Genes Towards Justice: Outstanding Paper Progresses Filipino Forensics

by Daniel Varias (Isochore)

Exploring genetic diversity in Filipinos has value not only in reconstructing how human pre-history unfolded in this region of the world but also in its social impact in improving forensic DNA practice in the country.

During its 42^nd Annual Scientific Meeting held on July 8-10, 2020, the National Academy of Science and Technology (NAST) awarded one of this year’s Outstanding Scientific Paper Award to the work entitled “Filipino DNA variation at 36 Y-chromosomal short tandem repeat (STR) marker units.”. The Special Genomics Issue of the Philippine Journal of Science published the paper in 2019. Researchers from the DNA Analysis Laboratory, Natural Sciences Research Institute, UP Diliman namely Jazelyn M. Salvador, GeneSoc Alumnus aProf. Jae Joseph Russell B. Rodriguez (batch Ribozymes), Lindsay Clare dL Carandang, Altair B. Agmata, Maria Lourdes D. Honrado, Frederick C. Delfin, and GeneSoc Honorary Member, Dr. Maria A. Corazon De Ungria co-authored the paper.

The DNA is one of the most powerful and objective tools in human identification and can aid in the rapid resolution of criminal cases. The most common markers used in DNA forensics are short tandem repeats (STRs) found in the autosomes and the Y-chromosome. Polymerase chain reaction (PCR) targets these STRs. Analyzed biological samples generate DNA profiles of an evidence, which enables its comparison to the reference DNA profile of a suspect. A match between these STR profiles can affirm the presence of the suspect in the crime scene, and in many cases provide support for other evidences that confirm the guilt of the accused. Autosomal STRs are highly variable and are used for direct identification and kinship comparisons. On the other hand, Y-chromosomal STRs are male-specific and can be used to identify male DNA profiles and to establish paternal relatedness. Read more about DNA profiling of Filipino men here.

In sexual assault cases, vaginal swab samples submitted for DNA testing contain a mixture of DNA coming from a female victim and the male perpetrator/s. Interpreting such male-female mixtures using autosomal STRs can be a complicated task for DNA analysts. However, the male-specificity of Y-chromosome markers enables the isolation of a male assailant’s DNA profile, thus its value in resolving sexual assault cases.

The weight of a DNA match depends on demonstrating its rarity in the population. This is made possible by establishing a database of reference DNA profiles representative of the population from which frequencies of alleles and haplotypes can be estimated. To establish such database for Filipinos, the team of scientists headed by Dr. De Ungria, invited 299 unrelated Filipino males from the Greater Manila Area. They took part in this genetic study where they consented to provide blood samples for Y-chromosome STR (Y-STR) DNA typing. The team analyzed 36 Y-STR marker units including 13 rapidly mutating (RM) Y-STRs. With the expansion of the database of the Filipino Y-STRs, the capacity to conduct forensic DNA investigation involving male comparisons is augmented. For example, the use of the RM Y-STRs will enable differentiation between paternal relatives, which was previously not possible with the slow mutating markers. This has important implications when suspects are related along the paternal line.

When compared with other populations, structuring was observed which can be explained by geographic proximity particularly for the 21 slow and moderately mutating Y-STR marker units. This reflects the distinct composition of our country’s Y-chromosome diversity. It also highlights the need for a specific Filipino DNA database when statistically evaluating the weight of DNA evidence in relation to criminal investigations and kinship tests. The database merits continuous expansion to include more samples from different groups, e.g. from other regional centers and those from specific ethno-linguistic groups, indigenous peoples/ indigenous cultural communities (IPs/ICCs) that are part of the Philippine population. “There is absolute need to further expand the database through the addition of more human samples in order to better represent the diverse communities and groups that we have in the Philippines, all of whom contribute to the Philippine identity.” Dr. De Ungria said.

“Being selected as one of the outstanding papers by NAST provides us a wonderful opportunity to talk about this aspect of our research at the DNA Analysis Laboratory, Natural Sciences Research Institute, UP Diliman. Besides being recognized for the passion in which we worked to do the science and the clarity to communicate this science to the public whilst asking vital questions about the Philippine genome highlight the value we place in studying our own genome. Our genome is like an ‘autobiography’ that contains the story of our past, the genetic signals that we have now and that we need to understand in order to survive the present, and the evolutionary mechanisms which we need to reach the future.” Dr. De Ungria stated.

Behind the success, however, are daunting challenges they have surpassed. Assistant Prof. Rodriguez mentioned that the main challenge is going through the various processes to obtain institutional approvals including the approval from an accredited ethics review committee after it has scrutinized the ethical aspect of our research, which Dr. De Ungria affirmed. “Because DNA contains the entire genetic code of an individual, there is absolute need to minimize risk and maximize the benefits from this type of research,” she said.

Amongst the many challenges faced in forensic genomics research is working to balance the need for openness in sharing scientific discovery and protecting the genetic privacy of the individuals who generously contribute their own samples to advance Philippine genomic science for the common good of this and future generations.