Mutation analysis for newly suggested 30 Y-STR loci with high mutation rates in Chinese father-son pairs

Rapidly mutating Y-STRs (RM Y-STRs) harbor great potential to distinguish male relatives and achieve male identification. However, forensic applications were greatly limited by the small number of the initially identified 14 RM Y-STRs. Recently, with the emergence of 12 novel RM Y-STRs, an integrated panel named RMplex was introduced, which contains all 26 RM Y-STRs and four fast mutating Y-STRs (FM Y-STRs). To obtain the first data on the mutation rates and father-son differentiation rates of the 30 newly proposed Y-STRs in Chinese populations, we performed an empirical mutation study on 307 DNA-confirmed Chinese paternal pairs. Previously reported mutation rates for 14 RM Y-STRs in Chinese and European populations were pooled and merged with our data. The highest meiosis number for the two groups reached 4771 and 2687, respectively. Five loci showed significant differences between the populations (DYS570, DYS399S1, DYS547, DYS612, and DYF403S1b). For the new panel covering 30 Y-STR loci, our results show extensive differences in the mutation rates between the two populations, as well. 10 RM Y-STR loci showed relatively low mutation rates (10^-3-10^-2 per meiosis) and 2 FM Y-STR loci had rapid mutation rates (> 10^-2 per meiosis) in the Chinese population. Several-fold differences in mutation rates were found in nine Y-STR loci between the Chinese and reference populations, with two loci having significantly higher mutation rates and one locus with a significantly lower mutation rate in the Chinese population (P < 0.05). Eighteen RM Y-STRs (> 10^-2 per meiosis), 8 FM Y-STR loci (5×10^-3-10^-2 per meiosis), 3 moderately mutating Y-STRs (MM Y-STRs, 10^-3-5×10^-3 per meiosis), and one locus with no observed mutation events were identified in the Chinese population. 40.06% of the Chinese paternity pairs were discriminated with RMplex while only 20.84% with the initial 14 RM Y-STRs, indicating that RMplex is beneficial for distinguishing paternally related males. Future studies on populations of different genetic backgrounds are necessary to obtain comprehensive estimates of mutation rates at these new loci.