Project description:Telomeres are the ends of linear chromosomes and together with the shelterin complex present an essential feature for genome integrity. Vertebrate telomeres usually consist of hexameric TTAGGG repeats, however, in cells that use the alternative lengthening of telomeres (ALT) mechanism, variant repeat sequences are interspersed throughout telomeres. Previously, it was shown that NR2C/F transcription factors bind to TCAGGG variant repeats and contribute to telomere maintenance in ALT cells. While specific binders to other variant repeat sequences have been lacking to date, we here identify ZBTB10 as the first TTGGGG-binding protein and demonstrate direct binding via the two zinc fingers with affinity in the nanomolar range. Concomitantly, ZBTB10 co-localizes with a subset of telomeres in ALT-positive U2OS cells and interacts with TRF2/RAP1 via the N-terminal region of TRF2. Our data establishes ZBTB10 as a novel variant repeat-specific binding protein at ALT telomeres.
Project description:Climate change is impacting human health through a historic rise in wildfire smoke across the United States and the world. Whereas the deleterious effects of wildfire smoke and associated air pollution on asthma outcomes are well-established epidemiologically, genetic risks and molecular mechanisms of how wildfire smoke affects asthma are unknown. This knowledge gap hinders the identification of high-risk individuals and the creation of targeted therapies or recommendations to protect these individuals. Here, we employ a genetic approach to identify common variant (minor allele frequency > 0.05) exposure-conditional genetic risk variants that localize with genomic responses to wood smoke particles (WSP), a model of wildfire smoke exposure, and associate with asthma in the Genetic Epidemiology Research on Aging (GERA) cohort. Our novel approach used nascent transcriptional signatures derived from WSP-exposed Beas-2B airway epithelial cells to reduce the genome sequence for discovery and allow a permutation-based statistical approach to identify 52 candidate SNPs. We applied biologic and bioinformatic filters to prioritize variants for direct testing of allele-dependent transcriptional regulatory function in plasmid reporters. The rs3861144 variant identified by this approach controls WSP responses of airway epithelial cells to SPRY2, which we showed is involved in mechanical injury repair in cell culture. Our results demonstrate that wildfire particulates contribute to asthma risk at the molecular level, and we have identified mechanistic targets and genetic variant candidates to apply for clinical risk prediction and development of targeted therapies for high-risk individuals.
Project description:Nucleosomes are the principal packaging units of chromatin and critical for gene regulation and genome stability. In mammals, a subset of nucleosomes fail to be replaced by protamines during spermatogenesis and are retained in mature spermatozoa providing opportunities for paternal epigenetic transmission. In humans, the remaining 10% localize at regulatory elements of genes. To assess evolutionary conservation and to dissect the molecular logic underlying nucleosome retention, we determined the genome wide nucleosome occupancy in mouse spermatozoa that only contain 1% residual histones. In striking contrast to mammalian somatic cells and haploid round spermatids, we observe high enrichment of nucleosomes at CpG-rich sequences throughout the genome, at conserved regulatory sequences as well as at intra- and intergenic regions and repetitive DNA. This preferred occupancy occurs mutually exclusive with DNA methylation both in mouse and human sperm. At unmethylated CpG-rich sequences, residing nucleosomes are largely composed of the H3.3 histone variant, and trimethylated at lysine 4 (H3K4me3). Both canonical H3.1/H3.2 and H3.3 variant histones are present at promoters marked by Polycomb-mediated H3K27me3, which is strongly predictive for gene repression in pre-implantation embryos. Our data indicate important roles of DNA sequence composition, DNA methylation, variant H3.3 and canonical H3.1/H3.2 histones and associated modifications in nucleosome retention versus eviction during the histone-to-protamine remodeling process in elongating spermatids and potentially in epigenetic inheritance by nucleosomes between generations. Identification of histone, histone variant and histone modification states in round spermatids and sperm
Project description:In this study, we recruited a patient with Hereditary spherocytosis (HS) detected to have a novel heterozygous variant in the SPTB in the proband. Sanger sequencing of variant alleles and haplotype linkage analysis were performed simultaneously. Five embryos were identified with one heterozygous and four not carrying the SPTB variant. Single-cell amplification and whole genome sequencing showed that three embryos had varying degrees of trisomy mosaicism.