Nuclear staining of telogen hair roots contributes to successful forensic nDNA analysis

Discrimination of mongoose hair from domestic cattle hair, human hair, and synthetic fiber using FTIR spectroscopy and chemometric analysis: a rapid, cost-effective, and field-deployable tool for wildlife forensics

Mongoose hair is used to prepare fine brushes, which increases the demand for mongooses to be poached from the wild and brutally bludgeoned to death. Mongooses were listed as Schedule I species under the Indian Wildlife (Protection) Act 1972. Species identification of wildlife case-related samples is necessary to convict a person under this legislation. Microscopy and DNA-based techniques are commonly used to identify mongoose hair in seized brushes. However, in painting brushes, the roots, and the lower part of the hair are mostly trimmed, and only the upper part is used to make the brushes. In addition, brushes are often prepared with mixed hair from mongoose, domestic cattle, human hair, and synthetic fibre. Therefore, the identification of mongoose hair by microscopy and DNA-based techniques is restricted due to the lack of complete strands of hair and the absence of hair roots. Therefore, there is an urgent need to develop an alternative methodology for the identification of mongoose hair from seized articles. FTIR spectroscopy for forensic analysis has gained significant attention over the years because of its sensitivity, specificity, and non-destructive nature. The present study aimed to discriminate Indian grey mongoose (Herpestes edwardsii) hair from domestic cattle hair (domestic water buffalo and domestic cow), human hair, and synthetic fiber based on their chemical composition using FTIR spectroscopy and chemometric analysis. We have taken hair from four individuals for each species, namely Indian grey mongoose, domestic cattle, human hair, and synthetic fibre. The FTIR spectrum was recorded, and partial least-squares discriminant analysis (PLS-DA) was used to discriminate hair and synthetic fiber. The established PLS-DA model showed an R-square value and an RMSE (root mean square error) value of 0.9 and 0.13 respectively. Our preliminary findings have shown that FTIR spectroscopy combined with chemometrics can quickly discriminate Indian grey mongoose hair, domestic cattle hair, human hair, and synthetic fiber, providing crucial evidence for judicial proceedings.

An evaluation of the RapidHIT™ ID system for hair roots stained with Diamond™ Nucleic Acid Dye

The RapidHIT™ ID (RHID) system was evaluated for its suitability in processing a single hair root to obtain informative DNA profiles. Hair samples were assessed for nuclear DNA prior to DNA analysis using Diamond™ Nucleic Acid Dye (DD) and real-time Extended Depth of Field (EDF) imaging to visualise and count nuclei if present. Hairs were viewed under an Optico N300F LED Fluorescent Microscope and imaged using a MIchrome 5 Pro camera. Hair roots were processed through both the ACE GlobalFiler™ Express sample cartridge and the RapidINTEL™ sample cartridge. A total of 44 hairs including shed hairs (9) and plucked hairs (35) from 8 donors were evaluated in this study. The processing of hairs using the RHID system required the modification of a standard swab that allowed for hairs to be easily collected and placed into the cartridge but also allowed for the re-collection of hair roots post RHID analysis (for potential standard DNA workflow). 90% of plucked hairs with a high nuclei count (>100) resulted in a high partial or full DNA profile, with the remaining 10% resulting in a low partial profile. 44% of shed hairs resulted in a low partial profile, with the remaining hairs resulting in a null profile. This study demonstrated that the RHID system could successfully obtain a DNA profile from a single hair root with nuclei present post-DD staining. According to these results, it is suggested that when dealing with hairs containing fewer than 50 nuclei, using the RapidINTEL™ cartridge can enhance allele recovery.

DNA and protein analyses of hair in forensic genetics

Hair is one of the most common pieces of biological evidence found at a crime scene and plays an essential role in forensic investigation. Hairs, especially non-follicular hairs, are usually found at various crime scenes, either by natural shedding or by forcible shedding. However, the genetic material in hairs is usually highly degraded, which makes forensic analysis difficult. As a result, the value of hair has not been fully exploited in forensic investigations and trials. In recent years, with advances in molecular biology, forensic analysis of hair has achieved remarkable strides and provided crucial clues in numerous cases. This article reviews recent developments in DNA and protein analysis of hair and attempts to provide a comprehensive solution to improve forensic hair analysis.

Hair root staining with Hematoxylin: Increasing the rate of obtaining DNA profiles in forensic casework

Hair evidence collected during a forensic investigation has the potential to provide valuable sourcing information through DNA analysis of its root. Over time, hair examiners at the North Carolina State Crime Laboratory observed hair roots being sent for DNA analysis were not yielding profiles as expected. Recent advancements in the Forensic Biology Section's detection limits prompted research into whether changes to the current root removal protocol could increase the likelihood of developing a DNA profile from a hair root. An internal validation was completed for the method of Hematoxylin staining to screen telogen roots for DNA analysis. Over 900 head hairs from approximately 15 living donors were examined for telogen roots. Those roots were stained using Hematoxylin and examined for nuclei. The roots were separated into groups based on nuclei present: Group I (1-10 nuclei), Group II (11-20 nuclei), Group III (21-30 nuclei), Group IV (31-40 nuclei), and Group V (41 or greater nuclei). A set of 64 roots, including a Negative Control (0 nuclei) and a Positive Control (anagen or catagen roots), were sent for quantitative DNA analysis. The data showed a clear separation between Groups I and II, where 36% of Group I verses 80% of Group II passed the quantification cutoff. All samples in the Negative Control, Group I, and the Positive Control were then amplified along with a representative sample in Groups II through V. After amplification, the delineation between Groups I and II maintained with 27% of Group I verses 89% of Group II obtaining DNA profiles. As a result, the nuclei required to obtain a potential DNA profile at our laboratory is eleven or more. Prior to Hematoxylin, anagen, catagen, or telogen roots with follicular tissue were sent for DNA analysis, resulting in 32% of roots yielding DNA results. Following implementation of Hematoxylin into casework in March 2019, the success rate has more than doubled to 69%, illustrating the utility of Hematoxylin root staining in improving casework efficiency. Through this methodology, only roots with the best potential to develop a DNA profile are sent for testing, thereby decreasing DNA caseload, cost, and time of analysis. In fact, Hematoxylin staining has resulted in a 14% reduction in the number of hair roots forwarded for DNA analysis, meaning hairs not meeting nuclear threshold are preserved for future examinations.

A quantitative method for selecting a hair for nulear DNA analysis

This study evaluated a quantitative method to predict the success of nuclear DNA (nuDNA) typing for head hair roots, using the minor-groove DNA binding dye, 4', 6-diamidino-2-phenylindole (DAPI). The procedure was successful in staining nuclear material in hair roots, regardless of soft tissue presence or growth phase. We found that the dye can even reveal an abundance of visible nuclei in hairs that were previously assumed to be unsuitable for nuDNA analysis (e.g., telogen hairs). The value of DAPI staining is particularly evident when considering the STR typing results for telogen hairs. Here, telogen hairs with greater than 100 visible nuclei frequently produced full or high-partial STR profiles, while telogen hairs with fewer than 100 visible nuclei rarely resulted in >20 % STR allele recovery. In addition, our findings indicated no interference by DAPI in the forensic examination of hair evidence, including preparation of hairs on microscopic slides, microscopic examination, DNA extraction, quantitative PCR, and short tandem repeat (STR) typing. Furthermore, the method remained steadfast for hairs washed by sonication as well as hairs retrieved from Permount™ mounting medium. When validated, this simple, quick, and quantitative screening method can be used in casework to select a hair for nuDNA analysis, especially for hairs that were previously sent directly for mitochondrial (mt) DNA analysis based on the lack of adhering soft tissue, regardless of growth phase. Conversely, nuDNA degradation may exist in hairs which exhibit microscopic characteristics typically associated with a potential to generate successful nuclear DNA profile including stretched roots with attached root sheath. DAPI staining of hairs gives forensic examiners the ability to have more information, other than growth phase, when selecting a hair or hairs for possible nuDNA analysis.

A rapid nuclear staining test using cationic dyes contributes to efficient STR analysis of telogen hair roots

Telogen hairs presented in the crime scene are commonly encountered as trace evidence. However, short tandem repeat (STR) profiling of the hairs currently have low and limited use due to poor success rate. To increase the success rate of STR profiling of telogen hairs, we developed a rapid and cost-effective method to estimate the number of nuclei in the hair roots. Five cationic dyes, Methyl green (MG), Harris hematoxylin (HH), Methylene blue (MB), Toluidine blue (TB), and Safranin O (SO) were evaluated in this study. We conducted a screening test based on microscopy and the percentage of loss with nuclear DNA, in order to select the best dye. MG was selected based on its specific nuclei staining and low adverse effect on the hair-associated nuclear DNA. We examined 330 scalp and 100 pubic telogen hairs with MG. Stained hairs were classified into five groups and analyzed by STR. The fast staining method revealed 70% (head hair) and 33.4% (pubic hair) of full (30 alleles) and high partial (18-29 alleles) STR profiling proportion from the lowest nuclei count group (one to ten nuclei). The results of this study demonstrated a rapid, specific, nondestructive, and high yield DNA profiling method applicable for screening telogen hairs.

A quantitative assessment of a reliable screening technique for the STR analysis of telogen hair roots

Human telogen hairs are commonly recovered as trace evidence but currently have limited use for forensic DNA analysis. Recent studies have revealed that telogen roots may be shed with adhering material that may contain cells, thus providing a potential source of nuclear DNA. A simple histological stain can be used to screen telogen roots for the presence of nuclei, thus increasing the chance of selecting roots that may yield nuclear DNA. Using this method to visualise nuclei, we surveyed 998 hairs from 136 individuals, quantified the number of nuclei, extracted DNA and evaluated corresponding DNA yield and STR profiling success. Of the hairs screened, 35% of telogen roots contained nuclei and in total 6% of all roots screened had more than 100 nuclei. The number of nuclei associated with telogen roots was independent of the presence or absence of visibly adhering material, highlighting the importance of using histological staining rather than simple microscopic examination. DNA yield and STR profiling were significantly and positively correlated with nuclei number. The methods presented here can be incorporated into routine trace and DNA analysis providing an efficient and cost effective method to screen telogen hairs, and predict STR profiling success prior to destructive DNA analysis. The results of this study indicate telogen hairs may provide a reliable source of nuclear DNA for use in routine casework.