Loss of function in ROBO1 is associated with tetralogy of Fallot and septal defects.

J Med Genet. 2017 Jun 07;:

Authors: Kruszka P, Tanpaiboon P, Neas K, Crosby K, Berger SI, Martinez AF, Addissie YA, Pongprot Y, Sittiwangkul R, Silvilairat S, Makonkawkeyoon K, Yu L, Wynn J, Bennett JT, Mefford HC, Reynolds WT, Liu X, Mommersteeg MTM, Chung WK, Lo CW, Muenke M

Abstract
BACKGROUND: Congenital heart disease (CHD) is a common birth defect affecting approximately 1% of newborns. Great progress has been made in elucidating the genetic aetiology of CHD with advances in genomic technology, which we leveraged in recovering a new pathway affecting heart development in humans previously known to affect heart development in an animal model.
METHODS: Four hundred and sixteen individuals from Thailand and the USA diagnosed with CHD and/or congenital diaphragmatic hernia were evaluated with chromosomal microarray and whole exome sequencing. The DECIPHER Consortium and medical literature were searched for additional patients. Murine hearts from ENU-induced mouse mutants and transgenic mice were evaluated using both episcopic confocal histopathology and troponin I stained sections.
RESULTS: Loss of function ROBO1 variants were identified in three families; each proband had a ventricular septal defect, and one proband had tetralogy of Fallot. Additionally, a microdeletion in an individual with CHD was found in the medical literature. Mouse models showed perturbation of the Slit-Robo signalling pathway, causing septation and outflow tract defects and craniofacial anomalies. Two probands had variable facial features consistent with the mouse model.
CONCLUSION: Our findings identify Slit-Robo as a significant pathway in human heart development and CHD.

PMID: 28592524 [PubMed - as supplied by publisher]

Germline CDKN2A/P16INK4A mutations contribute to genetic determinism of sarcoma.

J Med Genet. 2017 Jun 07;:

Authors: Jouenne F, Chauvot de Beauchene I, Bollaert E, Avril MF, Caron O, Ingster O, Lecesne A, Benusiglio P, Terrier P, Caumette V, Pissaloux D, de la Fouchardière A, Cabaret O, N'Diaye B, Velghe A, Bougeard G, Mann GJ, Koscielny S, Barrett JH, Harland M, Newton-Bishop J, Gruis N, Van Doorn R, Gauthier-Villars M, Pierron G, Stoppa-Lyonnet D, Coupier I, Guimbaud R, Delnatte C, Scoazec JY, Eggermont AM, Feunteun J, Tchertanov L, Demoulin JB, Frebourg T, Bressac-de Paillerets B

Abstract
BACKGROUND: Sarcomas are rare mesenchymal malignancies whose pathogenesis is poorly understood; both environmental and genetic risk factors could contribute to their aetiology.
METHODS AND RESULTS: We performed whole-exome sequencing (WES) in a familial aggregation of three individuals affected with soft-tissue sarcoma (STS) without TP53 mutation (Li-Fraumeni-like, LFL) and found a shared pathogenic mutation in CDKN2A tumour suppressor gene. We searched for individuals with sarcoma among 474 melanoma-prone families with a CDKN2A-/+ genotype and for CDKN2A mutations in 190 TP53-negative LFL families where the index case was a sarcoma. Including the initial family, eight independent sarcoma cases carried a germline mutation in the CDKN2A/p16(INK4A) gene. In five out of seven formalin-fixed paraffin-embedded sarcomas, heterozygosity was lost at germline CDKN2A mutations sites demonstrating complete loss of function. As sarcomas are rare in CDKN2A/p16(INK4A) carriers, we searched in constitutional WES of nine carriers for potential modifying rare variants and identified three in platelet-derived growth factor receptor (PDGFRA) gene. Molecular modelling showed that two never-described variants could impact the PDGFRA extracellular domain structure.
CONCLUSION: Germline mutations in CDKN2A/P16(INK4A), a gene known to predispose to hereditary melanoma, pancreatic cancer and tobacco-related cancers, account also for a subset of hereditary sarcoma. In addition, we identified PDGFRA as a candidate modifier gene.

PMID: 28592523 [PubMed - as supplied by publisher]

The genomic road to invasion-examining the similarities and differences in the genomes of associated oral pre-cancer and cancer samples.

Genome Med. 2017 Jun 07;9(1):53

Authors: Wood HM, Daly C, Chalkley R, Senguven B, Ross L, Egan P, Chengot P, Graham J, Sethi N, Ong TK, MacLennan K, Rabbitts P, Conway C

Abstract
BACKGROUND: It is frequently assumed that pre-invasive lesions are simpler precursors of cancer and will contain a limited subset of the genomic changes seen in their associated invasive disease. Driver mutations are thought to occur early, but it is not known how many of these are present in pre-invasive lesions. These assumptions need to be tested with the increasing focus on both personalised cancer treatments and early detection methodologies.
METHODS: We examined genomic copy number changes in 256 pre-invasive and invasive samples from 69 oral cancer patients. Forty-eight samples from 16 patients were further examined using exome sequencing.
RESULTS: Evidence of a shared ancestor of both dysplasia and carcinoma was seen in all but one patient. One-third of dysplasias showed independent copy number events. The remainder had a copy number pattern that was similar to or simpler than that of the carcinoma. All dysplasias examined contained somatic mutations absent in the related carcinoma. Previously observed copy number changes and TP53 mutations were very frequently observed, and almost always shared between dysplasia and carcinoma. Other gene changes were more sporadic. Pathway analysis confirmed that each patient's disease developed in a different way. Examining the numbers of shared mutations and the rate of accumulation of mutations showed evidence that all samples contain a population of sub-clones, with little evidence of selective advantage of a subset of these.
CONCLUSIONS: These findings suggest that most of the genomic changes driving oral cancer occur in the pre-cancerous state by way of gradual random accumulation rather than a dramatic single event.

PMID: 28592326 [PubMed - in process]

Identification of novel BCL11A variants in patients with epileptic encephalopathy: expanding the phenotypic spectrum.

Clin Genet. 2017 Jun 06;:

Authors: Yoshida M, Nakashima M, Okanishi T, Kanai S, Fujimoto A, Itomi K, Morimoto M, Saitsu H, Kato M, Matsumoto N, Chiyonobu T

Abstract
BCL11A encodes a zinc finger protein that is highly expressed in hematopoietic tissues and the brain, and that is known to function as a transcriptional repressor of fetal hemoglobin (HbF). Recently, de novo variants in BCL11A have been reported in individuals with intellectual disability syndrome without epilepsy. In this study, we performed whole-exome sequencing of 302 patients with epileptic encephalopathies (EEs), and identified two novel BCL11A variants, c.577delC (p.His193Metfs*3) and c.2351A>C (p.Lys784Thr). Both patients shared major physical features characteristic of BCL11A-related intellectual disability syndrome, suggesting that characteristic physical features and the persistence of HbF should lead clinicians to suspect EEs caused by BCL11A pathogenic variants. Patient 1, with a frameshift variant, presented with Lennox-Gastaut syndrome, which expands the phenotypic spectrum of BCL11A haploinsufficiency. Patient 2, with a p.Lys784Thr variant, presented with West syndrome followed by drug-resistant focal seizures and more severe developmental disability. These two newly described patients contribute to delineating the associated, yet uncertain phenotypic characteristics of BCL11A disease-causing variants.

PMID: 28589569 [PubMed - as supplied by publisher]

Distinguishing pathogenic mutations from background genetic noise in cardiology: the use of large genome databases for genetic interpretation.

Clin Genet. 2017 Jun 06;:

Authors: Ghouse J, Skov MW, Bigseth RS, Ahlberg G, Kanters JK, Olesen MS

Abstract
Advances in clinical genetic testing has led to increased insight into the human genome, including how challenging it is to interpret rare genetic variation. In some cases, the ability to detect genetic mutations exceeds the ability to understand their clinical impact, limiting the advantage of these technologies. Obstacles in genomic medicine are many and include: understanding the level of certainty/uncertainty behind pathogenicity determination, the numerous different variant interpretation-guidelines used by clinical laboratories, delivering the certain or uncertain result to the patient, helping patients evaluate medical decisions in light of uncertainty regarding the consequence of the findings. Through publication of large publicly available exome/genome databases, researchers and physicians are now able to highlight dubious variants previously associated with different cardiac traits. Also, continuous efforts through data sharing, international collaborative efforts to develop disease-gene specific guidelines, and computational analyses using large data, will indubitably assist in better variant interpretation and classification. This paper discusses the current, and quickly changing, state of variant interpretation resources within cardiovascular genetic research, i.e. publicly available databases and ways of how cardiovascular genetic counsellors and geneticists can aid in improving variant interpretation in cardiology.

PMID: 28589536 [PubMed - as supplied by publisher]

Syndrome of progressive bone marrow failure and pancreatic insufficiency remains cryptic despite whole exome sequencing: variant of Shwachman-Diamond syndrome or new condition?

Clin Case Rep. 2017 Jun;5(6):748-752

Authors: Fadus MC, Rush ET, Lettieri CK

Abstract
This case underscores the difficulty in diagnosis of bone marrow failure disorders, as the presentation of disease can be inconsistent, complicated by complex and ever-expanding genetic etiologies. A patient who presents with bone marrow failure and pancreatic insufficiency raises the question of Shwachman-Diamond syndrome (SDS) or a new condition which resembles SDS.

PMID: 28588803 [PubMed - in process]

Novel variant in the FGD1 gene causing Aarskog-Scott syndrome.

Exp Ther Med. 2017 Jun;13(6):2623-2628

Authors: Ge Y, Li N, Wang Z, Wang J, Cai H

Abstract
Aarskog-Scott syndrome (ASS) is a rare, X-linked recessive inherited disorder. Affected individuals may develop short stature and exhibit distinctive skeletal and genital development. Mutations in the FYVE, rhogef and pleckstrin homology domain-containing protein 1 (FGD1) gene, located within the Xp11.21 region, are responsible for the occurrence of ASS. Since it is rare and complex, it can take a long time to obtain a definitive clinical diagnosis unless clinicians are familiar with the disease. In the present study, whole-exome sequencing (WES) was performed to screen for causal variants in a Chinese pediatric patient who exhibited a number of clinical symptoms of ASS, including short stature, facial abnormalities, stubby metacarpals and swollen testis. DNA sequencing revealed a novel c.1270 A>G mutation in exon 6 of the FGD1 gene, which led to an amino acid conversion of asparagine to aspartic acid on codon 424 and in silico analysis indicated that this novel missense mutation was pathogenic. The present study identified a novel variant of the FGD1 gene and to the best of our knowledge, is the first report of ASS in a Chinese individual. The results indicated that WES is an effective tool for the diagnosis of rare and complex syndromes such as ASS.

PMID: 28587322 [PubMed - in process]

Rare variants in fox-1 homolog A (RBFOX1) are associated with lower blood pressure.

PLoS Genet. 2017 Mar;13(3):e1006678

Authors: He KY, Wang H, Cade BE, Nandakumar P, Giri A, Ware EB, Haessler J, Liang J, Smith JA, Franceschini N, Le TH, Kooperberg C, Edwards TL, Kardia SL, Lin X, Chakravarti A, Redline S, Zhu X

Abstract
Many large genome-wide association studies (GWAS) have identified common blood pressure (BP) variants. However, most of the identified BP variants do not overlap with the linkage evidence observed from family studies. We thus hypothesize that multiple rare variants contribute to the observed linkage evidence. We performed linkage analysis using 517 individuals in 130 European families from the Cleveland Family Study (CFS) who have been genotyped on the Illumina OmniExpress Exome array. The largest linkage peak was observed on chromosome 16p13 (MLOD = 2.81) for systolic blood pressure (SBP). Follow-up conditional linkage and association analyses in the linkage region identified multiple rare, coding variants in RBFOX1 associated with reduced SBP. In a 17-member CFS family, carriers of the missense variant rs149974858 are normotensive despite being obese (average BMI = 60 kg/m2). Gene-based association test of rare variants using SKAT-O showed significant association with SBP (p-value = 0.00403) and DBP (p-value = 0.0258) in the CFS participants and the association was replicated in large independent replication studies (N = 57,234, p-value = 0.013 for SBP, 0.0023 for PP). RBFOX1 is expressed in brain tissues, the atrial appendage and left ventricle in the heart, and in skeletal muscle tissues, organs/tissues which are potentially related to blood pressure. Our study showed that associations of rare variants could be efficiently detected using family information.

PMID: 28346479 [PubMed - indexed for MEDLINE]

COLEC10 is mutated in 3MC patients and regulates early craniofacial development.

PLoS Genet. 2017 Mar;13(3):e1006679

Authors: Munye MM, Diaz-Font A, Ocaka L, Henriksen ML, Lees M, Brady A, Jenkins D, Morton J, Hansen SW, Bacchelli C, Beales PL, Hernandez-Hernandez V

Abstract
3MC syndrome is an autosomal recessive heterogeneous disorder with features linked to developmental abnormalities. The main features include facial dysmorphism, craniosynostosis and cleft lip/palate; skeletal structures derived from cranial neural crest cells (cNCC). We previously reported that lectin complement pathway genes COLEC11 and MASP1/3 are mutated in 3MC syndrome patients. Here we define a new gene, COLEC10, also mutated in 3MC families and present novel mutations in COLEC11 and MASP1/3 genes in a further five families. The protein products of COLEC11 and COLEC10, CL-K1 and CL-L1 respectively, form heteromeric complexes. We show COLEC10 is expressed in the base membrane of the palate during murine embryo development. We demonstrate how mutations in COLEC10 (c.25C>T; p.Arg9Ter, c.226delA; p.Gly77Glufs*66 and c.528C>G p.Cys176Trp) impair the expression and/or secretion of CL-L1 highlighting their pathogenicity. Together, these findings provide further evidence linking the lectin complement pathway and complement factors COLEC11 and COLEC10 to morphogenesis of craniofacial structures and 3MC etiology.

PMID: 28301481 [PubMed - indexed for MEDLINE]

Rare variant association test with multiple phenotypes.

Genet Epidemiol. 2017 Apr;41(3):198-209

Authors: Lee S, Won S, Kim YJ, Kim Y, T2D-Genes Consortium, Kim BJ, Park T

Abstract
Although genome-wide association studies (GWAS) have now discovered thousands of genetic variants associated with common traits, such variants cannot explain the large degree of "missing heritability," likely due to rare variants. The advent of next generation sequencing technology has allowed rare variant detection and association with common traits, often by investigating specific genomic regions for rare variant effects on a trait. Although multiple correlated phenotypes are often concurrently observed in GWAS, most studies analyze only single phenotypes, which may lessen statistical power. To increase power, multivariate analyses, which consider correlations between multiple phenotypes, can be used. However, few existing multivariant analyses can identify rare variants for assessing multiple phenotypes. Here, we propose Multivariate Association Analysis using Score Statistics (MAAUSS), to identify rare variants associated with multiple phenotypes, based on the widely used sequence kernel association test (SKAT) for a single phenotype. We applied MAAUSS to whole exome sequencing (WES) data from a Korean population of 1,058 subjects to discover genes associated with multiple traits of liver function. We then assessed validation of those genes by a replication study, using an independent dataset of 3,445 individuals. Notably, we detected the gene ZNF620 among five significant genes. We then performed a simulation study to compare MAAUSS's performance with existing methods. Overall, MAAUSS successfully conserved type 1 error rates and in many cases had a higher power than the existing methods. This study illustrates a feasible and straightforward approach for identifying rare variants correlated with multiple phenotypes, with likely relevance to missing heritability.

PMID: 28039885 [PubMed - indexed for MEDLINE]

Whole exome sequencing in patients with white matter abnormalities.

Ann Neurol. 2016 Jun;79(6):1031-7

Authors: Vanderver A, Simons C, Helman G, Crawford J, Wolf NI, Bernard G, Pizzino A, Schmidt JL, Takanohashi A, Miller D, Khouzam A, Rajan V, Ramos E, Chowdhury S, Hambuch T, Ru K, Baillie GJ, Grimmond SM, Caldovic L, Devaney J, Bloom M, Evans SH, Murphy JL, McNeill N, Fogel BL, Leukodystrophy Study Group, Schiffmann R, van der Knaap MS, Taft RJ

Abstract
Here we report whole exome sequencing (WES) on a cohort of 71 patients with persistently unresolved white matter abnormalities with a suspected diagnosis of leukodystrophy or genetic leukoencephalopathy. WES analyses were performed on trio, or greater, family groups. Diagnostic pathogenic variants were identified in 35% (25 of 71) of patients. Potentially pathogenic variants were identified in clinically relevant genes in a further 7% (5 of 71) of cases, giving a total yield of clinical diagnoses in 42% of individuals. These findings provide evidence that WES can substantially decrease the number of unresolved white matter cases. Ann Neurol 2016;79:1031-1037.

PMID: 27159321 [PubMed - indexed for MEDLINE]

Specific Alleles of CLN7/MFSD8, a Protein That Localizes to Photoreceptor Synaptic Terminals, Cause a Spectrum of Nonsyndromic Retinal Dystrophy.

Invest Ophthalmol Vis Sci. 2017 Jun 01;58(7):2906-2914

Authors: Khan KN, El-Asrag ME, Ku CA, Holder GE, McKibbin M, Arno G, Poulter JA, Carss K, Bommireddy T, Bagheri S, Bakall B, Scholl HP, Raymond FL, Toomes C, Inglehearn CF, Pennesi ME, Moore AT, Michaelides M, Webster AR, Ali M, for NIHR BioResource-Rare Diseases and UK Inherited Retinal Disease Consortium

Abstract
Purpose: Recessive mutations in CLN7/MFSD8 usually cause variant late-infantile onset neuronal ceroid lipofuscinosis (vLINCL), a poorly understood neurodegenerative condition, though mutations may also cause nonsyndromic maculopathy. A series of 12 patients with nonsyndromic retinopathy due to novel CLN7/MFSD8 mutation combinations were investigated in this study.
Methods: Affected patients and their family members were recruited in ophthalmic clinics at each center where they were examined by retinal imaging and detailed electrophysiology. Whole exome or genome next generation sequencing was performed on genomic DNA from at least one affected family member. Immunofluorescence confocal microscopy of murine retina cross-sections were used to localize the protein.
Results: Compound heterozygous alleles were identified in six cases, one of which was always p.Glu336Gln. Such combinations resulted in isolated macular disease. Six further cases were homozygous for the variant p.Met454Thr, identified as a founder mutation of South Asian origin. Those patients had widespread generalized retinal disease, characterized by electroretinography as a rod-cone dystrophy with severe macular involvement. In addition, the photopic single flash electroretinograms demonstrated a reduced b- to a-wave amplitude ratio, suggesting dysfunction occurring after phototransduction. Immunohistology identified MFSD8 in the outer plexiform layer of the retina, a site rich in photoreceptor synapses.
Conclusions: This study highlights a hierarchy of MFSD8 variant severity, predicting three consequences of mutation: (1) nonsyndromic localized maculopathy, (2) nonsyndromic widespread retinopathy, or (3) syndromic neurological disease. The data also shed light on the underlying pathogenesis by implicating the photoreceptor synaptic terminals as the major site of retinal disease.

PMID: 28586915 [PubMed - in process]

A prospective pilot study of genome-wide exome and transcriptome profiling in patients with small cell lung cancer progressing after first-line therapy.

PLoS One. 2017;12(6):e0179170

Authors: Weiss GJ, Byron SA, Aldrich J, Sangal A, Barilla H, Kiefer JA, Carpten JD, Craig DW, Whitsett TG

Abstract
BACKGROUND: Small cell lung cancer (SCLC) that has progressed after first-line therapy is an aggressive disease with few effective therapeutic strategies. In this prospective study, we employed next-generation sequencing (NGS) to identify therapeutically actionable alterations to guide treatment for advanced SCLC patients.
METHODS: Twelve patients with SCLC were enrolled after failing platinum-based chemotherapy. Following informed consent, genome-wide exome and RNA-sequencing was performed in a CLIA-certified, CAP-accredited environment. Actionable targets were identified and therapeutic recommendations made from a pharmacopeia of FDA-approved drugs. Clinical response to genomically-guided treatment was evaluated by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1.
RESULTS: The study completed its accrual goal of 12 evaluable patients. The minimum tumor content for successful NGS was 20%, with a median turnaround time from sample collection to genomics-based treatment recommendation of 27 days. At least two clinically actionable targets were identified in each patient, and six patients (50%) received treatment identified by NGS. Two had partial responses by RECIST 1.1 on a clinical trial involving a PD-1 inhibitor + irinotecan (indicated by MLH1 alteration). The remaining patients had clinical deterioration before NGS recommended therapy could be initiated.
CONCLUSIONS: Comprehensive genomic profiling using NGS identified clinically-actionable alterations in SCLC patients who progressed on initial therapy. Recommended PD-1 therapy generated partial responses in two patients. Earlier access to NGS guided therapy, along with improved understanding of those SCLC patients likely to respond to immune-based therapies, should help to extend survival in these cases with poor outcomes.

PMID: 28586388 [PubMed - in process]

Whole Exome Sequencing in Eight Thai Patients With Leber Congenital Amaurosis Reveals Mutations in the CTNNA1 and CYP4V2 Genes.

Invest Ophthalmol Vis Sci. 2017 Apr 01;58(4):2413-2420

Authors: Jinda W, Taylor TD, Suzuki Y, Thongnoppakhun W, Limwongse C, Lertrit P, Trinavarat A, Atchaneeyasakul LO

Abstract
Purpose: Our goal was to describe the clinical and molecular genetic findings in Thai patients with Leber congenital amaurosis (LCA).
Methods: Whole exome sequencing (WES) was performed in eight unrelated patients. All genes responsible for inherited retinal diseases (IRDs) based on RetNet were selected for analysis. Potentially causative variants were filtered through a bioinformatics pipeline and validated using Sanger sequencing. Segregation analysis of the causative genes was performed in family members when available.
Results: Eleven deleterious variants, six nonsense and five missense, were identified in seven genes: four LCA-associated genes (CEP290, IQCB1, NMNAT1, and RPGRIP1), one gene responsible for syndromic LCA (ALMS1), and two IRDs-related genes (CTNNA1 and CYP4V2). Clinical reassessment supported the diagnosis of syndromic LCA in those patients harboring potentially pathogenic variants in the ALMS1. Interestingly, two causative genes, CTNNA1 and CYP4V2, previously reported to cause butterfly-shaped pigment dystrophy (BSPD) and Bietti's crystalline dystrophy (BCD), respectively, were detected in two other patients. These two patients developed rapid and severe visual loss in contrast to BSPD and BCD patients in previous studies. The results of this study demonstrate that causative variants identified in the CTNNA1 and CYP4V2 genes are also associated with LCA.
Conclusions: This is the first report describing the molecular genetics and clinical manifestations of Thai patients with LCA. The present study expands the spectrum of LCA-associated genes, which is a benefit for molecular diagnosis. The identification of mutations in the CTNNA1 and CYP4V2 genes requires further elucidation in larger cohorts with LCA.

PMID: 28453600 [PubMed - indexed for MEDLINE]

Efficiency of olaparib in colorectal cancer patients with an alteration of the homologous repair protein.

World J Gastroenterol. 2016 Dec 28;22(48):10680-10686

Authors: Ghiringhelli F, Richard C, Chevrier S, Végran F, Boidot R

Abstract
Precision medicine is defined by the administration of drugs based on the tumor's particular genetic characteristics. It is developing quickly in the field of cancer therapy. For example, KRAS, NRAS and BRAF genetic testing demonstrates its efficiency for precision medicine in colorectal cancer (CRC). Besides for these well-known mutations, the purpose of performing larger genetic testing in this pathology is unknown. Recent reports have shown that using the poly ADP ribose polymerase (PARP) inhibitor olaparib in patients with homologous repair enzyme deficiency gave positive clinical results in breast, ovarian and prostate cancers. We have reported here the cases of 2 patients with multi-treated metastatic CRC who underwent somatic and constitutional exome analyses. The analyses revealed a loss of function mutation in a homologous repair enzyme resulting in the loss of heterozygosity for both patients (Check2 for the first patient and RAD51C for the second one). Both patients were treated with off-label usage of olaparib. While the first patient showed clinical benefit, reduction of carcinoembryonic antigen tumor marker and radiologic response, the second patient quickly presented a progression of the tumor. Additional genetic analyses revealed a frameshift truncating mutation of the TP53BP1 gene in the patient who progressed. Interestingly, deficiency in TP53BP1 was previously described to confer resistance to olaparib in mice breast cancer models. Our findings suggest that exome analysis may be a helpful tool to highlight targetable mutations in CRC and that olaparib may be efficient in patients with a homologous repair deficiency.

PMID: 28082821 [PubMed - indexed for MEDLINE]

Region-based association tests for sequencing data on survival traits.

Genet Epidemiol. 2017 Jun 04;:

Authors: Chien LC, Bowden DW, Chiu YF

Abstract
Family-based designs enriched with affected subjects and disease associated variants can increase statistical power for identifying functional rare variants. However, few rare variant analysis approaches are available for time-to-event traits in family designs and none of them applicable to the X chromosome. We developed novel pedigree-based burden and kernel association tests for time-to-event outcomes with right censoring for pedigree data, referred to FamRATS (family-based rare variant association tests for survival traits). Cox proportional hazard models were employed to relate a time-to-event trait with rare variants with flexibility to encompass all ranges and collapsing of multiple variants. In addition, the robustness of violating proportional hazard assumptions was investigated for the proposed and four current existing tests, including the conventional population-based Cox proportional model and the burden, kernel, and sum of squares statistic (SSQ) tests for family data. The proposed tests can be applied to large-scale whole-genome sequencing data. They are appropriate for the practical use under a wide range of misspecified Cox models, as well as for population-based, pedigree-based, or hybrid designs. In our extensive simulation study and data example, we showed that the proposed kernel test is the most powerful and robust choice among the proposed burden test and the existing four rare variant survival association tests. When applied to the Diabetes Heart Study, the proposed tests found exome variants of the JAK1 gene on chromosome 1 showed the most significant association with age at onset of type 2 diabetes from the exome-wide analysis.

PMID: 28580640 [PubMed - as supplied by publisher]

Case Report: Making a diagnosis of familial renal disease - clinical and patient perspectives.

F1000Res. 2017;6:470

Authors: Iqbal Z, Sayer JA

Abstract
BACKGROUND: A precise molecular genetic diagnosis has become the gold standard for the correct identification and management of many inherited renal diseases.
METHODS: Here we describe a family with familial focal segmental glomerulosclerosis, and include a clinical and patient perspective on the diagnostic workup and relaying of genetic results following whole exome sequencing.
RESULTS: Through next generation sequencing approaches, we identified a pathogenic mutation in TRPC6, the underlying cause of the phenotype. The identification of this mutation had important clinical consequences for the family, including allowing a living-unrelated kidney transplant to proceed in the index case. There are also wider ranging social and ethical dilemmas presented when reaching a genetic diagnosis like this one, which are explored here by both physicians and the index case.
CONCLUSIONS: Through physician and patient perspectives in a family with inherited renal failure we explore the implications and the magnitude of a molecular genetic diagnosis.

PMID: 28580132 [PubMed - in process]

NALCN channelopathies: Distinguishing gain-of-function and loss-of-function mutations.

Neurology. 2016 Sep 13;87(11):1131-9

Authors: Bend EG, Si Y, Stevenson DA, Bayrak-Toydemir P, Newcomb TM, Jorgensen EM, Swoboda KJ

Abstract
OBJECTIVE: To perform genotype-phenotype analysis in an infant with congenital arthrogryposis due to a de novo missense mutation in the NALCN ion channel and explore the mechanism of pathogenicity using a Caenorhabditis elegans model.
METHODS: We performed whole-exome sequencing in a preterm neonate with congenital arthrogryposis and a severe life-threatening clinical course. We examined the mechanism of pathogenicity of the associated NALCN mutation by engineering the orthologous mutation into the nematode C elegans using CRISPR-Cas9.
RESULTS: We identified a de novo missense mutation in NALCN, c.1768C>T, in an infant with a severe neonatal lethal form of the recently characterized CLIFAHDD syndrome (congenital contractures of the limbs and face with hypotonia and developmental delay). We report novel phenotypic features including prolonged episodes of stimulus-sensitive sustained muscular contraction associated with life-threatening episodes of desaturation and autonomic instability, extending the severity of previously described phenotypes associated with mutations in NALCN. When engineered into the C elegans ortholog, this mutation results in a severe gain-of-function phenotype, with hypercontraction and uncoordinated movement. We engineered 6 additional CLIFAHDD syndrome mutations into C elegans and the mechanism of action could be divided into 2 categories: half phenocopied gain-of-function mutants and half phenocopied loss-of-function mutants.
CONCLUSIONS: The clinical phenotype of our patient and electrophysiologic studies show sustained muscular contraction in response to transient sensory stimuli. In C elegans, this mutation causes neuronal hyperactivity via a gain-of-function NALCN ion channel. Testing human variants of NALCN in C elegans demonstrates that CLIFAHDD can be caused by dominant loss- or gain-of-function mutations in ion channel function.

PMID: 27558372 [PubMed - indexed for MEDLINE]

A recurrent mutation in KCNA2 as a novel cause of hereditary spastic paraplegia and ataxia.

Ann Neurol. 2016 Oct;80(4):

Authors: Helbig KL, Hedrich UB, Shinde DN, Krey I, Teichmann AC, Hentschel J, Schubert J, Chamberlin AC, Huether R, Lu HM, Alcaraz WA, Tang S, Jungbluth C, Dugan SL, Vainionpää L, Karle KN, Synofzik M, Schöls L, Schüle R, Lehesjoki AE, Helbig I, Lerche H, Lemke JR

Abstract
The hereditary spastic paraplegias (HSPs) are heterogeneous neurodegenerative disorders with over 50 known causative genes. We identified a recurrent mutation in KCNA2 (c.881G>A, p.R294H), encoding the voltage-gated K(+) -channel, KV 1.2, in two unrelated families with HSP, intellectual disability (ID), and ataxia. Follow-up analysis of > 2,000 patients with various neurological phenotypes identified a de novo p.R294H mutation in a proband with ataxia and ID. Two-electrode voltage-clamp recordings of Xenopus laevis oocytes expressing mutant KV 1.2 channels showed loss of function with a dominant-negative effect. Our findings highlight the phenotypic spectrum of a recurrent KCNA2 mutation, implicating ion channel dysfunction as a novel HSP disease mechanism. Ann Neurol 2016.

PMID: 27543892 [PubMed - indexed for MEDLINE]

Stratification of endometrioid endometrial cancer patients into risk levels using somatic mutations.

Gynecol Oncol. 2016 Jul;142(1):150-7

Authors: Dai D, Thiel KW, Salinas EA, Goodheart MJ, Leslie KK, Gonzalez Bosquet J

Abstract
OBJECTIVE: Patients with endometrioid endometrial cancer are stratified as high risk and low risk for extrauterine disease by surgical staging. Since patients with low-grade, minimally invasive disease do not benefit from comprehensive staging, pre-surgery stratification into a risk category may prevent unnecessary surgical staging in low risk patients. Our objective was to develop a predictive model to identify risk levels using somatic mutations that could be used preoperatively.
METHODS: We classified endometrioid endometrial cancer patients in The Cancer Genome Atlas (TCGA) dataset into high risk and low risk categories: high risk patients presented with stage II, III or IV disease or stage I with high-intermediate risk features, whereas low risk patients consisted of the remaining stage I patients with either no myometrial invasion or low-intermediate risk features. Three strategies were used to build the prediction model: 1) mutational status for each gene; 2) number of somatic mutations for each gene; and 3) variant allele frequencies for each somatic mutation for each gene.
RESULTS: Each prediction strategy had a good performance, with an area under the curve (or AUC) between 61% and 80%. Analysis of variant allele frequency produced a superior prediction model for risk levels of endometrial cancer as compared to the other two strategies, with an AUC=91%. Lasso and Ridge methods identified 53 mutations that together had the highest predictability for high risk endometrioid endometrial cancer.
CONCLUSIONS: This prediction model will assist future retrospective and prospective studies to categorize endometrial cancer patients into high risk and low risk in the preoperative setting.

PMID: 27181389 [PubMed - indexed for MEDLINE]