CAGI4 Crohn's exome challenge: Marker SNP versus exome variant models for assigning risk of Crohn disease.

Hum Mutat. 2017 May 16;:

Authors: Pal LR, Kundu K, Yin Y, Moult J

Abstract
Understanding the basis of complex trait disease is a fundamental problem in human genetics. The CAGI Crohn's Exome challenges are providing insight into the adequacy of current disease models by requiring participants to identify which of a set of individuals has been diagnosed with the disease, given exome data. For the CAGI4 round, we developed a method that used the genotypes from exome sequencing data only to impute the status of Genome Wide Association Studies (GWAS) marker single nucleotide polymorphisms (SNPs). We then used the imputed genotypes as input to several machine learning methods that had been trained to predict disease status from marker SNP information. We achieved the best performance using Naïve Bayes and with a consensus machine learning method, obtaining an area under the curve (AUC) of 0.72, larger than other methods used in CAGI4. We also developed a model that incorporated the contribution from rare missense variants in the exome data, but this performed less well. Future progress is expected to come from the use of whole genome data rather than exomes. This article is protected by copyright. All rights reserved.

PMID: 28512778 [PubMed - as supplied by publisher]

Mutation screening in genes known to be responsible for Retinitis Pigmentosa in 98 Small Han Chinese Families.

Sci Rep. 2017 May 16;7(1):1948

Authors: Huang L, Zhang Q, Huang X, Qu C, Ma S, Mao Y, Yang J, Li Y, Li Y, Tan C, Zhao P, Yang Z

Abstract
Retinitis pigmentosa (RP) is highly heterogeneous in both clinical and genetic fields. Accurate mutation screening is very beneficial in improving clinical diagnosis and gene-specific treatment of RP patients. The reason for the difficulties in genetic diagnosis of RP is that the ethnic-specific mutation databases that contain both clinical and genetic information are largely insufficient. In this study, we recruited 98 small Han Chinese families clinically diagnosed as RP, including of 22 dominant, 19 recessive, 52 sporadic, and five X-linked. We then used whole exome sequencing (WES) analysis to detect mutations in the genes known for RP in 101 samples from these 98 families. In total, we identified 57 potential pathogenic mutations in 40 of the 98 (41%) families in 22 known RP genes, including 45 novel mutations. We detected mutations in 13 of the 22 (59%) typical autosomal dominant families, 8 of the 19 (42%) typical autosomal recessive families, 16 of the 52 (31%) sporadic small families, and four of the five (80%) X-linked families. Our results extended the mutation spectrum of known RP genes in Han Chinese, thus making a contribution to RP gene diagnosis and the pathogenetic study of RP genes.

PMID: 28512305 [PubMed - in process]

Obscurin variants and inherited cardiomyopathies.

Biophys Rev. 2017 May 05;:

Authors: Marston S

Abstract
The inherited cardiomyopathies, hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM) and left ventricular non-compaction (LVNC), have been frequently associated with mutations in sarcomeric proteins. In recent years, advances in DNA sequencing technology has allowed the study of the giant proteins of the sarcomere, such as titin and nebulin. Obscurin has been somewhat neglected in these studies, largely because its functional role is far from clear, although there was an isolated report in 2007 of obscurin mutations associated with HCM. Recently, whole exome sequencing methodology (WES) has been used to address mutations in OBSCN, the gene for obscurin, and OBSCN variants were found to be relatively common in inherited cardiomyopathies. In different studies, 5 OBSCN unique variants have been found in a group of 30 end-stage failing hearts, 6 OBSCN unique variants in 74 HCM cases and 3 OBSCN unique variants in 10 LVNC patients. As yet, the number of known potentially disease-causing OBSCN variants is quite small. The reason for this is that mutations in the OBSCN gene have not been recognised as potentially disease-causing until recently, and were not included in large-scale genetic surveys. OBSCN mutations may be causative of HCM, DCM and LVNC and other cardiomyopathies, or they may work in concert with other variants in the same or other genes to initiate the pathology. Currently, the function of obscurin is not well understood, but we anticipate that many more OBSCN variants linked to cardiomyopathy will be found when the large cohorts of patient sequences available are tested. It is to be hoped that the establishment of the importance of obscurin in pathology will stimulate a thorough investigation of obscurin function.

PMID: 28510120 [PubMed - as supplied by publisher]

Whole-Exome Sequencing Identifies a Novel Homozygous Frameshift Mutation in the MTMR2 Gene as a Causative Mutation in a Patient with Charcot-Marie-Tooth Disease Type 4B1.

Mol Neurobiol. 2017 May 16;:

Authors: Abdalla-Moady T, Peleg A, Sadeh O, Badarneh K, Fares F

Abstract
Charcot-Marie-Tooth (CMT) disease refers to a heterogeneous group of axonal and demyelinating polyneuropathies, characterized by chronic motor and sensory dysfunction. CMT is the most common genetic cause of neuropathy. The present study aimed to identify the gene mutation responsible for CMT in Ashkenazi Jew (AJ) patient. Genomic DNA was extracted from whole blood leukocytes of affected family and normal subject. Whole-exome sequencing was performed using the Illumina HiSeq2500. The DNA region containing the identified mutation was amplified by PCR and sequenced using dye-terminator chemistry and the forward primer. Physical examination of the patient revealed weakness and atrophy of the lower extremity muscles and Pes cavus foot deformity. Whole-exome sequencing indicated that the patient is homozygous for a novel frameshift mutation (c.1877_1878insAGAG, p.Arg630fs) in the myotubularin-related protein-2 gene (MTMR2), which resulted in an erroneous C-terminal sequence and extension by 15 amino acids. Patients' parents are healthy, and DNA sequencing analysis indicated that both are heterozygotes to the described mutation. The clinical feature of the patient may indicate a complete co-segregation of the p.Arg630fs mutation in MTMR2 gene with the CMT type 4B1 phenotype. Further studies are needed in order to estimate the prevalence of this mutation among AJ.

PMID: 28509084 [PubMed - as supplied by publisher]

Protein Truncating Variants at the Cholesteryl Ester Transfer Protein Gene and Risk for Coronary Heart Disease.

Circ Res. 2017 May 15;:

Authors: Nomura A, Won HH, Khera AV, Takeuchi F, Ito K, McCarthy S, Emdin CA, Klarin D, Natarajan P, Zekavat SM, Gupta N, Peloso GM, Borecki IB, Teslovich TM, Asselta R, Duga S, Merlini PA, Correa A, Kessler T, Wilson JG, Bown MJ, Hall AS, Braund PS, Carey DJ, Murray MF, Kirchner HL, Leader JB, Lavage DR, Manus JN, Hartzel DN, Samani NJ, Schunkert H, Marrugat J, Elosua R, McPherson R, Farrall M, Watkins H, Juang JJ, Hsiung CA, Lin SY, Wang JS, Tada H, Kawashiri MA, Inazu A, Yamagishi M, Katsuya T, Nakashima E, Nakatochi M, Yamamoto K, Yokota M, Momozawa Y, Rotter JI, Lander ES, Rader DJ, Danesh JN, Ardissino D, Gabriel SB, Willer CJ, Abecasis G, Saleheen D, Kubo M, Kato N, Chen YI, Dewey F, Kathiresan S

Abstract
Rationale: Therapies which inhibit cholesteryl ester transfer protein (CETP) have failed to demonstrate a reduction in risk for coronary heart disease (CHD). Human deoxyribonucleic acid sequence variants that truncate the CETP gene may provide insight into the efficacy of CETP inhibition. Objective: To test whether protein truncating variants (PTVs) at the CETP gene were associated with plasma lipid levels and CHD. Methods and Results: We sequenced the exons of the CETP gene in 58,469 participants from 12 case-control studies (18,817 CHD cases, 39,652 CHD-free controls). We defined PTV as those that lead to a premature stop, disrupt canonical splice-sites, or lead to insertions/deletions that shift frame. We also genotyped one Japanese-specific PTV in 27,561 participants from three case-control studies (14,286 CHD cases, 13,275 CHD-free controls). We tested association of CETP PTV carrier status with both plasma lipids and CHD. Among 58,469 participants with CETP gene sequencing data available, average age was 51.5 years and 43% were female; 1 in 975 participants carried a PTV at the CETP gene. Compared to non-carriers, carriers of PTV at CETP had higher high-density lipoprotein cholesterol (HDL-C; effect size, 22.6 mg/dL; 95% confidence interval [CI], 18 to 27; P < 1.0x10(-4)), lower low-density lipoprotein cholesterol (LDL-C; -12.2 mg/dL; 95% CI, -23 to -0.98; P = 0.033), and lower triglycerides (-6.3%; 95% CI, -12 to -0.22, P = 0.043). CETP PTV carrier status was associated with reduced risk for CHD (summary odds ratio, 0.70; 95% CI, 0.54 to 0.90; P = 5.1x10-3). Conclusions: Compared with non-carriers, carriers of PTV at CETP displayed higher HDL-C, lower LDL-C, lower triglycerides, and lower risk for CHD.

PMID: 28506971 [PubMed - as supplied by publisher]

RXRB is a MHC-encoded susceptibility gene associated with anti-topoisomerase I antibody-positive systemic sclerosis.

J Invest Dermatol. 2017 May 12;:

Authors: Oka A, Asano Y, Hasegawa M, Fujimoto M, Ishikawa O, Kuwana M, Kawaguchi Y, Yamamoto T, Takahashi H, Goto D, Endo H, Jinnin M, Mano S, Hosomichi K, Mabuchi T, Ueda MT, Nakagawa S, Beck S, Bahram S, Takehara K, Sato S, Ihn H

Abstract
Systemic sclerosis (SSc) is a systemic autoimmune and connective tissue disorder associated with the human leukocyte antigen (HLA) locus. However, the functional relationship between HLA gene(s) and disease development remains unknown. To elucidate major histocompatibility complex (MHC)-linked SSc genetics, we performed genotyping of MHC-borne microsatellites and HLA-DPB1 alleles using DNA obtained from 318 anti-topoisomerase I antibody-positive patients and 561 healthy controls, all of Japanese descent. Those results revealed 2 MHC haplotypes associated with SSc. Exome sequencing and targeted analysis of these risk haplotypes identified rs17847931 in retinoid X receptor beta (RXRB) as a susceptibility variant (P=1.3×10(-15); odds ratio (OR)=9.4) with amino acid substitution p.V95A on the risk haplotype harboring HLA-DPB1*13:01. No identical variant in the other haplotype including DPB1*09:01 was observed, though that haplotype also showed a significant association (P=8.5×10(-22); OR =4.3) with SSc. Furthermore, the number of risk factors was shown to be a predominant factor, as individuals with 2 factors had elevated risk (P=6.7 × 10(-13); OR=30.2). We concluded that RXRB may be involved in anti-fibrotic activity in skin and chromatin remodeling.

PMID: 28506627 [PubMed - as supplied by publisher]

New mutations in non-syndromic primary ovarian insufficiency patients identified via whole-exome sequencing.

Hum Reprod. 2017 May 13;:1-9

Authors: Patiño LC, Beau I, Carlosama C, Buitrago JC, González R, Suárez CF, Patarroyo MA, Delemer B, Young J, Binart N, Laissue P

Abstract
STUDY QUESTION: Is it possible to identify new mutations potentially associated with non-syndromic primary ovarian insufficiency (POI) via whole-exome sequencing (WES)?
SUMMARY ANSWER: WES is an efficient tool to study genetic causes of POI as we have identified new mutations, some of which lead to protein destablization potentially contributing to the disease etiology.
WHAT IS KNOWN ALREADY: POI is a frequently occurring complex pathology leading to infertility. Mutations in only few candidate genes, mainly identified by Sanger sequencing, have been definitively related to the pathogenesis of the disease.
STUDY DESIGN, SIZE, DURATION: This is a retrospective cohort study performed on 69 women affected by POI.
PARTICIPANTS/MATERIALS, SETTING, METHODS: WES and an innovative bioinformatics analysis were used on non-synonymous sequence variants in a subset of 420 selected POI candidate genes. Mutations in BMPR1B and GREM1 were modeled by using fragment molecular orbital analysis.
MAIN RESULTS AND THE ROLE OF CHANCE: Fifty-five coding variants in 49 genes potentially related to POI were identified in 33 out of 69 patients (48%). These genes participate in key biological processes in the ovary, such as meiosis, follicular development, granulosa cell differentiation/proliferation and ovulation. The presence of at least two mutations in distinct genes in 42% of the patients argued in favor of a polygenic nature of POI.
LIMITATIONS, REASONS FOR CAUTION: It is possible that regulatory regions, not analyzed in the present study, carry further variants related to POI.
WIDER IMPLICATIONS OF THE FINDINGS: WES and the in silico analyses presented here represent an efficient approach for mapping variants associated with POI etiology. Sequence variants presented here represents potential future genetic biomarkers.
STUDY FUNDING/COMPETING INTEREST(S): This study was supported by the Universidad del Rosario and Colciencias (Grants CS/CIGGUR-ABN062-2016 and 672-2014). Colciencias supported Liliana Catherine Patiño´s work (Fellowship: 617, 2013). The authors declare no conflict of interest.

PMID: 28505269 [PubMed - as supplied by publisher]

Whole exome sequencing of a consanguineous family identifies the possible modifying effect of a globally rare AK5 allelic variant in celiac disease development among Saudi patients.

PLoS One. 2017;12(5):e0176664

Authors: Al-Aama JY, Shaik NA, Banaganapalli B, Salama MA, Rashidi O, Sahly AN, Mohsen MO, Shawoosh HA, Shalabi HA, Edreesi MA, Alharthi SE, Wang J, Elango R, Saadah OI

Abstract
Celiac disease (CD), a multi-factorial auto-inflammatory disease of the small intestine, is known to occur in both sporadic and familial forms. Together HLA and Non-HLA genes can explain up to 50% of CD's heritability. In order to discover the missing heritability due to rare variants, we have exome sequenced a consanguineous Saudi family presenting CD in an autosomal recessive (AR) pattern. We have identified a rare homozygous insertion c.1683_1684insATT, in the conserved coding region of AK5 gene that showed classical AR model segregation in this family. Sequence validation of 200 chromosomes each of sporadic CD cases and controls, revealed that this extremely rare (EXac MAF 0.000008) mutation is highly penetrant among general Saudi populations (MAF is 0.62). Genotype and allelic distribution analysis have indicated that this AK5 (c.1683_1684insATT) mutation is negatively selected among patient groups and positively selected in the control group, in whom it may modify the risk against CD development [p<0.002]. Our observation gains additional support from computational analysis which predicted that Iso561 insertion shifts the existing H-bonds between 400th and 556th amino acid residues lying near the functional domain of adenylate kinase. This shuffling of amino acids and their H-bond interactions is likely to disturb the secondary structure orientation of the polypeptide and induces the gain-of-function in nucleoside phosphate kinase activity of AK5, which may eventually down-regulates the reactivity potential of CD4+ T-cells against gluten antigens. Our study underlines the need to have population-specific genome databases to avoid false leads and to identify true candidate causal genes for the familial form of celiac disease.

PMID: 28505210 [PubMed - in process]

Further Validation of the SIGMAR1 c.151+1G>T Mutation as Cause of Distal Hereditary Motor Neuropathy.

Child Neurol Open. 2016 Jan-Dec;3:2329048X16669912

Authors: Lee JJY, van Karnebeek CDM, Drögemoller B, Shyr C, Tarailo-Graovac M, Eydoux P, Ross CJ, Wasserman WW, Björnson B, Wu JK

Abstract
Distal hereditary motor neuropathies represent a group of rare genetic disorders characterized by progressive distal motor weakness without sensory loss. Their genetic heterogeneity is high and thus eligible for diagnostic whole exome sequencing. The authors report successful application of whole exome sequencing in diagnosing a second consanguineous family with distal hereditary motor neuropathy due to a homozygous c.151+1G>T variant in SIGMAR1. This variant was recently proposed as causal for the same condition in a consanguineous Chinese family. Compared to this family, the Afghan ethnic origin of our patient is distinct, yet the features are identical, validating the SIGMAR1 deficiency phenotype: progressive muscle wasting/weakness in lower and upper limbs without sensory loss. Rapid disease progression during adolescent growth is similar and may be due to SIGMAR1's role in regulating axon elongation and tau phosphorylation. Finally, the authors conclude that SIGMAR1 deficiency should be added to the differential diagnosis of distal hereditary motor neuropathies.

PMID: 28503617 [PubMed - in process]

A case of a novel mutation in HNF1β-related maturity-onset diabetes of the young type 5 with diabetic kidney disease complication in a Chinese family.

J Diabetes Complications. 2016 Nov 15;:

Authors: Wang Y, Zhao Y, Zhang J, Yang Y, Liu F

Abstract
AIMS: Precise diagnosis of maturity-onset diabetes of the young (MODY) has proven valuable for understanding mechanism of diabetes and selecting optimal therapy. A proband and her mother with diabetic kidney disease (DKD) were studied to investigate potential genes responsible for diabetes and different severity of DKD between the parent and offspring.
METHODS: The family with suspected MODY underwent mutational analyses by the whole exome sequencing (WES). Candidate pathogenic variants were validated by Sanger sequencing and tested for co-segregation. The clinical parameters of subjects were collected from medical records.
RESULTS: A novel missense heterozygous mutation in exon 4 of the hepatocyte nuclear factor 1β (HNF1β), c.1007A > G (p.H336R), was identified in both the proband and her mother. Moreover, comparing the family's WES results, we found that the proband had acquired a KCNQ1 gene mutation from her father and acquired ACE and SORBS1 gene mutations from her mother. These three genes are known susceptibility genes of DKD and may impose additional effects contributing to DKD severity.
CONCLUSIONS: A novel mutation in HNF1β-MODY was identified in a Chinese family complicated with DKD, and the additional effect of pathogenic variants in susceptibility genes was speculated to contribute to DKD severity.

PMID: 28502589 [PubMed - as supplied by publisher]

Differential analysis of mutations in the Jewish population and their implications for diseases.

Genet Res (Camb). 2017 May 15;99:e3

Authors: Einhorn Y, Weissglas-Volkov D, Carmi S, Ostrer H, Friedman E, Shomron N

Abstract
Sequencing large cohorts of ethnically homogeneous individuals yields genetic insights with implications for the entire population rather than a single individual. In order to evaluate the genetic basis of certain diseases encountered at high frequency in the Ashkenazi Jewish population (AJP), as well as to improve variant annotation among the AJP, we examined the entire exome, focusing on specific genes with known clinical implications in 128 Ashkenazi Jews and compared these data to other non-Jewish populations (European, African, South Asian and East Asian). We targeted American College of Medical Genetics incidental finding recommended genes and the Catalogue of Somatic Mutations in Cancer (COSMIC) germline cancer-related genes. We identified previously known disease-causing variants and discovered potentially deleterious variants in known disease-causing genes that are population specific or substantially more prevalent in the AJP, such as in the ATP and HGFAC genes associated with colorectal cancer and pancreatic cancer, respectively. Additionally, we tested the advantage of utilizing the database of the AJP when assigning pathogenicity to rare variants of independent whole-exome sequencing data of 49 Ashkenazi Jew early-onset breast cancer (BC) patients. Importantly, population-based filtering using our AJP database enabled a reduction in the number of potential causal variants in the BC cohort by 36%. Taken together, population-specific sequencing of the AJP offers valuable, clinically applicable information and improves AJP filter annotation.

PMID: 28502252 [PubMed - in process]

Genetic analysis of impaired trimethylamine metabolism using whole exome sequencing.

BMC Med Genet. 2017 Feb 15;18(1):11

Authors: Guo Y, Hwang LD, Li J, Eades J, Yu CW, Mansfield C, Burdick-Will A, Chang X, Chen Y, Duke FF, Zhang J, Fakharzadeh S, Fennessey P, Keating BJ, Jiang H, Hakonarson H, Reed DR, Preti G

Abstract
BACKGROUND: Trimethylaminuria (TMAU) is a genetic disorder whereby people cannot convert trimethylamine (TMA) to its oxidized form (TMAO), a process that requires the liver enzyme FMO3. Loss-of-function variants in the FMO3 gene are a known cause of TMAU. In addition to the inability to metabolize TMA precursors like choline, patients often emit a characteristic odor because while TMAO is odorless, TMA has a fishy smell. The Monell Chemical Senses Center is a research institute with a program to evaluate people with odor complaints for TMAU.
METHODS: Here we evaluated ten subjects by (1) odor evaluation by a trained sensory panel, (2) analysis of their urine concentration of TMA relative to TMAO before and after choline ingestion, and (3) whole exome sequencing as well as subsequent variant analysis of all ten samples to investigate the genetics of TMAU.
RESULTS: While all subjects reported they often emitted a fish-like odor, none had this malodor during sensory evaluation. However, all were impaired in their ability to produce >90% TMAO/TMA in their urine and thus met the criteria for TMAU. To probe for genetic causes, the exome of each subject was sequenced, and variants were filtered by genes with a known (FMO3) or expected effect on TMA metabolism function (other oxidoreductases). We filtered the remaining variants by allele frequency and predicated functional effects. We identified one subject that had a rare loss-of-function FMO3 variant and six with more common decreased-function variants. In other oxidoreductases genes, five subjects had four novel rare single-nucleotide polymorphisms as well as one rare insertion/deletion. Novel in this context means no investigators have previously linked these variants to TMAU although they are in dbSNP.
CONCLUSIONS: Thus, variants in genes other than FMO3 may cause TMAU and the genetic variants identified here serve as a starting point for future studies of impaired TMA metabolism.

PMID: 28196478 [PubMed - indexed for MEDLINE]

Novel UCHL1 mutations reveal new insights into ubiquitin processing.

Hum Mol Genet. 2017 Mar 15;26(6):1031-1040

Authors: Rydning SL, Backe PH, Sousa MML, Iqbal Z, Øye AM, Sheng Y, Yang M, Lin X, Slupphaug G, Nordenmark TH, Vigeland MD, Bjørås M, Tallaksen CM, Selmer KK

Abstract
Recessive loss of function of the neuronal ubiquitin hydrolase UCHL1 has been implicated in early-onset progressive neurodegeneration (MIM no. 615491), so far only in one family. In this study a second family is characterized, and the functional consequences of the identified mutations in UCHL1 are explored. Three siblings developed childhood-onset optic atrophy, followed by spasticity and ataxia. Whole exome sequencing identified compound heterozygous variants in UCHL1, c.533G > A (p.Arg178Gln) and c.647C > A (p.Ala216Asp), cosegregating with the phenotype. Enzymatic activity of purified recombinant proteins analysed by ubiquitin hydrolase assays showed a 4-fold increased hydrolytic activity of the recombinant UCHL1 mutant Arg178Gln compared to wild type, whereas the Ala216Asp protein was insoluble. Structural 3D analysis of UCHL1 by computer modelling suggests that Arg178 is a rate-controlling residue in catalysis which is partly abolished in the Arg178Gln mutant and, consequently, the Arg178Gln mutant increases the enzymatic turnover. UCHL1 protein levels in fibroblasts measured by targeted mass spectrometry showed a total amount of UCHL1 in control fibroblasts about 4-fold higher than in the patients. Hence, studies of the identified missense variants reveal surprisingly different functional consequences as the insoluble Ala216Asp variant leads to loss of function, whereas the Arg178Gln leads to increased enzyme activity. The reported patients have remarkably preserved cognition, and we propose that the increased enzyme activity of the Arg178Gln variant offers a protective effect on cognitive function. This study establishes the importance of UCHL1 in neurodegeneration, provides new mechanistic insight about ubiquitin processing, and underlines the complexity of the different roles of UCHL1.

PMID: 28007905 [PubMed - indexed for MEDLINE]

Evaluation of ACMG-Guideline-Based Variant Classification of Cancer Susceptibility and Non-Cancer-Associated Genes in Families Affected by Breast Cancer.

Am J Hum Genet. 2016 May 05;98(5):801-17

Authors: Maxwell KN, Hart SN, Vijai J, Schrader KA, Slavin TP, Thomas T, Wubbenhorst B, Ravichandran V, Moore RM, Hu C, Guidugli L, Wenz B, Domchek SM, Robson ME, Szabo C, Neuhausen SL, Weitzel JN, Offit K, Couch FJ, Nathanson KL

Abstract
Sequencing tests assaying panels of genes or whole exomes are widely available for cancer risk evaluation. However, methods for classification of variants resulting from this testing are not well studied. We evaluated the ability of a variant-classification methodology based on American College of Medical Genetics and Genomics (ACMG) guidelines to define the rate of mutations and variants of uncertain significance (VUS) in 180 medically relevant genes, including all ACMG-designated reportable cancer and non-cancer-associated genes, in individuals who met guidelines for hereditary cancer risk evaluation. We performed whole-exome sequencing in 404 individuals in 253 families and classified 1,640 variants. Potentially clinically actionable (likely pathogenic [LP] or pathogenic [P]) versus nonactionable (VUS, likely benign, or benign) calls were 95% concordant with locus-specific databases and Clinvar. LP or P mutations were identified in 12 of 25 breast cancer susceptibility genes in 26 families without identified BRCA1/2 mutations (11%). Evaluation of 84 additional genes associated with autosomal-dominant cancer susceptibility identified LP or P mutations in only two additional families (0.8%). However, individuals from 10 of 253 families (3.9%) had incidental LP or P mutations in 32 non-cancer-associated genes, and 9% of individuals were monoallelic carriers of a rare LP or P mutation in 39 genes associated with autosomal-recessive cancer susceptibility. Furthermore, 95% of individuals had at least one VUS. In summary, these data support the clinical utility of ACMG variant-classification guidelines. Additionally, evaluation of extended panels of cancer-associated genes in breast/ovarian cancer families leads to only an incremental clinical benefit but substantially increases the complexity of the results.

PMID: 27153395 [PubMed - indexed for MEDLINE]

Genetic and clinical characteristics of NEFL-related Charcot-Marie-Tooth disease.

J Neurol Neurosurg Psychiatry. 2017 May 13;:

Authors: Horga A, Laurà M, Jaunmuktane Z, Jerath NU, Gonzalez MA, Polke JM, Poh R, Blake JC, Liu YT, Wiethoff S, Bettencourt C, Lunn MP, Manji H, Hanna MG, Houlden H, Brandner S, Züchner S, Shy M, Reilly MM

Abstract
OBJECTIVES: To analyse and describe the clinical and genetic spectrum of Charcot-Marie-Tooth disease (CMT) caused by mutations in the neurofilament light polypeptide gene (NEFL).
METHODS: Combined analysis of newly identified patients with NEFL-related CMT and all previously reported cases from the literature.
RESULTS: Five new unrelated patients with CMT carrying the NEFL mutations P8R and N98S and the novel variant L311P were identified. Combined data from these cases and 62 kindreds from the literature revealed four common mutations (P8R, P22S, N98S and E396K) and three mutational hotspots accounting for 37 (55%) and 50 (75%) kindreds, respectively. Eight patients had de novo mutations. Loss of large-myelinated fibres was a uniform feature in a total of 21 sural nerve biopsies and 'onion bulb' formations and/or thin myelin sheaths were observed in 14 (67%) of them. The neurophysiological phenotype was broad but most patients with E90K and N98S had upper limb motor conduction velocities <38 m/s. Age of onset was ≤3 years in 25 cases. Pyramidal tract signs were described in 13 patients and 7 patients were initially diagnosed with or tested for inherited ataxia. Patients with E90K and N98S frequently presented before age 3 years and developed hearing loss or other neurological features including ataxia and/or cerebellar atrophy on brain MRI.
CONCLUSIONS: NEFL-related CMT is clinically and genetically heterogeneous. Based on this study, however, we propose mutational hotspots and relevant clinical-genetic associations that may be helpful in the evaluation of NEFL sequence variants and the differential diagnosis with other forms of CMT.

PMID: 28501821 [PubMed - as supplied by publisher]

Genetic modifiers of multiple sclerosis progression, severity and onset.

Clin Immunol. 2017 May 10;:

Authors: Dessa Sadovnick A, Traboulsee AL, Zhao Y, Bernales CQ, Encarnacion M, Ross JP, Yee IM, Criscuoli MG, Vilariño-Güell C

Abstract
The genetic contribution to clinical outcomes for multiple sclerosis (MS) has yet to be defined. We performed exome sequencing analysis in 100 MS patients presenting opposite extremes of clinical phenotype (discovery cohort), and genotyped variants of interest in 2016 MS patients (replication cohort). Linear and logistic regression analyses were used to identify significant associations with disease course, severity and onset. Our analysis of the discovery cohort nominated 38 variants in 21 genes. Replication analysis identified PSMG4 p.W99R and NLRP5 p.M459I to be associated with disease severity (p=0.002 and 0.008). CACNA1H p.R1871Q was found associated with patients presenting relapsing remitting MS at clinical onset (p=0.028) whereas NLRP5 p.M459I and EIF2AK1 p.K558R were associated with primary progressive disease (p=0.031 and 0.023). In addition, PSMG4 p.W99R and NLRP5 p.R761L were found to correlate with an earlier age at MS clinical onset, and MC1R p.R160W with delayed onset of clinical symptoms (p=0.010-0.041).

PMID: 28501589 [PubMed - as supplied by publisher]

HLAscan: genotyping of the HLA region using next-generation sequencing data.

BMC Bioinformatics. 2017 May 12;18(1):258

Authors: Ka S, Lee S, Hong J, Cho Y, Sung J, Kim HN, Kim HL, Jung J

Abstract
BACKGROUND: Several recent studies showed that next-generation sequencing (NGS)-based human leukocyte antigen (HLA) typing is a feasible and promising technique for variant calling of highly polymorphic regions. To date, however, no method with sufficient read depth has completely solved the allele phasing issue. In this study, we developed a new method (HLAscan) for HLA genotyping using NGS data.
RESULTS: HLAscan performs alignment of reads to HLA sequences from the international ImMunoGeneTics project/human leukocyte antigen (IMGT/HLA) database. The distribution of aligned reads was used to calculate a score function to determine correctly phased alleles by progressively removing false-positive alleles. Comparative HLA typing tests using public datasets from the 1000 Genomes Project and the International HapMap Project demonstrated that HLAscan could perform HLA typing more accurately than previously reported NGS-based methods such as HLAreporter and PHLAT. In addition, the results of HLA-A, -B, and -DRB1 typing by HLAscan using data generated by NextGen were identical to those obtained using a Sanger sequencing-based method. We also applied HLAscan to a family dataset with various coverage depths generated on the Illumina HiSeq X-TEN platform. HLAscan identified allele types of HLA-A, -B, -C, -DQB1, and -DRB1 with 100% accuracy for sequences at ≥ 90× depth, and the overall accuracy was 96.9%.
CONCLUSIONS: HLAscan, an alignment-based program that takes read distribution into account to determine true allele types, outperformed previously developed HLA typing tools. Therefore, HLAscan can be reliably applied for determination of HLA type across the whole-genome, exome, and target sequences.

PMID: 28499414 [PubMed - in process]

The New Genomics: What Molecular Databases Can Tell us About Human Population Variation and Endocrine Disease.

Endocrinology. 2017 May 11;:

Authors: Rotwein P

Abstract
Major recent advances in genetics and genomics present unique opportunities for enhancing our understanding of human physiology and disease predisposition. Here I demonstrate how analysis of genomic information can provide new understanding of endocrine systems, using the human growth hormone (GH) signaling pathway as an illustrative example. GH is essential for normal postnatal growth in children, and plays important roles in other biological processes throughout life. GH actions are mediated by the GH receptor, primarily via the JAK2 protein tyrosine kinase and the STAT5B transcription factor, and inactivating mutations in this pathway all lead to impaired somatic growth. Variation in GH signaling genes has been evaluated using DNA sequence data from the Exome Aggregation Consortium, a compendium of information from over 60,000 individuals. Results reveal many potential missense and other alterations in the coding regions of GH1, GHR, JAK2, and STAT5B, with most changes being uncommon. The total number of different alleles per gene varied by ∼3-fold, from 101 for GH1 to 338 for JAK2. Several known disease-linked mutations in GH1, GHR, and JAK2 were present but infrequent in the population, although three amino acid changes in the GHR were sufficiently prevalent (∼4% to 44% of chromosomes) to suggest that they are not disease causing. Collectively these data provide new opportunities to understand how genetically driven variability in GH signaling and action may modify human physiology and disease.

PMID: 28498917 [PubMed - as supplied by publisher]

Identification of a missense HOXD13 mutation in a Chinese family with syndactyly type I-c using exome sequencing.

Mol Med Rep. 2017 May 11;:

Authors: Deng H, Tan T, He Q, Lin Q, Yang Z, Zhu A, Guan L, Xiao J, Song Z, Guo Y

Abstract
Syndactyly is one of the most common hereditary limb malformations, and is characterized by the fusion of specific fingers and/or toes. Syndactyly type I‑c is associated with bilateral cutaneous or bony webbing of the third and fourth fingers and occasionally of the third to fifth fingers, with normal feet. The aim of the present study was to identify the genetic basis of syndactyly type I‑c in four generations of a Chinese Han family by exome sequencing. Exome sequencing was conducted in the proband of the family, followed by direct sequencing of other family members of the same ancestry, as well as 100 ethnically‑matched, unrelated normal controls. A missense mutation, c.917G>A (p.R306Q), was identified in the homeobox D13 gene (HOXD13). Sanger sequencing verified the presence of this mutation in all of the affected family members. By contrast, this mutation was absent in the unaffected family members and the 100 ethnically‑matched normal controls. The results suggest that the c.917G>A (p.R306Q) mutation in the HOXD13 gene, may be responsible for syndactyly type I‑c in this family. Exome sequencing may therefore be a powerful tool for identifying mutations associated with syndactyly, which is a disorder with high genetic and clinical heterogeneity. The results provide novel insights into the etiology and diagnosis of syndactyly, and may influence genetic counseling and the clinical management of the disease.

PMID: 28498426 [PubMed - as supplied by publisher]

Determination of disease phenotypes and pathogenic variants from exome sequence data in the CAGI 4 gene panel challenge.

Hum Mutat. 2017 May 12;:

Authors: Kundu K, Pal LR, Yin Y, Moult J

Abstract
The use of gene panel sequence for diagnostic and prognostic testing is now widespread, but there are so far few objective tests of methods to interpret these data. We describe the design and implementation of a gene panel sequencing data analysis pipeline (VarP) and its assessment in a CAGI4 community experiment. The method was applied to clinical gene panel sequencing data of 106 patients, with the goal of determining which of 14 disease classes each patient has and the corresponding causative variant(s). The disease class was correctly identified for 36 cases, including 10 where the original clinical pipeline did not find causative variants. For a further seven cases, we found strong evidence of an alternative disease to that tested. Many of the potentially causative variants are missense, with no previous association with disease, and these proved the hardest to correctly assign pathogenicity or otherwise. Post analysis showed that three-dimensional structure data could have helped for up to half of these cases. Over-reliance on HGMD annotation led to a number of incorrect disease assignments. We used a largely ad hoc method to assign probabilities of pathogenicity for each variant, and there is much work still to be done in this area. This article is protected by copyright. All rights reserved.

PMID: 28497567 [PubMed - as supplied by publisher]