Duplex-specific nuclease (DSN) is a type of nuclease, that is isolated from the hepatopancreas of the Kamchatka crab. DSN displays a strong preference for cleaving double-stranded DNA or DNA in DNA-RNA heteroduplexes, and is practically inactive toward single-stranded DNA or RNA. Moreover, this enzyme shows excellent discrimination capability between perfectly and imperfectly matched (up to one mismatch) short duplexes. Owing to its unique feature of cleaving DNA, DSN enzyme is widely applied in the fields of biomedicine and molecular biology, including full-length cDNA library normalization,genomic single-nucleotide polymorphism (SNP) detection and high throughput sequencing. The recent research on DSN are mainly focused on the applications in microRNAs (miRNAs) detection using a DSN-mediated signal amplification strategy. miRNAs are a group of short, endogenous, noncoding RNAs that play vital regulatory roles in physiologic and pathologic processes, including hematopoietic differentiation, cell cycle, regulation, and metabolism. So miRNA is one of the most important biomarkers in individualized treatment, which has great value in terms of improving the diagnosis and treatment of diseases. However, detection of miRNAs is challenging owing to their unique characteristics, including a small size, sequence homology among family members, low abundance in total RNA samples, and susceptibility to degradation in solution. In recent years, isothermal signal amplification and detection of trace miRNA in fluids are reported by many researchers using DSN-mediated biosensors. According to different detection principle of biosensors, DSN-mediated biosensors can be classified as colorimetric, fluorescent, and electrochemical. In this review, we intensively summarize the advantages of DSN in miRNAs detection using DSN-based signal amplification strategy, expanded applications in SNP detection, high throughput sequencing and cDNA library normalization especially when being combined with SMART (Switching Mechanism At 5'end of RNA Transcript) technique.

Contents
1 Introduction
2 The application of DSN enzyme in microRNA detection
2.1 Colorimetric analyses
2.2 Fluorescent analyses
2.3 Electrochemical analyses
3 The application of DSN enzyme in SNP detection
4 Other biological applications of DSN enzyme
4.1 Construction of cDNA Library
4.2 High throughput sequencing
5 Conclusion and outlook