Project description:Mutations in genes encoding components of the telomerase holoenzyme complex result in a spectrum of rare genetic disorders known as telomere diseases, including dyskeratosis congenita (DC). A consistent finding in DC due to pathogenic mutations in DKC1, which encodes dyskerin, is decreased steady-state levels of the non-coding RNA component of telomerase (TERC) and thus impaired telomere maintenance. Dyskerin binds hundreds of other small nucleolar RNAs (snoRNAs). However, the mechanisms by which DKC1 mutations cause variable impacts on these snoRNAs are poorly understood, which is a barrier to understanding disease mechanisms in DC beyond impaired telomere maintenance. Here, using somatic and induced pluripotent stem cells (iPSCs) from DC patients with DKC1 mutations and CRISPR-Cas9-engineered iPSCs, we show that mutations in the N-terminal extension domain (NTE) of dyskerin dysregulate the biogenesis of a subset of snoRNAs, with the most prominent effect on scaRNA13 (small Cajal body-specific RNA 13). In patient iPSCs carrying the del37L dyskerin NTE-domain mutation but not in those with C-terminal mutations, nascent scaRNA13 transcripts showed a discrete population of 3´-extended forms, as seen in the setting of DC-causing mutations in the PARN (polyA-specific ribonuclease) gene. By deep sequencing of RNA 3´ ends, we found that aberrant scaRNA13 transcripts were composed of genomically-encoded extensions and post-transcriptionally oligoadenylated species, mediated by the noncanonical polymerase PAPD5, which counters PARN. NTE domain mutations generated using CRISPR-Cas9 engineering of the endogenous DKC1 recapitulated the scaRNA13 3´-end processing defects seen in del37L patient cells. Conversely, repair of the DKC1 del37L mutation and genetic or pharmacological manipulation of PAPD5 rescued scaRNA13 end processing defects and steady-state levels. Analysis of the human telomerase cryo-EM structure showed that the dyskerin NTE interacts with 3´ end of bound RNA, suggesting that mutations in this domain impair 3´ end protection of nascent scaRNA13 in addition to canonical functions in snoRNA stabilization. Our results provide mechanistic insights into the interplay of dyskerin and the PARN/PAPD5 axis in the biogenesis and accumulation of snoRNAs beyond TERC, which has important implications for our broader understanding of ncRNA dysregulation in human diseases.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes
Project description:SPO11-promoted DNA double-strand breaks (DSBs) formation is a crucial step for meiotic recombination, and it is indispensable to detect the broken DNA ends accurately for dissecting the molecular mechanisms behind. Here, we report a novel technique, named DEtail-seq (DNA End tailing followed by sequencing), that can directly and quantitatively capture the meiotic DSB 3’ overhang hotspots at single-nucleotide resolution.
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes Sequence library of miRNAs from a single sample of human foetal mesenchymal stem cells. Results tested and confirmed by northern blotting. Please note that only raw data files are available for the embryonic and neual samples and thus, directly submitted to SRA (SRX547311, SRX548700, respectively under SRP042115/PRJNA247767)