Marked yield of re-evaluating phenotype and exome/target sequencing data in 33 individuals with intellectual disabilities.

Am J Med Genet A. 2018 Jan;176(1):107-115

Authors: Xiao B, Qiu W, Ji X, Liu X, Huang Z, Liu H, Fan Y, Xu Y, Liu Y, Yie H, Wei W, Yan H, Gong Z, Shen L, Sun Y

Abstract
The diagnosis of intellectual disability/developmental delay (ID/DD) benefits from the clinical application of target/exome sequencing. The yield in Mendelian diseases varies from 25% to 68%. The aim of the present study was to identify the genetic causes of 33 ID/DD patients using target/exome sequencing. Recent studies have demonstrated that reanalyzing undiagnosed exomes could yield additional diagnosis. Therefore, in addition to the normal data analysis, in this study, re-evaluation was performed prior to manuscript preparation after updating OMIM annotations, calling copy number variations (CNVs) and reviewing the current literature. Molecular diagnosis was obtained for 19/33 patients in the first round of analysis. Notably, five patients were diagnosed during the re-evaluation of the geno/phenotypic data. This study confirmed the utility of exome sequencing in the diagnosis of ID/DD. Furthermore, re-evaluation leads to a 15% improvement in diagnostic yield. Thus, to maximize the diagnostic yield of next-generation sequencing (NGS), periodical re-evaluation of the geno/phenotypic data of undiagnosed individuals is recommended by updating the OMIM annotation, applying new algorithms, reviewing the literature, sharing pheno/genotypic data, and re-contacting patients.

PMID: 29159939 [PubMed - indexed for MEDLINE]

Whole exome sequencing reveals a mutation in ARMC9 as a cause of mental retardation, ptosis, and polydactyly.

Am J Med Genet A. 2018 Jan;176(1):34-40

Authors: Kar A, Phadke SR, Das Bhowmik A, Dalal A

Abstract
Intellectual disability (ID) refers to deficits in mental abilities, social behavior, and motor skills to perform activities of daily living as compared to peers. Numerous genetic and environmental factors may be responsible for ID. We report on elucidation of molecular basis for syndromic ID associated with ptosis, polydactyly, and MRI features suggestive of Joubert syndrome using homozygosity mapping followed by exome sequencing. The analysis revealed a novel synonymous variation p.T293T (c.879G>A) which leads to a splicing defect in ARMC9 gene. The variant is present in conserved region of ARM domain of ARMC9 protein, which is predicted to form a platform for protein interaction. This domain is likely to be altered in patient due to splicing defect caused by this synonymous variation. Our report of variant in ARMC9 Leading to Joubert syndrome phenotype (JS30), elucidates the genetic heterogeneity of Joubert syndrome, and expands the gene list for ciliopathies.

PMID: 29159890 [PubMed - indexed for MEDLINE]

Expanding the neurodevelopmental phenotype of PURA syndrome.

Am J Med Genet A. 2018 Jan;176(1):56-67

Authors: Lee BH, Reijnders MRF, Abubakare O, Tuttle E, Lape B, Minks KQ, Stodgell C, Bennetto L, Kwon J, Fong CT, Gripp KW, Marsh ED, Smith WE, Huq AM, Coury SA, Tan WH, Solis O, Mehta RI, Leventer RJ, Baralle D, Hunt D, Paciorkowski AR

Abstract
PURA syndrome is a recently described developmental encephalopathy presenting with neonatal hypotonia, feeding difficulties, global developmental delay, severe intellectual disability, and frequent apnea and epilepsy. We describe 18 new individuals with heterozygous sequence variations in PURA. A neuromotor disorder starting with neonatal hyptonia, but ultimately allowing delayed progression to walking, was present in nearly all individuals. Congenital apnea was present in 56% during infancy, but all cases in this cohort resolved during the first year of life. Feeding difficulties were frequently reported, with gastrostomy tube placement required in 28%. Epilepsy was present in 50% of the subjects, including infantile spasms and Lennox-Gastaut syndrome. Skeletal complications were found in 39%. Disorders of gastrointestinal motility and nystagmus were also recurrent features. Autism was diagnosed in one individual, potentially expanding the neurodevelopmental phenotype associated with this syndrome. However, we did not find additional PURA sequence variations in a cohort of 120 subjects with autism. We also present the first neuropathologic studies of PURA syndrome, and describe chronic inflammatory changes around the arterioles within the deep white matter. We did not find significant correlations between mutational class and severity, nor between location of the sequence variation in PUR repeat domains. Further studies are required in larger cohorts of subjects with PURA syndrome to clarify these genotype-phenotype associations.

PMID: 29150892 [PubMed - indexed for MEDLINE]

Updated strategies for the management, pathogenesis and molecular genetics of different forms of ichthyosis syndromes with prominent hair abnormalities.

Arch Dermatol Res. 2017 Dec;309(10):773-785

Authors: Rasheed M, Shahzad S, Zaeem A, Afzal I, Gul A, Khalid S

Abstract
Syndromic ichthyosis is rare inherited disorders of cornification with varied disease complications. This disorder appears in seventeen subtypes associated with severe systematic manifestations along with medical, cosmetic and social problems. Syndromic ichthyosis with prominent hair abnormalities covers five major subtypes: Netherton syndrome, trichothiodystrophy, ichthyosis hypotrichosis syndrome, ichthyosis hypotrichosis sclerosing cholangitis and ichthyosis follicularis atrichia photophobia syndrome. These syndromes mostly prevail in high consanguinity states, with distinctive clinical features. The known pathogenic molecules involved in ichthyosis syndromes with prominent hair abnormalities include SPINK5, ERCC2, ERCC3, GTF2H5, MPLKIP, ST14, CLDN1 and MBTPS2. Despite underlying genetic origin, most of the health professionals solely rely on phenotypic expression of these disorders that leads to improper management of patients, hence making these patients living an orphanage life. After dermal features, association of other systems such as nervous system, skeletal system, hair abnormalities or liver problems may sometimes give clues for diagnosis but still leaving place for molecular screening for efficient diagnosis. In this paper, we have presented a review of ichthyosis syndrome with prominent hair abnormalities, with special emphasis on their updated genetic consequences and disease management. Additionally, we aim to update health professionals about the practice of molecular screening in ichthyosis syndromes for appropriate diagnosis and treatment.

PMID: 28913623 [PubMed - indexed for MEDLINE]

The HHID syndrome of hypertrichosis, hyperkeratosis, abnormal corpus callosum, intellectual disability, and minor anomalies is caused by mutations in ARID1B.

Am J Med Genet A. 2017 May;173(5):1440-1443

Authors: Zweier M, Peippo MM, Pöyhönen M, Kääriäinen H, Begemann A, Joset P, Oneda B, Rauch A

PMID: 28323383 [PubMed - indexed for MEDLINE]

Kleine-Levin syndrome is associated with LMOD3 variants.

J Sleep Res. 2018 Jun 19;:e12718

Authors: Al Shareef SM, Basit S, Li S, Pfister C, Pradervand S, Lecendreux M, Mayer G, Dauvilliers Y, Salpietro V, Houlden H, BaHammam AS, Tafti M

Abstract
Kleine-Levin syndrome (KLS) is a rare periodic hypersomnia with associated behavioural abnormalities but with often favourable prognosis. There is excess risk of KLS in first-degree relatives, suggesting a strong genetic contribution. So far, no mutation is identified in KLS and comprehensive genetic analysis of affected individuals is lacking. Here we performed whole genome single-nucleotide polymorphism (SNP) genotyping and exome sequencing in a large family with seven affected members. The identified gene with a mutation was resequenced in 38 sporadic KLS patients and the expression of the gene product was mapped in the mouse brain. Linkage analysis mapped the disease locus to chromosome 3 and exome analysis identified a heterozygous missense variant in LMOD3 (p.E142D) in the linkage interval. The variant was found to segregate in all affected and one presumably unaffected member of the family. Resequencing LMOD3 in 38 other KLS patients and their families revealed three other low frequency or rare missense variants in seven cases that were inherited with incomplete penetrance. LMOD3 is expressed in the brain and colocalized with major structures involved in the regulation of vigilance states. LMOD proteins are structural proteins and seem to be developmentally regulated. Our findings suggest that KLS might be a structural/neurodevelopmental brain disease.

PMID: 29923248 [PubMed - as supplied by publisher]

CIRCULATING TUMOR DNA ANALYSIS ENABLES MOLECULAR CHARACTERIZATION OF PEDIATRIC RENAL TUMORS AT DIAGNOSIS.

Int J Cancer. 2018 Jun 19;:

Authors: Jiménez I, Chicard M, Colmet-Daage L, Clément N, Danzon A, Lapouble E, Pierron G, Bohec M, Baulande S, Berrebi D, Fréneaux P, Coulomb A, Galmiche-Rolland L, Sarnacki S, Audry G, Philippe-Chomette P, Brisse HJ, Doz F, Michon J, Delattre O, Schleiermacher G

Abstract
Circulating tumor DNA (ctDNA) is a powerful tool for the molecular characterization of cancer. The most frequent pediatric kidney tumors (KT) are Wilms' tumors (WT), but other diagnoses may occur. According to the SIOP strategy, in most countries pediatric KT have a presumptive diagnosis of WT if they are clinically and radiologically compatible. The histologic confirmation is established after post-chemotherapy nephrectomy. Thus, there is a risk for a small fraction of patients to receive neoadjuvant chemotherapy that is not adapted to the disease. The aim of this work is to perform molecular diagnosis of pediatric KT by tumor genetic characterization based on the analysis of ctDNA. We analyzed ctDNA extracted from plasma samples of 18 pediatric patients with KT by whole-exome sequencing and compared the results to their matched tumor and germline DNA. Copy number alterations (CNAs) and single nucleotide variations (SNVs) were analyzed. We were able to detect tumor cell specific genetic alterations -CNAs, SNVs or both- in ctDNA in all patients except in one (for whom the plasma sample was obtained long after nephrectomy). These results open the door to new applications for the study of ctDNA with regards to the molecular diagnosis of KT, with a possibility of its usefulness for adapting the treatment early after diagnosis, but also for disease monitoring and follow up. This article is protected by copyright. All rights reserved.

PMID: 29923174 [PubMed - as supplied by publisher]

De novo ATP1A3 and compound heterozygous NLRP3 mutations in a child with autism spectrum disorder, episodic fatigue and somnolence, and muckle-wells syndrome.

Mol Genet Metab Rep. 2018 Sep;16:23-29

Authors: Torres A, Brownstein CA, Tembulkar SK, Graber K, Genetti C, Kleiman RJ, Sweadner KJ, Mavros C, Liu KX, Smedemark-Margulies N, Maski K, Yang E, Agrawal PB, Shi J, Beggs AH, D'Angelo E, Lincoln SH, Carroll D, Dedeoglu F, Gahl WA, Biggs CM, Swoboda KJ, Berry GT, Gonzalez-Heydrich J

Abstract
Complex phenotypes may represent novel syndromes that are the composite interaction of several genetic and environmental factors. We describe an 9-year old male with high functioning autism spectrum disorder and Muckle-Wells syndrome who at age 5  years of age manifested perseverations that interfered with his functioning at home and at school. After age 6, he developed intermittent episodes of fatigue and somnolence lasting from hours to weeks that evolved over the course of months to more chronic hypersomnia. Whole exome sequencing showed three mutations in genes potentially involved in his clinical phenotype. The patient has a predicted pathogenic de novo heterozygous p.Ala681Thr mutation in the ATP1A3 gene (chr19:42480621C>T, GRCh37/hg19). Mutations in this gene are known to cause Alternating Hemiplegia of Childhood, Rapid Onset Dystonia Parkinsonism, and CAPOS syndrome, sometimes accompanied by autistic features. The patient also has compound heterozygosity for p.Arg490Lys/p.Val200Met mutations in the NLRP3 gene (chr1:247588214G>A and chr1:247587343G>A, respectively). NLRP3 mutations are associated in an autosomal dominant manner with clinically overlapping auto-inflammatory conditions including Muckle-Wells syndrome. The p.Arg490Lys is a known pathogenic mutation inherited from the patient's father. The p.Val200Met mutation, inherited from his mother, is a variant of unknown significance (VUS). Whether the de novoATP1A3mutation is responsible for or plays a role in the patient's episodes of fatigue and somnolence remains to be determined. The unprecedented combination of two NLRP3 mutations may be responsible for other aspects of his complex phenotype.

PMID: 29922587 [PubMed]

Clinical implications of systematic phenotyping and exome sequencing in patients with primary antibody deficiency.

Genet Med. 2018 Jun 19;:

Authors: Abolhassani H, Aghamohammadi A, Fang M, Rezaei N, Jiang C, Liu X, Pan-Hammarström Q, Hammarström L

Abstract
PURPOSE: The etiology of 80% of patients with primary antibody deficiency (PAD), the second most common type of human immune system disorder after human immunodeficiency virus infection, is yet unknown.
METHODS: Clinical/immunological phenotyping and exome sequencing of a cohort of 126 PAD patients (55.5% male, 95.2% childhood onset) born to predominantly consanguineous parents (82.5%) with unknown genetic defects were performed. The American College of Medical Genetics and Genomics criteria were used for validation of pathogenicity of the variants.
RESULTS: This genetic approach and subsequent immunological investigations identified potential disease-causing variants in 86 patients (68.2%); however, 27 of these patients (31.4%) carried autosomal dominant (24.4%) and X-linked (7%) gene defects. This genetic approach led to the identification of new phenotypes in 19 known genes (38 patients) and the discovery of a new genetic defect (CD70 pathogenic variants in 2 patients). Medical implications of a definite genetic diagnosis were reported in ~50% of the patients.
CONCLUSION: Due to misclassification of the conventional approach for targeted sequencing, employing next-generation sequencing as a preliminary step of molecular diagnostic approach to patients with PAD is crucial for management and treatment of the patients and their family members.

PMID: 29921932 [PubMed - as supplied by publisher]

Unexpected cancer-predisposition gene variants in Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome patients without underlying germline PTEN mutations.

PLoS Genet. 2018 04;14(4):e1007352

Authors: Yehia L, Ni Y, Sesock K, Niazi F, Fletcher B, Chen HJL, LaFramboise T, Eng C

Abstract
Patients with heritable cancer syndromes characterized by germline PTEN mutations (termed PTEN hamartoma tumor syndrome, PHTS) benefit from PTEN-enabled cancer risk assessment and clinical management. PTEN-wildtype patients (~50%) remain at increased risk of developing certain cancers. Existence of germline mutations in other known cancer susceptibility genes has not been explored in these patients, with implications for different medical management. We conducted a 4-year multicenter prospective study of incident patients with features of Cowden/Cowden-like (CS/CS-like) and Bannayan-Riley-Ruvalcaba syndromes (BRRS) without PTEN mutations. Exome sequencing and targeted analysis were performed including 59 clinically actionable genes from the American College of Medical Genetics and Genomics (ACMG) and 24 additional genes associated with inherited cancer syndromes. Pathogenic or likely pathogenic cancer susceptibility gene alterations were found in 7 of the 87 (8%) CS/CS-like and BRRS patients and included MUTYH, RET, TSC2, BRCA1, BRCA2, ERCC2 and HRAS. We found classic phenotypes associated with the identified genes in 5 of the 7 (71.4%) patients. Variant positive patients were enriched for the presence of second malignant neoplasms compared to patients without identified variants (OR = 6.101, 95% CI 1.143-35.98, p = 0.035). Germline variant spectrum and frequencies were compared to The Cancer Genome Atlas (TCGA), including 6 apparently sporadic cancers associated with PHTS. With comparable overall prevalence of germline variants, the spectrum of mutated genes was different in our patients compared to TCGA. Intriguingly, we also found notable enrichment of variants of uncertain significance (VUS) in our patients (OR = 2.3, 95% CI 1.5-3.5, p = 0.0002). Our data suggest that only a small subset of PTEN-wildtype CS/CS-like and BRRS patients could be accounted for by germline variants in some of the known cancer-related genes. Thus, the existence of alterations in other and more likely non-classic cancer-associated genes is plausible, reflecting the complexity of these heterogeneous hereditary cancer syndromes.

PMID: 29684080 [PubMed - indexed for MEDLINE]

Clinical Manifestations Associated With the N-Terminal-Acetyltransferase NAA10 Gene Mutation in a Girl: Ogden Syndrome.

Pediatr Neurol. 2017 Nov;76:82-85

Authors: Sidhu M, Brady L, Tarnopolsky M, Ronen GM

Abstract
BACKGROUND: Ogden syndrome is a rare X-linked disorder caused by pathogenic variants in the NAA10 gene. This syndrome, reported in just over 20 children, has been associated with dysmorphic features, failure to thrive, developmental impairments, hypotonia, and cardiac arrhythmias.
PATIENT DESCRIPTION: We describe a 14-year-old girl who presented in infancy with hypotonia, global developmental delay, and dysmorphic features. She later developed autism spectrum disorder, epileptic encephalopathy, extrapyramidal signs, early morning lethargy with hypersomnolence, and hypertension with left ventricular hypertrophy. Magnetic resonance imaging showed a thin corpus callosum and progressive white matter loss. Whole exome sequencing identified a de novo pathogenic variant in the NAA10 gene (c.247C>T, p.R83C). Much of her early presentation was in keeping with what has been previously described with Ogden syndrome.
CONCLUSIONS: We have identified additional evolving neurological impairments in this, to date, oldest documented girl with Ogden syndrome. We recommend screening patients with Ogden syndrome for these newly identified features of early life trajectories to guide management.

PMID: 28967461 [PubMed - indexed for MEDLINE]

Genetic and clinical characterization of Pakistani families with Bardet-Biedl syndrome extends the genetic and phenotypic spectrum.

Sci Rep. 2016 10 06;6:34764

Authors: Maria M, Lamers IJ, Schmidts M, Ajmal M, Jaffar S, Ullah E, Mustafa B, Ahmad S, Nazmutdinova K, Hoskins B, van Wijk E, Koster-Kamphuis L, Khan MI, Beales PL, Cremers FP, Roepman R, Azam M, Arts HH, Qamar R

Abstract
Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder that is both genetically and clinically heterogeneous. To date 19 genes have been associated with BBS, which encode proteins active at the primary cilium, an antenna-like organelle that acts as the cell's signaling hub. In the current study, a combination of mutation screening, targeted sequencing of ciliopathy genes associated with BBS, and whole-exome sequencing was used for the genetic characterization of five families including four with classic BBS symptoms and one BBS-like syndrome. This resulted in the identification of novel mutations in BBS genes ARL6 and BBS5, and recurrent mutations in BBS9 and CEP164. In the case of CEP164, this is the first report of two siblings with a BBS-like syndrome with mutations in this gene. Mutations in this gene were previously associated with nephronophthisis 15, thus the current results expand the CEP164-associated phenotypic spectrum. The clinical and genetic spectrum of BBS and BBS-like phenotypes is not fully defined in Pakistan. Therefore, genetic studies are needed to gain insights into genotype-phenotype correlations, which will in turn improve the clinician's ability to make an early and accurate diagnosis, and facilitate genetic counseling, leading to directly benefiting families with affected individuals.

PMID: 27708425 [PubMed - indexed for MEDLINE]

Genomic insights into the causes of type 2 diabetes.

Lancet. 2018 Jun 16;391(10138):2463-2474

Authors: Langenberg C, Lotta LA

Abstract
Genome-wide association studies have implicated around 250 genomic regions in predisposition to type 2 diabetes, with evidence for causal variants and genes emerging for several of these regions. Understanding of the underlying mechanisms, including the interplay between β-cell failure, insulin sensitivity, appetite regulation, and adipose storage has been facilitated by the integration of multidimensional data for diabetes-related intermediate phenotypes, detailed genomic annotations, functional experiments, and now multiomic molecular features. Studies in diverse ethnic groups and examples from population isolates have shown the value and need for a broad genomic approach to this global disease. Transethnic discovery efforts and large-scale biobanks in diverse populations and ancestries could help to address some of the Eurocentric bias. Despite rapid progress in the discovery of the highly polygenic architecture of type 2 diabetes, dominated by common alleles with small, cumulative effects on disease risk, these insights have been of little clinical use in terms of disease prediction or prevention, and have made only small contributions to subtype classification or stratified approaches to treatment. Successful development of academia-industry partnerships for exome or genome sequencing in large biobanks could help to deliver economies of scale, with implications for the future of genomics-focused research.

PMID: 29916387 [PubMed - in process]

Targeted exome analysis identifies the genetic basis of disease in over 50% of patients with a wide range of ataxia-related phenotypes.

Genet Med. 2018 Jun 18;:

Authors: Sun M, Johnson AK, Nelakuditi V, Guidugli L, Fischer D, Arndt K, Ma L, Sandford E, Shakkottai V, Boycott K, Chardon JW, Li Z, Del Gaudio D, Burmeister M, Gomez CM, Waggoner DJ, Das S

Abstract
PURPOSE: To examine the impact of a targeted exome approach for the molecular diagnosis of patients nationwide with a wide range of ataxia-related phenotypes.
METHODS: One hundred and seventy patients with ataxia of unknown etiology referred from clinics throughout the United States and Canada were studied using a targeted exome approach. Patients ranged in age from 2 to 88 years. Analysis was focused on 441 curated genes associated with ataxia and ataxia-like conditions.
RESULTS: Pathogenic and suspected diagnostic variants were identified in 88 of the 170 patients, providing a positive molecular diagnostic rate of 52%. Forty-six different genes were implicated, with the six most commonly mutated genes being SPG7, SYNE1, ADCK3, CACNA1A, ATP1A3, and SPTBN2, which accounted for >40% of the positive cases. In many cases a diagnosis was provided for conditions that were not suspected and resulted in the broadening of the clinical spectrum of several conditions.
CONCLUSION: Exome sequencing with targeted analysis provides a high-yield approach for the genetic diagnosis of ataxia-related conditions. This is the largest targeted exome study performed to date in patients with ataxia and ataxia-like conditions and represents patients with a wide range of ataxia phenotypes typically encountered in neurology and genetics clinics.

PMID: 29915382 [PubMed - as supplied by publisher]

The genotypic and phenotypic spectrum of PARS2-related infantile-onset encephalopathy.

J Hum Genet. 2018 Jun 18;:

Authors: Yin X, Tang B, Mao X, Peng J, Zeng S, Wang Y, Jiang H, Li N

Abstract
Mitochondrial aminoacyl-tRNA synthetases (mt-aaRSs) are a family of enzymes that play critical roles in protein biosynthesis. Mutations in mt-aaRSs are associated with various diseases. As a member of the mt-aaRS family, PARS2 encoding prolyl-tRNA synthetase 2 was recently shown to be associated with Alpers syndrome and certain infantile-onset neurodegenerative disorders in four patients. Here, we present two patients in a pedigree with early developmental delay, epileptic spasms, delayed myelination combined with cerebellar white matter abnormalities, and progressive cortical atrophy. Whole-exome sequencing revealed pathogenic compound heterozygous variants [c.283 G > A (p.95 V > I)] and [c.604 G > C (p.202 R > G)] in PARS2. Nearly all patients had epileptic spasms with early response to treatment, early developmental delay and/or regression followed by generalized hypotonia, postnatal microcephaly, elevated lactate levels, and progressive cerebral atrophy. Our study provides further evidence for validating the role of PARS2 in the pathology of related infantile-onset encephalopathy, contributing to the phenotypic features of this condition, and providing clinical and molecular insight for the diagnosis of this disease entity.

PMID: 29915213 [PubMed - as supplied by publisher]

Analysis of SDHAF3 in familial and sporadic pheochromocytoma and paraganglioma.

BMC Cancer. 2017 Jul 24;17(1):497

Authors: Dwight T, Na U, Kim E, Zhu Y, Richardson AL, Robinson BG, Tucker KM, Gill AJ, Benn DE, Clifton-Bligh RJ, Winge DR

Abstract
BACKGROUND: Germline mutations in genes encoding subunits of succinate dehydrogenase (SDH) are associated with the development of pheochromocytoma (PC) and/or paraganglioma (PGL). As assembly factors have been identified as playing a role in maturation of individual SDH subunits and assembly of the functioning SDH complex, we hypothesized that SDHAF3 variants may be associated with PC/PGL and functionality of SDH.
METHODS: DNA was extracted from the blood of 37 individuals (from 23 families) with germline SDH mutations and 18 PC/PGL (15 sporadic, 3 familial) and screened for mutations using a custom gene panel, containing SDHAF3 (SDH assembly factor 3) as well as eight known PC/PGL susceptibility genes. Molecular and functional consequences of an identified sequence variant of SDHAF3 were assessed in yeast and mammalian cells (HEK293).
RESULTS: Using massively parallel sequencing, we identified a variant in SDHAF3, c.157 T > C (p.Phe53Leu), associated with increased prevalence in familial and sporadic PC/PGL (6.6%) when compared to normal populations (1.2% [1000 Genomes], p = 0.003; 2.1% [Exome Aggregation Consortium], p = 0.0063). In silico prediction tools suggest this variant is probably damaging to protein function, hence we assessed molecular and functional consequences of the resulting amino acid change (p.Phe53Leu) in yeast and human cells. We showed that introduction of SDHAF3 p.Phe53Leu into Sdh7 (ortholog of SDHAF3 in humans) null yeast resulted in impaired function, as observed by its failure to restore SDH activity when expressed in Sdh7 null yeast relative to WT SDHAF3. As SDHAF3 is involved in maturation of SDHB, we tested the functional impact of SDHAF3 c.157 T > C and various clinically relevant SDHB mutations on this interaction. Our in vitro studies in human cells show that SDHAF3 interacts with SDHB (residues 46 and 242), with impaired interaction observed in the presence of the SDHAF3 c.157 T > C variant.
CONCLUSIONS: Our studies reveal novel insights into the biogenesis of SDH, uncovering a vital interaction between SDHAF3 and SDHB. We have shown that SDHAF3 interacts directly with SDHB (residue 242 being key to this interaction), and that a variant in SDHAF3 (c.157 T > C [p.Phe53Leu]) may be more prevalent in individuals with PC/PGL, and is hypomorphic via impaired interaction with SDHB.

PMID: 28738844 [PubMed - indexed for MEDLINE]

Assessment of a Targeted Gene Panel for Identification of Genes Associated With Movement Disorders.

JAMA Neurol. 2018 Jun 18;:

Authors: Montaut S, Tranchant C, Drouot N, Rudolf G, Guissart C, Tarabeux J, Stemmelen T, Velt A, Fourrage C, Nitschké P, Gerard B, Mandel JL, Koenig M, Chelly J, Anheim M, French Parkinson’s and Movement Disorders Consortium

Abstract
Importance: Movement disorders are characterized by a marked genotypic and phenotypic heterogeneity, complicating diagnostic work in clinical practice and molecular diagnosis.
Objective: To develop and evaluate a targeted sequencing approach using a customized panel of genes involved in movement disorders.
Design, Setting and Participants: We selected 127 genes associated with movement disorders to create a customized enrichment in solution capture array. Targeted high-coverage sequencing was applied to DNA samples taken from 378 eligible patients at 1 Luxembourgian, 1 Algerian, and 25 French tertiary movement disorder centers between September 2014 and July 2016. Patients were suspected of having inherited movement disorders because of early onset, family history, and/or complex phenotypes. They were divided in 5 main movement disorder groups: parkinsonism, dystonia, chorea, paroxysmal movement disorder, and myoclonus. To compare approaches, 23 additional patients suspected of having inherited cerebellar ataxia were included, on whom whole-exome sequencing (WES) was done. Data analysis occurred from November 2015 to October 2016.
Main Outcomes and Measures: Percentages of individuals with positive diagnosis, variants of unknown significance, and negative cases; mutational frequencies and clinical phenotyping of genes associated with movement disorders.
Results: Of the 378 patients (of whom 208 were male [55.0%]), and with a median (range) age at disease onset of 31 (0-84) years, probable pathogenic variants were identified in 83 cases (22.0%): 46 patients with parkinsonism (55% of 83 patients), 21 patients (25.3%) with dystonia, 7 patients (8.4%) with chorea, 7 patients (8.4%) with paroxysmal movement disorders, and 2 patients (2.4%) with myoclonus as the predominant phenotype. Some genes were mutated in several cases in the cohort. Patients with pathogenic variants were significantly younger (median age, 27 years; interquartile range [IQR], 5-36 years]) than the patients without diagnosis (median age, 35 years; IQR, 15-46 years; P = .04). Diagnostic yield was significantly lower in patients with dystonia (21 of 135; 15.6%; P = .03) than in the overall cohort. Unexpected genotype-phenotype correlations in patients with pathogenic variants deviating from the classic phenotype were highlighted, and 49 novel probable pathogenic variants were identified. The WES analysis of the cohort of 23 patients with cerebellar ataxia led to an overall diagnostic yield of 26%, similar to panel analysis but at a cost 6 to 7 times greater.
Conclusions and Relevance: High-coverage sequencing panel for the delineation of genes associated with movement disorders was efficient and provided a cost-effective diagnostic alternative to whole-exome and whole-genome sequencing.

PMID: 29913018 [PubMed - as supplied by publisher]

Familial impairment of vocal cord mobility in childhood with clubfoot.

Clin Dysmorphol. 2018 Jun 14;:

Authors: Shaw R, Dias C, Ludemann J, Rupps R, Tsai V, Lehman A

Abstract
We report on a family with three siblings, male and female, affected by congenital bilateral limitation of vocal cord abduction, with the additional finding of clubfeet in two. The paternal family history suggests an autosomal dominant inheritance. The siblings and father also have mild craniofacial features, which may be an expression of variability or may be unrelated. The association between congenital vocal cord paralysis and clubfeet has been reported with additional major features or in the context of Charcot-Marie-Tooth disease. However, the two in isolation have only been reported in one other family previously. Genomic analyses of the family, including chromosomal microarray and exome sequencing, showed neither a likely pathogenic variant in a known disease gene nor a compelling candidate gene variant. We propose that the association of these two findings constitutes a novel recognizable phenotype, for which a genetic cause remains undetermined.

PMID: 29912011 [PubMed - as supplied by publisher]

A novel compound heterozygous mutation in the POMK gene causing limb-girdle muscular dystrophy-dystroglycanopathy in a sib pair.

Neuromuscul Disord. 2018 May 16;:

Authors: Strang-Karlsson S, Johnson K, Töpf A, Xu L, Lek M, MacArthur DG, Casar-Borota O, Williams M, Straub V, Wallgren-Pettersson C

Abstract
We describe two Finnish siblings in whom an incidentally detected elevated creatine kinase activity eventually led to a diagnosis of limb-girdle muscular dystrophy-dystroglycanopathy (Type C12; MDDGC12). When diagnosed at age 10 and 13 years, they were mildly affected with a slow or non-progressive disease course. The main symptoms comprised infrequent hip cramps triggered by flexion, neck cramps triggered by yawning, transient growing pains, calf hypertrophy and mild proximal muscle weakness. Their cognitive and motor developments were unremarkable and they were physically active. Whole-exome sequencing revealed compound heterozygous mutations, both of which were novel, in the protein O-mannosyl kinase (POMK) gene in both siblings; a missense mutation, p.Pro322Leu (c.965C > T), and a nonsense mutation, p.Arg46Ter (c.136C > T). The results were confirmed by Sanger sequencing, showing that the parents were heterozygous carriers of one mutation each. This report adds to the literature by providing phenotype and genotype data on this ultra-rare POMK-related dystroglycanopathy.

PMID: 29910097 [PubMed - as supplied by publisher]

Neonatal-Onset Chronic Diarrhea Caused by Homozygous Nonsense WNT2B Mutations.

Am J Hum Genet. 2018 Jun 04;:

Authors: O'Connell AE, Zhou F, Shah MS, Murphy Q, Rickner H, Kelsen J, Boyle J, Doyle JJ, Gangwani B, Thiagarajah JR, Kamin DS, Goldsmith JD, Richmond C, Breault DT, Agrawal PB

Abstract
Homozygous nonsense mutations in WNT2B were identified in three individuals from two unrelated families with severe, neonatal-onset osmotic diarrhea after whole-exome sequencing was performed on trios from the two families. Intestinal biopsy samples from affected individuals were used for histology and immunofluorescence and to generate enteroids ex vivo. Histopathologic evaluation demonstrated chronic inflammatory changes in the stomach, duodenum, and colon. Immunofluorescence demonstrated diminished staining for OLFM4, a marker for intestinal stem cells (ISCs). The enteroids generated from WNT2B-deficient intestinal epithelium could not be expanded and did not survive passage. Addition of CHIR-99021 (a GSK3A and GSK3B inhibitor and activator of canonical WNT/β-CATENIN signaling) could not rescue WNT2B-deficient enteroids. Addition of supplemental recombinant murine WNT2B was able to perpetuate small enteroids for multiple passages but failed to expand their number. Enteroids showed a 10-fold increase in the expression of LEF1 mRNA and a 100-fold reduction in TLR4 expression, compared with controls by quantitative RT-PCR, indicating alterations in canonical WNT and microbial pattern-recognition signaling. In summary, individuals with homozygous nonsense mutations in WNT2B demonstrate severe intestinal dysregulation associated with decreased ISC number and function, likely explaining their diarrheal phenotype. WNT2B deficiency should be considered for individuals with neonatal-onset diarrhea.

PMID: 29909964 [PubMed - as supplied by publisher]