Development and validation for identity testing of I-DNADuo, a combination of I-DNA1 and a new multiplex system, I-DNA2

I-DNASE21 system: development and SWGDAM validation of a new STR 21-plex reaction

I-DNASE21 is a new STR multiplex system that amplifies 21 STR autosomal loci, plus the amelogenin locus in one reaction. This system has been designed to analyze all the STR loci included in the Combined DNA Index System (CODIS), Interpol Standard Set of Loci (ISSL), Extended European Standard Set (ESS-Extended), UK National Criminal Intelligence DNA Database (NDNAD) and German Core loci (GCL). This manuscript presents the validation of the I-DNASE21 system according to the revised guidelines issued by the Scientific Working Group on DNA Analysis Methods (SWGDAM). The results of this validation, added to the extremely high discriminatory power showed, suggest that I-DNASE21 could be a potentially helpful tool for identification and kinship determination even in complex paternity cases.

Chimerism analysis in transplant patients: a hypothesis-free approach in the absence of reference genotypes

INTRODUCTION

During routine analysis of chimerism in bone marrow transplant patients pre-transplant genotype of the recipient or the donor might lack. We aimed to develop a new method to analyze DNA results suitable when reference genotypes are not available.

METHODS

The method was based on the balance between heterozygotes. It was implemented in a standard computer spreadsheet, and considered the hypothetical donor-recipient genotype combinations. Hypotheses with peak height ratios and allele sharing tendency above a critical threshold were accepted. The results were compared with those obtained with prior knowledge of reference genotypes.

RESULTS

The algorithm predicted correctly the proportion of donor/recipient chimerism, even in the absence of reference genotypes. In fact, the predicted values were closely correlated (r(2)>0.98) and free of systematic bias (slope 0.98-1.04), in comparison with the reference values obtained with prior knowledge of the donor and recipient genetic profiles.

CONCLUSIONS

This study constitutes a proof-of-concept of the application of the heterozygote balance for the quantitative study of chimerism. The algorithm computes post-transplant chimerism in an easy and time-efficient way, even when the donor and recipient reference genotypes are unavailable. Therefore, it can be a useful tool for laboratories involved in chimerism analysis.

Development and validation of a multiplex reaction analyzing eight miniSTRs of the X chromosome for identity and kinship testing with degraded DNA

We report the development of an effective system for analyzing X chromosome-linked mini short tandem repeat loci with reduced-size amplicons (less than 220 bp), useful for analyzing highly degraded DNA samples. To generate smaller amplicons, we redesigned primers for eight X-linked microsatellites (DXS7132, DXS10079, DXS10074, DXS10075, DXS6801, DXS6809, DXS6789, and DXS6799) and established efficient conditions for a multiplex PCR system (miniX). The validation tests confirmed that it has good sensitivity, requiring as little as 20 pg of DNA, and performs well with DNA from paraffin-embedded tissues, thus showing potential for improved analysis and identification of highly degraded and/or very limited DNA samples. Consequently, this system may help to solve complex forensic cases, particularly when autosomal markers convey insufficient information.