Sheth, Nidhi, Swaminathan, Harish, Gonzalez, Amanda G., Duffy, Ken R. and Grgicak, Catherine (2021) Towards developing forensically relevant single-cell pipelines by incorporating direct-to-PCR extraction: compatibility, signal quality, and allele detection. International Journal of Legal Medicine, 135. pp. 727-738. ISSN 1437-1596
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Abstract
Current analysis of forensic DNA stains relies on the probabilistic interpretation of bulk-processed samples that represent mixed
profiles consisting of an unknown number of potentially partial representations of each contributor. Single-cell methods, in
contrast, offer a solution to the forensic DNA mixture problem by incorporating a step that separates cells before extraction. A
forensically relevant single-cell pipeline relies on efficient direct-to-PCR extractions that are compatible with standard down-
stream forensic reagents. Here we demonstrate the feasibility of implementing single-cell pipelines into the forensic process by
exploring four metrics of electropherogram (EPG) signal quality—i.e., allele detection rates, peak heights, peak height ratios, and
peak height balance across low- to high-molecular-weight short tandem repeat (STR) markers—obtained with four direct-to-PCR
extraction treatments and a common post-PCR laboratory procedure. Each treatment was used to extract DNA from 102 single
buccal cells, whereupon the amplification reagents were immediately added to the tube and the DNA was amplified/injected
using post-PCR conditions known to elicit a limit of detection (LoD) of one DNA molecule. The results show that most cells,
regardless of extraction treatment, rendered EPGs with at least a 50% true positive allele detection rate and that allele drop-out
was not cell independent. Statistical tests demonstrated that extraction treatments significantly impacted all metrics of EPG
quality, where the Arcturus® PicoPure™ extraction method resulted in the lowest median allele drop-out rate, highest median
average peak height, highest median average peak height ratio, and least negative median values of EPG sloping for
GlobalFiler™ STR loci amplified at half volume. We, therefore, conclude the feasibility of implementing single-cell pipelines
for casework purposes and demonstrate that inferential systems assuming cell independence will not be appropriate in the
probabilistic interpretation of a collection of single-cell EPGs.
Item Type: | Article |
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Keywords: | Forensic DNA; Human identification; Single-cell forensic DNA; Direct-to-PCR; Forensic DNA Mixtures; |
Academic Unit: | Faculty of Science and Engineering > Research Institutes > Hamilton Institute |
Item ID: | 15187 |
Identification Number: | 10.1007/s00414-021-02503-4 |
Depositing User: | Dr Ken Duffy |
Date Deposited: | 06 Jan 2022 15:37 |
Journal or Publication Title: | International Journal of Legal Medicine |
Publisher: | Springer |
Refereed: | Yes |
Related URLs: | |
URI: | https://mural.maynoothuniversity.ie/id/eprint/15187 |
Use Licence: | This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here |
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