Mitochondrial DNA in a population of individuals from the City of São Paulo. DNA extraction from head and pubic hair and blood

Abstract

In biological samples with low copy DNA or DNA degraded samples, such as hair and pubic hair, there is a greater probability of obtaining a mitochondrial DNA profile. Hair and pubic hair are often found at crime scenes; in cases of sexual violence is common to find the suspect's pubic hair in the victim's body. This study analyzed, blood, head and pubic hair samples of 25 males to perform the analysis of mtDNA. Each three hair shafts were grouped and divided into 0.5 cm sections: with the bulbs, and the other with 2 cm, the proximal portion, without the bulbs. The DNA extraction of hair samples was performed using QIAamp DNA Micro Kit (QIAGEN) and the PCR amplification of HV1 and HV2 carried out. The amplified products were purified and sequenced using Big Dye™ Terminator and ABI 3130 (Applied Biosystems). To insure that hair samples were from the same individual, the AmpFLSTR Identifiler Kit ® (Applied Biosystems) were used. The success rate of genotyping of hair samples with the bulb was: 56% for head hairs and in 64% for pubic hair samples, for a complete profile of the 15 STR (Identifiler). There was no statistically significant difference between the DNA concentration samples from hair with bulb and without bulb, as well as samples of pubic hair with bulb and without bulb. The overall success rate obtained with the extraction method used was approximately 60% and the success rate obtained in the sequencing was higher for pubic hair, both with and without bulb, than in head hair samples. Partial profiles of HV1 and HV2 were observed in most cases. Point heteroplasmy was detected in a sample of hair without bulb at hotspot position 16192 and another individual showed point heteroplasmy in pubic hair sample with bulb and without bulb at position 204, also observed in the blood sample of the same individual. In the preliminary results, 193 different haplotypes were detected; the most frequent haplotype was shared by 3 individuals. The most frequent lineage observed was African, showing the contribution of this haplotype group in São Paulo City population. This data were used to analyze and to compare the haplotypes of hair samples.