De novo PIK3R2 variant causes polymicrogyria, corpus callosum hyperplasia and focal cortical dysplasia.

Eur J Hum Genet. 2016 Aug;24(9):1359-62

Authors: Terrone G, Voisin N, Abdullah Alfaiz A, Cappuccio G, Vitiello G, Guex N, D'Amico A, James Barkovich A, Brunetti-Pierri N, Del Giudice E, Reymond A

Abstract
We report an 8-year-old boy with a complex cerebral malformation, intellectual disability, and complex partial seizures. Whole-exome sequencing revealed a yet unreported de novo variant in the PIK3R2 gene that was recently associated with megalencephaly-polymicrogyria-polydactyly-hydrocephalus (MPPH) syndrome and bilateral perisylvian polymicrogyria (BPP). Our patient showed cerebral abnormalities (megalencephaly, perisylvian polymicrogyria, and mega corpus callosum) that were consistent with these conditions. Imaging also showed right temporal anomalies suggestive of cortical dysplasia. Until now, only three variants (c.1117G>A (p.(G373R)), c.1126A>G (p.(K376E)) and c.1202T>C (p.(L401P))) affecting the SH2 domain of the PIK3R2 protein have been reported in MPPH and BPP syndromes. In contrast to the variants reported so far, the patient described herein exhibits the c.1669G>C (p.(D557H)) variant that affects a highly conserved residue at the interface with the PI3K catalytic subunit α. The phenotypic spectrum associated with variants in this gene and its pathway are likely to continue to expand as more cases are identified.

PMID: 26860062 [PubMed - indexed for MEDLINE]

Evidence for genetic association between chromosome 1q loci and predisposition to colorectal neoplasia.

Br J Cancer. 2017 Jul 25;:

Authors: Schubert SA, Ruano D, Elsayed FA, Boot A, Crobach S, Sarasqueta AF, Wolffenbuttel B, van der Klauw MM, Oosting J, Tops CM, van Eijk R, Vasen HF, Vossen RH, Nielsen M, Castellví-Bel S, Ruiz-Ponte C, Tomlinson I, Dunlop MG, Vodicka P, Wijnen JT, Hes FJ, Morreau H, de Miranda NF, Sijmons RH, van Wezel T

Abstract
BACKGROUND: A substantial fraction of familial colorectal cancer (CRC) and polyposis heritability remains unexplained. This study aimed to identify predisposing loci in patients with these disorders.
METHODS: Homozygosity mapping was performed using 222 563 SNPs in 302 index patients with various colorectal neoplasms and 3367 controls. Linkage analysis, exome and whole-genome sequencing were performed in a family affected by microsatellite stable CRCs. Candidate variants were genotyped in 10 554 cases and 21 480 controls. Gene expression was assessed at the mRNA and protein level.
RESULTS: Homozygosity mapping revealed a disease-associated region at 1q32.3 which was part of the linkage region 1q32.2-42.2 identified in the CRC family. This includes a region previously associated with risk of CRC. Sequencing identified the p.Asp1432Glu variant in the MIA3 gene (known as TANGO1 or TANGO) and 472 additional rare, shared variants within the linkage region. In both cases and controls the population frequency was 0.02% for this MIA3 variant. The MIA3 mutant allele showed predominant mRNA expression in normal, cancer and precancerous tissues. Furthermore, immunohistochemistry revealed increased expression of MIA3 in adenomatous tissues.
CONCLUSIONS: Taken together, our two independent strategies associate genetic variations in chromosome 1q loci and predisposition to familial CRC and polyps, which warrants further investigation.British Journal of Cancer advance online publication: 25 July 2017; doi:10.1038/bjc.2017.240 www.bjcancer.com.

PMID: 28742792 [PubMed - as supplied by publisher]

MED resulting from recessively inherited mutations in the gene encoding calcium-activated nucleotidase CANT1.

Am J Med Genet A. 2017 Jul 25;:

Authors: Balasubramanian K, Li B, Krakow D, Nevarez L, Ho PJ, Ainsworth JA, Nickerson DA, Bamshad MJ, Immken L, Lachman RS, Cohn DH

Abstract
Multiple Epiphyseal Dysplasia (MED) is a relatively mild skeletal dysplasia characterized by mild short stature, joint pain, and early-onset osteoarthropathy. Dominantly inherited mutations in COMP, MATN3, COL9A1, COL9A2, and COL9A3, and recessively inherited mutations in SLC26A2, account for the molecular basis of disease in about 80-85% of the cases. In two families with recurrent MED of an unknown molecular basis, we used exome sequencing and candidate gene analysis to identify homozygosity for recessively inherited missense mutations in CANT1, which encodes calcium-activated nucleotidase 1. The MED phenotype is thus allelic to the more severe Desbuquois dysplasia phenotype and the results identify CANT1 as a second locus for recessively inherited MED.

PMID: 28742282 [PubMed - as supplied by publisher]

Whole exome sequencing identified genetic variations in Chinese hemangioblastoma patients.

Am J Med Genet A. 2017 Jul 25;:

Authors: Ma D, Yang J, Wang Y, Huang X, Du G, Zhou L

Abstract
Hemangioblastomas (HBs) are uncommon tumors characterized by the presence of inactivating alterations in the von Hippel-Lindau (VHL) gene in inherited cases and by infrequent somatic mutation in sporadic entities. We performed whole exome sequencing on 11 HB patients to further elucidate the genetics of HBs. A total of 270 somatic variations in 219 genes, of which there were 86 mutations in 67 genes, were found in sporadic HBs, and 184 mutations were found in 154 genes in familial HBs. C: G>T: A and T: A>C: G mutations are relatively common in most HB patients. Genes harboring the most significant mutations include PCDH9, KLHL12, DCAF4L1, and VHL in sporadic HBs, and ZNF814, DLG2, RIMS1, PNN, and MUC7 in familial HBs. The frequency of CNV varied considerably within sporadic HBs but was relatively similar within familial HBs. Five genes, including OTOGL, PLCB4, SCEL, THSD4, and WWOX, have CNVs in the six patients with sporadic HBs, and three genes, including ABCA6, CWC27, and LAMA2, have CNVs in the five patients with familial HBs. We found new genetic mutations and CNVs that might be involved in HBs; these findings highlight the complexity of the tumorigenesis of HBs and pinpoint potential therapeutic targets for the treatment of HBs.

PMID: 28742274 [PubMed - as supplied by publisher]

A Gene Implicated in Activation of Retinoic Acid Receptor Targets is a Novel Renal Agenesis Gene in Humans.

Genetics. 2017 Jul 24;:

Authors: Brophy PD, Rasmussen M, Parida M, Bonde G, Darbro BW, Hong X, Clarke JC, Peterson KA, Denegre J, Schneider M, Sussman CR, Sunde L, Lildballe DL, Hertz JM, Cornell RA, Murray SA, Manak JR

Abstract
Renal agenesis (RA) is one of the more extreme examples of congenital anomalies of the kidney and urinary tract (CAKUT). Bilateral renal agenesis is almost invariably fatal at birth, and unilateral renal agenesis can lead to future health issues including end stage renal disease. Genetic investigations have identified several gene variants which cause RA, including EYA1, LHX1, and WT1 However, whereas compound null mutations of genes encoding α and γ retinoic acid receptors (RARs) cause RA in mice, to date there have been no reports of variants in RAR genes causing RA in humans. In this study, we carried out whole exome sequence analysis of two families showing inheritance of an RA phenotype, and in both identified a single candidate gene, GREB1L Analysis of a zebrafish greb1l loss-of-function mutant revealed defects in the pronephric kidney just prior to death, and F0 CRISPR/Cas9 mutagenesis of Greb1l in the mouse revealed kidney agenesis phenotypes, implicating Greb1l in this disorder. GREB1L resides in a chromatin complex with RAR members, and our data implicate GREB1L as a coactivator for RARs. This study is the first to associate a component of the RAR pathway with renal agenesis in humans.

PMID: 28739660 [PubMed - as supplied by publisher]

Mutations in the ABCG8 gene are associated with sitosterolaemia in the homozygous form and xanthelasmas in the heterozygous form.

Eur J Dermatol. 2017 Jul 25;:

Authors: Bardawil T, Rebeiz A, Chaabouni M, El Halabi J, Kambris Z, Abbas O, Abou Hassan O, Hamie L, Bitar F, Ghani Kibbi A, Nemer G, Kurban M

Abstract
Sitosterol is the most abundant plant sterol found in our diet. Sitosterolemia (OMIM 210250), also known as phytosterolaemia, is a rare autosomal recessive disease caused by the inability to efficiently excrete plant sterol, and is characterized by cutaneous xanthomas and accelerated atherosclerosis. Sitosterolaemia is caused by homozygous or compound heterozygous mutations in either ABCG5 or ABCG8 (both on chromosome 2p21), which encode the sterol efflux transporter ABCG5 (sterolin-1) and ABCG8 (sterolin-2), respectively. To investigate a Tunisian family with several members who manifested with generalized cutaneous xanthomas, whereas others had only isolated xanthelasmas. Genetic analysis was performed based on exome sequencing of DNA obtained from five affected individuals and one unaffected individual from a Tunisian family.
RESULTS: A novel mutation in the ABCG8 gene, designated c.965-1G>C, was identified by exome sequencing in the members of this family. The homozygous form was associated with generalized cutaneous xanthomatosis while the heterozygous form was linked to isolated xanthelasmas. Our results indicate a gene dosage effect of ABCG8 and suggest that individuals at risk should be followed closely.

PMID: 28739549 [PubMed - as supplied by publisher]

The evolving genetic risk for sporadic ALS.

Neurology. 2017 Jul 18;89(3):226-233

Authors: Gibson SB, Downie JM, Tsetsou S, Feusier JE, Figueroa KP, Bromberg MB, Jorde LB, Pulst SM

Abstract
OBJECTIVE: To estimate the genetic risk conferred by known amyotrophic lateral sclerosis (ALS)-associated genes to the pathogenesis of sporadic ALS (SALS) using variant allele frequencies combined with predicted variant pathogenicity.
METHODS: Whole exome sequencing and repeat expansion PCR of C9orf72 and ATXN2 were performed on 87 patients of European ancestry with SALS seen at the University of Utah. DNA variants that change the protein coding sequence of 31 ALS-associated genes were annotated to determine which were rare and deleterious as predicted by MetaSVM. The percentage of patients with SALS with a rare and deleterious variant or repeat expansion in an ALS-associated gene was calculated. An odds ratio analysis was performed comparing the burden of ALS-associated genes in patients with SALS vs 324 normal controls.
RESULTS: Nineteen rare nonsynonymous variants in an ALS-associated gene, 2 of which were found in 2 different individuals, were identified in 21 patients with SALS. Further, 5 deleterious C9orf72 and 2 ATXN2 repeat expansions were identified. A total of 17.2% of patients with SALS had a rare and deleterious variant or repeat expansion in an ALS-associated gene. The genetic burden of ALS-associated genes in patients with SALS as predicted by MetaSVM was significantly higher than in normal controls.
CONCLUSIONS: Previous analyses have identified SALS-predisposing variants only in terms of their rarity in normal control populations. By incorporating variant pathogenicity as well as variant frequency, we demonstrated that the genetic risk contributed by these genes for SALS is substantially lower than previous estimates.

PMID: 28642336 [PubMed - indexed for MEDLINE]

Identification of a novel CTCF mutation responsible for syndromic intellectual disability - a case report.

BMC Med Genet. 2017 Jun 15;18(1):68

Authors: Bastaki F, Nair P, Mohamed M, Malik EM, Helmi M, Al-Ali MT, Hamzeh AR

Abstract
BACKGROUND: Autosomal dominant mental retardation 21 (MRD21) is a very rare condition, characterized by short stature, microcephaly, mild facial dysmorphisms and intellectual disability that ranged from mild to severe. MRD21 is caused by mutations in CCCTC-binding factor (CTCF) and this was established through only four unrelated cases, two of which had frameshift mutations. CTCF is a master transcriptional regulator that controls chromatin structure and may serve as insulator and transcriptional activator and repressor.
CASE PRESENTATION: This study presents, clinically and molecularly, an Emirati patient with de novo frameshift mutation in CTCF. This novel mutation was uncovered using whole exome sequencing and was confirmed by Sanger sequencing in the trio. In silico analysis, using SIFT Indel, indicates that this frameshift; p.Lys206Profs*13 is functionally damaging with the likely involvement of nonsense-mediated mRNA decay.
CONCLUSIONS: Upon comparing the clinical picture of the herewith-reported individual with previously reported cases of MRD21, there seems to be many common symptoms, and few new ones that were not observed before. This helps to further define this rare condition and its molecular underpinnings.

PMID: 28619046 [PubMed - indexed for MEDLINE]

Integrative genomic and functional analysis of human oral squamous cell carcinoma cell lines reveals synergistic effects of FAT1 and CASP8 inactivation.

Cancer Lett. 2016 Dec 01;383(1):106-114

Authors: Hayes TF, Benaich N, Goldie SJ, Sipilä K, Ames-Draycott A, Cai W, Yin G, Watt FM

Abstract
Oral squamous cell carcinoma (OSCC) is genetically highly heterogeneous, which contributes to the challenges of treatment. To create an in vitro model that accurately reflects this heterogeneity, we generated a panel of HPV-negative OSCC cell lines. By whole exome sequencing of the lines and matched patient blood samples, we demonstrate that the mutational spectrum of the lines is representative of primary OSCC in The Cancer Genome Atlas. We show that loss of function mutations in FAT1 (an atypical cadherin) and CASP8 (Caspase 8) frequently occur in the same tumour. OSCC cells with inactivating FAT1 mutations exhibited reduced intercellular adhesion. Knockdown of FAT1 and CASP8 individually or in combination in OSCC cells led to increased cell migration and clonal growth, resistance to Staurosporine-induced apoptosis and, in some cases, increased terminal differentiation. The OSCC lines thus represent a valuable resource for elucidating the impact of different mutations on tumour behaviour.

PMID: 27693639 [PubMed - indexed for MEDLINE]

Semiconductor Whole Exome Sequencing for the Identification of Genetic Variants in Colombian Patients Clinically Diagnosed with Long QT Syndrome.

Mol Diagn Ther. 2016 Aug;20(4):353-62

Authors: Burgos M, Arenas A, Cabrera R

Abstract
BACKGROUND AND OBJECTIVE: Inherited long QT syndrome (LQTS) is a cardiac channelopathy characterized by a prolongation of QT interval and the risk of syncope, cardiac arrest, and sudden cardiac death. Genetic diagnosis of LQTS is critical in medical practice as results can guide adequate management of patients and distinguish phenocopies such as catecholaminergic polymorphic ventricular tachycardia (CPVT). However, extensive screening of large genomic regions is required in order to reliably identify genetic causes. Semiconductor whole exome sequencing (WES) is a promising approach for the identification of variants in the coding regions of most human genes.
METHODS: DNA samples from 21 Colombian patients clinically diagnosed with LQTS were enriched for coding regions using multiplex polymerase chain reaction (PCR) and subjected to WES using a semiconductor sequencer.
RESULTS: Semiconductor WES showed mean coverage of 93.6 % for all coding regions relevant to LQTS at >10× depth with high intra- and inter-assay depth heterogeneity. Fifteen variants were detected in 12 patients in genes associated with LQTS. Three variants were identified in three patients in genes associated with CPVT. Co-segregation analysis was performed when possible. All variants were analyzed with two pathogenicity prediction algorithms. The overall prevalence of LQTS and CPVT variants in our cohort was 71.4 %. All LQTS variants previously identified through commercial genetic testing were identified.
CONCLUSION: Standardized WES assays can be easily implemented, often at a lower cost than sequencing panels. Our results show that WES can identify LQTS-causing mutations and permits differential diagnosis of related conditions in a real-world clinical setting. However, high heterogeneity in sequencing depth and low coverage in the most relevant genes is expected to be associated with reduced analytical sensitivity.

PMID: 27251404 [PubMed - indexed for MEDLINE]

De novo loss-of-function mutations in WAC cause a recognizable intellectual disability syndrome and learning deficits in Drosophila.

Eur J Hum Genet. 2016 Aug;24(8):1145-53

Authors: Lugtenberg D, Reijnders MR, Fenckova M, Bijlsma EK, Bernier R, van Bon BW, Smeets E, Vulto-van Silfhout AT, Bosch D, Eichler EE, Mefford HC, Carvill GL, Bongers EM, Schuurs-Hoeijmakers JH, Ruivenkamp CA, Santen GW, van den Maagdenberg AM, Peeters-Scholte CM, Kuenen S, Verstreken P, Pfundt R, Yntema HG, de Vries PF, Veltman JA, Hoischen A, Gilissen C, de Vries BB, Schenck A, Kleefstra T, Vissers LE

Abstract
Recently WAC was reported as a candidate gene for intellectual disability (ID) based on the identification of a de novo mutation in an individual with severe ID. WAC regulates transcription-coupled histone H2B ubiquitination and has previously been implicated in the 10p12p11 contiguous gene deletion syndrome. In this study, we report on 10 individuals with de novo WAC mutations which we identified through routine (diagnostic) exome sequencing and targeted resequencing of WAC in 2326 individuals with unexplained ID. All but one mutation was expected to lead to a loss-of-function of WAC. Clinical evaluation of all individuals revealed phenotypic overlap for mild ID, hypotonia, behavioral problems and distinctive facial dysmorphisms, including a square-shaped face, deep set eyes, long palpebral fissures, and a broad mouth and chin. These clinical features were also previously reported in individuals with 10p12p11 microdeletion syndrome. To investigate the role of WAC in ID, we studied the importance of the Drosophila WAC orthologue (CG8949) in habituation, a non-associative learning paradigm. Neuronal knockdown of Drosophila CG8949 resulted in impaired learning, suggesting that WAC is required in neurons for normal cognitive performance. In conclusion, we defined a clinically recognizable ID syndrome, caused by de novo loss-of-function mutations in WAC. Independent functional evidence in Drosophila further supported the role of WAC in ID. On the basis of our data WAC can be added to the list of ID genes with a role in transcription regulation through histone modification.

PMID: 26757981 [PubMed - indexed for MEDLINE]

Expansion of the spectrum of ITGB6-related disorders to adolescent alopecia, dentogingival abnormalities and intellectual disability.

Eur J Hum Genet. 2016 Aug;24(8):1223-7

Authors: Ansar M, Jan A, Santos-Cortez RL, Wang X, Suliman M, Acharya A, Habib R, Abbe I, Ali G, Lee K, Smith JD, University of Washington Center for Mendelian Genomics, Nickerson DA, Shendure J, Bamshad MJ, Ahmad W, Leal SM

Abstract
Alopecia with mental retardation (APMR) is a very rare disorder. In this study, we report on a consanguineous Pakistani family (AP91) with mild-to-moderate intellectual disability, adolescent alopecia and dentogingival abnormalities. Using homozygosity mapping, linkage analysis and exome sequencing, we identified a novel rare missense variant c.898G>A (p.(Glu300Lys)) in ITGB6, which co-segregates with the phenotype within the family and is predicted to be deleterious. Structural modeling shows that Glu300 lies in the β-propeller domain, and is surrounded by several residues that are important for heterodimerization with α integrin. Previous studies showed that ITGB6 variants can cause amelogenesis imperfecta in humans, but patients from family AP91 who are homozygous for the c.898G>A variant present with neurological and dermatological features, indicating a role for ITGB6 beyond enamel formation. Our study demonstrates that a rare deleterious variant within ITGB6 causes not only dentogingival anomalies but also intellectual disability and alopecia.

PMID: 26695873 [PubMed - indexed for MEDLINE]

A novel multiple joint dislocation syndrome associated with a homozygous nonsense variant in the EXOC6B gene.

Eur J Hum Genet. 2016 Aug;24(8):1206-10

Authors: Girisha KM, Kortüm F, Shah H, Alawi M, Dalal A, Bhavani GS, Kutsche K

Abstract
We report two brothers from a consanguineous couple with spondyloepimetaphyseal dysplasia (SEMD), multiple joint dislocations at birth, severe joint laxity, scoliosis, gracile metacarpals and metatarsals, delayed bone age and poorly ossified carpal and tarsal bones, probably representing a yet uncharacterized SEMD with laxity and dislocations. This condition has clinical overlap with autosomal dominantly inherited SEMD with joint laxity, leptodactylic type caused by recurrent missense variants in the kinesin family member 22 gene (KIF22). Single-nucleotide polymorphism array analysis and whole-exome sequencing in the two affected siblings revealed a shared homozygous nonsense variant [c.906T>A/p.(Tyr302*)] in EXOC6B as the most likely cause. EXOC6B encodes a component of the exocyst complex required for tethering secretory vesicles to the plasma membrane. As transport of vesicles from the golgi apparatus to the plasma membrane occurs through kinesin motor proteins along microtubule tracks, the function of EXOC6B is linked to KIF22 suggesting a common pathogenic mechanism in skeletal dysplasias with joint laxity and dislocations.

PMID: 26669664 [PubMed - indexed for MEDLINE]

Genes for spinocerebellar ataxia with blindness and deafness (SCABD/SCAR3, MIM# 271250 and SCABD2).

Eur J Hum Genet. 2016 Aug;24(8):1154-9

Authors: Guissart C, Drouot N, Oncel I, Leheup B, Gershoni-Barush R, Muller J, Ferdinandusse S, Larrieu L, Anheim M, Arslan EA, Claustres M, Tranchant C, Topaloglu H, Koenig M

Abstract
Ataxia is a symptom that is often associated with syndromic inherited diseases. We previously reported the linkage of a novel syndrome, ataxia with blindness and deafness (SCAR3/SCABD, OMIM# 271250), to chromosome 6p21-p23 by linkage mapping of an Arab Israeli consanguineous family. We have now identified by whole-exome sequencing a homozygous missense mutation in the Arab Israeli family in the SLC52A2 gene located in 8qter, therefore excluding linkage of this family to 6p. We confirmed the involvement of SLC52A2 by the identification of a second mutation in an independent family with an identical syndromic presentation, which we suggest to name SCABD2. SCABD2 is therefore allelic to Brown-Vialleto-Van Laere syndrome type 2 defined by prominent motoneuronopathy and deafness, and also caused by SLC52A2 mutations. In the course of this project, we identified a clinically similar family with a homozygous missense mutation in PEX6, which is located in 6p21. Therefore, despite false linkage in the initial family, SCABD1/SCAR3 is located in 6p21 and is caused by PEX6 mutations. Both SLC52A2 and PEX6 should be included in screening panels for the diagnosis of syndromic inherited ataxias, particularly as patients with mutations in SLC52A2 can be ameliorated by riboflavin supplementation.

PMID: 26669662 [PubMed - indexed for MEDLINE]

Identification of the first dominant mutation of LAMA5 gene causing a complex multisystem syndrome due to dysfunction of the extracellular matrix.

J Med Genet. 2017 Jul 22;:

Authors: Sampaolo S, Napolitano F, Tirozzi A, Reccia MG, Lombardi L, Farina O, Barra A, Cirillo F, Melone MAB, Gianfrancesco F, Iorio GD, Esposito T

Abstract
BACKGROUND: The laminin alpha 5 gene (LAMA5) plays a master role in the maintenance and function of the extracellular matrix (ECM) in mammalian tissues, which is critical in developmental patterning, stem cell niches, cancer and genetic diseases. Its mutations have never been reported in human disease so far. The aim of this study was to associate the first mutation in LAMA5 gene to a novel multisystem syndrome.
METHODS: A detailed characterisation of a three-generation family, including clinical, biochemical, instrumental and morphological analysis, together with genetics and expression (WES and RNAseq) studies, was performed.
RESULTS: The heterozygous LAMA5 mutation c.9418G>A (p.V3140M) was associated with skin anomalies, impaired scarring, night blindness, muscle weakness, osteoarthritis, joint and internal organs ligaments laxity, malabsorption syndrome and hypothyroidism. We demonstrated that the mutation alters the amount of LAMA5 peptides likely derived from protein cleavage and perturbs the activation of the epithelial-mesenchymal signalling, producing an unbalanced expression of Sonic hedgehog and GLI1, which are upregulated in cells from affected individuals, and of ECM proteins (COL1A1, MMP1 and MMP3), which are strongly inhibited. Studies carried out using human skin biopsies showed alteration of dermal papilla with a reduction of the germinative layer and an early arrest of hair follicle downgrowth. The knock-in mouse model, generated in our laboratory, shows similar changes in the tissues studied so far.
CONCLUSIONS: This is the first report of a disease phenotype associated with LAMA5 mutation in humans.

PMID: 28735299 [PubMed - as supplied by publisher]

An update on the genetics of dementia with Lewy bodies.

Parkinsonism Relat Disord. 2017 Jul 13;:

Authors: Vergouw LJM, van Steenoven I, van de Berg WDJ, Teunissen CE, van Swieten JC, Bonifati V, Lemstra AW, de Jong FJ

Abstract
The genetic architecture of dementia with Lewy bodies (DLB) is increasingly taking shape. Initially, genetic research focused mainly on linkage and candidate gene studies in small series of DLB patients. More recently, association and exome sequencing studies in larger groups have been conducted, and have shown that several variants in GBA and the APOE ε4 allele are important genetic risk factors for DLB. However, genetic research in DLB is still in its infancy. So far, many genetic studies have been biased and performed in clinically and pathologically heterogeneous populations. Therefore, it is likely that multiple DLB-specific genetic determinants still have to be identified. To further our understanding of the role of genetics in DLB, future genetic studies should be unbiased and performed in large series of DLB patients, ideally with both a clinical diagnosis and pathological confirmation. The combination of genomic techniques with other research modalities, such as proteomic research, is a promising approach to identify novel genetic determinants. More knowledge about the genetics of DLB will increase our understanding of the pathophysiology of the disease and its relation with Parkinson's Disease and Alzheimer's Disease, and may eventually lead to the development of disease modifying treatments.

PMID: 28734699 [PubMed - as supplied by publisher]

Identification of a rare COCH mutation by whole-exome sequencing : Implications for personalized therapeutic rehabilitation in an Austrian family with non-syndromic autosomal dominant late-onset hearing loss.

Wien Klin Wochenschr. 2017 Jul 21;:

Authors: Parzefall T, Frohne A, Koenighofer M, Kirchnawy A, Streubel B, Schoefer C, Gstoettner W, Frei K, Lucas T

Abstract
BACKGROUND: Non-syndromic autosomal dominant hearing impairment is characteristically postlingual in onset. Genetic diagnostics are essential for genetic counselling, disease prognosis and understanding of the molecular mechanisms of disease. To date, 36 causative genes have been identified, many in only individual families. Gene selection for genetic screening by traditional methods and genetic diagnosis in autosomal dominant patients has therefore been fraught with difficulty. Whole-exome sequencing provides a powerful tool to analyze all protein-coding genomic regions in parallel, thus allowing the comprehensive screening of all known genes and associated alterations.
METHODS: In this study, a previously undiagnosed late-onset progressive autosomal dominant hearing loss in an Austrian family was investigated by means of whole-exome sequencing. Results were confirmed by Sanger sequencing.
RESULTS: A previously described c.151C>T missense (p.Pro51Ser) mutation in the LCCL (limulus factor C, cochlin, late gestation lung protein Lgl1) domain of the cochlin gene (COCH) was identified as causative and segregated with disease in five members of the family. Molecular diagnostics led to the decision to perform cochlear implantation in an index patient who subsequently showed excellent postoperative auditory performance. The c.151C>T mutation was not found in 18 screened Austrian families with autosomal dominant hearing loss but was represented alongside other known pathogenic mutant COCH alleles in the Genome Aggregation Database (gnomAD) in European populations. A combined allele frequency of 0.000128 implies an orphan disease frequency for COCH-induced hearing loss of 1:3900 in Europe.
CONCLUSIONS: Exome sequencing successfully resolved the genetic diagnosis in a family suffering from autosomal dominant hearing impairment and allowed prediction of purported auditory outcome after cochlear implantation in an index patient. Personalized treatment approaches based on the molecular mechanisms of disease may become increasingly important in the future.

PMID: 28733840 [PubMed - as supplied by publisher]

A homozygous MYO7A mutation associated to Usher syndrome and unilateral auditory neuropathy spectrum disorder.

Mol Med Rep. 2017 Jul 21;:

Authors: Xia H, Hu P, Yuan L, Xiong W, Xu H, Yi J, Yang Z, Deng X, Guo Y, Deng H

Abstract
Usher syndrome (USH) is an autosomal recessive disorder characterized by sensorineural hearing loss, progressive visual loss and night blindness due to retinitis pigmentosa (RP), with or without vestibular dysfunction. The purpose of this study was to detect the causative gene in a consanguineous Chinese family with USH. A c.3696_3706del (p.R1232Sfs*72) variant in the myosin VIIa gene (MYO7A) was identified in the homozygous state by exome sequencing. The co‑segregation of the MYO7A c.3696_3706del variant with the phenotype of deafness and progressive visual loss in the USH family was confirmed by Sanger sequencing. The variant was absent in 200 healthy controls. Therefore, the c.3696_3706del variant may disrupt the interaction between myosin VIIa and other USH1 proteins, and impair melanosome transport in retinal pigment epithelial cells. Notably, bilateral auditory brainstem responses were absent in two patients of the USH family, while distortion product otoacoustic emissions were elicited in the right ears of the two patients, consistent with clinical diagnosis of unilateral auditory neuropathy spectrum disorder. These data suggested that the homozygous c.3696_3706del variant in the MYO7A gene may be the disease‑causing mutation for the disorder in this family. These findings broaden the phenotype spectrum of the MYO7A gene, and may facilitate understanding of the molecular pathogenesis of the disease, and genetic counseling for the family.

PMID: 28731162 [PubMed - as supplied by publisher]

Early Diagnosis of ABCB11 Spectrum Liver Disorders by Next Generation Sequencing.

Pediatr Gastroenterol Hepatol Nutr. 2017 Jun;20(2):114-123

Authors: Lee SJ, Kim JE, Choe BH, Seo AN, Bae HI, Hwang SK

Abstract
PURPOSE: The goal of this study was the early diagnosis of ABCB11 spectrum liver disorders, especially those focused on benign recurrent intrahepatic cholestasis and progressive familial intrahepatic cholestasis.
METHODS: Fifty patients presenting neonatal cholestasis were evaluated to identify underlying etiologies. Genetic analysis was performed on patients suspected to have syndromic diseases or ABCB11 spectrum liver disorders. Two families with proven ABCB11 spectrum liver disorders were subjected to genetic analyses to confirm the diagnosis and were provided genetic counseling. Whole exome sequencing and Sanger sequencing were performed on the patients and the family members.
RESULTS: Idiopathic or viral hepatitis was diagnosed in 34%, metabolic disease in 20%, total parenteral nutrition induced cholestasis in 16%, extrahepatic biliary atresia in 14%, genetic disease in 10%, neonatal lupus in 2%, congenital syphilis in 2%, and choledochal cyst in 2% of the patients. The patient with progressive familial intrahepatic cholestasis had novel heterozygous mutations of ABCB11 c.11C>G (p.Ser4(*)) and c.1543A>G (p.Asn515Asp). The patient with benign recurrent intrahepatic cholestasis had homozygous mutations of ABCB11 c.1331T>C (p.Val444Ala) and heterozygous, c.3084A>G (p.Ala1028Ala). Genetic confirmation of ABCB11 spectrum liver disorder led to early liver transplantation in the progressive familial intrahepatic cholestasis patient. In addition, the atypically severe benign recurrent intrahepatic cholestasis patient was able to avoid unnecessary liver transplantation after genetic analysis.
CONCLUSION: ABCB11 spectrum liver disorders can be clinically indistinguishable as they share similar characteristics related to acute episodes. A comprehensive genetic analysis will facilitate optimal diagnosis and treatment.

PMID: 28730136 [PubMed]

A Chinese family with Axenfeld-Rieger syndrome: report of the clinical and genetic findings.

Int J Ophthalmol. 2017;10(6):847-853

Authors: Sun DP, Dai YH, Pan XJ, Shan T, Wang DQ, Chen P

Abstract
AIM: To describe a Chinese family affected by a severe form of Axenfeld-Rieger syndrome (ARS) and characterize the molecular defect in PITX2 in the family.
METHODS: Patients presented with typical ARS from a Chinese family were investigated. We performed genome-wide linkage scan and exome sequencing to identify the pathogenic mutations. Candidate mutations were verified for co-segregation in the whole pedigree using Sanger sequencing. Real-time polymerase chain reaction (RT-PCR) and Western blotting were performed to verify the expression of the pathogenic gene.
RESULTS: Genome-wide linkage and exome sequencing analyses showed PITX2 as the disease candidate gene. A>G substitution at position -11 of 3'ss of exon 5 (IVS5-11A>G) that co-segregated with the disease phenotype was discovered in the family. The PITX2 messenger ribonucleic acid and protein levels were about 50% lower in patients with ARS than in unaffected family members in the family.
CONCLUSION: Our findings implicate the first intronic mutation of the PITX2 gene in the pathogenesis of a severe form of ARS in a Chinese family. This study highlights the importance of a systematic search for intronic mutation in ARS cases for which no mutations in the exons of PITX2 have been found.

PMID: 28730073 [PubMed]