A collaboration between a group of Chinese scientists has led to the development of a new sequencing technique for characterizing the 3′ ends of meiotic double-stranded breaks (DSBs). The new technique, called DNA End tailing and sequencing (DEtail-seq), can successfully characterize the DSBs with high single-nucleotide resolution across a variety of species.
Mapping meiotic DSBs is important for researchers working to better understand meiotic recombination. During the process of meiosis, meiotic recombination occurs when chromosomal DNA is swapped between the homologous chromosomes. This process is crucial for maintaining genetic diversity. In order to exchange DNA between chromosomes, meiotic recombination is initiated by DSBs made by the Spo11 protein.
DSBs created from Spo11 are generally separated into three categories: upstream ends of the DNA, downstream ends of the DNA, and oligos bound to Spo11. The DSBs on the upstream and downstream ends create 3’ overhangs with a region of ssDNA. Unfortunately, the current techniques used for mapping these 3’ ends of the DSBs are not efficient or sensitive enough for high-level resolution. This prompted the research team to develop DEtail-seq for improved mapping of the 3’ ends of DSBs.
DEtail-seq begins by using adaptase for single-stranded DNA ligation of the hanging 3’ ends of DNA onto an adapter. Then through denaturation, ligation of another adapter, and several routine preparation steps, the constructed libraries are ready to be loaded and sequenced. The 3’ ends of the DNA breaks are then mapped during the data analysis. Using detection of restriction endonuclease cleavage sites, the researchers were able to show that DEtail-seq is accurate to almost a single nucleotide resolution.
The efficiency of DEtail-seq was investigated in budding yeast, mouse, and human germ cells with novel features of DSBs identified in each of the organisms. Additionally, the meiotic DSBs in the mouse genome were strongly enriched in de novo H3K4me3 peaks at the leptotene stage. Analysis of the human samples during meiosis showed that the DSB hotspots are enriched near the common fragile sites, most notably at CCCTC-binding factor (CTCF)-associated enhancers.
These results give valuable insights into the distribution and regulation of meiotic DSB hotspots. The researchers are hopeful that DEtail-seq will continue to be used as a method to investigate meiosis in different species. For more information about DEtail-seq, read the original study here.
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