Project description:interactions that require remodeling proteins like the Helicase, Lymphoid-specific (HELLS). Here, we generate HELLS and de novo DNA methyltransferase 3 A and B (DNMT3A/B) knockout hu-man pluripotent stem cells and assemble telomere-to-telomere maps of whole genome bisulfite sequencing data combined with ATAC-sequencing. Disrupting HELLS induces a global loss of DNA methylation that is distinct from the de novo DNMTs, in particular over peri/centromeric satellite repeats as defined in the telomere-to-telomere genome assembly. However, HELLS is dispensable for local enhancer remodeling and the potential to differentiate into the three germ layers. Taken together, these findings further clarify the genomic targets and role of HELLS in human cells.
Project description:Activating mutations in tyrosine kinase (TK) genes (e.g. FLT3 and KIT) are found in more than 30% of patients with de novo acute myeloid leukemia (AML); many groups have speculated that mutations in other TK genes may be present in the remaining 70%. We performed high-throughput re-sequencing of the kinase domains of 26 TK genes (11 receptor TK and 15 cytoplasmic TK) that are expressed in most AML patients, using genomic DNA from the bone marrow (tumor) and matched skin biopsy samples (germline) from 94 patients with de novo AML; sequence variants were validated in an additional 94 AML tumor samples (14.3 million base pairs of sequence were obtained and analyzed). We identified known somatic mutations in FLT3, KIT, and JAK2 TK genes at the expected frequencies, and found four novel somatic mutations, JAK1V623A, JAK1T478S, DDR1A803V and NTRK1S677N, once each in four respective patients out of 188 tested. We also identified novel germline sequence changes encoding amino acid substitutions (i.e. non-synonymous changes) in 14 TK genes, including TYK2, which had the largest number of non-synonymous sequence variants (11 total detected). Additional studies will be required to define the roles that these somatic and germline TK gene variants play in AML pathogenesis. In this ongoing study, we have performed high-throughput sequencing of whole genomes, exomes, and transcriptomes, as well as SNP and expression microarrays, and methylation microarrays, using genomic DNA or RNA from the bone marrow (tumor) and matched skin biopsy samples (germline) from over 300 patients with de novo AML. These samples are also part of the Cancer Genome Atlas (TCGA) study of AML.
Project description:Shotgun protein sequencing with meta-contig assembly.
Full-length de novo sequencing from tandem mass (MS/MS) spectra of unknown proteins such as antibodies or proteins from organisms with unsequenced genomes remains a challenging open problem. Conventional algorithms designed to individually sequence each MS/MS spectrum are limited by incomplete peptide fragmentation or low signal to noise ratios and tend to result in short de novo sequences at low sequencing accuracy. Our shotgun protein sequencing (SPS) approach was developed to ameliorate these limitations by first finding groups of unidentified spectra from the same peptides (contigs) and then deriving a consensus de novo sequence for each assembled set of spectra (contig sequences). But whereas SPS enables much more accurate reconstruction of de novo sequences longer than can be recovered from individual MS/MS spectra, it still requires error-tolerant matching to homologous proteins to group smaller contig sequences into full-length protein sequences, thus limiting its effectiveness on sequences from poorly annotated proteins. Using low and high resolution CID and high resolution HCD MS/MS spectra, we address this limitation with a Meta-SPS algorithm designed to overlap and further assemble SPS contigs into Meta-SPS de novo contig sequences extending as long as 100 amino acids at over 97% accuracy without requiring any knowledge of homologous protein sequences. We demonstrate Meta-SPS using distinct MS/MS data sets obtained with separate enzymatic digestions and discuss how the remaining de novo sequencing limitations relate to MS/MS acquisition settings.
Project description:Crassulacean acid metabolism (CAM) is a water-use efficient adaptation of photosynthesis that has evolved independently many times in diverse lineages of flowering plants. We hypothesize that convergent evolution of protein sequence and temporal gene expression underpins the independent emergences of CAM from C3 photosynthesis. To test this hypothesis, we generated a de novo genome assembly and genome-wide transcript expression data for Kalanchoe fedtschenkoi, an obligate CAM species within the core eudicots with a relatively small genome (~260 Mb). Our comparative analyses identified signatures of convergence in protein sequence and re-scheduling of diel transcript expression of genes involved in nocturnal CO2 fixation, stomatal movement, heat tolerance, circadian clock and carbohydrate metabolism in K. fedtschenkoi and other CAM species in comparison with non-CAM species. These findings provide new insights into molecular convergence and building blocks of CAM and will facilitate CAM-into-C3 photosynthesis engineering to enhance water-use efficiency in crops.
Project description:Activating mutations in tyrosine kinase (TK) genes (e.g. FLT3 and KIT) are found in more than 30% of patients with de novo acute myeloid leukemia (AML); many groups have speculated that mutations in other TK genes may be present in the remaining 70%. We performed high-throughput re-sequencing of the kinase domains of 26 TK genes (11 receptor TK and 15 cytoplasmic TK) that are expressed in most AML patients, using genomic DNA from the bone marrow (tumor) and matched skin biopsy samples (germline) from 94 patients with de novo AML; sequence variants were validated in an additional 94 AML tumor samples (14.3 million base pairs of sequence were obtained and analyzed). We identified known somatic mutations in FLT3, KIT, and JAK2 TK genes at the expected frequencies, and found four novel somatic mutations, JAK1V623A, JAK1T478S, DDR1A803V and NTRK1S677N, once each in four respective patients out of 188 tested. We also identified novel germline sequence changes encoding amino acid substitutions (i.e. non-synonymous changes) in 14 TK genes, including TYK2, which had the largest number of non-synonymous sequence variants (11 total detected). Additional studies will be required to define the roles that these somatic and germline TK gene variants play in AML pathogenesis. Experiment Overall Design: 188 patient samples analysed
Project description:DNA methylation is an epigenetic modification associated with transcriptional repression of promoters and is essential for mammalian development. Establishment of DNA methylation is mediated by the de novo DNA methyltransferases DNMT3A and DNMT3B, whereas DNMT1 ensures maintenance of methylation through replication. Absence of these enzymes is lethal, and somatic mutations in these genes have been associated with several human diseases. How genomic DNA methylation patterns are regulated remains poorly understood, as the mechanisms that guide recruitment and activity of DNMTs in vivo are largely unknown. To gain insights into this matter we determined chromosomal binding and site-specific activity of the mammalian de novo DNA methyltransferases DNMT3A and DNMT3B. We show that both enzymes localize to methylated, CpG dense regions in mouse stem cells, yet are excluded from active promoters and enhancers. By specifically measuring sites of de novo methylation, we observe that enzymatic activity reflects chromosomal binding. De novo methylation increases with CpG density, yet is excluded from nucleosomes. Notably, we observed selective binding of DNMT3B to the bodies of transcribed genes, which leads to their preferential methylation. This targeting to transcribed sequences requires SETD2-mediated methylation of lysine 36 on histone H3 and a functional PWWP domain of DNMT3B. Together these findings reveal how sequence and chromatin cues guide de novo methyltransferase activity to ensure methylome integrity. Whole-genome bisulfite sequencing for Dnmt1,3a,3b-triple-KO ES cells expressing DNMT3A2 or DNMT3B1 and for Dnmt1,3a,3b,Setd2-KO ES cells expressing DNMT3B1
Project description:DNA methylation is essential for genome integrity and involves multi-layered chromatin interac-tions that require remodeling proteins like the Helicase, Lymphoid-specific (HELLS). Here, we generate HELLS and de novo DNA methyltransferase 3 A and B (DNMT3A/B) knockout human pluripotent stem cells and assemble telomere-to-telomere maps of whole genome bisulfite se-quencing data combined with ATAC-sequencing. Disrupting HELLS induces a global loss of DNA methylation that is distinct from the de novo DNMTs, in particular over peri/centromeric satellite repeats as defined in the telomere-to-telomere genome assembly. However, HELLS is dispen-sable for local enhancer remodeling and the potential to differentiate into the three germ layers. Taken together, these findings further clarify the genomic targets and role of HELLS in human cells.
Project description:DNA methylation is an epigenetic modification associated with transcriptional repression of promoters and is essential for mammalian development. Establishment of DNA methylation is mediated by the de novo DNA methyltransferases DNMT3A and DNMT3B, whereas DNMT1 ensures maintenance of methylation through replication. Absence of these enzymes is lethal, and somatic mutations in these genes have been associated with several human diseases. How genomic DNA methylation patterns are regulated remains poorly understood, as the mechanisms that guide recruitment and activity of DNMTs in vivo are largely unknown. To gain insights into this matter we determined chromosomal binding and site-specific activity of the mammalian de novo DNA methyltransferases DNMT3A and DNMT3B. We show that both enzymes localize to methylated, CpG dense regions in mouse stem cells, yet are excluded from active promoters and enhancers. By specifically measuring sites of de novo methylation, we observe that enzymatic activity reflects chromosomal binding. De novo methylation increases with CpG density, yet is excluded from nucleosomes. Notably, we observed selective binding of DNMT3B to the bodies of transcribed genes, which leads to their preferential methylation. This targeting to transcribed sequences requires SETD2-mediated methylation of lysine 36 on histone H3 and a functional PWWP domain of DNMT3B. Together these findings reveal how sequence and chromatin cues guide de novo methyltransferase activity to ensure methylome integrity. Genome-wide binding analysis for biotin-tagged DNMT3A2 and DNMT3B and variants in wild type ES, wild type neuroprogenitor cells, ES cells triple-KO for Dnmt1,3a,3b and ES cell mutant for Setd2