sequencing era.
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http://dx.doi.org/10.1038/ejhg.2015.105DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4717196PMC
February 2016

15q11.2 microdeletion (BP1-BP2) and developmental delay, behaviour issues, epilepsy and congenital heart disease: a series of 52 patients.

Eur J Med Genet 2015 Mar 14;58(3):140-7. Epub 2015 Jan 14.

Service de génétique médicale, CHRU Montpellier, France.

Proximal region of chromosome 15 long arm is rich in duplicons that, define five breakpoints (BP) for 15q rearrangements. 15q11.2 microdeletion between BP1 and BP2 has been previously associated with developmental delay and atypical psychological patterns. This region contains four highly-conserved and non-imprinted genes: NIPA1, NIPA2, CYFIP1, TUBGCP5. Our goal was to investigate the phenotypes associated with this microdeletion in a cohort of 52 patients. This copy number variation (CNV) was prevalent in 0.8% patients presenting with developmental delay, psychological pattern issues and/or multiple congenital malformations. This was studied by array-CGH at six different French Genetic laboratories. We collected data from 52 unrelated patients (including 3 foetuses) after excluding patients with an associated genetic alteration (known CNV, aneuploidy or known monogenic disease). Out of 52 patients, mild or moderate developmental delay was observed in 68.3%, 85.4% had speech impairment and 63.4% had psychological issues such as Attention Deficit and Hyperactivity Disorder, Autistic Spectrum Disorder or Obsessive-Compulsive Disorder. Seizures were noted in 18.7% patients and associated congenital heart disease in 17.3%. Parents were analysed for abnormalities in the region in 65.4% families. Amongst these families, 'de novo' microdeletions were observed in 18.8% and 81.2% were inherited from one of the parents. Incomplete penetrance and variable expressivity were observed amongst the patients. Our results support the hypothesis that 15q11.2 (BP1-BP2) microdeletion is associated with developmental delay, abnormal behaviour, generalized epilepsy and congenital heart disease. The later feature has been rarely described. Incomplete penetrance and variability of expression demands further assessment and studies.
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http://dx.doi.org/10.1016/j.ejmg.2015.01.002DOI Listing
March 2015

Early-onset osteoarthritis, Charcot-Marie-Tooth like neuropathy, autoimmune features, multiple arterial aneurysms and dissections: an unrecognized and life threatening condition.

PLoS One 2014 7;9(5):e96387. Epub 2014 May 7.

INSERM U698, Hôpital Bichat, Paris, France; AP-HP, Hôpital Bichat, Centre de référence pour les syndromes de Marfan et apparentés, Service de Cardiologie, Paris, France; Université Denis Diderot, Paris 7, UFR de Médecine, Paris, France.

Background: Severe osteoarthritis and thoracic aortic aneurysms have recently been associated with mutations in the SMAD3 gene, but the full clinical spectrum is incompletely defined.

Methods: All SMAD3 gene mutation carriers coming to our centre and their families were investigated prospectively with a structured panel including standardized clinical workup, blood tests, total body computed tomography, joint X-rays. Electroneuromyography was performed in selected cases.

Results: Thirty-four SMAD3 gene mutation carriers coming to our centre were identified and 16 relatives were considered affected because of aortic surgery or sudden death (total 50 subjects). Aortic disease was present in 72%, complicated with aortic dissection, surgery or sudden death in 56% at a mean age of 45 years. Aneurysm or tortuosity of the neck arteries was present in 78%, other arteries were affected in 44%, including dissection of coronary artery. Overall, 95% of mutation carriers displayed either aortic or extra-aortic arterial disease. Acrocyanosis was also present in the majority of patients. Osteoarticular manifestations were recorded in all patients. Joint involvement could be severe requiring surgery in young patients, of unusual localization such as tarsus or shoulder, or mimicking crystalline arthropathy with fibrocartilage calcifications. Sixty eight percent of patients displayed neurological symptoms, and 9 suffered peripheral neuropathy. Electroneuromyography revealed an axonal motor and sensory neuropathy in 3 different families, very evocative of type II Charcot-Marie-Tooth (CMT2) disease, although none had mutations in the known CMT2 genes. Autoimmune features including Sjogren's disease, rheumatoid arthritis, Hashimoto's disease, or isolated autoantibodies- were found in 36% of patients.

Interpretation: SMAD3 gene mutations are associated with aortic dilatation and osteoarthritis, but also autoimmunity and peripheral neuropathy which mimics type II Charcot-Marie-Tooth.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096387PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4012990PMC
October 2015

New insights into genotype-phenotype correlation for GLI3 mutations.

Eur J Hum Genet 2015 Jan 16;23(1):92-102. Epub 2014 Apr 16.

Service de Génétique, Hospices Civils de Lyon, CHU de Lyon, France.

The phenotypic spectrum of GLI3 mutations includes autosomal dominant Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS). PHS was first described as a lethal condition associating hypothalamic hamartoma, postaxial or central polydactyly, anal atresia and bifid epiglottis. Typical GCPS combines polysyndactyly of hands and feet and craniofacial features. Genotype-phenotype correlations have been found both for the location and the nature of GLI3 mutations, highlighting the bifunctional nature of GLI3 during development. Here we report on the molecular and clinical study of 76 cases from 55 families with either a GLI3 mutation (49 GCPS and 21 PHS), or a large deletion encompassing the GLI3 gene (6 GCPS cases). Most of mutations are novel and consistent with the previously reported genotype-phenotype correlation. Our results also show a correlation between the location of the mutation and abnormal corpus callosum observed in some patients with GCPS. Fetal PHS observations emphasize on the possible lethality of GLI3 mutations and extend the phenotypic spectrum of malformations such as agnathia and reductional limbs defects. GLI3 expression studied by in situ hybridization during human development confirms its early expression in target tissues.
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http://dx.doi.org/10.1038/ejhg.2014.62DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4266745PMC
January 2015

Integrin alpha 8 recessive mutations are responsible for bilateral renal agenesis in humans.

Am J Hum Genet 2014 Feb 16;94(2):288-94. Epub 2014 Jan 16.

Institut National de la Santé et de la Recherche Médicale U983, Hôpital Necker-Enfants Malades, 75015 Paris, France; Université Paris Descartes - Sorbonne Paris Cité, Institut Imagine, 75015 Paris, France. Electronic address:

Renal hypodysplasia (RHD) is a heterogeneous condition encompassing a spectrum of kidney development defects including renal agenesis, hypoplasia, and (cystic) dysplasia. Heterozygous mutations of several genes have been identified as genetic causes of RHD with various severity. However, these genes and mutations are not associated with bilateral renal agenesis, except for RET mutations, which could be involved in a few cases. The pathophysiological mechanisms leading to total absence of kidney development thus remain largely elusive. By using a whole-exome sequencing approach in families with several fetuses with bilateral renal agenesis, we identified recessive mutations in the integrin α8-encoding gene ITGA8 in two families. Itga8 homozygous knockout in mice is known to result in absence of kidney development. We provide evidence of a damaging effect of the human ITGA8 mutations. These results demonstrate that mutations of ITGA8 are a genetic cause of bilateral renal agenesis and that, at least in some cases, bilateral renal agenesis is an autosomal-recessive disease.
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http://dx.doi.org/10.1016/j.ajhg.2013.12.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3928807PMC
February 2014

Mutations in CNTNAP1 and ADCY6 are responsible for severe arthrogryposis multiplex congenita with axoglial defects.

Hum Mol Genet 2014 May 6;23(9):2279-89. Epub 2013 Dec 6.

Pathology Laboratory and NeoVasc Region-Inserm Team ERI28, Institute of Research for Innovation in Biomedicine, University of Rouen, 76031 Rouen, France.

Non-syndromic arthrogryposis multiplex congenita (AMC) is characterized by multiple congenital contractures resulting from reduced fetal mobility. Genetic mapping and whole exome sequencing (WES) were performed in 31 multiplex and/or consanguineous undiagnosed AMC families. Although this approach identified known AMC genes, we here report pathogenic mutations in two new genes. Homozygous frameshift mutations in CNTNAP1 were found in four unrelated families. Patients showed a marked reduction in motor nerve conduction velocity (<10 m/s) and transmission electron microscopy (TEM) of sciatic nerve in the index cases revealed severe abnormalities of both nodes of Ranvier width and myelinated axons. CNTNAP1 encodes CASPR, an essential component of node of Ranvier domains which underlies saltatory conduction of action potentials along the myelinated axons, an important process for neuronal function. A homozygous missense mutation in adenylate cyclase 6 gene (ADCY6) was found in another family characterized by a lack of myelin in the peripheral nervous system (PNS) as determined by TEM. Morpholino knockdown of the zebrafish orthologs led to severe and specific defects in peripheral myelin in spite of the presence of Schwann cells. ADCY6 encodes a protein that belongs to the adenylate cyclase family responsible for the synthesis of cAMP. Elevation of cAMP can mimic axonal contact in vitro and upregulates myelinating signals. Our data indicate an essential and so far unknown role of ADCY6 in PNS myelination likely through the cAMP pathway. Mutations of genes encoding proteins of Ranvier domains or involved in myelination of Schwann cells are responsible for novel and severe human axoglial diseases.
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http://dx.doi.org/10.1093/hmg/ddt618DOI Listing
May 2014

Finger creases lend a hand in Kabuki syndrome.

Eur J Med Genet 2013 Oct 7;56(10):556-60. Epub 2013 Aug 7.

Département de Génétique, Unité Inserm U781, Institut Imagine, Hôpital Necker enfants Malades, CLAD Ile de France, Paris, France.

Kabuki syndrome (KS) is a rare syndrome associating malformations with intellectual deficiency and numerous visceral, orthopedic, endocrinological, immune and autoimmune complications. The early establishment of a diagnostic of KS leads to better care of the patients and therefore prevents complications such as perception deafness, severe complications of auto-immune diseases or obesity. However, the diagnosis of KS remains difficult because based on the appreciation of facial features combined with other highly variable features. We describe a novel sign, namely the attenuation and/or congenital absence of the IPD crease of the third and fourth fingers associated with limitation of flexion of the corresponding joints, which seems to be specific of KS and could help the clinician to diagnose KS.
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http://dx.doi.org/10.1016/j.ejmg.2013.07.005DOI Listing
October 2013

Clinical and molecular spectrum of renal malformations in Kabuki syndrome.

J Pediatr 2013 Sep 25;163(3):742-6. Epub 2013 Mar 25.

Pediatrics 1 and Medical Genetics, Center of Reference for Developmental Abnormalities and Malformative Syndromes, Children's Hospital, University of Burgundy, Dijon, France.

Objective: To determine the frequency and types of renal malformations, and to evaluate renal function in a cohort of patients with Kabuki syndrome (KS).

Study Design: Renal ultrasound scans and plasma creatinine measurements were collected from a French cohort of 94 patients with genotyped KS. Renal function was evaluated based on the estimated glomerular filtration rate. A genotype-phenotype study was conducted for renal and urinary tract malformations.

Results: Renal malformations were present in 22% of cases, and urinary tract anomalies were present in 15%. Renal malformations were observed in 28% of the MLL2 mutation-positive group and in 0% of the MLL2 mutation-negative group (P = .015). No correlation was found between the presence or absence of renal or urinary tract malformations and the location or type of MLL2 mutation. Renal function was normal except for 1 patient with a MLL2 mutation diagnosed in the first days of life and severe renal disease due to unilateral renal agenesia and controlateral severe hypoplasia that progressed to the terminal stage at age 2 years.

Conclusion: Our study emphasizes the need for ultrasound and renal function screening in children diagnosed with KS.
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http://dx.doi.org/10.1016/j.jpeds.2013.02.032DOI Listing
September 2013

Exome sequencing identifies INPPL1 mutations as a cause of opsismodysplasia.

Am J Hum Genet 2013 Jan 27;92(1):144-9. Epub 2012 Dec 27.

Département de Génétique, Unité INSERM U781, Université Paris Descartes-Sorbonne Paris Cité, Fondation Imagine, Hôpital Necker Enfants Malades, Paris 75015, France.

Opsismodysplasia (OPS) is a severe autosomal-recessive chondrodysplasia characterized by pre- and postnatal micromelia with extremely short hands and feet. The main radiological features are severe platyspondyly, squared metacarpals, delayed skeletal ossification, and metaphyseal cupping. In order to identify mutations causing OPS, a total of 16 cases (7 terminated pregnancies and 9 postnatal cases) from 10 unrelated families were included in this study. We performed exome sequencing in three cases from three unrelated families and only one gene was found to harbor mutations in all three cases: inositol polyphosphate phosphatase-like 1 (INPPL1). Screening INPPL1 in the remaining cases identified a total of 12 distinct INPPL1 mutations in the 10 families, present at the homozygote state in 7 consanguinous families and at the compound heterozygote state in the 3 remaining families. Most mutations (6/12) resulted in premature stop codons, 2/12 were splice site, and 4/12 were missense mutations located in the catalytic domain, 5-phosphatase. INPPL1 belongs to the inositol-1,4,5-trisphosphate 5-phosphatase family, a family of signal-modulating enzymes that govern a plethora of cellular functions by regulating the levels of specific phosphoinositides. Our finding of INPPL1 mutations in OPS, a severe spondylodysplastic dysplasia with major growth plate disorganization, supports a key and specific role of this enzyme in endochondral ossification.
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http://dx.doi.org/10.1016/j.ajhg.2012.11.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3542463PMC
January 2013

NEK1 and DYNC2H1 are both involved in short rib polydactyly Majewski type but not in Beemer Langer cases.

J Med Genet 2012 Apr;49(4):227-33

Department of Genetics, INSERM U781, Hôpital Necker, Université Paris Descartes, Sorbonne Paris Cité, Paris 75015, France.

Background: The lethal short rib polydactyly syndromes (SRP type I-IV) are characterised by notably short ribs, short limbs, polydactyly, multiple anomalies of major organs, and autosomal recessive mode of inheritance. Among them, SRP type II (Majewski; MIM 263520) is characterised by short ovoid tibiae or tibial agenesis and is radiographically closely related to SRP type IV (Beemer-Langer; MIM 269860) which is distinguished by bowed radii and ulnae and relatively well tubulated tibiae. NEK1 mutations have been recently identified in SRP type II. Double heterozygosity for mutations in both NEK1 and DYNC2H1 in one SRP type II case supported possible digenic diallelic inheritance.

Methods: The aim of this study was to screen DYNC2H1 and NEK1 in 13 SRP type II cases and seven SRP type IV cases. It was not possible to screen DYNC2H1 in two patients due to insufficient amount of DNA.

Results: The study identified homozygous NEK1 mutations in 5/13 SRP type II and compound heterozygous DYNC2H1 mutations in 4/12 cases. Finally, NEK1 and DYNC2H1 were excluded in 3/12 SRP type II and in all SRP type IV cases. The main difference between the mutation positive SRP type II group and the mutation negative SRP type II group was the presence of holoprosencephaly and polymycrogyria in the mutation negative group.

Conclusion: This study confirms that NEK1 is one gene causing SRP type II but also reports mutations in DYNC2H1, expanding the phenotypic spectrum of DYNC2H1 mutations. The exclusion of NEK1 and DYNC2H1 in 3/12 SRP type II and in all SRP type IV cases further support genetic heterogeneity.
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http://dx.doi.org/10.1136/jmedgenet-2011-100717DOI Listing
April 2012

Novel FH mutations in families with hereditary leiomyomatosis and renal cell cancer (HLRCC) and patients with isolated type 2 papillary renal cell carcinoma.

J Med Genet 2011 Apr 12;48(4):226-34. Epub 2011 Mar 12.

Génétique Oncologique EPHE, INSERM U753, Institut de cancérologie Gustave Roussy Villejuif, Faculté de Médecine Paris-Sud, 63 avenue du Général Leclerc, 94276 Le Kremlin-Bicêtre, France.

Background: Hereditary leiomyomatosis and renal cell cancer (HLRCC) is an autosomal dominant disorder predisposing humans to cutaneous and uterine leiomyomas; in 20% of affected families, type 2 papillary renal cell cancers (PRCCII) also occur with aggressive course and poor prognosis. HLRCC results from heterozygous germline mutations in the tumour suppressor fumarate hydratase (FH) gene.

Methods: As part of the French National Cancer Institute (INCa) 'Inherited predispositions to kidney cancer' network, sequence analysis and a functional study of FH were preformed in 56 families with clinically proven or suspected HLRCC and in 23 patients with isolated PRCCII (5 familial and 18 sporadic).

Results: The study identified 32 different germline FH mutations (15 missense, 6 frameshifts, 4 nonsense, 1 deletion/insertion, 5 splice site, and 1 complete deletion) in 40/56 (71.4%) families with proven or suspected HLRCC and in 4/23 (17.4%) probands with PRCCII alone, including 2 sporadic cases. 21 of these were novel and all were demonstrated as deleterious by significant reduction of FH enzymatic activity. In addition, 5 asymptomatic parents in 3 families were confirmed as carrying disease-causing mutations.

Conclusions: This study identified and characterised 21 novel FH mutations and demonstrated that PRCCII can be the only one manifestation of HLRCC. Due to the incomplete penetrance of HLRCC, the authors propose to extend the FH mutation analysis to every patient with PRCCII occurring before 40 years of age or when renal tumour harbours characteristic histologic features, in order to discover previously ignored HLRCC affected families.
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http://dx.doi.org/10.1136/jmg.2010.085068DOI Listing
April 2011

High-throughput sequencing of a 4.1 Mb linkage interval reveals FLVCR2 deletions and mutations in lethal cerebral vasculopathy.

Hum Mutat 2010 Oct;31(10):1134-41

INSERM U-781, Hôpital Necker-Enfants Malades, Paris, France.

Rare lethal disease gene identification remains a challenging issue, but it is amenable to new techniques in high-throughput sequencing (HTS). Cerebral proliferative glomeruloid vasculopathy (PGV), or Fowler syndrome, is a severe autosomal recessive disorder of brain angiogenesis, resulting in abnormally thickened and aberrant perforating vessels leading to hydranencephaly. In three multiplex consanguineous families, genome-wide SNP analysis identified a locus of 14 Mb on chromosome 14. In addition, 280 consecutive SNPs were identical in two Turkish families unknown to be related, suggesting a founder mutation reducing the interval to 4.1 Mb. To identify the causative gene, we then specifically enriched for this region with sequence capture and performed HTS in a proband of seven families. Due to technical constraints related to the disease, the average coverage was only 7×. Nonetheless, iterative bioinformatic analyses of the sequence data identified mutations and a large deletion in the FLVCR2 gene, encoding a 12 transmembrane domain-containing putative transporter. A striking absence of alpha-smooth muscle actin immunostaining in abnormal vessels in fetal PGV brains, suggests a deficit in pericytes, cells essential for capillary stabilization and remodeling during brain angiogenesis. This is the first lethal disease-causing gene to be identified by comprehensive HTS of an entire linkage interval.
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http://dx.doi.org/10.1002/humu.21329DOI Listing
October 2010

Mutations in TMEM216 perturb ciliogenesis and cause Joubert, Meckel and related syndromes.

Nat Genet 2010 Jul 30;42(7):619-25. Epub 2010 May 30.

Mendel Laboratory, Istituto di Ricovero e Cura a Carattere Scientifico Casa Sollievo della Sofferenza, San Giovanni Rotondo, Italy.

Joubert syndrome (JBTS), related disorders (JSRDs) and Meckel syndrome (MKS) are ciliopathies. We now report that MKS2 and CORS2 (JBTS2) loci are allelic and caused by mutations in TMEM216, which encodes an uncharacterized tetraspan transmembrane protein. Individuals with CORS2 frequently had nephronophthisis and polydactyly, and two affected individuals conformed to the oro-facio-digital type VI phenotype, whereas skeletal dysplasia was common in fetuses affected by MKS. A single G218T mutation (R73L in the protein) was identified in all cases of Ashkenazi Jewish descent (n=10). TMEM216 localized to the base of primary cilia, and loss of TMEM216 in mutant fibroblasts or after knockdown caused defective ciliogenesis and centrosomal docking, with concomitant hyperactivation of RhoA and Dishevelled. TMEM216 formed a complex with Meckelin, which is encoded by a gene also mutated in JSRDs and MKS. Disruption of tmem216 expression in zebrafish caused gastrulation defects similar to those in other ciliary morphants. These data implicate a new family of proteins in the ciliopathies and further support allelism between ciliopathy disorders.
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http://dx.doi.org/10.1038/ng.594DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2894012PMC
July 2010