Use of next-generation sequencing and other whole-genome strategies to dissect neurological disease

A microglia clonal inflammatory disorder in Alzheimer's Disease

Somatic genetic heterogeneity resulting from post-zygotic DNA mutations is widespread in human tissues and can cause diseases, however few studies have investigated its role in neurodegenerative processes such as Alzheimer's Disease (AD). Here we report the selective enrichment of microglia clones carrying pathogenic variants, that are not present in neuronal, glia/stromal cells, or blood, from patients with AD in comparison to age-matched controls. Notably, microglia-specific AD-associated variants preferentially target the MAPK pathway, including recurrent CBL ring-domain mutations. These variants activate ERK and drive a microglia transcriptional program characterized by a strong neuro-inflammatory response, both in vitro and in patients. Although the natural history of AD-associated microglial clones is difficult to establish in human, microglial expression of a MAPK pathway activating variant was previously shown to cause neurodegeneration in mice, suggesting that AD-associated neuroinflammatory microglial clones may contribute to the neurodegenerative process in patients.

FedGMMAT: Federated generalized linear mixed model association tests

Increasing genetic and phenotypic data size is critical for understanding the genetic determinants of diseases. Evidently, establishing practical means for collaboration and data sharing among institutions is a fundamental methodological barrier for performing high-powered studies. As the sample sizes become more heterogeneous, complex statistical approaches, such as generalized linear mixed effects models, must be used to correct for the confounders that may bias results. On another front, due to the privacy concerns around Protected Health Information (PHI), genetic information is restrictively protected by sharing according to regulations such as Health Insurance Portability and Accountability Act (HIPAA). This limits data sharing among institutions and hampers efforts around executing high-powered collaborative studies. Federated approaches are promising to alleviate the issues around privacy and performance, since sensitive data never leaves the local sites. Motivated by these, we developed FedGMMAT, a federated genetic association testing tool that utilizes a federated statistical testing approach for efficient association tests that can correct for confounding fixed and additive polygenic random effects among different collaborating sites. Genetic data is never shared among collaborating sites, and the intermediate statistics are protected by encryption. Using simulated and real datasets, we demonstrate FedGMMAT can achieve the virtually same results as pooled analysis under a privacy-preserving framework with practical resource requirements.

Unveiling the genetic tapestry: Rare disease genomics of spinal muscular atrophy and phenylketonuria proteins

Rare diseases, defined by their low prevalence, present significant challenges, including delayed detection, expensive treatments, and limited research. This study delves into the genetic basis of two noteworthy rare diseases in Saudi Arabia: Phenylketonuria (PKU) and Spinal Muscular Atrophy (SMA). PKU, resulting from mutations in the phenylalanine hydroxylase (PAH) gene, exhibits geographical variability and impacts intellectual abilities. SMA, characterized by motor neuron loss, is linked to mutations in the survival of motor neuron 1 (SMN1) gene. Recognizing the importance of unveiling signature genomics in rare diseases, we conducted a quantitative study on PAH and SMN1 proteins of multiple organisms by employing various quantitative techniques to assess genetic variations. The derived signature-genomics contributes to a deeper understanding of these critical genes, paving the way for enhanced diagnostics for disorders associated with PAH and SMN1.

Epigenetic editing for autosomal dominant neurological disorders

Epigenetics refers to the molecules and mechanisms that modify gene expression states without changing the nucleotide context. These modifications are what encode the cell state during differentiation or epigenetic memory in mitosis. Epigenetic modifications can alter gene expression by changing the chromatin architecture by altering the affinity for DNA to wrap around histone octamers, forming nucleosomes. The higher affinity the DNA has for the histones, the tighter it will wrap and therefore induce a heterochromatin state, silencing gene expression. Several groups have shown the ability to harness the cell's natural epigenetic modification pathways to engineer proteins that can induce changes in epigenetics and consequently regulate gene expression. Therefore, epigenetic modification can be used to target and treat disorders through the modification of endogenous gene expression. The use of epigenetic modifications may prove an effective path towards regulating gene expression to potentially correct or cure genetic disorders.

Socrates: A Novel N-Ethyl-N-nitrosourea-Induced Mouse Mutant with Audiogenic Epilepsy

Epilepsy is one of the common neurological diseases that affects not only adults but also infants and children. Because epilepsy has been studied for a long time, there are several pharmacologically effective anticonvulsants, which, however, are not suitable as therapy for all patients. The genesis of epilepsy has been extensively investigated in terms of its occurrence after injury and as a concomitant disease with various brain diseases, such as tumors, ischemic events, etc. However, in the last decades, there are multiple reports that both genetic and epigenetic factors play an important role in epileptogenesis. Therefore, there is a need for further identification of genes and loci that can be associated with higher susceptibility to epileptic seizures. Use of mouse knockout models of epileptogenesis is very informative, but it has its limitations. One of them is due to the fact that complete deletion of a gene is not, in many cases, similar to human epilepsy-associated syndromes. Another approach to generating mouse models of epilepsy is N-Ethyl-N-nitrosourea (ENU)-directed mutagenesis. Recently, using this approach, we generated a novel mouse strain, soc (socrates, formerly s8-3), with epileptiform activity. Using molecular biology methods, calcium neuroimaging, and immunocytochemistry, we were able to characterize the strain. Neurons isolated from soc mutant brains retain the ability to differentiate in vitro and form a network. However, soc mutant neurons are characterized by increased spontaneous excitation activity. They also demonstrate a high degree of Ca2+ activity compared to WT neurons. Additionally, they show increased expression of NMDA receptors, decreased expression of the Ca2+-conducting GluA2 subunit of AMPA receptors, suppressed expression of phosphoinositol 3-kinase, and BK channels of the cytoplasmic membrane involved in protection against epileptogenesis. During embryonic and postnatal development, the expression of several genes encoding ion channels is downregulated in vivo, as well. Our data indicate that soc mutation causes a disruption of the excitation-inhibition balance in the brain, and it can serve as a mouse model of epilepsy.

Evaluating long-read de novo assembly tools for eukaryotic genomes: insights and considerations

BACKGROUND

Assembly algorithm choice should be a deliberate, well-justified decision when researchers create genome assemblies for eukaryotic organisms from third-generation sequencing technologies. While third-generation sequencing by Oxford Nanopore Technologies (ONT) and Pacific Biosciences (PacBio) has overcome the disadvantages of short read lengths specific to next-generation sequencing (NGS), third-generation sequencers are known to produce more error-prone reads, thereby generating a new set of challenges for assembly algorithms and pipelines. However, the introduction of HiFi reads, which offer substantially reduced error rates, has provided a promising solution for more accurate assembly outcomes. Since the introduction of third-generation sequencing technologies, many tools have been developed that aim to take advantage of the longer reads, and researchers need to choose the correct assembler for their projects.

RESULTS

We benchmarked state-of-the-art long-read de novo assemblers to help readers make a balanced choice for the assembly of eukaryotes. To this end, we used 12 real and 64 simulated datasets from different eukaryotic genomes, with different read length distributions, imitating PacBio continuous long-read (CLR), PacBio high-fidelity (HiFi), and ONT sequencing to evaluate the assemblers. We include 5 commonly used long-read assemblers in our benchmark: Canu, Flye, Miniasm, Raven, and wtdbg2 for ONT and PacBio CLR reads. For PacBio HiFi reads , we include 5 state-of-the-art HiFi assemblers: HiCanu, Flye, Hifiasm, LJA, and MBG. Evaluation categories address the following metrics: reference-based metrics, assembly statistics, misassembly count, BUSCO completeness, runtime, and RAM usage. Additionally, we investigated the effect of increased read length on the quality of the assemblies and report that read length can, but does not always, positively impact assembly quality.

CONCLUSIONS

Our benchmark concludes that there is no assembler that performs the best in all the evaluation categories. However, our results show that overall Flye is the best-performing assembler for PacBio CLR and ONT reads, both on real and simulated data. Meanwhile, best-performing PacBio HiFi assemblers are Hifiasm and LJA. Next, the benchmarking using longer reads shows that the increased read length improves assembly quality, but the extent to which that can be achieved depends on the size and complexity of the reference genome.

Application of second-generation sequencing in congenital pulmonary airway malformations

To investigate the differential expression of genes in whole transcripts of congenital pulmonary airway malformation (CPAM) using second-generation sequencing (also known as next-generation sequencing, NGS) technology. Children with CPAM were strictly screened after setting the criteria, and grouped by taking CPAM parietal tissue and CPAM lesion tissue respectively, and RNA-Seq libraries were established separately using second-generation sequencing technology, followed by differential expression analysis and GO (gene ontology) functional enrichment analysis, KEGG (Kyoto encyclopedia of genes and genomes, a database) pathway analysis and GSEA (Gene Set Enrichment Analysis) analysis. Five cases were screened from 36 children with CPAM, and high-throughput sequencing was performed to obtain 10 whole transcripts of samples with acceptable sequence quality and balanced gene coverage. One aberrantly expressed sample (3b) was found by analysis of principal components, which was excluded and then subjected to differential expression analysis, and 860 up-regulated genes and 203 down-regulated genes. GO functional enrichment analysis of differentially expressed genes demonstrates the functional class and cellular localization of target genes. The whole transcript of CPAM shows obvious gene up and down-regulation, differentially expressed genes are located in specific cells and belong to different functional categories, and NGS can provide an effective means to study the transcriptional regulation of CPAM from the overall transcriptional level.

A Mini-Review Regarding the Clinical Outcomes of In Vitro Fertilization (IVF) Following Pre-Implantation Genetic Testing (PGT)-Next Generation Sequencing (NGS) Approach

Background: PGT-based NGS revolutionized the field of reproductive medicine, becoming an integrated component within current assisted reproductive technology (ART) protocols. Methods: We searched the literature published in the last half a decade in four databases (PubMed/Medline, ISI Web of Knowledge, ScienceDirect, and Scopus) between 2018 and 2022. Results: A total of 1388 articles were filtered, from which 60 met, initially, the eligibility criteria, but only 42 were included (≥100 patients/couples—62,465 patients and 6628 couples in total) in the present mini-review. In total, forty-two (70.0%) reported reproductive outcomes, while eighteen (30.0%) had distinct objectives. Furthermore, n = 1, 1.66% of the studies focused on PGT, n = 1, 1.66% on pre-implantation genetic testing for monogenic disorders (PGT-M), n = 3, 5.0% on pre-implantation genetic testing for structural rearrangements (PGT-SR) and n = 55, 91.66% on pre-implantation genetic testing for aneuploidies (PGT-A). Conclusions: PGT using NGS proved to be an excellent companion that folds within the current ascending tendency among couples that require specialty care. We strongly encourage future studies to provide a systematic overview expanded at a larger scale on the role of the PGT-NGS.

Estimated prevalence of Niemann-Pick type C disease in Quebec

Niemann–Pick type C (NP-C) disease is an autosomal recessive disease caused by variants in the NPC1 or NPC2 genes. It has a large range of symptoms depending on age of onset, thus making it difficult to diagnose. In adults, symptoms appear mainly in the form of psychiatric problems. The prevalence varies from 0.35 to 2.2 per 100,000 births depending on the country. The aim of this study is to calculate the estimated prevalence of NP-C in Quebec to determine if it is underdiagnosed in this population. The CARTaGENE database is a unique database that regroups individuals between 40 and 69 years old from metropolitan regions of Quebec. RNA-sequencing data was available for 911 individuals and exome sequencing for 198 individuals. We used a bioinformatic pipeline on those individuals to extract the variants in the NPC1/2 genes. The prevalence in Quebec was estimated assuming Hardy–Weinberg Equilibrium. Two pathogenic variants were used. The variant p.Pro543Leu was found in three heterozygous individuals that share a common haplotype, which suggests a founder French-Canadian pathogenic variant. The variant p.Ile1061Thr was found in two heterozygous individuals. Both variants have previously been reported and are usually associated with infantile onset. The estimated prevalence calculated using those two variants is 0.61:100,000 births. This study represents the first estimate of NP-C in Quebec. The estimated prevalence for NP-C is likely underestimated due to misdiagnosis or missed cases. It is therefore important to diagnose all NP-C patients to initiate early treatment.

Clinical relevance of targeted exome sequencing in patients with rare syndromic short stature

BACKGROUND

Large-scale genomic analyses have provided insight into the genetic complexity of short stature (SS); however, only a portion of genetic causes have been identified. In this study, we identified disease-causing mutations in a cohort of Korean patients with suspected syndromic SS by targeted exome sequencing (TES).

METHODS

Thirty-four patients in South Korea with suspected syndromic disorders based on abnormal growth and dysmorphic facial features, developmental delay, or accompanying anomalies were enrolled in 2018-2020 and evaluated by TES.

RESULTS

For 17 of 34 patients with suspected syndromic SS, a genetic diagnosis was obtained by TES. The mean SDS values for height, IGF-1, and IGFBP-3 for these 17 patients were - 3.27 ± 1.25, - 0.42 ± 1.15, and 0.36 ± 1.31, respectively. Most patients displayed distinct facial features (16/17) and developmental delay or intellectual disability (12/17). In 17 patients, 19 genetic variants were identified, including 13 novel heterozygous variants, associated with 15 different genetic diseases, including many inherited rare skeletal disorders and connective tissue diseases (e.g., cleidocranial dysplasia, Hajdu-Cheney syndrome, Sheldon-Hall, acromesomelic dysplasia Maroteaux type, and microcephalic osteodysplastic primordial dwarfism type II). After re-classification by clinical reassessment, including family member testing and segregation studies, 42.1% of variants were pathogenic, 42.1% were likely pathogenic variant, and 15.7% were variants of uncertain significance. Ultra-rare diseases accounted for 12 out of 15 genetic diseases (80%).

CONCLUSIONS

A high positive result from genetic testing suggests that TES may be an effective diagnostic approach for patients with syndromic SS, with implications for genetic counseling. These results expand the mutation spectrum for rare genetic diseases related to SS in Korea.

Nutraceutical regulation of miRNAs involved in neurodegenerative diseases and brain cancers

The human brain is a well-connected, intricate network of neurons and supporting glial cells. Neurodegenerative diseases arise as a consequence of extensive loss of neuronal cells leading to disruption of their natural structure and function. On the contrary, rapid proliferation and growth of glial as well as neuronal cells account for the occurrence of malignancy in brain. In both cases, the molecular microenvironment holds pivotal importance in the progression of the disease. MicroRNAs (miRNA) are one of the major components of the molecular microenvironment. miRNAs are small, noncoding RNAs that control gene expression post-transcriptionally. As compared to other tissues, the brain expresses a substantially high number of miRNAs. In the early stage of neurodegeneration, miRNA expression upregulates, while in oncogenesis, miRNA expression is gradually lost. Neurodegeneration and brain cancer is presumed to be under the influence of identical pathways of cell proliferation, differentiation and cell death which are tightly regulated by miRNAs. It has been confirmed experimentally that miRNA expression can be regulated by nutraceuticals - macronutrients, micronutrients or natural products derived from food; thereby making dietary supplements immensely significant for targeting miRNAs having altered expression patterns during neurodegeneration or oncogenesis. In this review, we will discuss in detail, about the common miRNAs involved in brain cancers and neurodegenerative diseases along with the comprehensive list of miRNAs involved separately in both pathological conditions. We will also discuss the role of nutraceuticals in the regulation of those miRNAs which are involved in both of these pathological conditions.

Next generation sequencing exome data analysis aids in the discovery of SNP and INDEL patterns in Parkinson's disease

Whole exome sequencing is an adept method to reveal novel and disease-related SNPs and INDELs as it screen the actionable areas of the genome. We evaluated the exome sequenced datasets of patients with Parkinson's disease (PD) in South African ethnic origin. The primary focus of this study was to discover the SNPs and INDELs patterns responsible for PD. The variant discovery was performed with genome analysis tool kit best practices variant detection pipelines. The SNPs were linked to the genes and categorized based on the filter-based annotation from ANNOVAR. We identified a total of 7955 SNPs and 9952 INDELs in all seven datasets together. A total of 130 missense nsSNPs were prioritized based on its damaging effect predicted from SIFT and Polyphen2 annotation. We noticed a novel nsSNP rs111655870 in gene LRRK2 that shows the mutation of a Leucine to Phenylalanine at position 208 which can alter the protein function. The study also filtered seven nsSNPs in genes NAGA, SULT4A1, MYH8, FLNA, TPM3, ATP13A1, CLN8 that have potentially deleterious effects predicted by various computational tools. This analysis suggested that the above filtered nsSNPs and INDELs have a functional impact and provide the footing for genetic studies related to PD. Further screening of these variations provides deeper insight for molecular mechanism of disease progression.

A chromosome-scale draft sequence of the Canada fleabane genome

BACKGROUND

Due to the accessibility of underlying technologies the 'Omics', in particular genomics, are becoming commonplace in several fields of research, including the study of agricultural pests. The weed community is starting to embrace these approaches; genome sequences have been made available in the past years, with several other sequencing projects underway, as promoted by the International Weed Genome Consortium. Chromosome-scale sequences are essential to fully exploit the power of genetics and genomics.

RESULTS

We report such an assembly for Conyza canadensis, an important agricultural weed. Third-generation sequencing technology was used to create a genome assembly of 426 megabases, of which nine chromosome-scale scaffolds cover more than 98% of the entire assembled sequence. As this weed was the first to be identified with glyphosate resistance, and since we do not have a firm handle on the genetic mechanisms responsible for several herbicide resistances in the species, the genome sequence was annotated with genes known to be associated with herbicide resistance. A high number of ABC-type transporters, cytochrome P450 and glycosyltransferases (159, 352 and 181, respectively) were identified among the list of ab initio predicted genes.

CONCLUSION

As C. canadensis has a small genome that is syntenic with other Asteraceaes, has a short life cycle and is relatively easy to cross, it has the potential to become a model weed species and, with the chromosome-scale genome sequence, contribute to a paradigm shift in the way non-target site resistance is studied. © 2020 Her Majesty the Queen in Right of CanadaPest Management Science © 2020 Society of Chemical Industry.

Genetic tests by next-generation sequencing in children with developmental delay and/or intellectual disability

Developments in next-generation sequencing (NGS) techogies have assisted in clarifying the diagnosis and treatment of developmental delay/intellectual disability (DD/ID) via molecular genetic testing. Advances in DNA sequencing technology have not only allowed the evolution of targeted panels but also, and more currently enabled genome-wide analyses to progress from research era to clinical practice. Broad acceptance of accuracy- guided targeted gene panel, whole-exome sequencing (WES), and whole-genome sequencing (WGS) for DD/ID need prospective analyses of the increasing cost-effectiveness versus conventional genetic testing. Choosing the appropriate sequencing method requires individual planning. Data are required to guide best-practice recommendations for genomic testing, regarding various clinical phenotypes in an etiologic approach. Targeted panel testing may be recommended as a first-tier testing approach for children with DD/ID. Family-based trio testing by WES/WGS can be used as a second test for DD/ ID in undiagnosed children who previously tested negative on a targeted panel. The role of NGS in molecular diagnostics, treatment, prediction of prognosis will continue to increase further in the coming years. Given the rapid pace of changes in the past 10 years, all medical providers should be aware of the changes in the transformative genetics field.

A multiomics approach to heterogeneity in Alzheimer's disease: focused review and roadmap

Aetiological and clinical heterogeneity is increasingly recognized as a common characteristic of Alzheimer's disease and related dementias. This heterogeneity complicates diagnosis, treatment, and the design and testing of new drugs. An important line of research is discovery of multimodal biomarkers that will facilitate the targeting of subpopulations with homogeneous pathophysiological signatures. High-throughput 'omics' are unbiased data-driven techniques that probe the complex aetiology of Alzheimer's disease from multiple levels (e.g. network, cellular, and molecular) and thereby account for pathophysiological heterogeneity in clinical populations. This review focuses on data reduction analyses that identify complementary disease-relevant perturbations for three omics techniques: neuroimaging-based subtypes, metabolomics-derived metabolite panels, and genomics-related polygenic risk scores. Neuroimaging can track accrued neurodegeneration and other sources of network impairments, metabolomics provides a global small-molecule snapshot that is sensitive to ongoing pathological processes, and genomics characterizes relatively invariant genetic risk factors representing key pathways associated with Alzheimer's disease. Following this focused review, we present a roadmap for assembling these multiomics measurements into a diagnostic tool highly predictive of individual clinical trajectories, to further the goal of personalized medicine in Alzheimer's disease.

Identification of a low frequency missense mutation in MUC6 contributing to pulmonary artery hypertension by whole-exome sequencing

Pulmonary arterial hypertension (PAH) represents a progressive disease characterized by abnormally high blood pressure in the pulmonary artery. Although mutations in the bone morphogenetic receptor 2 (BMPR2) are found in 80% of heritable, their low penetrance suggests that other unidentified genetic modifiers are required for this disease. In this report, whole-exome sequencing (WES) and a linkage analysis were performed on genomic DNA isolated from four affected relatives and one non-affected relative in two PAH families. By focusing on meaningful variants which were presented in the four affected family members, but not presented in the non-affected individual, 49 SNP and eight indel variants in 39 genes were identified as candidates. Further high-throughput multiplex genotyping and Sanger sequencing were carried out to confirm the putative causal mutations in 150 individuals (30 idiopathic PAH [IPAH] patients, 30 chronic thromboembolic pulmonary hypertension [CTEPH] patients, and 90 normal controls). A heterozygous and deleterious mutation in the gene MUC6 (p.Pro1716Ser) was confirmed in the IPAH group (20/30, 67%) and CTEPH group (1/30, 3.33%); no variant was detected in the 90 normal controls. MUC6, which is short for mucin 6, encodes high molecular weight glycoprotein produced by many epithelial tissues and forms an insoluble mucous barrier that protects the lumens. We re-confirmed this low frequency mutation with the 1000 Genomes database across all species; no population or frequency data of this allele were acquired. We also found that this mutation site was highly conserved in different species and predicted MUC6 has the protection function of the airway and pneumoangiogram based on genomic sequence data. The compound heterozygous MUC6 gene mutation (p.Pro1716Ser) suggests a novel disease mechanism leading to PAH.

Genetic literacy series: Primer part 2-Paradigm shifts in epilepsy genetics

This is the second of a 2-part primer on the genetics of the epilepsies within the Genetic Literacy Series of the Genetics Commission of the International League Against Epilepsy. In Part 1, we covered types of genetic variation, inheritance patterns, and their relationship to disease. In Part 2, we apply these basic principles to the case of a young boy with epileptic encephalopathy and ask 3 important questions: (1) Is the gene in question an established genetic etiology for epilepsy? (2) Is the variant in this particular gene pathogenic by established variant interpretation criteria? (3) Is the variant considered causative in the clinical context? These questions are considered and then answered for the clinical case in question.

ERLIN1 mutations cause teenage-onset slowly progressive ALS in a large Turkish pedigree

Amyotrophic lateral sclerosis (ALS) is a late-onset motor neuron disease with mostly dominant inheritance and a life expectancy of 2-5 years; however, a quite common occurrence of atypical forms of the disease, due to recessive inheritance, has become evident with the use of NGS technologies. In this paper, we describe a family with close consanguinity for at least four generations, suffering from a slowly progressive form of ALS. Spastic walking is observed since teenage years, while bulbar symptoms start much later, at the fifth or sixth decade of life. Patients usually die because of respiratory failure. Using whole-exome sequencing, we identified a novel homozygous p.(Val94Ala) (c.281T>C) (NG_052910.1) (NM_006459) variation in the endoplasmic reticulum lipid raft associated protein 1 (ERLIN1) gene, which segregates with the disease in the family. Here we suggest that ERLIN1 variants, previously shown in juvenile hereditary spastic paraplegia cases, may also be the cause of a slowly progressive early-onset ALS, starting with upper motor neuron features and developing into classical ALS with the addition of lower motor neuron dysfunction. We also demonstrate that ATP-binding cassette subfamily C member 2 (ABCC2) gene, responsible for hyperbilirubinemia, is linked to ERLIN1.

Targeted next generation sequencing in Italian patients with Usher syndrome: phenotype-genotype correlations

We report results of DNA analysis with next generation sequencing (NGS) of 21 consecutive Italian patients from 17 unrelated families with clinical diagnosis of Usher syndrome (4 USH1 and 17 USH2) searching for mutations in 11 genes: MYO7A, CDH23, PCDH15, USH1C, USH1G, USH2A, ADGVR1, DFNB31, CLRN1, PDZD7, HARS. Likely causative mutations were found in all patients: 25 pathogenic variants, 18 previously reported and 7 novel, were identified in three genes (USH2A, MYO7A, ADGRV1). All USH1 presented biallelic MYO7A mutations, one USH2 exhibited ADGRV1 mutations, whereas 16 USH2 displayed USH2A mutations. USH1 patients experienced hearing problems very early in life, followed by visual impairment at 1, 4 and 6 years. Visual symptoms were noticed at age 20 in a patient with homozygous novel MYO7A missense mutation c.849G > A. USH2 patients' auditory symptoms, instead, arose between 11 months and 14 years, while visual impairment occurred later on. A homozygous c.5933_5940del;5950_5960dup in USH2A was detected in one patient with early deafness. One patient with homozygous deletion from exon 23 to 32 in USH2A suffered early visual symptoms. Therefore, the type of mutation in USH2A and MYO7A genes seems to affect the age at which both auditory and visual impairment occur in patients with USH.

Analysis and Annotation of Whole-Genome or Whole-Exome Sequencing Derived Variants for Clinical Diagnosis

Over the last 10 years, next-generation sequencing (NGS) has transformed genomic research through substantial advances in technology and reduction in the cost of sequencing, and also in the systems required for analysis of these large volumes of data. This technology is now being used as a standard molecular diagnostic test in some clinical settings. The advances in sequencing have come so rapidly that the major bottleneck in identification of causal variants is no longer the sequencing or analysis (given access to appropriate tools), but rather clinical interpretation. Interpretation of genetic findings in a complex and ever changing clinical setting is scarcely a new challenge, but the task is increasingly complex in clinical genome-wide sequencing given the dramatic increase in dataset size and complexity. This increase requires application of appropriate interpretation tools, as well as development and application of appropriate methodologies and standard procedures. This unit provides an overview of these items. Specific challenges related to implementation of genome-wide sequencing in a clinical setting are discussed. © 2017 by John Wiley & Sons, Inc.

Multiple Testing in the Context of Gene Discovery in Sickle Cell Disease Using Genome-Wide Association Studies

The issue of multiple testing, also termed multiplicity, is ubiquitous in studies where multiple hypotheses are tested simultaneously. Genome-wide association study (GWAS), a type of genetic association study that has gained popularity in the past decade, is most susceptible to the issue of multiple testing. Different methodologies have been employed to address the issue of multiple testing in GWAS. The purpose of the review is to examine the methodologies employed in dealing with multiple testing in the context of gene discovery using GWAS in sickle cell disease complications.

Mutational spectrum of Chinese LGMD patients by targeted next-generation sequencing

This study aimed to study the diagnostic value of targeted next-generation sequencing (NGS) in limb-girdle muscular dystrophies (LGMDs), and investigate the mutational spectrum of Chinese LGMD patients. We performed targeted NGS covering 420 genes in 180 patients who were consecutively suspected of LGMDs and underwent muscle biopsies from January 2013 to May 2015. The association between genotype and myopathological profiles was analyzed in the genetically confirmed LGMD patients. With targeted NGS, one or more rare variants were detected in 138 patients, of whom 113 had causative mutations, 10 sporadic patients had one pathogenic heterozygous mutation related to a recessive pattern of LGMDs, and 15 had variants of uncertain significance. No disease-causing mutation was found in the remaining 42 patients. Combined with the myopathological findings, we achieved a positive genetic diagnostic rate as 68.3% (123/180). Totally 105 patients were diagnosed as LGMDs with genetic basis. Among these 105 patients, the most common subtypes were LGMD2B in 52 (49.5%), LGMD2A in 26 (24.8%) and LGMD 2D in eight (7.6%), followed by LGMD1B in seven (6.7%), LGMD1E in four (3.8%), LGMD2I in three (2.9%), and LGMD2E, 2F, 2H, 2K, 2L in one patient (1.0%), respectively. Although some characteristic pathological changes may suggest certain LGMD subtypes, both heterogeneous findings in a certain subtype and overlapping presentations among different subtypes were not uncommon. The application of NGS, together with thorough clinical and myopathological evaluation, can substantially improve the molecular diagnostic rate in LGMDs. Confirming the genetic diagnosis in LGMD patients can help improve our understanding of their myopathological changes.

LncRNAs: macromolecules with big roles in neurobiology and neurological diseases

Long noncoding RNAs (lncRNAs) are recently defined as thousands of RNA molecules longer than 200 nucleotides and lacking an appreciable open reading frame in mammals. Although lncRNAs lack protein-coding function, they play critical roles in the regulation of almost all the protein-coding genes in a cell at various stages including chromatin modification, transcription and post-transcriptional processing. It is thus not surprising that lncRNAs may be the crucial regulators in the normal development, physiology and pathology. LncRNAs in neuroscience is a novel research field. Interestingly, recent studies have demonstrated that many lncRNAs are highly expressed in brain and their dysregulations occur in neurological disorders. In this review, we describe the current understanding of lncRNAs in neurobiology and neurological diseases including cerebral injury. LncRNAs could be novel biomarkers and could be potential new targets for new drugs for many neurological diseases in the future, although the related studies are still at in the early stages.

The Revolution in Migraine Genetics: From Aching Channels Disorders to a Next-Generation Medicine

Channelopathies are a heterogeneous group of neurological disorders resulting from dysfunction of ion channels located in cell membranes and organelles. The clinical scenario is broad and symptoms such as generalized epilepsy (with or without fever), migraine (with or without aura), episodic ataxia and periodic muscle paralysis are some of the best known consequences of gain- or loss-of-function mutations in ion channels. We review the main clinical effects of ion channel mutations associated with a significant impact on migraine headache. Given the increasing and evolving use of genetic analysis in migraine research-greater emphasis is now placed on genetic markers of dysfunctional biological systems-we also show how novel information in rare monogenic forms of migraine might help to clarify the disease mechanisms in the general population of migraineurs. Next-generation sequencing (NGS) and more accurate and precise phenotyping strategies are expected to further increase understanding of migraine pathophysiology and genetics.

Next generation sequencing technology and genomewide data analysis: Perspectives for retinal research

The advent of high throughput next generation sequencing (NGS) has accelerated the pace of discovery of disease-associated genetic variants and genomewide profiling of expressed sequences and epigenetic marks, thereby permitting systems-based analyses of ocular development and disease. Rapid evolution of NGS and associated methodologies presents significant challenges in acquisition, management, and analysis of large data sets and for extracting biologically or clinically relevant information. Here we illustrate the basic design of commonly used NGS-based methods, specifically whole exome sequencing, transcriptome, and epigenome profiling, and provide recommendations for data analyses. We briefly discuss systems biology approaches for integrating multiple data sets to elucidate gene regulatory or disease networks. While we provide examples from the retina, the NGS guidelines reviewed here are applicable to other tissues/cell types as well.

Cell type-specific transcriptome profiling in mammalian brains

A mammalian brain contains numerous types of cells. Advances in neuroscience in the past decade allow us to identify and isolate neural cells of interest from mammalian brains. Recent developments in high-throughput technologies, such as microarrays and next-generation sequencing (NGS), provide detailed information on gene expression in pooled cells on a genomic scale. As a result, many novel genes have been found critical in cell type-specific transcriptional regulation. These differentially expressed genes can be used as molecular signatures, unique to a particular class of neural cells. Use of this gene expression-based approach can further differentiate neural cell types into subtypes, potentially linking some of them with neurological diseases. In this article, experimental techniques used to purify neural cells are described, followed by a review on recent microarray- or NGS-based transcriptomic studies of common neural cell types. The future prospects of cell type-specific research are also discussed.

Mutation of TBCK causes a rare recessive developmental disorder

Objective:

To characterize the underlying genetic defect in a family with 3 siblings affected by a severe, yet viable, congenital disorder.

Methods:

Extensive genetic and metabolic investigations were performed, and the affected children were imaged at different ages. Whole-genome genotyping and whole-exome sequencing were undertaken. A single large region (>8 Mb) of homozygosity in chromosome 4 (chr4:100,268,553–108,609,628) was identified that was shared only in affected siblings. Inspection of genetic variability within this region led to the identification of a novel mutation. Sanger sequencing confirmed segregation of the mutation with disease.

Results:

All affected siblings share homozygosity for a novel 4-bp deletion in the gene TBCK (NM_033115:c.614_617del:p.205_206del).

Conclusions:

This finding provides the genetic cause of a severe inherited disease in a family and extends the number of mutations and phenotypes associated with this recently identified disease gene.

Precision medicine in spinocerebellar ataxias: treatment based on common mechanisms of disease

Spinocerebellar ataxias (SCAs) are a heterogeneous group of dominantly inherited neurodegenerative disorders affecting the cerebellum and its associated pathways. There are no available symptomatic or disease-modifying therapies available for any of the over 30 known causes of SCA. In order to develop precise treatments for SCAs, two strategies can be employed: (I) the use of gene-targeting strategies to silence disease-causing mutant protein expression; and (II) the identification and targeting of convergent mechanisms of disease across SCAs as a basis for treatment. Gene targeting strategies include RNA interference and antisense oligonucleotides designed to silence mutant genes in order to prevent mutant protein expression. These therapies can be precise, but delivery is difficult and many disease-causing mutations remain unknown. Emerging evidence suggests that several common disease mechanisms may exist across SCAs. Disrupted protein homeostasis, RNA toxicity, abnormal synaptic signaling, altered intracellular calcium handling, and altered Purkinje neuron membrane excitability are all disease mechanisms which are seen in multiple etiologies of SCA and could potentially be targeted for treatment. Clinical trials with drugs such as riluzole, a potassium channel activator, show promise for multiple SCAs and suggest that convergent disease mechanisms do exist and can be targeted. Precise treatment of SCAs may be best achieved through pharmacologic agents targeting specific disrupted pathways.

FASTKD2 is associated with memory and hippocampal structure in older adults

Memory impairment is the cardinal early feature of Alzheimer's disease, a highly prevalent disorder whose causes remain only partially understood. To identify novel genetic predictors, we used an integrative genomics approach to perform the largest study to date of human memory (n=14 781). Using a genome-wide screen, we discovered a novel association of a polymorphism in the pro-apoptotic gene FASTKD2 (fas-activated serine/threonine kinase domains 2; rs7594645-G) with better memory performance and replicated this finding in independent samples. Consistent with a neuroprotective effect, rs7594645-G carriers exhibited increased hippocampal volume and gray matter density and decreased cerebrospinal fluid levels of apoptotic mediators. The MTOR (mechanistic target of rapamycin) gene and pathways related to endocytosis, cholinergic neurotransmission, epidermal growth factor receptor signaling and immune regulation, among others, also displayed association with memory. These findings nominate FASTKD2 as a target for modulating neurodegeneration and suggest potential mechanisms for therapies to combat memory loss in normal cognitive aging and dementia.

Targeted exome sequencing reveals novel USH2A mutations in Chinese patients with simplex Usher syndrome

BACKGROUND

Usher syndrome (USH) is an autosomal recessive disorder characterized by hearing impairment and vision dysfunction due to retinitis pigmentosa. Phenotypic and genetic heterogeneities of this disease make it impractical to obtain a genetic diagnosis by conventional Sanger sequencing.

METHODS

In this study, we applied a next-generation sequencing approach to detect genetic abnormalities in patients with USH. Two unrelated Chinese families were recruited, consisting of two USH afflicted patients and four unaffected relatives. We selected 199 genes related to inherited retinal diseases as targets for deep exome sequencing. Through systematic data analysis using an established bioinformatics pipeline, all variants that passed filter criteria were validated by Sanger sequencing and co-segregation analysis.

RESULTS

A homozygous frameshift mutation (c.4382delA, p.T1462Lfs*2) was revealed in exon20 of gene USH2A in the F1 family. Two compound heterozygous mutations, IVS47 + 1G > A and c.13156A > T (p.I4386F), located in intron 48 and exon 63 respectively, of USH2A, were identified as causative mutations for the F2 family. Of note, the missense mutation c.13156A > T has not been reported so far.

CONCLUSION

In conclusion, targeted exome sequencing precisely and rapidly identified the genetic defects in two Chinese USH families and this technique can be applied as a routine examination for these disorders with significant clinical and genetic heterogeneity.

A systematic screening to identify de novo mutations causing sporadic early-onset Parkinson's disease

Despite the many advances in our understanding of the genetic basis of Mendelian forms of Parkinson's disease (PD), a large number of early-onset cases still remain to be explained. Many of these cases, present with a form of disease that is identical to that underlined by genetic causes, but do not have mutations in any of the currently known disease-causing genes. Here, we hypothesized that de novo mutations may account for a proportion of these early-onset, sporadic cases. We performed exome sequencing in full parent–child trios where the proband presents with typical PD to unequivocally identify de novo mutations. This approach allows us to test all genes in the genome in an unbiased manner. We have identified and confirmed 20 coding de novo mutations in 21 trios. We have used publicly available population genetic data to compare variant frequencies and our independent in-house dataset of exome sequencing in PD (with over 1200 cases) to identify additional variants in the same genes. Of the genes identified to carry de novo mutations, PTEN, VAPB and ASNA1 are supported by various sources of data to be involved in PD. We show that these genes are reported to be within a protein–protein interaction network with PD genes and that they contain additional rare, case-specific, mutations in our independent cohort of PD cases. Our results support the involvement of these three genes in PD and suggest that testing for de novo mutations in sporadic disease may aid in the identification of novel disease-causing genes.

Dissecting Complex and Multifactorial Nature of Alzheimer's Disease Pathogenesis: a Clinical, Genomic, and Systems Biology Perspective

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by loss of memory and other cognitive functions. AD can be classified into familial AD (FAD) and sporadic AD (SAD) based on heritability and into early onset AD (EOAD) and late onset AD (LOAD) based on age of onset. LOAD cases are more prevalent with genetically complex architecture. In spite of significant research focused on understanding the etiological mechanisms, search for diagnostic biomarker(s) and disease-modifying therapy is still on. In this article, we aim to comprehensively review AD literature on established etiological mechanisms including role of beta-amyloid and apolipoprotein E (APOE) along with promising newer etiological factors such as epigenetic modifications that have been associated with AD suggesting its multifactorial nature. As genomic studies have recently played a significant role in elucidating AD pathophysiology, a systematic review of findings from genome-wide linkage (GWL), genome-wide association (GWA), genome-wide expression (GWE), and epigenome-wide association studies (EWAS) was conducted. The availability of multi-dimensional genomic data has further coincided with the advent of computational and network biology approaches in recent years. Our review highlights the importance of integrative approaches involving genomics and systems biology perspective in elucidating AD pathophysiology. The promising newer approaches may provide reliable means of early and more specific diagnosis and help identify therapeutic interventions for LOAD.

Genomic analysis in the clinic: benefits and challenges for health care professionals and patients in Brazil

Despite significant advances in the diagnosis and treatment of genetic diseases in the last two decades, there is still a significant proportion where a causative mutation cannot be identified and a definitive genetic diagnosis remains elusive. New genome-wide or high-throughput multiple gene tests have brought new hope to the field, since they can offer fast, cost-effective and comprehensive analysis of genetic variation. This is particularly interesting in disorders with high genetic heterogeneity. There are, however, limitations and concerns regarding the implementation of genomic analysis in everyday clinical practice, including some particular to emerging and developing economies, as Brazil. They include the limited number of actionable genetic variants known to date, difficulties in determining the clinical validity and utility of novel variants, growth of direct-to-consumer genetic testing using a genomic approach and lack of proper training of health care professionals to adequately request, interpret and use genetic information. Despite all these concerns and limitations, the availability of genomic tests has grown at an extremely rapid pace and commercially available services include initiatives in almost all areas of clinical genetics, including newborn and carrier screening. We discuss the benefits and limitations of genomic testing, as well as the ethical implications and the challenges for genetic education and enough available and qualified health care professionals, to ensure the adequate process of informed consent, meaningful interpretation and use of genomic data and definition of a clear regulatory framework in the particular context of Brazil.

Whole exome sequencing and the clinician: we need clinical skills and functional validation in variant filtering

Whole exome sequencing (WES) is a recently developed technique in genetics research that attempts to identify causative mutations in complex, undiagnosed genetic conditions. Causative mutations are usually identified after filtering the hundreds of variants on WES from an individual’s DNA selected by the phenotype. We investigated a patient with a slowly progressive chronic axonal distal motor neuropathy and extrapyramidal syndrome using WES, in whom common genetic mutations had been excluded. Variant filtering identified potentially deleterious mutations in three known disease genes: DCTN1, KIF5A and NEFH, which have been all associated with similar clinical presentations of amyotrophic lateral sclerosis, Parkinsonism and/or hereditary spastic paraplegia. Predicting the functional effect of the mutations were analysed in parallel with detailed clinical investigations. This case highlights the difficulties and pitfalls of applying WES in patients with complex neurological diseases and serves as an instructive tale.

Adult-onset painful axonal polyneuropathy caused by a dominant NAGLU mutation

Late-onset painful sensory neuropathies are usually acquired conditions associated with common diseases. Adult presentations of known hereditary forms are often accompanied by other organ involvement. We recruited a large French-Canadian family with a dominantly inherited late-onset painful sensory neuropathy. The main clinical feature is recurrent leg pain that progresses to constant painful paraesthesias in the feet and later the hands. As it evolves, some patients develop a mild sensory ataxia. We selected four affected individuals for whole exome sequencing. Analysis of rare variants shared by all cases led to a list of four candidate variants. Segregation analysis in all 45 recruited individuals has shown that only the p.Ile403Thr variant in the α-N-acetyl-glucosaminidase (NAGLU) gene segregates with the disease. Recessive NAGLU mutations cause the severe childhood lysosomal disease mucopolysacharidosis IIIB. Family members carrying the mutation showed a significant decrease of the enzymatic function (average 45%). The late-onset and variable severity of the symptoms may have precluded the description of such symptoms in parents of mucopolysaccharidosis IIIB cases. The identification of a dominant phenotype associated with a NAGLU mutation supports that some carriers of lysosomal enzyme mutations may develop later in life much milder phenotypes.

Next-generation sequencing-based genome diagnostics across clinical genetics centers: implementation choices and their effects

Implementation of next-generation DNA sequencing (NGS) technology into routine diagnostic genome care requires strategic choices. Instead of theoretical discussions on the consequences of such choices, we compared NGS-based diagnostic practices in eight clinical genetic centers in the Netherlands, based on genetic testing of nine pre-selected patients with cardiomyopathy. We highlight critical implementation choices, including the specific contributions of laboratory and medical specialists, bioinformaticians and researchers to diagnostic genome care, and how these affect interpretation and reporting of variants. Reported pathogenic mutations were consistent for all but one patient. Of the two centers that were inconsistent in their diagnosis, one reported to have found 'no causal variant', thereby underdiagnosing this patient. The other provided an alternative diagnosis, identifying another variant as causal than the other centers. Ethical and legal analysis showed that informed consent procedures in all centers were generally adequate for diagnostic NGS applications that target a limited set of genes, but not for exome- and genome-based diagnosis. We propose changes to further improve and align these procedures, taking into account the blurring boundary between diagnostics and research, and specific counseling options for exome- and genome-based diagnostics. We conclude that alternative diagnoses may infer a certain level of 'greediness' to come to a positive diagnosis in interpreting sequencing results. Moreover, there is an increasing interdependence of clinic, diagnostics and research departments for comprehensive diagnostic genome care. Therefore, we invite clinical geneticists, physicians, researchers, bioinformatics experts and patients to reconsider their role and position in future diagnostic genome care.

Application of next-generation sequencing technologies in Neurology

Genetic risk factors that underlie many rare and common neurological diseases remain poorly understood because of the multi-factorial and heterogeneous nature of these disorders. Although genome-wide association studies (GWAS) have successfully uncovered numerous susceptibility genes for these diseases, odds ratios associated with risk alleles are generally low and account for only a small proportion of estimated heritability. These results implicated that there are rare (present in <5% of the population) but not causative variants exist in the pathogenesis of these diseases, which usually have large effect size and cannot be captured by GWAS. With the decreasing cost of next-generation sequencing (NGS) technologies, whole-genome sequencing (WGS) and whole-exome sequencing (WES) have enabled the rapid identification of rare variants with large effect size, which made huge progress in understanding the basis of many Mendelian neurological conditions as well as complex neurological diseases. In this article, recent NGS-based studies that aimed to investigate genetic causes for neurological diseases, including Alzheimer's disease, Parkinson's disease, epilepsy, multiple sclerosis, stroke, amyotrophic lateral sclerosis and spinocerebellar ataxias, have been reviewed. In addition, we also discuss the future directions of NGS applications in this article.

Genetic determinants of depression: recent findings and future directions

LEARNING OBJECTIVES

After participating in this activity, learners should be better able to: 1. Evaluate current evidence regarding the genetic determinants of depression 2. Assess findings from studies of gene-environment interaction 3. Identify challenges to gene discovery in depression Depression is one of the most prevalent, disabling, and costly mental health conditions in the United States and also worldwide. One promising avenue for preventing depression and informing its clinical treatment lies in uncovering the genetic and environmental determinants of the disorder as well as their interaction (G × E). The overarching goal of this review article is to translate recent findings from studies of genetic association and G × E related to depression, particularly for readers without in-depth knowledge of genetics or genetic methods. The review is organized into three major sections. In the first, we summarize what is currently known about the genetic determinants of depression, focusing on findings from genome-wide association studies (GWAS). In the second section, we review findings from studies of G × E, which seek to simultaneously examine the role of genes and exposure to specific environments or experiences in the etiology of depression. In the third section, we describe the challenges to genetic discovery in depression and promising strategies for future progress.

Nonsense mutation in PRNP associated with clinical Alzheimer's disease

Here, we describe a nonsense haplotype in PRNP associated with clinical Alzheimer's disease. The patient presented an early-onset of cognitive decline with memory loss as the primary cognitive problem. Whole-exome sequencing revealed a nonsense mutation in PRNP (NM_000311, c.C478T; p.Q160*; rs80356711) associated with homozygosity for the V allele at position 129 of the protein, further highlighting how very similar genotypes in PRNP result in strikingly different phenotypes.

Evaluating Familial Essential Tremor with Novel Genetic Approaches: Is it a Genotyping or Phenotyping Issue?

Background

Essential tremor is a common movement disorder with a strong heritable component. Large families with inherited forms of essential tremor have undergone genetic analyses by different approaches. However, our knowledge of genetic variants unequivocally linked to essential tremor is remarkably limited. Several explanations have been put forth to explain this challenge, including the possibility of mutations in non-coding areas of the genome.

Methods

We encountered a family with highly penetrant, autosomal dominant tremor. We hypothesized that, if a single coding gene mutation was responsible for the phenotype, novel genetic tools would allow us to identify it. We employed single nucleotide polymorphism (SNP) arrays in 17 members of this family followed by next generation whole-exome sequencing in five affected subjects.

Results

We did not identify any copy number variant or mutation that segregated with the disease phenotype.

Discussion

This study emphasizes the remarkably challenging field of tremor genetics and indicates that future studies should perhaps shift to analysis of the non-coding genome.

Genetics of Alzheimer's disease

The analyses of genetic factors contributing to Alzheimer's disease (AD) and other dementias have evolved at the same pace as genetic and genomic technologies are developed and improved. The identification of the first genes involved in AD arose from family-based studies, but risk factors have mainly been identified by studies comparing groups of patients with groups of controls. The best outcomes have been heavily associated with the capacity of interrogating genetic variability at the genome level without any particular a priori hypothesis. In this review we assess the role of genetic family studies in Alzheimer's disease and other dementias within the current status of dementias' and, particularly, AD's genetic architecture.

Next-generation sequencing technologies: breaking the sound barrier of human genetics

Demand for new technologies that deliver fast, inexpensive and accurate genome information has never been greater. This challenge has catalysed the rapid development of advances in next-generation sequencing (NGS). The generation of large volumes of sequence data and the speed of data acquisition are the primary advantages over previous, more standard methods. In 2013, the Food and Drug Administration granted marketing authorisation for the first high-throughput NG sequencer, Illumina's MiSeqDx, which allowed the development and use of a large number of new genome-based tests. Here, we present a review of template preparation, nucleic acid sequencing and imaging, genome assembly and alignment approaches as well as recent advances in current and near-term commercially available NGS instruments. We also outline the broad range of applications for NGS technologies and provide guidelines for platform selection to best address biological questions of interest. DNA sequencing has revolutionised biological and medical research, and is poised to have a similar impact on the practice of medicine. This tool is but one of an increasing arsenal of developing tools that enhance our capabilities to identify, quantify and functionally characterise the components of biological networks that keep us healthy or make us sick. Despite advances in other 'omic' technologies, DNA sequencing and analysis, in many respects, have played the leading role to date. The new technologies provide a bridge between genotype and phenotype, both in man and model organisms, and have revolutionised how risk of developing a complex human disease may be assessed. The generation of large DNA sequence data sets is producing a wealth of medically relevant information on a large number of individuals and populations that will potentially form the basis of truly individualised medical care in the future.

SeqControl: process control for DNA sequencing

As high-throughput sequencing continues to increase in speed and throughput, routine clinical and industrial application draws closer. These 'production' settings will require enhanced quality monitoring and quality control to optimize output and reduce costs. We developed SeqControl, a framework for predicting sequencing quality and coverage using a set of 15 metrics describing overall coverage, coverage distribution, basewise coverage and basewise quality. Using whole-genome sequences of 27 prostate cancers and 26 normal references, we derived multivariate models that predict sequencing quality and depth. SeqControl robustly predicted how much sequencing was required to reach a given coverage depth (area under the curve (AUC) = 0.993), accurately classified clinically relevant formalin-fixed, paraffin-embedded samples, and made predictions from as little as one-eighth of a sequencing lane (AUC = 0.967). These techniques can be immediately incorporated into existing sequencing pipelines to monitor data quality in real time. SeqControl is available at http://labs.oicr.on.ca/Boutros-lab/software/SeqControl/.

Whole-exome sequencing in an extended family with myocardial infarction unmasks familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia (FH) is an autosomal-dominant disease leading to markedly elevated low-density lipoprotein (LDL) cholesterol levels and increased risk for premature myocardial infarction (MI). Mutation carriers display variable LDL cholesterol levels, which may obscure the diagnosis. We examined by whole-exome sequencing a family in which multiple myocardial infarctions occurred at a young age with unclear etiology.

METHODS

Whole-exome sequencing of three affected family members, validation of the identified variant with Sanger-sequencing, and subsequent co-segregation analysis in the family.

RESULTS

The index patient (LDL cholesterol 188 mg/dL) was referred for molecular-genetic investigations. He had coronary artery bypass graft (CABG) at the age of 59 years; 12 out of 15 1st, 2nd and 3rd degree relatives were affected with coronary artery disease (CAD) and/or premature myocardial infarction (MI). We sequenced the whole-exome of the patient and two cousins with premature MI. After filtering, we were left with a potentially disease causing variant in the LDL receptor (LDLR) gene, which we validated by Sanger-sequencing (nucleotide substitution in the acceptor splice-site of exon 10, c.1359-1G > A). Sequencing of all family members available for genetic analysis revealed co-segregation of the variant with CAD (LOD 3.0) and increased LDLC (>190 mg/dL), following correction for statin treatment (LOD 4.3). Interestingly, mutation carriers presented with highly variable corrected (183-354 mg/dL) and on-treatment LDL levels (116-274 mg/dL) such that the diagnosis of FH in this family was made only after the molecular-genetic analysis.

CONCLUSION

Even in families with unusual clustering of CAD FH remains to be underdiagnosed, which underscores the need for implementation of systematic screening programs. Whole-exome sequencing may facilitate identification of disease-causing variants in families with unclear etiology of MI and enable preventive treatment of mutation carriers in a more timely fashion.

Next generation sequencing techniques in neurological diseases: redefining clinical and molecular associations

The development of next-generation sequencing technologies has allowed for the identification of several new genes and genetic factors in human genetics. Common results from the application of these technologies have revealed unexpected presentations for mutations in known disease genes. In this review, we summarize the major contributions of exome sequencing to the study of neurodegenerative disorders and other neurological conditions and discuss the interface between Mendelian and complex neurological diseases with a particular focus on pleiotropic events.

Genetic counselors' views and experiences with the clinical integration of genome sequencing

In recent years, new sequencing technologies known as next generation sequencing (NGS) have provided scientists the ability to rapidly sequence all known coding as well as non-coding sequences in the human genome. As the two emerging approaches, whole exome (WES) and whole genome (WGS) sequencing, have started to be integrated in the clinical arena, we sought to survey health care professionals who are likely to be involved in the implementation process now and/or in the future (e.g., genetic counselors, geneticists and nurse practitioners). Two hundred twenty-one genetic counselors- one third of whom currently offer WES/WGS-participated in an anonymous online survey. The aims of the survey were first, to identify barriers to the implementation of WES/WGS, as perceived by survey participants; second, to provide the first systematic report of current practices regarding the integration of WES/WGS in clinic and/or research across the US and Canada and to illuminate the roles and challenges of genetic counselors participating in this process; and third to evaluate the impact of WES/WGS on patient care. Our results showed that genetic counseling practices with respect to WES/WGS are consistent with the criteria set forth in the ACMG 2012 policy statement, which highlights indications for testing, reporting, and pre/post test considerations. Our respondents described challenges related to offering WES/WGS, which included billing issues, the duration and content of the consent process, result interpretation and disclosure of incidental findings and variants of unknown significance. In addition, respondents indicated that specialty area (i.e., prenatal and cancer), lack of clinical utility of WES/WGS and concerns about interpretation of test results were factors that prevented them from offering this technology to patients. Finally, study participants identified the aspects of their professional training which have been most beneficial in aiding with the integration of WES/WGS into the clinical setting (molecular/clinical genetics, counseling and bioethics) and suggested that counseling aids (to assist them when explaining aspects of these tests to patients) and webinars focused on WES/WGS (for genetic counselors and other health care professionals) would be useful educational tools. Future research should permit us to further enhance our knowledge of pitfalls and benefits associated with the introduction of these powerful technologies in patient care and to further explore the roles and opportunities for genetic counselors in this rapidly evolving field.