ABSTRACT: Optical Mapping of the 22q11.2DS Region Reveals Complex Repeat Structures and Preferred Locations for Non-Allelic Homologous Recombination (NAHR)
Project description:Optical Mapping of the 22q11.2DS Region Reveals Complex Repeat Structures and Preferred Locations for Non-Allelic Homologous Recombination (NAHR)
Project description:Many loci in the human genome harbor complex genomic structures that can result in susceptibility to genomic rearrangements leading to various genomic disorders. Nephronophthisis 1 (NPHP1, MIM# 256100) is an autosomal recessive disorder that can be caused by defects of NPHP1; the gene maps within the human 2q13 region where low copy repeats (LCRs) are abundant. Loss of function of NPHP1 is responsible for approximately 85% of the NPHP1 cases - about 80% of such individuals carry a large recurrent homozygous NPHP1 deletion that occurs via non-allelic homologous recombination (NAHR) between two flanking directly oriented ~45 kb LCRs. Published data revealed a non-pathogenic inversion polymorphism involving the NPHP1 gene flanked by two inverted ~358 kb LCRs. Using optical mapping and array-comparative genomic hybridization, we identified three potential novel structural variant (SV) haplotypes at the NPHP1 locus that may protect a haploid genome from genomic instability and NPHP1 deletion. Inter-species comparative genomic analyses among primate genomes revealed massive genomic changes during evolution. The aggregated data suggest that dynamic genomic rearrangements occurred historically within the NPHP1 locus and generated SV haplotypes observed in the human population today, which may have differential susceptibility to the NPHP1 deletion within a personal genome. Our study documents diverse SV haplotypes at a complex LCR-laden human genomic region. Comparative analyses provide a model for how this complex region arose during primate evolution, and studies among humans reflect the possibility that intra-species polymorphism may potentially modulate an individual’s susceptibility to acquiring disease-associated alleles.
Project description:In a study to elucidate the genetic defects in patients with X-linked intellectual disability (XLID) we performed X chromosome-specific BAC-array-CGH and identified 0.33 to 1.0 Mb nonrecurrent copy number gains at Xp11.22 in affected males of unrelated XLID families. All aberrations segregate with the disease in the families and the carrier mothers show a nonrandom X-inactivation. Affected males suffered from mild to moderate ID. Tiling Xp11.22 region-specific oligo-array (ChrX:52.50 - 54.50 Mb) revealed that all aberrations had different start and stop sites. The twofold copy number gain included up to 20 genes but only the HUWE1 gene is located in the minimal common region of overlap in these families. Moreover, expression analysis revealed about twofold increased HUWE1 mRNA levels in affected patients when compared to control individuals. Breakpoint analysis revealed Non-homologous end-joining (4 cases), serial replication slippage (1 case) and non-allelic homologous recmbination (one case) as the potential recombination mechanism. For duplication mapping and exact copy number analysis in all four families, differentially-labeled patient versus male control DNA samples were hybridized onto a custom designed 4x44k oligo-array (Agilent Technologies) that covers the repeat-masked region 52.50 Mb to 54.50 Mb at tiling resolution.
Project description:HS-10502 is a Poly(ADP-ribose) polymerase 1 (PARP1)-specific selective inhibitor. The purpose if this study is to assess the safety, tolerability, pharmacokinetics (PK), and efficacy of HS-10502 in subjects with homologous recombination repair (HRR) gene mutant or homologous recombination deficiency (HRD) positive advanced solid tumors.
Project description:We report 12 individuals from ten unrelated families with epilepsy, learning difficulties, intellectual disability, and neurobehavioral abnormalities, who segregated a microdeletion distally adjacent to the Williams-Beuren syndrome region. In six families, a recurrent ~ 1.1 Mb deletion likely resulted from nonallelic homologous recombination between flanking large complex low-copy repeats. Three smaller sized microdeletions (~ 180-500 kb) enabled us to narrow the critical region to one gene, HIP1, encoding Huntington interacting protein 1. genomic DNA from blood was used to analyse 12 samples with control sample using custom made NimbleGen 12x135K microarrays for chr7 region.
Project description:Triple negative breast cancers (TNBCs) are characterised by a wide spectrum of genomic aberrations representing underlying repair defects that may be targeted therapeutically. However, means to measure these defects in tumours and an understanding of their effect on sensitivity to DNA damaging agents is limited. We sought to address this by establishing methods to trace underlying deficiencies in DNA repair processes using patterns of genomic instability. Here, we demonstrate that a pattern related to Homologous Recombination defects, allelic-imbalanced Copy Number Aberration, predicts response to platinum containing chemotherapeutics in TNBC patients. These patterns also enabled us to identify a meiotic gene HORMAD1, as a functional driver of allelic-imbalanced Copy Number Aberration and genomic instability in TNBC. Additionally, HORMAD1 expression is also a predictive marker of carboplatin response in TNBC. Mechanistically, expression of HORMAD1 in cell lines inhibited Homologous Recombination representing outÐof-context activation of its meiotic function.
Project description:We report 12 individuals from ten unrelated families with epilepsy, learning difficulties, intellectual disability, and neurobehavioral abnormalities, who segregated a microdeletion distally adjacent to the Williams-Beuren syndrome region. In six families, a recurrent ~ 1.1 Mb deletion likely resulted from nonallelic homologous recombination between flanking large complex low-copy repeats. Three smaller sized microdeletions (~ 180-500 kb) enabled us to narrow the critical region to one gene, HIP1, encoding Huntington interacting protein 1.
Project description:Copy number expansions such as amplifications and duplications contribute to human phenotypic variation, promote molecular diversification during evolution, and drive the initiation and/or progression of various cancers. The mechanisms underlying these copy number changes are still incompletely understood, however. We recently demonstrated that transient, limited re-replication from a single origin in Saccharomyces cerevisiae efficiently induces segmental amplification of the re-replicated region. Structural analyses of such re-replication induced gene amplifications (RRIGA) suggested that RRIGA could provide a new mechanism for generating copy number variation by non-allelic homologous recombination (NAHR). Here we elucidate this new mechanism and provide insight into why it is so efficient. We establish that sequence homology is both necessary and sufficient for repetitive elements to participate in RRIGA and show that their recombination occurs by a single-strand annealing (SSA) mechanism. We also find that re-replication forks are prone to breakage, accounting for the widespread DNA damage associated with deregulation of replication proteins. These breaks appear to stimulate NAHR between re-replicated repeat sequences flanking a re-initiating replication origin. Our results support a RRIGA model where the expansion of a re-replication bubble beyond flanking homologous sequences followed by breakage at both forks in trans provides an ideal structural context for SSA–mediated NAHR to form a head-to-tail duplication. Given the remarkable efficiency of RRIGA, we suggest it may be an unappreciated contributor to copy number expansions in both disease and evolution.