MicroRNA profile analysis for discrimination of monozygotic twins using massively parallel sequencing and real-time PCR.

In general, it is extremely problematic to discriminate between monozygotic twins (MZTs), who share the same genomic DNA sequence, using traditional DNA-based identification methods such as short tandem repeat profiling. MicroRNAs (miRNAs) have shown potential in forensic applications owing to their low molecular weight, abundant and tissue-specific expression. In this study, we utilized massively parallel sequencing technology to perform genome-wide profiling of miRNAs in the blood from four pairs of healthy MZTs. On average, 158 miRNAs were detected in each individual and 14% of which were differentially expressed within each pair of MZTs. The miRNAs with the most significant differences in expression between the twins were confirmed using real-time polymerase chain reaction. Our results demonstrated that miRNAs have potential for use as molecular markers in MZTs discrimination.

Tri-allelic patterns of STRs and partially homologous non-sister chromatid crossover observed in a parentage test.

A maternity testing case is reported, in which the child showed tri-allelic patterns in two short tandem repeat (STR) loci. The genotypes of Penta D of the mother and the child were 9,13 and 9,10,13, respectively. Those of D21S11 were 32.2,35 and 29,35, respectively, but intensity ratio of alleles 29 and 35 of the child was 1:2. These results suggested the copy number variations (CNVs) or trisomy of chromosome 21. By further examination using STR-based chromosome aneuploidy detection kit, three alleles were detected in D21S1411, LFG21 and Penta D, and 2 alleles with intensity ratio of 1:2 were observed in D21S2502, D21S1435, D21S11 and D21S1246. Karyotype and whole-genome SNP array analyses showed that the child had a free trisomy 21. In addition, partially homologous non-sister chromatid crossover occurred at the region 19181770-39499178 on the long arm of chromosome 21.