Mutations of conserved non-coding elements of PITX2 in patients with ocular dysgenesis and developmental glaucoma.

Hum Mol Genet. 2017 Sep 15;26(18):3630-3638

Authors: Protas ME, Weh E, Footz T, Kasberger J, Baraban SC, Levin AV, Katz LJ, Ritch R, Walter MA, Semina EV, Gould DB

Abstract
Mutations in FOXC1 and PITX2 constitute the most common causes of ocular anterior segment dysgenesis (ASD), and confer a high risk for secondary glaucoma. The genetic causes underlying ASD in approximately half of patients remain unknown, despite many of them being screened by whole exome sequencing. Here, we performed whole genome sequencing on DNA from two affected individuals from a family with dominantly inherited ASD and glaucoma to identify a 748-kb deletion in a gene desert that contains conserved putative PITX2 regulatory elements. We used CRISPR/Cas9 to delete the orthologous region in zebrafish in order to test the pathogenicity of this structural variant. Deletion in zebrafish reduced pitx2 expression during development and resulted in shallow anterior chambers. We screened additional patients for copy number variation of the putative regulatory elements and found an overlapping deletion in a second family and in a potentially-ancestrally-related index patient with ASD and glaucoma. These data suggest that mutations affecting conserved non-coding elements of PITX2 may constitute an important class of mutations in patients with ASD for whom the molecular cause of their disease have not yet been identified. Improved functional annotation of the human genome and transition to sequencing of patient genomes instead of exomes will be required before the magnitude of this class of mutations is fully understood.

PMID: 28911203 [PubMed - in process]

Whole-exome analysis of a Li-Fraumeni family trio with a novel TP53 PRD mutation and anticipation profile.

Carcinogenesis. 2017 Sep 01;38(9):938-943

Authors: Franceschi S, Spugnesi L, Aretini P, Lessi F, Scarpitta R, Galli A, Congregati C, Caligo MA, Mazzanti CM

Abstract
Li-Fraumeni syndrome is a clinically heterogeneous familial cancer predisposition syndrome with autosomal-dominant inheritance caused by heterozygous germline mutations in the TP53 gene. We here analyze the genetic background of a family with a 4-year-proband presented with a Li-Fraumeni tumor. The mother developed breast cancer at age 37 and the proband died at age 8. We performed Sanger sequencing and whole-exome sequencing on peripheral blood DNA from proband and relatives. Data analysis selected only high-quality score and depth reads, rare variants and protein impact involving missense, non-sense, frameshift and splice disrupt mutations. Disease implicated variants and predicted deleterious alterations were also chosen. TP53 genetic testing revealed a never reported TP53 deletion arose as de novo mutation in the mother and inherited by the proband. We then performed whole-exome analysis of the trio to uncover inherited variants from the father that potentially worsen the already altered genetic background in the proband. No pathogenic variants were inherited in autosomal recessive, de novo dominant or X-linked recessive manner. Comparing proband and father exome we detected 25 predicted deleterious variants including a nonsense mutation in ERCC3. Those inherited mutations are possible candidate modifiers linked to TP53, explaining the proband accelerated tumor onset compared to the mother and providing a possible explanation of the genetic anticipation event in this Li-Fraumeni family.

PMID: 28911001 [PubMed - in process]

Novel mutations in LRP6 highlight the role of WNT signaling in tooth agenesis.

Genet Med. 2016 Nov;18(11):1158-1162

Authors: Ockeloen CW, Khandelwal KD, Dreesen K, Ludwig KU, Sullivan R, van Rooij IALM, Thonissen M, Swinnen S, Phan M, Conte F, Ishorst N, Gilissen C, RoaFuentes L, van de Vorst M, Henkes A, Steehouwer M, van Beusekom E, Bloemen M, Vankeirsbilck B, Bergé S, Hens G, Schoenaers J, Poorten VV, Roosenboom J, Verdonck A, Devriendt K, Roeleveldt N, Jhangiani SN, Vissers LELM, Lupski JR, de Ligt J, Von den Hoff JW, Pfundt R, Brunner HG, Zhou H, Dixon J, Mangold E, van Bokhoven H, Dixon MJ, Kleefstra T, Hoischen A, Carels CEL

Abstract
PURPOSE: We aimed to identify a novel genetic cause of tooth agenesis (TA) and/or orofacial clefting (OFC) by combining whole-exome sequencing (WES) and targeted resequencing in a large cohort of TA and OFC patients.
METHODS: WES was performed in two unrelated patients: one with severe TA and OFC and another with severe TA only. After deleterious mutations were identified in a gene encoding low-density lipoprotein receptor-related protein 6 (LRP6), all its exons were resequenced with molecular inversion probes in 67 patients with TA, 1,072 patients with OFC, and 706 controls.
RESULTS: We identified a frameshift (c.4594delG, p.Cys1532fs) and a canonical splice-site mutation (c.3398-2A>C, p.?) in LRP6, respectively, in the patient with TA and OFC and in the patient with severe TA only. The targeted resequencing showed significant enrichment of unique LRP6 variants in TA patients but not in nonsyndromic OFC patients. Of the five variants in patients with TA, two affected the canonical splice site and three were missense variants; all variants segregated with the dominant phenotype, and in one case the missense mutation occurred de novo.
CONCLUSION: Mutations in LRP6 cause TA in humans.Genet Med 18 11, 1158-1162.

PMID: 26963285 [PubMed - indexed for MEDLINE]

Defining the Clinical Value of a Genomic Diagnosis in the Era of Next-Generation Sequencing.

Annu Rev Genomics Hum Genet. 2016 Aug 31;17:303-32

Authors: Strande NT, Berg JS

Abstract
As with all fields of medicine, the first step toward medical management of genetic disorders is obtaining an accurate diagnosis, which often requires testing at the molecular level. Unfortunately, given the large number of genetic conditions without a specific intervention, only rarely does a genetic diagnosis alter patient management-which raises the question, what is the added value of obtaining a molecular diagnosis? Given the fast-paced advancement of genomic technologies, this is an important question to address in the context of genome-scale testing. Here, we address the value of establishing a diagnosis using genome-scale testing and highlight the benefits and drawbacks of such testing. We also review and compare recent major studies implementing genome-scale sequencing methods to identify a molecular diagnosis in cohorts manifesting a broad range of Mendelian monogenic disorders. Finally, we discuss potential future applications of genomic sequencing, such as screening for rare conditions.

PMID: 27362341 [PubMed - indexed for MEDLINE]

Oncologists' and cancer patients' views on whole-exome sequencing and incidental findings: results from the CanSeq study.

Genet Med. 2016 Oct;18(10):1011-9

Authors: Gray SW, Park ER, Najita J, Martins Y, Traeger L, Bair E, Gagne J, Garber J, Jänne PA, Lindeman N, Lowenstein C, Oliver N, Sholl L, Van Allen EM, Wagle N, Wood S, Garraway L, Joffe S

Abstract
PURPOSE: Although targeted sequencing improves outcomes for many cancer patients, it remains uncertain how somatic and germ-line whole-exome sequencing (WES) will integrate into care.
METHODS: We conducted surveys and interviews within a study of WES integration at an academic center to determine oncologists' attitudes about WES and to identify lung and colorectal cancer patients' preferences for learning WES findings.
RESULTS: One-hundred sixty-seven patients (85% white, 58% female, mean age 60) and 27 oncologists (22% female) participated. Although oncologists had extensive experience ordering somatic tests (median 100/year), they had little experience ordering germ-line tests. Oncologists intended to disclose most WES results to patients but anticipated numerous challenges in using WES. Patients had moderately low levels of genetic knowledge (mean 4 correct out of 7). Most patients chose to learn results that could help select a clinical trial, pharmacogenetic and positive prognostic results, and results suggesting inherited predisposition to cancer and treatable noncancer conditions (all ≥95%). Fewer chose to receive negative prognostic results (84%) and results suggesting predisposition to untreatable noncancer conditions (85%).
CONCLUSION: The majority of patients want most cancer-related and incidental WES results. Patients' low levels of genetic knowledge and oncologists' inexperience with large-scale sequencing present challenges to implementing paired WES in practice.Genet Med 18 10, 1011-1019.

PMID: 26866579 [PubMed - indexed for MEDLINE]

Case of Childhood Ataxia with Central Nervous System Hypomyelination with a Novel Mutation in EIF2B3 gene.

J Pediatr Neurosci. 2017 Apr-Jun;12(2):196-198

Authors: Gowda VK, Srinivasan VM, Bhat M, Benakappa A

Abstract
A 4-year-old boy presented with loss of motor milestones following viral fever. On examination, the child had increased tone and exaggerated deep tendon reflexes. Magnetic resonance imaging of the brain showed white matter hyperintensities on T2-weighted images, which revealed partial inversion on fluid-attenuated inversion recovery images. Clinical exome sequencing revealed a novel homozygous mutation c.1270T>G: pCys424Gly in exon 11 of the EIF2B3 gene. This novel mutation is reported in this article along with a literature review.

PMID: 28904586 [PubMed]

Mutations in RARS cause a hypomyelination disorder akin to Pelizaeus-Merzbacher disease.

Eur J Hum Genet. 2017 Oct;25(10):1134-1141

Authors: Nafisinia M, Sobreira N, Riley L, Gold W, Uhlenberg B, Weiß C, Boehm C, Prelog K, Ouvrier R, Christodoulou J

Abstract
Pelizaeus-Merzbacher disease (PMD) is a rare Mendelian disorder characterised by central nervous system hypomyelination. PMD typically manifests in infancy or early childhood and is caused by mutations in proteolipid protein-1 (PLP1). However, variants in several other genes including gap junction protein gamma 2 (GJC2) can also cause a similar phenotype and are referred to PMD-like disease (PMLD). Whole-exome sequencing in two siblings presenting with clinical symptoms of PMD revealed a homozygous variant in the arginyl-tRNA synthetase (RARS) gene: NM_002887.3: c.[5A>G] p.(Asp2Gly). Subsequent screening of a PMD cohort without a genetic diagnosis identified an unrelated individual with novel compound heterozygous variants including a missense variant c.[1367C>T] p.(Ser456Leu) and a de novo deletion c.[1846_1847delTA] p.(Tyr616Leufs*6). Protein levels of RARS and the multi-tRNA synthetase complex into which it assembles were found to be significantly reduced by 80 and 90% by western blotting and Blue native-PAGE respectively using patient fibroblast extracts. As RARS is involved in protein synthesis whereby it attaches arginine to its cognate tRNA, patient cells were studied to determine their ability to proliferate with limiting amounts of this essential amino acid. Patient fibroblasts cultured in medium with limited arginine at 30 °C and 40 °C, showed a significant decrease in fibroblast proliferation (P<0.001) compared to control cells, suggestive of inefficiency of protein synthesis in the patient cells. Our functional studies provide further evidence that RARS is a PMD-causing gene.

PMID: 28905880 [PubMed - in process]

Biallelic variants in WARS2 encoding mitochondrial tryptophanyl-tRNA synthase in six individuals with mitochondrial encephalopathy.

Hum Mutat. 2017 Sep 14;:

Authors: Wortmann SB, Timal S, Venselaar H, Wintjes LT, Kopajtich R, Feichtinger RG, Onnekink C, Mühlmeister M, Brandt U, Smeitink JA, Veltman JA, Sperl W, Lefeber D, Pruijn G, Stojanovic V, Freisinger P, V Spronsen F, Derks TG, Veenstra-Knol HE, Mayr JA, Rötig A, Tarnopolsky M, Prokisch H, Rodenburg RJ

Abstract
Mitochondrial protein synthesis involves an intricate interplay between mitochondrial DNA encoded RNAs and nuclear DNA encoded proteins, such as ribosomal proteins and aminoacyl-tRNA synthases. Eukaryotic cells contain 17 mitochondria-specific aminoacyl-tRNA synthases. WARS2 encodes mitochondrial tryptophanyl-tRNA synthase (mtTrpRS), a homodimeric class Ic enzyme (mitochondrial tryptophan-tRNA ligase; EC 6.1.1.2). Here, we report six individuals from five families presenting with either severe neonatal onset lactic acidosis, encephalomyopathy and early death or a later onset, more attenuated course of disease with predominating intellectual disability. Respiratory chain enzymes were usually normal in muscle and fibroblasts, while a severe combined respiratory chain deficiency was found in the liver of a severely affected individual. Exome sequencing revealed rare biallelic variants in WARS2 in all affected individuals. An increase of uncharged mitochondrial tRNA(Trp) and a decrease of mtTrpRS protein content were found in fibroblasts of affected individuals. We hereby define the clinical, neuroradiological and metabolic phenotype of WARS2 defects. This confidently implicates that mutations in WARS2 cause mitochondrial disease with a broad spectrum of clinical presentation. This article is protected by copyright. All rights reserved.

PMID: 28905505 [PubMed - as supplied by publisher]

Whole Exome Sequencing of Aberrant Plasma Cells in a Patient with Multiple Myeloma Minimal Residual Disease.

Klin Onkol. 2017;30(Supplementum2):75-80

Authors: Zatopkova M, Filipová J, Jelínek T, Vojta P, Sevcikova T, Simicek M, Rihova L, Bezdekova R, Growkova K, Kufová Z, Smejkalová J, Hajdúch M, Pour L, Minárik J, Jungová A, Maisnar V, Kryukov F, Hájek R

Abstract
Multiple myeloma is a plasma cell dyscrasia. It is the second most common hematological malignancy which is characterized by proliferation of clonal plasma cells producing harmful monoclonal immunoglobulin. Despite treatment modalities greatly evolved during the last decade, small amount of aberrant residual cells reside in patients after therapy and can cause relapse of the disease. Characterization of the residual, resistant clones can help to reveal important therapeutic targets for application of effective and precious treatment. We use CD38, CD45, CD56 and CD19 sorted aberrant plasma cells to perform next generation sequencing of their exome. Among the 213 genes in which at least one variant was present, the most interesting was found gene NRAS, one of the most often mutated gene in multiple myeloma, and homologs of 88 gene panel previously used for multiple myeloma sequencing among which was a gene previously identified as gene meaningful in bortezomib resistance. Nevertheless, the results of next generation exome sequencing need to be interpreted with caution, since they rely on bioinformatical analysis, which is still being optimized. The results of next generation sequencing will also have to be confirmed by Sanger sequencing. Final results supported by larger cohort of patients will be published soon.Key words: multiple myeloma - minimal residual disease - exome - next generation sequencing.

PMID: 28903574 [PubMed - in process]

Establishing a patient-derived xenograft model of human myxoid and round-cell liposarcoma.

Oncotarget. 2017 Aug 15;8(33):54320-54330

Authors: Qi Y, Hu Y, Yang H, Zhuang R, Hou Y, Tong H, Feng Y, Huang Y, Jiang Q, Ji Q, Gu Q, Zhang Z, Tang X, Lu W, Zhou Y

Abstract
Myxoid and round cell liposarcoma (MRCL) is a common type of soft tissue sarcoma. The lack of patient-derived tumor xenograft models that are highly consistent with human tumors has limited the drug experiments for this disease. Hence, we aimed to develop and validate a patient-derived tumor xenograft model of MRCL. A tumor sample from a patient with MRCL was implanted subcutaneously in an immunodeficient mouse shortly after resection to establish a patient-derived tumor xenograft model. After the tumor grew, it was resected and divided into several pieces for re-implantation and tumor passage. After passage 1, 3, and 5 (i.e. P1, P3, and P5, respectively), tumor morphology and the presence of the FUS-DDIT3 gene fusion were consistent with those of the original patient tumor. Short tandem repeat analysis demonstrated consistency from P1 to P5. Whole exome sequencing also showed that P5 tumors harbored many of the same gene mutations present in the original patient tumor, one of which was a PIK3CA mutation. PF-04691502 significantly inhibited tumor growth in P5 models (tumor volumes of 492.62 ± 652.80 vs 3303.81 ± 1480.79 mm(3), P < 0.001, in treated vs control tumors, respectively) after 29 days of treatment. In conclusion, we have successfully established the first patient-derived xenograft model of MRCL. In addition to surgery, PI3K/mTOR inhibitors could potentially be used for the treatment of PIK3CA-positive MRCLs.

PMID: 28903344 [PubMed - in process]

Opportunities and challenges of whole-genome and -exome sequencing.

BMC Genet. 2017 Feb 14;18(1):14

Authors: Petersen BS, Fredrich B, Hoeppner MP, Ellinghaus D, Franke A

Abstract
Recent advances in the development of sequencing technologies provide researchers with unprecedented possibilities for genetic analyses. In this review, we will discuss the history of genetic studies and the progress driven by next-generation sequencing (NGS), using complex inflammatory bowel diseases as an example. We focus on the opportunities, but also challenges that researchers are facing when working with NGS data to unravel the genetic causes underlying diseases.

PMID: 28193154 [PubMed - indexed for MEDLINE]

Analysis of potential protein-modifying variants in 9000 endometriosis patients and 150000 controls of European ancestry.

Sci Rep. 2017 Sep 12;7(1):11380

Authors: Sapkota Y, Vivo I, Steinthorsdottir V, Fassbender A, Bowdler L, Buring JE, Edwards TL, Jones S, O D, Peterse D, Rexrode KM, Ridker PM, Schork AJ, Thorleifsson G, Wallace LM, iPSYCH-SSI-Broad Group, Kraft P, Morris AP, Nyholt DR, Edwards DRV, Nyegaard M, D'Hooghe T, Chasman DI, Stefansson K, Missmer SA, Montgomery GW

Abstract
Genome-wide association (GWA) studies have identified 19 independent common risk loci for endometriosis. Most of the GWA variants are non-coding and the genes responsible for the association signals have not been identified. Herein, we aimed to assess the potential role of protein-modifying variants in endometriosis using exome-array genotyping in 7164 cases and 21005 controls, and a replication set of 1840 cases and 129016 controls of European ancestry. Results in the discovery sample identified significant evidence for association with coding variants in single-variant (rs1801232-CUBN) and gene-level (CIITA and PARP4) meta-analyses, but these did not survive replication. In the combined analysis, there was genome-wide significant evidence for rs13394619 (P = 2.3 × 10(-9)) in GREB1 at 2p25.1 - a locus previously identified in a GWA meta-analysis of European and Japanese samples. Despite sufficient power, our results did not identify any protein-modifying variants (MAF > 0.01) with moderate or large effect sizes in endometriosis, although these variants may exist in non-European populations or in high-risk families. The results suggest continued discovery efforts should focus on genotyping large numbers of surgically-confirmed endometriosis cases and controls, and/or sequencing high-risk families to identify novel rare variants to provide greater insights into the molecular pathogenesis of the disease.

PMID: 28900119 [PubMed - in process]

A Missense Mutation within the Helix Termination Motif of KRT25 Causes Autosomal Dominant Woolly Hair/Hypotrichosis.

J Invest Dermatol. 2017 Sep 09;:

Authors: Yu X, Chen F, Ni C, Zhang G, Zheng L, Zhang J, Li C, A S, Yao Z, Li M

PMID: 28899683 [PubMed - as supplied by publisher]

Organic Solute Transporter-beta (SLC51B) Deficiency in Two Brothers with Congenital Diarrhea and Features of Cholestasis.

Hepatology. 2017 Sep 12;:

Authors: Sultan M, Rao A, Elpeleg O, Vaz FM, Abu Libdeh BY, Karpen SJ, Dawson PA

Abstract
Primary bile acid malabsorption (PBAM) is associated with congenital diarrhea, steatorrhea, and a block in the intestinal return of bile acids in the enterohepatic circulation. Mutations in the ileal Na(+) -dependent bile acid transporter (ASBT; SLC10A2) can cause PBAM, but do not appear to account for most familial cases. Another major transporter involved in the intestinal reclamation of bile acids is the heteromeric Organic Solute Transporter alpha-beta (OSTα-OSTβ; SLC51A-SLC51B), which exports bile acid across the basolateral membrane. Here we report the first patients with OSTβ deficiency, clinically characterized by chronic diarrhea, severe fat soluble vitamin deficiency, and features of cholestatic liver disease including elevated serum gamma-glutamyltransferase activity. Whole exome sequencing revealed a homozygous single nucleotide deletion in codon 27 of SLC51B, resulting in a frameshift and premature termination at codon 50. Functional studies in transfected cells showed that the SLC51B mutation resulted in markedly reduced taurocholic acid uptake activity and reduced expression of the OSTα partner protein.
CONCLUSION: The findings identify OSTβ deficiency as a new cause of congenital chronic diarrhea with features of cholestatic liver disease. These studies underscore OSTα-OSTβ's key role in the enterohepatic circulation of bile acids in humans. This article is protected by copyright. All rights reserved.

PMID: 28898457 [PubMed - as supplied by publisher]

Whole exome sequencing frequently detects a monogenic cause in early onset nephrolithiasis and nephrocalcinosis.

Kidney Int. 2017 Sep 08;:

Authors: Daga A, Majmundar AJ, Braun DA, Gee HY, Lawson JA, Shril S, Jobst-Schwan T, Vivante A, Schapiro D, Tan W, Warejko JK, Widmeier E, Nelson CP, Fathy HM, Gucev Z, Soliman NA, Hashmi S, Halbritter J, Halty M, Kari JA, El-Desoky S, Ferguson MA, Somers MJG, Traum AZ, Stein DR, Daouk GH, Rodig NM, Katz A, Hanna C, Schwaderer AL, Sayer JA, Wassner AJ, Mane S, Lifton RP, Milosevic D, Tasic V, Baum MA, Hildebrandt F

Abstract
The incidence of nephrolithiasis continues to rise. Previously, we showed that a monogenic cause could be detected in 11.4% of individuals with adult-onset nephrolithiasis or nephrocalcinosis and in 16.7-20.8% of individuals with onset before 18 years of age, using gene panel sequencing of 30 genes known to cause nephrolithiasis/nephrocalcinosis. To overcome the limitations of panel sequencing, we utilized whole exome sequencing in 51 families, who presented before age 25 years with at least one renal stone or with a renal ultrasound finding of nephrocalcinosis to identify the underlying molecular genetic cause of disease. In 15 of 51 families, we detected a monogenic causative mutation by whole exome sequencing. A mutation in seven recessive genes (AGXT, ATP6V1B1, CLDN16, CLDN19, GRHPR, SLC3A1, SLC12A1), in one dominant gene (SLC9A3R1), and in one gene (SLC34A1) with both recessive and dominant inheritance was detected. Seven of the 19 different mutations were not previously described as disease-causing. In one family, a causative mutation in one of 117 genes that may represent phenocopies of nephrolithiasis-causing genes was detected. In nine of 15 families, the genetic diagnosis may have specific implications for stone management and prevention. Several factors that correlated with the higher detection rate in our cohort were younger age at onset of nephrolithiasis/nephrocalcinosis, presence of multiple affected members in a family, and presence of consanguinity. Thus, we established whole exome sequencing as an efficient approach toward a molecular genetic diagnosis in individuals with nephrolithiasis/nephrocalcinosis who manifest before age 25 years.

PMID: 28893421 [PubMed - as supplied by publisher]

Exome Sequencing Identifies Two Variants of the Alkylglycerol Monooxygenase Gene as a Cause of Relapses in Visceral Leishmaniasis in Children, in Sudan.

J Infect Dis. 2017 Jul 01;216(1):22-28

Authors: Marquet S, Bucheton B, Reymond C, Argiro L, El-Safi SH, Kheir MM, Desvignes JP, Béroud C, Mergani A, Hammad A, Dessein AJ

Abstract
Background: Visceral leishmaniasis (kala-azar, KA) is the most severe form of leishmaniasis, characterized by fever, weight loss, hepatosplenomegaly, and lymphadenopathy. During an outbreak of KA in Babar El Fugara (Sudan), 5.7% of cured patients displayed relapses, with familial clustering in half the cases.
Methods: We performed whole-exome sequencing on 10 relapsing individuals and 11 controls from 5 nuclear families.
Results: Rare homozygous and compound-heterozygous nonsense (c.1213C > T, rs139309795, p.Arg405*) and missense (c.701A > G, rs143439626, p.Lys234Arg) mutations of the alkylglycerol monooxygenase (AGMO) gene were associated with KA relapse in 3 families. Sequencing in additional family members confirmed the segregation of these mutations with relapse and revealed an autosomal dominant mode of transmission. These mutations were detected heterozygous in 2 subjects among 100 unrelated individuals with KA who never relapsed after cure, suggesting incomplete penetrance of AGMO deficiency. AGMO is expressed in hematopoietic cells, and is strongly expressed in the liver. AGMO modulates PAF production by mouse macrophages, suggesting that it may act through the PAF/PAF receptor pathway previously shown to have anti-Leishmania activity.
Conclusions: This is the first demonstration that relapses after a first episode of KA are due to differences in human genetic susceptibility and not to modifications of parasite pathogenicity.

PMID: 28586473 [PubMed - indexed for MEDLINE]

Large-scale analyses of common and rare variants identify 12 new loci associated with atrial fibrillation.

Nat Genet. 2017 Jun;49(6):946-952

Authors: Christophersen IE, Rienstra M, Roselli C, Yin X, Geelhoed B, Barnard J, Lin H, Arking DE, Smith AV, Albert CM, Chaffin M, Tucker NR, Li M, Klarin D, Bihlmeyer NA, Low SK, Weeke PE, Müller-Nurasyid M, Smith JG, Brody JA, Niemeijer MN, Dörr M, Trompet S, Huffman J, Gustafsson S, Schurmann C, Kleber ME, Lyytikäinen LP, Seppälä I, Malik R, Horimoto ARVR, Perez M, Sinisalo J, Aeschbacher S, Thériault S, Yao J, Radmanesh F, Weiss S, Teumer A, Choi SH, Weng LC, Clauss S, Deo R, Rader DJ, Shah SH, Sun A, Hopewell JC, Debette S, Chauhan G, Yang Q, Worrall BB, Paré G, Kamatani Y, Hagemeijer YP, Verweij N, Siland JE, Kubo M, Smith JD, Van Wagoner DR, Bis JC, Perz S, Psaty BM, Ridker PM, Magnani JW, Harris TB, Launer LJ, Shoemaker MB, Padmanabhan S, Haessler J, Bartz TM, Waldenberger M, Lichtner P, Arendt M, Krieger JE, Kähönen M, Risch L, Mansur AJ, Peters A, Smith BH, Lind L, Scott SA, Lu Y, Bottinger EB, Hernesniemi J, Lindgren CM, Wong JA, Huang J, Eskola M, Morris AP, Ford I, Reiner AP, Delgado G, Chen LY, Chen YI, Sandhu RK, Li M, Boerwinkle E, Eisele L, Lannfelt L, Rost N, Anderson CD, Taylor KD, Campbell A, Magnusson PK, Porteous D, Hocking LJ, Vlachopoulou E, Pedersen NL, Nikus K, Orho-Melander M, Hamsten A, Heeringa J, Denny JC, Kriebel J, Darbar D, Newton-Cheh C, Shaffer C, Macfarlane PW, Heilmann-Heimbach S, Almgren P, Huang PL, Sotoodehnia N, Soliman EZ, Uitterlinden AG, Hofman A, Franco OH, Völker U, Jöckel KH, Sinner MF, Lin HJ, Guo X, METASTROKE Consortium of the ISGC, Neurology Working Group of the CHARGE Consortium, Dichgans M, Ingelsson E, Kooperberg C, Melander O, Loos RJF, Laurikka J, Conen D, Rosand J, van der Harst P, Lokki ML, Kathiresan S, Pereira A, Jukema JW, Hayward C, Rotter JI, März W, Lehtimäki T, Stricker BH, Chung MK, Felix SB, Gudnason V, Alonso A, Roden DM, Kääb S, Chasman DI, Heckbert SR, Benjamin EJ, Tanaka T, Lunetta KL, Lubitz SA, Ellinor PT, AFGen Consortium

Abstract
Atrial fibrillation affects more than 33 million people worldwide and increases the risk of stroke, heart failure, and death. Fourteen genetic loci have been associated with atrial fibrillation in European and Asian ancestry groups. To further define the genetic basis of atrial fibrillation, we performed large-scale, trans-ancestry meta-analyses of common and rare variant association studies. The genome-wide association studies (GWAS) included 17,931 individuals with atrial fibrillation and 115,142 referents; the exome-wide association studies (ExWAS) and rare variant association studies (RVAS) involved 22,346 cases and 132,086 referents. We identified 12 new genetic loci that exceeded genome-wide significance, implicating genes involved in cardiac electrical and structural remodeling. Our results nearly double the number of known genetic loci for atrial fibrillation, provide insights into the molecular basis of atrial fibrillation, and may facilitate the identification of new potential targets for drug discovery.

PMID: 28416818 [PubMed - indexed for MEDLINE]

Validation of copy number variation analysis for next-generation sequencing diagnostics.

Eur J Hum Genet. 2017 Jun;25(6):719-724

Authors: Ellingford JM, Campbell C, Barton S, Bhaskar S, Gupta S, Taylor RL, Sergouniotis PI, Horn B, Lamb JA, Michaelides M, Webster AR, Newman WG, Panda B, Ramsden SC, Black GC

Abstract
Although a common cause of disease, copy number variants (CNVs) have not routinely been identified from next-generation sequencing (NGS) data in a clinical context. This study aimed to examine the sensitivity and specificity of a widely used software package, ExomeDepth, to identify CNVs from targeted NGS data sets. We benchmarked the accuracy of CNV detection using ExomeDepth v1.1.6 applied to targeted NGS data sets by comparison to CNV events detected through whole-genome sequencing for 25 individuals and determined the sensitivity and specificity of ExomeDepth applied to these targeted NGS data sets to be 100% and 99.8%, respectively. To define quality assurance metrics for CNV surveillance through ExomeDepth, we undertook simulation of single-exon (n=1000) and multiple-exon heterozygous deletion events (n=1749), determining a sensitivity of 97% (n=2749). We identified that the extent of sequencing coverage, the inter- and intra-sample variability in the depth of sequencing coverage and the composition of analysis regions are all important determinants of successful CNV surveillance through ExomeDepth. We then applied these quality assurance metrics during CNV surveillance for 140 individuals across 12 distinct clinical areas, encompassing over 500 potential rare disease diagnoses. All 140 individuals lacked molecular diagnoses after routine clinical NGS testing, and by application of ExomeDepth, we identified 17 CNVs contributing to the cause of a Mendelian disorder. Our findings support the integration of CNV detection using ExomeDepth v1.1.6 with routine targeted NGS diagnostic services for Mendelian disorders. Implementation of this strategy increases diagnostic yields and enhances clinical care.

PMID: 28378820 [PubMed - indexed for MEDLINE]

Gonadal mosaicism of a novel IQSEC2 variant causing female limited intellectual disability and epilepsy.

Eur J Hum Genet. 2017 Jun;25(6):763-767

Authors: Ewans LJ, Field M, Zhu Y, Turner G, Leffler M, Dinger ME, Cowley MJ, Buckley MF, Scheffer IE, Jackson MR, Roscioli T, Shoubridge C

Abstract
We report a family with four girls with moderate to severe intellectual disability and epilepsy. Two girls showed regression in adolescence and died of presumed sudden unexpected death in epilepsy at 16 and 22 years. Whole exome sequencing identified a truncating pathogenic variant in IQSEC2 at NM_001111125.2: c.2679_2680insA, p.(D894fs*10), a recently identified cause of epileptic encephalopathy in females (MIM 300522). The IQSEC2 variant was identified in both surviving affected sisters but in neither parent. We describe the phenotypic spectrum associated with IQSEC2 variants, highlighting how IQSEC2 is adding to a growing list of X-linked genes that have a female-specific phenotype typically associated with de novo mutations. This report illustrates the need for careful review of all whole exome data, incorporating all possible modes of inheritance including that suggested by the family history.

PMID: 28295038 [PubMed - indexed for MEDLINE]

Loss of DDRGK1 modulates SOX9 ubiquitination in spondyloepimetaphyseal dysplasia.

J Clin Invest. 2017 Apr 03;127(4):1475-1484

Authors: Egunsola AT, Bae Y, Jiang MM, Liu DS, Chen-Evenson Y, Bertin T, Chen S, Lu JT, Nevarez L, Magal N, Raas-Rothschild A, Swindell EC, Cohn DH, Gibbs RA, Campeau PM, Shohat M, Lee BH

Abstract
Shohat-type spondyloepimetaphyseal dysplasia (SEMD) is a skeletal dysplasia that affects cartilage development. Similar skeletal disorders, such as spondyloepiphyseal dysplasias, are linked to mutations in type II collagen (COL2A1), but the causative gene in SEMD is not known. Here, we have performed whole-exome sequencing to identify a recurrent homozygous c.408+1G>A donor splice site loss-of-function mutation in DDRGK domain containing 1 (DDRGK1) in 4 families affected by SEMD. In zebrafish, ddrgk1 deficiency disrupted craniofacial cartilage development and led to decreased levels of the chondrogenic master transcription factor sox9 and its downstream target, col2a1. Overexpression of sox9 rescued the zebrafish chondrogenic and craniofacial phenotype generated by ddrgk1 knockdown, thus identifying DDRGK1 as a regulator of SOX9. Consistent with these results, Ddrgk1-/- mice displayed delayed limb bud chondrogenic condensation, decreased SOX9 protein expression and Col2a1 transcript levels, and increased apoptosis. Furthermore, we determined that DDRGK1 can directly bind to SOX9 to inhibit its ubiquitination and proteasomal degradation. Taken together, these data indicate that loss of DDRGK1 decreases SOX9 expression and causes a human skeletal dysplasia, identifying a mechanism that regulates chondrogenesis via modulation of SOX9 ubiquitination.

PMID: 28263186 [PubMed - indexed for MEDLINE]