Amplification of overlapping DNA amplicons in a single-tube multiplex PCR for targeted next-generation sequencing of BRCA1 and BRCA2

Current PCR-based target enrichment methods for next generation sequencing (NGS) of overlapping amplicons often requires separate PCR reactions and subsequent pooling of amplicons from the different reactions. The study presents a novel method, deemed stemloop inhibition mediated amplification (SLIMamp), for amplifying overlapping or tiled amplicons in a single multiplex PCR reaction. During a SLIMamp PCR reaction, a stem loop structure formed by the overlapping amplicon suppresses additional amplification of itself by preventing the annealing of the primers. Using the SLIMamp strategy, we designed a nextgeneration sequencing (NGS) assay to enrich the exon regions of BRCA1 and BRCA2 for sequencing on an Illumina MiSeq system. We used 35 cell line DNAs and 6 patient blood DNAs in the study to evaluate the assay performance. For each sample, all targeted regions were successfully amplified and sequenced with excellent coverage uniformity and specificity. >99% of the total sequencing reads were mapped to the human reference genome (hg19) and >99% of the mapped reads were on the targeted exons. >98% of bases were covered at >0.20x of the mean coverage and >99% are covered at >0.15x of the mean depth. Among 34 independently sequenced samples, all variants were reliably detected with no false positives or false negatives. SLIMamp provides a robust method for singletube multiplex PCR amplification of numerous, overlapping amplicons that tile for targeted next-generation sequencing.