Successful direct amplification of nuclear markers from a single hair follicle

Abstract

We report on successful amplification of DNA profiles from a single hair. Direct amplification was used on the root tip of both anagen and telogen hairs using a kit to amplify 15 STR loci. All 30 anagen hairs tested from five different people gave full DNA profiles after 29 cycles with no allelic drop-in or heterozygous imbalance. Six of the 30 telogen hairs tested resulted in a full DNA profile, and a further four telogen hair samples tested produced a DNA profile of five or more complete loci that could be up-loaded to the National DNA Database (Australia). A full DNA profile was also obtained from the shaft of an anagen hair. Current practice for many laboratories is that a single hair may not be subjected to DNA testing as there is little chance of success, hence this 100 % success rate from anagen hairs is a significant advancement. A full DNA profile was obtained from a 5 year-old single hair illustrating the success when using direct PCR rather than attempting an extraction prior to the amplification step. The process described deliberately uses current DNA profiling methods with no increase in cycle number, such that the methodology can be incorporated readily into operational practice. For the first time in the field of human identification, single hairs can be analyzed with confidence that a meaningful DNA profile will be generated and the data accepted by the criminal justice system.

The biology of human hair: A multidisciplinary review

“…Hair growth and development has been studied by developmental biologists, geneticists, and dermatologists (Bernard, 2016;Fuchs et al, 2001;Kaplan & Holbrook, 1994;Legué, Sequeira, & Nicolas, 2010). Occasionally the term "hair follicle" has been inaccurately interchanged with the bulbous proximal end of a hair otherwise known as the "hair root" (Haines & Linacre, 2016;Ottens, Taylor, Abarno, & Linacre, 2013). The hair follicle is the organ from which the hair grows and remains in the scalp when a hair shaft is pulled or shed, while the root is the bulbous portion of the hair shaft that resides in the follicle until the hair is shed or pulled (Bassukas & Hornstein, 1989;Langbein et al, 2002).…”

Successful direct amplification of nuclear markers from single dog hairs using DogFiler multiplex

“…Studies implementing direct PCR methods on single fibres and touch DNA samples also indicate that the likely source of DNA, nucleated, or cell‐free, is present on the surface of the sample . Studies into direct PCR of human hairs showed an increased success rate compared to methods that use a DNA extraction step . The aim of this study was to demonstrate the success rate of nuclear DNA recovery from single dog hairs that represent forensic casework scenarios thus allowing routine STR typing of a single shed hair.…”

“…Naturally shed hairs are the most commonly found hair types at crimes scenes. These telogen hairs have finished the growth cycle and lack the sheathing and root bulb, which typically contain high amounts of nuclear DNA required for successful profiling . Mitochondrial DNA (mtDNA) has a much higher copy number within cells, which has made it the primary focus of DNA analysis involving the domestic dog .…”

“…The successful analysis of mtDNA from dog hairs has been reported , however only limited data or anagen hair data from one canine individual exists for nuclear DNA STR analysis from dog hairs. Previous studies conducted on human hairs and human fingernails indicate the most likely source of directly amplified DNA is from nucleated cells or cell‐free DNA on the surface of the hair or nail . Studies implementing direct PCR methods on single fibres and touch DNA samples also indicate that the likely source of DNA, nucleated, or cell‐free, is present on the surface of the sample .…”

“…Hair samples were not treated in any manner prior to amplification in order to minimize the loss of DNA that may be present on the surface of the hair. Previous studies have demonstrated poor success rates in yielding sufficient autosomal DNA from human and canine hairs using standard extraction methods , and therefore were not attempted in this study.…”