Kemri develops forensic database for cr*me control, human identification

Kenya through the Kenya Medical Research Institute (Kemri) has started to establish its reference DNA database to help the country better understand its genetic diversity.

Kemri research officer Eva Aluvaala Nambati says that soon a mitogenome also known as Mitochondrial DNA (MtDNA) reference database will be available for use.

This reference database will particularly be useful in aiding forensic investigation where mitochondrial DNA is used. The data base will provide a basis through which frequency estimates of observed mitogenome haplotypes can be expressed hence giving strength to forensic evidence.

 The reference database is not an offender database hence its purpose is not for “catching” criminals, but rather aid in statistical interpretation of forensic evidence.

“For the last three years we have collected and analysed MtDNA from all the ethnolinguistic groups in Kenya spanning all the geographical regions. We are currently reporting on the genetic diversity of the human mitochondrial genome at the Kenyan coast. The results from this study will be used in the establishment of a forensic reference database for Kenyan population,” she said.

Inherited from mothers

The human mitochondrial genome refers to the DNA present in the mitochondria of human cells. Mitochondria are small, membrane-bound organelles found in the cells of the body, and they are often referred to as the “powerhouses” of the cell because they generate energy in the form of adenosine triphosphate (ATP) through a process known as oxidative phosphorylation.

Unlike nuclear DNA, which is inherited from both parents, mitochondrial DNA (MtDNA) is exclusively inherited from mothers. Both egg and sperm cells contain mitochondria with mitochondrial DNA, but it’s only the egg that contributes the mitochondria and mitochondrial DNA to the zygote.

MtDNA changes very little across generations, so scientists can use it to trace maternal lineage through hundreds of thousands of years. Some studies have looked at the MtDNA of modern-day populations to help determine the migration patterns of early humans after they left Africa.

So far, over 1500 samples have been collected across the country, at the coast where the team is currently reporting on. The study samples were randomly collected from consenting individuals from the five coastal counties of Kwale, Kilifi, Taita Taveta, Tana River, and Lamu. “From the study, we found that the most prevalent haplogroup on the Kenyan coast is L3, particularly L3e. Haplogroups are population groups defined by one or more unique mutations in their MtDNA,” said Nambati.

Biogeographical ancestry

She added; “Mitochondrial genome diversity is often described using haplogroups, as individuals from the same geographic region tend to cluster within the same haplogroups. Haplogroups can be informative for inferring the biogeographical ancestry of individuals.”

The organisation, she said decided to embark on this journey because as a country we do not have a mitogenome reference database for the Kenyan population hence statistical inferences and estimations of strength of forensic evidence cannot be made for MtDNA evidence.

She revealed that Kenya is not the only country without this database. African mitogenomes are also poorly represented in global databases such as EMPOP and mitomap. This move will be a major contribution towards bridging the gap in the underrepresentation of African genomes in public databases. “Significant gains have been made towards developing these databases, particularly in the Caucasian populations, however, an African database is lacking. We do not want to be left behind,” said Nambati.

Since one can only get MtDNA from their mother, she said this database can be used to trace one’s maternal ancestry.

The team has  now developed capacity for mitochondrial DNA analysis in the country; this was lacking. This can in future be used in disaster victim identification and missing person identification such as the Shakahola incidence.

With a reference database in place even in the absence relatives the victims haplogroup can be determined and possible or likely geographical ancestry determined hence provide investigative leads. In cases where close relatives are unavailable or unwilling to be tested, employing the mitochondrial DNA approach, expands the scope of individuals available for testing.

This is possible since all maternal relatives possess the same mtDNA. A grandmother passed her MtDNA to her daughters who then transmit their MtDNA to their respective children.Thus it provides a powerful alternative where father-child, mother-child  relationship or siblings cannot be used.”

Can MtDNA be used in forensics? Nambati says that this is possible, especially in situations where crime scene evidence, such as hair or bone is old or degraded. In such a situation, forensic scientists can turn to MtDNA to aid their investigations.

“Mitochondrial DNA boasts a high copy number per cell, ranging from hundreds to thousands of copies, making it particularly advantageous when dealing with degraded or aged samples. Additionally, the absence of recombination on MtDNA allows for the identification of maternally related individuals,” added Nambati.

Will population-specific MtDNA databases be helpful in forensics? Nambati says that yes they will be helpful as they will be used in estimating the expected frequency of mitochondrial haplotypes which makes evidence stronger. Having a high-quality population-based databases will also facilitate a reliable estimate of the frequency of a random match.