Verification of a loss of heterozygosity at the D8S1179 locus in a paternity case by the MiSeq FGx system

Capillary electrophoresis is widely used to study short tandem repeats (STRs) in forensic genetics. However, next-generation sequencing platforms have become a new strategy for forensic DNA typing. In this study, we report a false four-step STR mutation between an alleged father (AF) and child in a paternity case. A total of 23 autosomal STR loci were evaluated using the Huaxia™ Platinum and Goldeneye™ 20A kits, revealing a single mismatch in D8S1179 between the AF (10/10) and the male child (14/14). Additional Y-STR typing of the AF and child was performed, and the results were consistent with those based on 27 Y-STR loci. To further confirm the experimental results, we sequenced the individuals using the MiSeq FGx system and detected 10/15 unbalanced alleles in the D8S1179 locus of the AF and 14/15 unbalanced alleles in the D8S1179 locus of the child. Sanger sequencing revealed that both the AF and child had the C→G point mutation in the primer binding region of D8S1179 resulting in allelic dropout. Therefore, the verification of STR typing by different sequencing systems is helpful for the interpretation of results in cases of multistep STR mutations.

Application of 2,4-Dinitrophenylhydrazine (DNPH) in High-Throughput Screening for Microorganism Mutants Accumulating 9α-Hydroxyandrost-4-ene-3,17-dione (9α-OH-AD)

To develop a quick method for the preliminarily screening of mutant strains that can accumulate 9α-hydroxyandrost-4-ene-3,17-dione (9α-OH-AD), a high-throughput screening method was presented by applying the principle that 2,4-dinitrophenylhydrazine (DNPH) can react with ketones to produce precipitation. The optimal color assay conditions were the substrate androst-4-ene-3,17-dione (AD) concentration at 2.0 g/L, the ratio of AD to DNPH solution at 1:4, and the sulfuric acid and ethanol solution percentages in DNPH solution at 2% and 35%, respectively. This method was used to preliminarily screen the mutants of Rhodococcus rhodochrous DSM43269, from which the three ones obtained could produce more 9α-OH-AD. This DNPH color assay method not only broadens screening methods and increases screening efficiency in microbial mutation breeding but also establishes a good foundation for obtaining strains for industrial application.