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Autosomal recessive Stargardt disease (STGD1, MIM 248200) is caused by mutations in the ABCA4 gene. Complete sequencing of the ABCA4 locus in STGD1 patients identifies two expected disease-causing alleles in ∼75% of patients and only one mutation in ∼15% of patients. Recently, many possibly pathogenic variants in deep intronic sequences of ABCA4 have been identified in the latter group. We extended our analyses of deep intronic ABCA4 variants and determined that one of these, c.4253+43G>A (rs61754045), is present in 29/1155 (2.6%) of STGD1 patients. The variant is found at statistically significantly higher frequency in patients with only one pathogenic ABCA4 allele, 23/160 (14.38%), MAF = 0.072, compared to MAF = 0.013 in all STGD1 cases and MAF = 0.006 in the matching general population (P < 1 × 10-7). The variant, which is not predicted to have any effect on splicing, is the first reported intronic "extremely hypomorphic allele" in the ABCA4 locus; that is, it is pathogenic only when in trans with a loss-of-function ABCA4 allele. It results in a distinct clinical phenotype characterized by late onset of symptoms and foveal sparing. In ∼70% of cases the variant was allelic with the c.6006-609T>A (rs575968112) variant, which was deemed nonpathogenic. Another rare deep intronic variant, c.5196+1056A>G (rs886044749), found in 5/834 (0.6%) of STGD1 cases is, conversely, a severe allele. This study determines pathogenicity for three noncoding variants in STGD1 patients of European descent accounting for ∼3% of the disease. Defining disease-associated alleles in the noncoding sequences of the ABCA4 locus can be accomplished by integrated clinical and genetic analyses.
Pubmed ID: 29848554
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Software tool to help study pre-mRNA splicing and to better understand intronic and exonic mutations leading to splicing defects. To calculate the consensus values of potential splice sites and search for branch points, new algorithms were developed. Furthermore, they have integrated all available matrices to identify exonic and intronic motifs, as well as new matrices to identify hnRNP A1, Tra2-? and 9G8.
View all literature mentionsPortal to interactively visualize genomic data. Provides reference sequences and working draft assemblies for collection of genomes and access to ENCODE and Neanderthal projects. Includes collection of vertebrate and model organism assemblies and annotations, along with suite of tools for viewing, analyzing and downloading data.
View all literature mentionsInternational collaboration producing an extensive public catalog of human genetic variation, including SNPs and structural variants, and their haplotype contexts, in an effort to provide a foundation for investigating the relationship between genotype and phenotype. The genomes of about 2500 unidentified people from about 25 populations around the world were sequenced using next-generation sequencing technologies. Redundant sequencing on various platforms and by different groups of scientists of the same samples can be compared. The results of the study are freely and publicly accessible to researchers worldwide. The consortium identified the following populations whose DNA will be sequenced: Yoruba in Ibadan, Nigeria; Japanese in Tokyo; Chinese in Beijing; Utah residents with ancestry from northern and western Europe; Luhya in Webuye, Kenya; Maasai in Kinyawa, Kenya; Toscani in Italy; Gujarati Indians in Houston; Chinese in metropolitan Denver; people of Mexican ancestry in Los Angeles; and people of African ancestry in the southwestern United States. The goal Project is to find most genetic variants that have frequencies of at least 1% in the populations studied. Sequencing is still too expensive to deeply sequence the many samples being studied for this project. However, any particular region of the genome generally contains a limited number of haplotypes. Data can be combined across many samples to allow efficient detection of most of the variants in a region. The Project currently plans to sequence each sample to about 4X coverage; at this depth sequencing cannot provide the complete genotype of each sample, but should allow the detection of most variants with frequencies as low as 1%. Combining the data from 2500 samples should allow highly accurate estimation (imputation) of the variants and genotypes for each sample that were not seen directly by the light sequencing. All samples from the 1000 genomes are available as lymphoblastoid cell lines (LCLs) and LCL derived DNA from the Coriell Cell Repository as part of the NHGRI Catalog. The sequence and alignment data generated by the 1000genomes project is made available as quickly as possible via their mirrored ftp sites. ftp://ftp.1000genomes.ebi.ac.uk ftp://ftp-trace.ncbi.nlm.nih.gov/1000genomes
View all literature mentionsDatabase that aggregates exome and genome sequencing data from large-scale sequencing projects. The gnomAD data set contains individuals sequenced using multiple exome capture methods and sequencing chemistries. Raw data from the projects have been reprocessed through the same pipeline, and jointly variant-called to increase consistency across projects.
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