Forensic evaluation of mitochondrial DNA heteroplasmy in Gujarat population, India

Abstract

Background

Owing to its high copy number and its small size, mtDNA analysis is the most reliable choice when biological materials from crime scenes are degraded or have mixed STR profiles.

Aim

To examine the occurrence of heteroplasmy along with its frequency and pattern in both HV1 and HV2 regions of the mtDNA among unrelated individuals from India.

Subjects and methods

Mitochondrial DNA control region [hypervariable region one (HV1) and hypervariable region two (HV2)] were analysed in blood and buccal tissues of 104 unrelated individuals from the Indian state of Gujarat.

Results

A high frequency of point heteroplasmy (PH) and length heteroplasmy (LH) was revealed. PH was detected in 7.69% of the population, with a higher frequency observed in blood than in buccal samples. However, there were no statistically significant differences in PH between the two tissues (Chi-square = 0.552, p ≥ 0.05). A total of six PH positions were detected: three at HV1, and another three at HV2. The studied population showed 46.15% LH in the HV1 and HV2 regions of both tissues. The LH positions observed in the Gujarat population were the same as those previously reported at HV1 np16184–16193 and HV2 np303–315.

Conclusions

Our findings suggest that differences in the pattern of heteroplasmy found in different tissues can complicate the forensic analysis, on the other hand, the probability of a match between the questioned and reference samples increases when the heteroplasmy is identical in both tissues. Variability of PH among persons and even within tissues recommends analysing multiple tissue samples before drawing a conclusion in forensic mtDNA analyses.

Keywords:

• Mitochondrial DNA
• forensic
• heteroplasmy
• mtDNA control region
• Indian population

Acknowledgements

The authors greatly appreciate the generosity and kind support of Walther Parson. Thank you to our lab mates Harshit Ganatra and Blessy Baby. Mohammed H. M Alqaisi would like to acknowledge the Indian Council for Cultural Relations (ICCR) for the fellowship.

Ethical approval

This study was approved by the Ethical Committee of National Forensic Sciences University. All samples were collected with detailed informed consent.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The nucleotide sequences have been submitted to NCBI GenBank^® under accession numbers OM908544 – OM908751. The dataset generated is accessible in EMPOP database under accession number EMP00859.

Additional information

Funding

This work was financially supported by the regular academic grant from National Forensic Sciences University, Gujarat, India to School of Forensic Science. Mohammed H. M Alqaisi would like to acknowledge the Indian Council for Cultural Relations (ICCR) for their financial support for this work.