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RPA and RAD51 ChIP-seq from genetically modified Dmc1-knockout B6xCAST PRDM9-Humanized/CAST mouse testes

ABSTRACT: Mammalian meiotic recombination proceeds via repair of hundreds of programmed DNA double-strand breaks (DSBs). This process requires choreographed binding of RPA, DMC1 and RAD51 to single-stranded DNA (ssDNA) substrates and in vivo binding maps of these proteins provide insights into the underlying molecular mechanisms. When assayed in F1-hybrid mice, these maps can distinguish the broken chromosome from the homologous chromosome used as template for repair, which reveals further mechanistic detail and enables the structure of the recombination intermediates to be inferred. By applying CRISPR/Cas9 mutagenesis directly on F1-hybrid embryos, we have extended this powerful analysis technique to explore the molecular detail of recombination when a key component is knocked-out. As a proof-of-concept, we have generated biallelic knockouts of Dmc1 and built maps of meiotic binding of RAD51 and RPA in these knockout hybrid mice. Dmc1 mutants undergo meiotic arrest and comparison of these maps with those from wild-type mice is informative about the structure and timing of recombination intermediates in both genotypes. We confirm a complete abrogation of strand exchange in Dmc1 mutants, and observe a redistribution of RAD51 binding across both the distal and proximal ends of the resected DNA. We observe unexpected RPA and DMC1 binding in the wild-type, which suggests multiple rounds of strand invasion with template-switching in mouse. The methodology used involves direct phenotyping of hybrid “founder” mice following CRISPR mutagenesis and provides a high-throughput approach for the analysis of gene function during meiotic recombination, at low animal cost.

ORGANISM(S): Mus musculus

PROVIDER: GSE239997 | GEO | 2023/10/16

REPOSITORIES: GEO

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Project description:DNA double-strand breaks (DSBs) initiate meiotic recombination. Past DSB-mapping studies have used rad50S or sae2? mutants, which are defective in break processing, to accumulate DSBs, and report large (= 50 kb) “DSB-hot” regions that are separated by “DSB-cold” domains of similar size. Substantial recombination occurs in some DSB-cold regions, suggesting that DSB patterns are not normal in rad50S or sae2? mutants. We therefore developed novel methods that detect DSBs using ssDNA enrichment and microarray hybridization, and that use background-based normalization to allow cross-comparison between array datasets, to map genome-wide the DSBs that accumulate in processing-capable, repair-defective dmc1î and dmc1î rad51î mutants. DSBs were observed at known hotspots, but also in most previously-identified “DSB-cold” regions, including near centromeres and telomeres. While about 40% of the genome is DSB-cold in rad50S mutants, analysis of meiotic ssDNA from dmc1? shows that most of these regions have significant DSB activity. Thus, DSBs are distributed much more uniformly than was previously believed. Southern-blot assays of DSBs in selected regions in dmc1?, rad50S and wild-type cells confirm these findings. Comparisons of DSB signals in dmc1, dmc1 rad51, and dmc1 spo11 mutant strains identify Dmc1 as the primary strand transfer activity genome-wide, and Spo11-induced lesions as initiating all meiotic recombination. Keywords: DSB mapping, ChIP-chip, single strand DNA , BND cellulose We use two different strategies to map the genome-wide distribution of meiotic DSBs in the yeast Saccharomyces cerevisiae. The first is a chromatin immunoprecipitation (ChIP) based approach that targets the Spo11p protein, which remains covalently attached to DSB ends in the rad50S mutant background. The second approach involves BND cellulose enrichment of the single strand DNA (ssDNA) recombination intermediate formed by end-resection at DSB sites following Spo11p removal. We use dmc1 and dmc1 rad51 mutants that accumulates meiotic single strand DNA intermediates