Search

Contains fulltext : 290548.pdf (Publisher’s version ) (Open Access)

To characterize the phenotype observed in a case series with macular disease and determine the cause.Multicenter case series.Six families (7 patients) with sporadic or multiplex macular disease with onset at 20 to 78 years, and 1 patient with age-related macular degeneration.Patients underwent ophthalmic examination; exome, genome, or targeted sequencing; and/or polymerase chain reaction (PCR) amplification of the breakpoint, followed by cloning and Sanger sequencing or direct Sanger sequencing.Clinical phenotypes, genomic findings, and a hypothesis explaining the mechanism underlying disease in these patients.All 8 cases carried the same deletion encompassing the genes TPRX1, CRX, and SULT2A1, which was absent from 382 control individuals screened by breakpoint PCR and 13 096 Clinical Genetics patients with a range of other inherited conditions screened by array comparative genomic hybridization. Microsatellite genotypes showed that these 7 families are not closely related, but genotypes immediately adjacent to the deletion breakpoints suggest they may share a distant common ancestor.Previous studies had found that carriers for a single defective CRX allele that was predicted to produce no functional CRX protein had a normal ocular phenotype. Here, we show that CRX whole-gene deletion in fact does cause a dominant late-onset macular disease.

BACKGROUND: The U.K. 100,000 Genomes Project is in the process of investigating the role of genome sequencing in patients with undiagnosed rare diseases after usual care and the alignment of this research with health care implementation in the U.K. National Health Service. Other parts of this project focus on patients with cancer and infection.METHODS: We conducted a pilot study involving 4660 participants from 2183 families, among whom 161 disorders covering a broad spectrum of rare diseases were present. We collected data on clinical features with the use of Human Phenotype Ontology terms, undertook genome sequencing, applied automated variant prioritization on the basis of applied virtual gene panels and phenotypes, and identified novel pathogenic variants through research analysis.RESULTS: Diagnostic yields varied among family structures and were highest in family trios (both parents and a proband) and families with larger pedigrees. Diagnostic yields were much higher for disorders likely to have a monogenic cause (35%) than for disorders likely to have a complex cause (11%). Diagnostic yields for intellectual disability, hearing disorders, and vision disorders ranged from 40 to 55%. We made genetic diagnoses in 25% of the probands. A total of 14% of the diagnoses were made by means of the combination of research and automated approaches, which was critical for cases in which we found etiologic noncoding, structural, and mitochondrial genome variants and coding variants poorly covered by exome sequencing. Cohortwide burden testing across 57,000 genomes enabled the discovery of three new disease genes and 19 new associations. Of the genetic diagnoses that we made, 25% had immediate ramifications for clinical decision making for the patients or their relatives.CONCLUSIONS: Our pilot study of genome sequencing in a national health care system showed an increase in diagnostic yield across a range of rare diseases. (Funded by the National Institute for Health Research and others.).

Newborn screening for treatable disorders is one of the great public health success stories of the twentieth century worldwide. This commentary examines the potential use of a new technology, next generation sequencing, in newborn screening through the lens of the Wilson and Jungner criteria. Each of the ten criteria are examined to show how they might be applied by programmes using genomic sequencing as a screening tool. While there are obvious advantages to a method that can examine all disease-causing genes in a single assay at an ever-diminishing cost, implementation of genomic sequencing at scale presents numerous challenges, some which are intrinsic to screening for rare disease and some specifically linked to genomics-led screening. In addition to questions specific to routine screening considerations, the ethical, communication, data management, legal, and social implications of genomic screening programmes require consideration.

The transformative potential of whole genome sequencing (WGS) as a diagnostic tool in healthcare has been demonstrated by initiatives including the 100,000 Genomes Project and is now offered to certain patients in the National Health Service (NHS) in England. Building on these foundations, the utility of WGS in the newborn period can now be explored. Genomics England is working in partnership with NHS England and NHS Improvement and other healthcare, patient and public interest groups to design a research program embedded in the NHS to explore the potential challenges and implications of offering WGS in all newborns. The program will aim to: 1) evaluate the feasibility, utility and impact on the NHS of screening for childhood-onset rare actionable genetic conditions; 2) understand how, with consent, genomic and healthcare data could be used to enable research to develop new diagnostics and treatments; and 3) explore the implications of storing an individual’s genome for use over their lifetime. Recognizing the important practical, scientific and ethical questions that we must explore in dialogue with the public and experts, we are taking a collaborative, evidence-based and ethically deliberate approach to designing the program. An iterative co-design process including a nationwide public dialogue has identified emergent themes and ethical considerations which are the focus of the program’s design. These themes will be further developed through continued engagement with healthcare professionals, researchers, ethics experts, patient groups and the public, with an ongoing commitment to embedding ongoing ethics research and co-design into the delivery of the program.

Subcortical brain structures are integral to motion, consciousness, emotions, and learning. We identified common genetic variation related to the volumes of nucleus accumbens, amygdala, brainstem, caudate nucleus, globus pallidus, putamen, and thalamus, using genome-wide association analyses in over 40,000 individuals from CHARGE, ENIGMA and the UK-Biobank. We show that variability in subcortical volumes is heritable, and identify 25 significantly associated loci (20 novel). Annotation of these loci utilizing gene expression, methylation, and neuropathological data identified 62 candidate genes implicated in neurodevelopment, synaptic signaling, axonal transport, apoptosis, and susceptibility to neurological disorders. This set of genes is significantly enriched for Drosophila orthologs associated with neurodevelopmental phenotypes, suggesting evolutionarily conserved mechanisms. Our findings uncover novel biology and potential drug targets underlying brain development and disease.

The commonly prescribed antiepileptic drug phenytoin has a narrow therapeutic range and wide interindividual variability in clearance explained in part by CYP2C9 and CYP2C19 coding variants. After finding a paradoxically low urinary phenytoin metabolite (S)/(R) ratio in subjects receiving phenytoin maintenance therapy with a CYP2C9*1/*1 and CYP2C19*1/*2 genotype, we hypothesized that CYP2C9 regulatory polymorphisms (rPMs), G-3089A and −2663delTG, in linkage disequilibrium with CYP2C19*2 were responsible. These rPMs explained as much as 10% of the variation in phenytoin maintenance dose in epileptic patients, but were not correlated with other patients' warfarin dose requirements or with phenytoin metabolite ratio in human liver microsomes. We hypothesized the rPMs affected CYP2C9 induction by phenytoin, a pregnane X receptor (PXR), and constitutive androstane receptor (CAR) activator. Transfection studies showed that CYP2C9 reporters with wild-type versus variant alleles had similar basal activity but significantly greater phenytoin induction by cotransfected PXR, CAR, and Nrf2 and less Yin Yang 1 transcription factor repression. Phenytoin induction of CYP2C9 was greater in human hepatocytes with the CYP2C9 wild type versus variant haplotype. Therefore, CYP2C9 rPMs affect phenytoin-dependent induction of CYP2C9 and phenytoin metabolism in humans, with an effect size comparable with that for CYP2C9*2 and 2C9*3. These findings may also be relevant to the clinical use of other PXR, CAR, and Nrf2 activators.

Summary Background The cause of sporadic ALS is currently unknown. Despite evidence for a role for genetics, no common genetic variants have been unequivocally linked to sporadic ALS. We sought to identify genetic variants associated with an increased or decreased risk for developing ALS in a cohort of American sporadic cases. Methods We undertook a genome-wide association study using publicly available samples from 276 patients with sporadic ALS and 271 neurologically normal controls. 555 352 unique SNPs were assayed in each sample using the Illumina Infinium II HumanHap550 SNP chip. Findings More than 300 million genotypes were produced in 547 participants. These raw genotype data are freely available on the internet and represent the first publicly accessible SNP data for ALS cases. 34 SNPs with a p value less than 0·0001 (two degrees of freedom) were found, although none of these reached significance after Bonferroni correction. Interpretation We generated publicly available genotype data for sporadic ALS patients and controls. No single locus was definitively associated with increased risk of developing disease, although potentially associated candidate SNPs were identified.

Recent studies indicate that 40% of chronic myeloid leukemia patients who achieve sustained undetectable BCR-ABL1 transcripts on tyrosine kinase inhibitor therapy remain disease-free after drug discontinuation. In contrast, 60% experience return of detectable disease and have to restart treatment, thus highlighting the need for an improved method of identifying patients with the lowest likelihood of relapse. Here we describe the validation of a personalized DNA-based digital PCR (dPCR) approach for quantifying very low levels of residual disease, which involves the rapid identification of t(9;22) fusion junctions using targeted next-generation sequencing coupled with the use of a dPCR platform. t(9;22) genomic breakpoints were successfully mapped in samples from 32 of 32 patients with early stage disease. Disease quantification by DNA-based dPCR was performed using the Fluidigm BioMark platform on 46 follow-up samples from 6 of the 32 patients, including 36 samples that were in deep molecular remission. dPCR detected persistent disease in 81% of molecular-remission samples, outperforming both RT-dPCR (25%) and DNA-based quantitative PCR (19%). We conclude that dPCR for BCR-ABL1 DNA is the most sensitive available method of residual-disease detection in chronic myeloid leukemia and may prove useful in the management of tyrosine kinase inhibitor withdrawal.

The genetic composition of the Lithuanian population was investigated by analysing mitochondrial DNA hypervariable region 1, RFLP polymorphisms and Y chromosomal biallelic and STR markers in six ethnolinguistic groups of Lithuanians, to address questions about the origin and genetic structure of the present day population. There were no significant genetic differences among ethnolinguistic groups, and an analysis of molecular variance confirmed the homogeneity of the Lithuanian population. MtDNA diversity revealed that Lithuanians are close to both Slavic (Indo-European) and Finno-Ugric speaking populations of Northern and Eastern Europe. Y-chromosome SNP haplogroup analysis showed Lithuanians to be closest to Latvians and Estonians. Significant differences between Lithuanian and Estonian Y chromosome STR haplotypes suggested that these populations have had different demographic histories. We suggest that the observed pattern of Y chromosome diversity in Lithuanians may be explained by a population bottleneck associated with Indo-European contact. Different Y chromosome STR distributions in Lithuanians and Estonians might be explained by different origins or, alternatively, be the result of some period of isolation and genetic drift after the population split.

Recent studies indicate that 40% of CML patients on imatinib who achieve complete molecular remission (CMR; equivalent to MR4 or better in current terminology) remain disease-free after drug discontinuation, raising the possibility of an “operational cure”. However, the safe introduction of TKI withdrawal into clinical practice would require a method of evaluating risk of relapse, which is likely to be related to the presence of residual disease undetectable by RT-qPCR. A PCR method based on the use of genomic DNA has been shown to be more sensitive for the detection of residual disease than one that relies on cDNA and may, therefore, help to predict outcome post-withdrawal. However, the former method is arduous requiring a customised patient-specific assay. We describe here a method based on targeted next-generation sequencing (NGS) which allows the rapid identification of BCR-ABL1 breakpoints and the generation of DNA-based qPCR assays. The location of the BCR-ABL1 fusion junction was mapped in disease samples from 32 CML patients using Illumina's MiSeq platform. A custom TruSeq DNA target enrichment system (Illumina) was used to enrich for fragments containing sequences from the BCR and ABL1 genes using probes covering both genes including an additional 50kb of sequence in both 5’ and 3’ directions. All 32 patients’ t(9;22) translocation junctions were successfully mapped using a custom designed bioinformatics algorithm. To date we have designed and validated DNA qPCR assays for 26 of these. On testing consecutive clinical samples from all 26 patients after achievement of MR4 or better (previously defined as CMR; mean 6 samples per patient), the DNA-qPCR assays detected residual disease in 8 out of 26 patients (31%), demonstrating that a DNA-based method is capable of identifying the presence of residual leukaemia in a proportion of patients who would be defined as “disease-free” using conventional RNA-based methodology. One area in which inaccuracy may be introduced into the DNA qPCR technique is in the use of a standard curve generated using serial dilutions of patient’s diagnostic material. We therefore sought to further enhance the sensitivity of a DNA-based approach by optimising this technique for use on a digital quantitative PCR (dqPCR) platform, which provides absolute molecular quantification without the need for standard curve. Using DNA dqPCR on a Fludigm BioMark HD instrument, we measured the level of BCR-ABL1 in 48 samples from 6 CML patients after achievement of a sustained response of MR4 or better. At the time point at which patients were first determined to have achieved at least MR4, all samples tested positive by DNA dqPCR. However, in subsequent samples collected two years following achievement of at least an MR4 (the point of entry into ongoing withdrawal trials, at which point all six patients had achieved MR4.5 or better), we found that patients fell into two distinct categories: 1) those whose disease continued to be detectable by DNA dqPCR (n=3), and 2) those whose disease had fallen to a level that was no longer detectable by DNA dqPCR (n=3). In contrast the conventional BCR-ABL1 DNA qPCR method detected disease in only one of these six patients at this time point, suggesting superior sensitivity of a digital PCR-based screening platform. From this pilot study we conclude that NGS-facilitated DNA dqPCR may be used to stratify patients with RT-qPCR-undetectable disease according to residual disease burden and may therefore prove valuable in the identification of patients for whom TKI therapy could be safely reduced or stopped. Disclosures: Milojkovic: BMS: Honoraria; Pfizer: Honoraria; Ariad: Honoraria; Novartis: Honoraria. Apperley:Novartis: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria; Pfizer, Ariad: Honoraria (not direct from company), Honoraria (not direct from company) Other.

Abstract 2369 Diamond-Blackfan anaemia (DBA) is a rare autosomal dominant disorder associated with inactivating mutations in ribosomal protein (RP) genes, causing defects in erythroid progenitor and precursor cell development. Many cases are due to de novo mutations and in family cases there is often clinical heterogeneity due to variable penetrance. Mutations in RPS19 account for 25% of all DBA cases and single nucleotide variations (SNV), indels and allele-loss deletions have been found in 11 other RP genes in a further ∼50% of patients. Around 25% of patients with DBA have no identifiable mutations. Given that (with the exception of 2 cases with GATA1 mutations) all mutations in DBA characterised so far affect RP genes, it is likely that mutations in one of the 80 RP genes will be eventually identified in a significant proportion of the patients. Current screening methods are primarily based on Sanger sequencing on a per-exon/per-gene basis, with the associated time, labour and cost restrictions. We therefore aimed to evaluate high-throughput sequencing technology, including a bespoke target enrichment platform, to screen all 80 known RP genes to facilitate rapid, cost-effective identification of DBA associated mutations. DNA was extracted from peripheral blood samples that had been referred to Imperial Molecular Pathology for DBA screening from 10 individuals, including 3 family pairs: affected mother and daughter; 2 affected siblings; and another sibling pair, one of whom was unaffected/low-penetrance (no defining clinical symptoms, except for high adenine deaminase). Only one patient had a known mutation (RPS19 c.280C>T) and was included as a control. Agilent SureSelect XP was used for the target enrichment, which employed a custom designed tiled-RNA bait hybridisation solution to capture the target genes, including non-masked intronic regions and 500bp of flanking sequence. The DNA was sheared using a Covaris e220, QC was performed via QIAxcel capillary electrophoresis and the hybridisation was carried out at 65°C for 48h. Individual libraries were quantified using qPCR against the supplied standard curve and pooled proportionally. The sequencing was performed on an Illumina MiSeq, using 150bp paired-end reads and multiplexed using the supplied ScriptSeq barcodes. The sequencing reads were aligned to the build 37 reference genome using BWA software, and the variant calls made using GATK. Annovar was used for functional annotations of the variants. Protein truncating mutations were found in RP genes in 7 of the 10 samples, including the positive control and 6 of the 8 clinically confirmed DBA patient samples., All mutations were in RP genes previous described as being involved in DBA, although 3 affected novel codons: RPL5 c.G244T (stop-gain SNV; novel; mother-daughter pair); RPL5 c.166_169delACAA (frameshift); RPS10 c.C337T (stop-gain SNV); RPL11 c.472–473delAA (frameshift; novel); RPS26 c.212–213insA (frameshift; novel). Validation was by Sanger sequencing and further confirmation testing will include unaffected family members. The remaining 2 DBA patients, a brother-sister pair, showed no definable mutations in the captured regions and neither did the unaffected/low-penetrance sibling of the RPS10 patient. In summary, a rapid and cost effective methodology for screening genetic lesions associated with the causation of DBA is warranted, especially given the magnitude of attaining global coverage by conventional techniques. Whole-gene enrichment followed by multiplexed runs on a bench-top class high-throughput sequencing platform is arguably the approach of choice; although as the cost of exome and even genome sequencing continues to fall, these may well become realistic options in the coming few years. This work is ongoing, with a second group of 10 samples already sequenced and undergoing analysis, and bioinformatic refinements, especially for the detection of larger deletions, may yet yield results for the two undetected samples. These preliminary results suggest that high throughput sequencing technology with a bespoke target enrichment platform for RP genes is a feasible, efficient and relatively rapid diagnostic tool for detection of causative mutations DBA. Disclosures: No relevant conflicts of interest to declare.