Identification of new genes of recessive ataxias, involvment of mitochondira and new pathophysiological pathways

Nous avons analysé un ensemble de 97 familles consanguines par puces de génotypage 10K ou 50K. Nous avons ainsi pu identifier 10 mutations dans 4 gènes déjà connus d'ataxie (sacsin, aprataxin, senataxin, ATM). Grâce à notre stratégie de cartographie par hPatients from 97 families were analyzed with GeneChip Mapping 10K 50K SNP Affymetrix microarrays. We identified 10 mutations in 4 known ataxia genes (sacsin. Aprataxin, senataxin, ATM). Our homozygosity mapping strategy allowed us also to identify 4 new

Identification of new genes of recessive ataxias, involvment of mitochondira and new pathophysiological pathways

Nous avons analysé un ensemble de 97 familles consanguines par puces de génotypage 10K ou 50K. Nous avons ainsi pu identifier 10 mutations dans 4 gènes déjà connus d'ataxie (sacsin, aprataxin, senataxin, ATM). Grâce à notre stratégie de cartographie par homozygotie, nous avons pu identifier quatre nouveaux gènes responsables d'ataxies autosomiques récessives. Nous avons identifié des mutations dans le gène ADCK3 codant pour une kinase atypique mitochondriale impliquée dans la synthèse du coenzyme Q10. Ces mutations sont responsables d'une ataxie cérébelleuse précoce et associée à un déficit en coenzyme Q10. Nous avons identifié des mutations dans le gène ABHD12 responsables du syndrome PHARC ( pour Polyneuropathy, Hearing loss, Ataxia, Retinitis pigmentosa and Cataract). Le gène ABHD12 code pour une a/b hydrolase impliquée dans l'hydrolyse de l'acide 2-arachidonique-glycérol, un endocannabinoïde majeur du SNC. Une collaboration avec S.Vermeer et collègues (Nimègue) a permis d'identifier des mutations dans le gène ANO10 dans une nouvelle forme d'ataxie avec atrophie cérébelleuse sévère. ANO10 est un membre de la famille des anoctamines et code pour un canal chlore activé par le calcium. Finalement, nous avons identifié la mutation causale ches les 3 patientes d'une grande famille originaire d'Arabie Saoudite consanguine. La mutation, une délétion homozygote (2927delC) au niveau du gène KIAAO226, entraîne un décalage du cadre de lecture. KIAAO226 code pour une nouvelle protéine nommée Rubicon. Rubicon (rundataxine) colocalise avec Rab7 au niveau des endosomes précoces. La rundataxine mutante exprimée dans les cellules Hela présente une localisation cytosolique diffuse.Patients from 97 families were analyzed with GeneChip Mapping 10K 50K SNP Affymetrix microarrays. We identified 10 mutations in 4 known ataxia genes (sacsin. Aprataxin, senataxin, ATM). Our homozygosity mapping strategy allowed us also to identify 4 new genes responsible of new forms of reçessive ataxias. We have identified mutations in the ADCK3 gene coding for a mitochondrial atypical kinase involved in CoQ10 biosynthesis. ADCK3 mutations are responsible for an early onset cerebellar ataxia associated with coenzyme Ql0 deficiency. We have also identified mutations in the ABHD12 responsible for PHARC (Polyneuropathy, hearing loss, ataxia, retinitis pigmenltosa, and cataract). The ABfHD12 gene encodes an a/b hydrolase recently shown to hydrolyze 2-arachidonoyl glycerol (2-AG), one of the 2 main endocannabinoid neurotransmitters. The collaboration \\ith S.Vermeer and colleagues (Nijmegen) permited to identify mutations in the gene ANO10 involved in a new form of cerebellar ataxia with severe cerebellar atrophy. ANO10 is a member of the human Ianoctamins (ANO) family. ANO10 encodes a calcium-activated chloride channel. Finally, with the same approach. we identified the causative gene in three children affected with childhood onset ataxia in a large consanguineous Saudi Arabian famiy. The mutation, a single nucleotide deletion, 2927delC in the KIAA0226 gene, results in a frame-sbift and in the usage of a novel 145 amino-acid reading frame which is longer than the normal C-terminal sequence. The K1AA0226 gene encodes a protein, we named rundataxin (Rubicon) which colocalizes with Rab7 on the late endosomes. The mutation leads to a diffuse cytoplasmic distribution of rundataxin

Identification de nouveaux gènes d ataxies récessives (Implication de la mitochondrie et de nouvelles voies physiopathologiques)

Nous avons analysé un ensemble de 97 familles consanguines par puces de génotypage 10K ou 50K. Nous avons ainsi pu identifier 10 mutations dans 4 gènes déjà connus d'ataxie (sacsin, aprataxin, senataxin, ATM). Grâce à notre stratégie de cartographie par homozygotie, nous avons pu identifier quatre nouveaux gènes responsables d'ataxies autosomiques récessives. Nous avons identifié des mutations dans le gène ADCK3 codant pour une kinase atypique mitochondriale impliquée dans la synthèse du coenzyme Q10. Ces mutations sont responsables d'une ataxie cérébelleuse précoce et associée à un déficit en coenzyme Q10. Nous avons identifié des mutations dans le gène ABHD12 responsables du syndrome PHARC ( pour Polyneuropathy, Hearing loss, Ataxia, Retinitis pigmentosa and Cataract). Le gène ABHD12 code pour une a/b hydrolase impliquée dans l'hydrolyse de l'acide 2-arachidonique-glycérol, un endocannabinoïde majeur du SNC. Une collaboration avec S.Vermeer et collègues (Nimègue) a permis d'identifier des mutations dans le gène ANO10 dans une nouvelle forme d'ataxie avec atrophie cérébelleuse sévère. ANO10 est un membre de la famille des anoctamines et code pour un canal chlore activé par le calcium. Finalement, nous avons identifié la mutation causale ches les 3 patientes d'une grande famille originaire d'Arabie Saoudite consanguine. La mutation, une délétion homozygote (2927delC) au niveau du gène KIAAO226, entraîne un décalage du cadre de lecture. KIAAO226 code pour une nouvelle protéine nommée Rubicon. Rubicon (rundataxine) colocalise avec Rab7 au niveau des endosomes précoces. La rundataxine mutante exprimée dans les cellules Hela présente une localisation cytosolique diffuse.Patients from 97 families were analyzed with GeneChip Mapping 10K 50K SNP Affymetrix microarrays. We identified 10 mutations in 4 known ataxia genes (sacsin. Aprataxin, senataxin, ATM). Our homozygosity mapping strategy allowed us also to identify 4 new genes responsible of new forms of reçessive ataxias. We have identified mutations in the ADCK3 gene coding for a mitochondrial atypical kinase involved in CoQ10 biosynthesis. ADCK3 mutations are responsible for an early onset cerebellar ataxia associated with coenzyme Ql0 deficiency. We have also identified mutations in the ABHD12 responsible for PHARC (Polyneuropathy, hearing loss, ataxia, retinitis pigmenltosa, and cataract). The ABfHD12 gene encodes an a/b hydrolase recently shown to hydrolyze 2-arachidonoyl glycerol (2-AG), one of the 2 main endocannabinoid neurotransmitters. The collaboration \\ith S.Vermeer and colleagues (Nijmegen) permited to identify mutations in the gene ANO10 involved in a new form of cerebellar ataxia with severe cerebellar atrophy. ANO10 is a member of the human Ianoctamins (ANO) family. ANO10 encodes a calcium-activated chloride channel. Finally, with the same approach. we identified the causative gene in three children affected with childhood onset ataxia in a large consanguineous Saudi Arabian famiy. The mutation, a single nucleotide deletion, 2927delC in the KIAA0226 gene, results in a frame-sbift and in the usage of a novel 145 amino-acid reading frame which is longer than the normal C-terminal sequence. The K1AA0226 gene encodes a protein, we named rundataxin (Rubicon) which colocalizes with Rab7 on the late endosomes. The mutation leads to a diffuse cytoplasmic distribution of rundataxin.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

The clinical utility of rapid exome sequencing in a consanguineous population

Abstract Background The clinical utility of exome sequencing is now well documented. Rapid exome sequencing (RES) is more resource-intensive than regular exome sequencing and is typically employed in specialized clinical settings wherein urgent molecular diagnosis is thought to influence acute management. Studies on the clinical utility of RES have been largely limited to outbred populations. Methods Here, we describe our experience with rapid exome sequencing (RES) in a highly consanguineous population. Clinical settings included intensive care units, prenatal cases approaching the legal cutoff for termination, and urgent transplant decisions. Results A positive molecular finding (a pathogenic or likely pathogenic variant that explains the phenotype) was observed in 80 of 189 cases (42%), while 15 (8%) and 94 (50%) received ambiguous (variant of uncertain significance (VUS)) and negative results, respectively. The consanguineous nature of the study population gave us an opportunity to observe highly unusual and severe phenotypic expressions of previously reported genes. Clinical utility was observed in nearly all (79/80) cases with positive molecular findings and included management decisions, prognostication, and reproductive counseling. Reproductive counseling is a particularly important utility in this population where the overwhelming majority (86%) of identified variants are autosomal recessive, which are more actionable in this regard than the de novo variants typically reported by RES elsewhere. Indeed, our cost-effectiveness analysis shows compelling cost savings in the study population. Conclusions This work expands the diversity of environments in which RES has a demonstrable clinical utility

Increased diagnostic and new genes identification outcome using research reanalysis of singleton exome sequencing

International audienceIn clinical exome sequencing (cES), the American College of Medical Genetics and Genomics recommends limiting variant interpretation to established human-disease genes. The diagnostic yield of cES in intellectual disability and/or multiple congenital anomalies (ID/MCA) is currently about 30%. Though the results may seem acceptable for rare diseases, they mean that 70% of affected individuals remain genetically undiagnosed. Further analysis extended to all mutated genes in a research environment is a valuable strategy for improving diagnostic yields. This study presents the results of systematic research reanalysis of negative cES in a cohort of 313 individuals with ID/MCA. We identified 17 new genes not related to human disease, implicated 22 non-OMIM disease-causing genes recently or previously rarely related to disease, and described 1 new phenotype associated with a known gene. Twenty-six candidate genes were identified and are waiting for future recurrence. Overall, we diagnose 15% of the individuals with initial negative cES, increasing the diagnostic yield from 30% to more than 40% (or 46% if strong candidate genes are considered). This study demonstrates the power of such extended research reanalysis to increase scientific knowledge of rare diseases. These novel findings can then be applied in the field of diagnostics

WDR73 Mutations Cause Infantile Neurodegeneration and Variable Glomerular Kidney Disease

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Further delineation of the clinical spectrum of de novo TRIM8 truncating mutations

IF 2.264International audienceDe novo mutations of the TRIM8 gene, which codes for a tripartite motif protein, have been identified using whole exome sequencing (WES) in two patients with epileptic encephalopathy (EE), but these reports were not sufficient to conclude that TRIM8 was a novel gene responsible for EE. Here we report four additional patients presenting with EE and de novo truncating mutations of TRIM8 detected by WES, and give further details of the patient previously reported by the Epi4K consortium. Epilepsy of variable severity was diagnosed in children aged 2 months to 3.5 years of age. All patients had developmental delay of variable severity with no or very limited language, often associated with behavioral anomalies and unspecific facial features or MRI brain abnormalities. The phenotypic variability observed in these patients appeared related to the severity of the epilepsy. One patient presented pharmacoresistant EE with regression, recurrent infections and nephrotic syndrome, compatible with the brain and kidney expression of TRIM8. Interestingly, all mutations were located at the highly conserved C-terminus section of TRIM8. This collaborative study confirms that TRIM8 is a novel gene responsible for EE, possibly associated with nephrotic syndrome. This report brings new evidence on the pathogenicity of TRIM8 mutations and highlights the value of data-sharing to delineate the phenotypic characteristics and biological basis of extremely rare disorders

PMPCA mutations cause abnormal mitochondrial protein processing in patients with non-progressive cerebellar ataxia

Non-progressive cerebellar ataxias are a rare group of disorders that comprise approximately 10% of static infantile encephalopathies. We report the identification of mutations in PMPCA in 17 patients from four families affected with cerebellar ataxia, including the large Lebanese family previously described with autosomal recessive cerebellar ataxia and short stature of Norman type and localized to chromosome 9q34 (OMIM #213200). All patients present with non-progressive cerebellar ataxia, and the majority have intellectual disability of variable severity. PMPCA encodes α-MPP, the alpha subunit of mitochondrial processing peptidase, the primary enzyme responsible for the maturation of the vast majority of nuclear-encoded mitochondrial proteins, which is necessary for life at the cellular level. Analysis of lymphoblastoid cells and fibroblasts from patients homozygous for the PMPCA p.Ala377Thr mutation and carriers demonstrate that the mutation impacts both the level of the alpha subunit encoded by PMPCA and the function of mitochondrial processing peptidase. In particular, this mutation impacts the maturation process of frataxin, the protein which is depleted in Friedreich ataxia. This study represents the first time that defects in PMPCA and mitochondrial processing peptidase have been described in association with a disease phenotype in humans

PMPCA mutations cause abnormal mitochondrial protein processing in patients with non-progressive cerebellar ataxia

International audienceNon-progressive cerebellar ataxias are a rare group of disorders that comprise approximately 10% of static infantile encephalopathies. We report the identification of mutations in PMPCA in 17 patients from four families affected with cerebellar ataxia, including the large Lebanese family previously described with autosomal recessive cerebellar ataxia and short stature of Norman type and localized to chromosome 9q34 (OMIM #213200). All patients present with non-progressive cerebellar ataxia, and the majority have intellectual disability of variable severity. PMPCA encodes α-MPP, the alpha subunit of mitochondrial processing peptidase, the primary enzyme responsible for the maturation of the vast majority of nuclear-encoded mitochondrial proteins, which is necessary for life at the cellular level. Analysis of lymphoblastoid cells and fibroblasts from patients homozygous for the PMPCA p.Ala377Thr mutation and carriers demonstrate that the mutation impacts both the level of the alpha subunit encoded by PMPCA and the function of mitochondrial processing peptidase. In particular, this mutation impacts the maturation process of frataxin, the protein which is depleted in Friedreich ataxia. This study represents the first time that defects in PMPCA and mitochondrial processing peptidase have been described in association with a disease phenotype in humans