A Method for Detection of Somatic LINE-1 Insertions at the Single-Cell Level from Postmortem Human Brain

Long Interspersed Element-1 (LINE-1, L1) is a retrotransposon that has the ability to amplify its copy in the genome autonomously. L1Hs is a human-specific active subtype of L1 reported to amplify its copy in neural progenitor cells causing genomic mosaicism. This chapter describes a new method named NECO-seq (Novel Elements Concentrated-sequence) to identify the genomic locus of L1Hs insertions at the single-cell level. This protocol contains the steps of (1) preparation of neuronal cell nuclei from a postmortem human brain, (2) whole genome amplification from single neural nuclei (snWGA), (3) single nucleotide polymorphisms (SNPs) genotyping for quality control of snWGA products, (4) library preparation for next-generation sequencing to enrich the genomic locus of L1Hs insertions, and (5) bioinformatic analysis to detect novel somatic L1Hs insertions. This method can detect approximately 97% of L1Hs originally existing in reference human genome and approximately 10-20 newly inserted L1Hs copies in a neuronal cell of a postmortem human brain.