Advances in ligase chain reaction and ligation-based amplifications for genotyping assays: Detection and applications

Genetic variants have been reported to cause several genetic diseases. Various genotyping assays have been developed for diagnostic and screening purposes but with certain limitations in sensitivity, specificity, cost effectiveness and/or time savings. Since the discovery of ligase chain reaction (LCR) in the late nineties, it became one of the most favored platforms for detecting these variants and also for genotyping low abundant contaminants. Recent and powerful modifications with the integration of various detection strategies such as electrochemical and magnetic biosensors, nanoparticles (NPs), quantum dots, quartz crystal and leaky surface acoustic surface biosensors, DNAzyme, rolling circle amplification (RCA), strand displacement amplification (SDA), surface enhanced raman scattering (SERS), chemiluminescence and fluorescence resonance energy transfer have been introduced to both LCR and ligation based amplifications to enable high-throughput and inexpensive multiplex genotyping with improved robustness, simplicity, sensitivity and specificity. In this article, classical and up to date modifications in LCR and ligation based amplifications are critically evaluated and compared with emphasis on points of strength and weakness, sensitivity, cost, running time, equipment needed, applications and multiplexing potential. Versatile genotyping applications such as genetic diseases detection, bacterial and viral pathogens detection are also detailed. Ligation based gold NPs biosensor, ligation based RCA and ligation mediated SDA assays enhanced detection limit tremendously with a discrimination power approaching 1.5 aM, 2 aM and 0.1 fM respectively. MLPA (multiplexed ligation dependent probe amplification) and SNPlex assays have been commercialized for multiplex detection of at least 48 SNPs at a time. MOL-PCR (multiplex oligonucleotide ligation) has high-throughput capability with multiplex detection of 50 SNPs/well in a 96 well plate. Ligase detection reaction (LDR) is one of the most widely used LCR versions that have been successfully integrated with several detection strategies with improved sensitivity down to 0.4 fM.