Project description:Retroelement activation is emerging as a significant factor in the pathogenesis of neurodegenerative diseases. SINE-VNTR-Alu (SVAs) are hominid-specific retroelements that create genetic variation through insertion polymorphisms and variable short tandem repeat (STR) lengths. We investigate how the SVA (CCCTCT)n STR contributes to the striatal neurodegenerative disorder X-linked Dystonia Parkinsonism (XDP), where the repeat expansion length within the pathogenic SVA is inversely correlated with disease onset age. Phenotypic and transcriptomic analysis of XDP and isogenic SVA-deleted striatal organoids revealed that the SVA insertion drives hallmarks of neurodegeneration, including transcriptional dysregulation, decreased neuronal activity, and apoptosis, which are ameliorated by SVA deletion. We identify a (AGAGGG)n hexamer-containing RNA in the SVA that increases expression during organoid maturation and drives R-loop formation in organoids and XDP brain tissue. Knockdown of the (AGAGGG)n hexamer-containing RNA by antisense oligonucleotides rescues apoptosis in the XDP organoids. We demonstrate that a retrotransposon-derived tandem repeat RNA could cause neurodegeneration.
Project description:More than 60 human disorders have been linked to unstable expansion of short tandem repeat (STR) tracts. STR length and the extent of DNA methylation is linked to disease pathology and can be mosaic in a cell type-specific manner in several repeat expansion disorders. Mosaic phenomenon have been difficult to study to date due to technical bias intrinsic to repeat sequences and the need for multi-modal measurements at single-allele resolution. Nanopore long-read sequencing accurately measures STR length and DNA methylation in the same single molecule but is cost prohibitive for studies assessing a target locus across multiple experimental conditions or patient samples. Here, we describe MASTR-seq, Multiplexed Analysis of Short Tandem Repeats, for cost-effective, high-throughput, accurate, multi-modal measurements of DNA methylation and STR genotype at single-allele resolution. MASTR-seq couples long-read sequencing, Cas9-mediated target enrichment, and PCR-free multiplexed barcoding to achieve a >ten-fold increase in on-target read mapping for 8-12 pooled samples in a single MinION flow cell. We provide a detailed experimental protocol and computational tools and present evidence that MASTR-seq quantifies tract length and DNA methylation status for CGG and CAG STR loci in normal-length and mutation-length human cell lines. The MASTR-seq protocol takes approximately eight days for experiments and one additional day for data processing and analyses.
Project description:Comparison of multilocus variable number tandem repeat analysis and whole genome sequencing for investigation of Clostridium difficile transmission
Project description:Targeted DNA sequencing approaches will improve how the size of short tandem repeats is measured for diagnostic tests and pre-clinical studies. The expansion of these sequences causes dozens of disorders, with longer tracts generally leading to a more severe disease. In addition, interruptions are sometimes present within repeats and can alter disease manifestation. Despite advances in methodologies, determining repeat size and identifying interruptions in targeted sequencing datasets remains a major challenge. This is because standard alignment tools are ill-suited for the repetitive nature of these sequences. To address this, we have developed Repeat Detector (RD), a deterministic profile weighting algorithm for counting repeats in targeted sequencing data. We tested RD using blood-derived DNA samples from Huntington’s disease (HD) and Fuchs endothelial corneal dystrophy patients sequenced using either Illumina MiSeq or Pacific Biosciences single-molecule, real-time sequencing platforms. RD was highly accurate in determining repeat sizes of 609 HD blood-derived samples and did not require prior knowledge of the flanking sequences or their polymorphisms within the patient population. We demonstrate that RD can be used to identify individuals with repeat interruptions and may provide a measure of repeat instability within an individual. RD is therefore highly versatile and may find applications in the diagnosis of expanded repeat disorders and the development of novel therapies.
Project description:In vertebrates, DNA methylation-mediated repression of retrotransposons is essential for the maintenance of genomic integrity. In the current study, we developed a technique termed HT-TREBS (High-Throughput Targeted Repeat Element Bisulfite Sequencing). This technique is designed to measure the DNA methylation levels of individual loci of any repeat families with next-generation sequencing approaches. To test the feasibility of HT-TREBS, we analyzed the DNA methylation levels of the IAPLTR family using a set of 12 different genomic DNA isolated from the brain, liver and kidney of 4 one-week-old littermates of the mouse strain C57BL/6N. This technique has successfully generated the CpG methylation data of 5,233 loci common in all the samples, representing more than 80% of the individual loci of the five targeted subtypes of the IAPLTR family. According to the results, approximately 5% of the IAPLTR loci have less than 80% average CpG methylation levels with no genomic position preference. Further analyses of the IAPLTR loci also revealed the presence of extensive DNA methylation variations between different tissues and individuals. Overall, these data demonstrate the efficiency and robustness of the new technique, HT-TREBS, and also provide new insights regarding the genome-wide DNA methylation patterns of the IAPLTR repeat elements. High-throughput, single-base resolution, singlicate DNA methylation profiles of IAPLTR retrotransposons in the brain, liver , and kidney of four 1-week-old mouse littemates using the developed technique, HT-TREBS.