Professor Yiping Hou is Dean of the West China College of Preclinical and Forensic Medicine at Sichuan University. He has held numerous positions in forensic medicine, including Professor of West China University of Medical Sciences, and visiting scholar at the Institute of Forensics, University of Cologne. Professor Hou received the Alexander von Humboldt Foundation Research Fellowship while performing genetic research at the University of Bremen in Germany.
What is the focus of the College?
The West China College of Preclinical and Forensic Medicine at Sichuan University is one of two National Key Forensic Discipline Centers, providing solid basics and strong technologies for state-funded research projects and education. The college is also home to the Forensics Teaching Guidance Committee of Higher Education for the Ministry of Education and the chairman and secretary of the Board of the Forensic Research Committee of the China Institute of Higher Medical Education. The forensic center of the college, the West China Center of Forensics Service in Sichuan, has gained National Forensics Identification Accreditation and has been validated by different labs and institutions. The Center is qualified for all five types of forensic testing prescribed by national laws: forensic pathology, forensic clinical medicine, forensic psychiatry, forensic genetics, and forensic toxicology.
What are your specific research interests?
We perform forensic genetic studies and research the development of forensic techniques. Our research activities include human identification using casework samples and the analysis of highly complex relative relationships.
How many casework, reference work, and paternity cases do you routinely process?
We have an average of 6000 cases per year, including primary identification and reappraisal. Paternity testing is one of our regular tasks.
What is your opinion about the new European Standard Set of Loci?
The new European Standard Set (ESS) of Loci is verified by European forensic genetics experts to fit the development of a European forensics database. The main idea is to increase from 7 to 12 STR loci to meet the demands of European international database queries and the practical needs of European forensic work. However, it must be pointed out that the new ESS only includes some of the same marker sets as those used in other national forensics databases, including those of the US and China. Therefore, worldwide data comparison and DNA data query efficiency will be different from internal European results.
Do you think that we will ever have a harmonized set of markers that will be used in all labs around the world? What should this look like?
It would be easy to consolidate all of the markers requested in major databases into one kit. This should be developed so that DNA data can be searched for worldwide.
For paternity testing, do you routinely use markers other than those in the major databases, such as 16plex CODIS markers?
Different paternity tests require different numbers of STR markers. We select the number of markers that will ensure we obtain a cumulative excluding paternity ratio over 0.9999, depending on the testing type. Additional STR markers are needed in the case of unusual testing types or abnormal STR marker testing results. Our lab regularly uses autosomal markers, Y-chromosome markers, X-chromosome markers, and mitochondrial DNA for testing. Even considering autosomal markers alone, we test up to 20–35 markers for regular cases to keep the highest efficiency of the testing system.
How important is the assessment of X-chromosomal markers in deficiency cases?
X-chromosomal markers are very important in mother-son maternity testing, father-daughter paternity testing, and grandmother-granddaughter testing. X chromosomes offer haplotype information, dramatically increasing the efficiency of testing.
Some special deficiency cases have been resolved by your laboratory. Could you give us one technically challenging example that was successfully prosecuted?
We performed father-daughter paternity testing using 19 routine STR markers, and 2 of the markers did not indicate a paternal relationship (0.0001 < PI < 10,000). To clarify the results, we further tested using the Investigator HDplex Kit and Investigator Argus X-12 Kit, and the results clearly showed a paternal relationship (PI > 10,000) for all loci, giving evidence to support the hypothesis that the man was the girl’s biological father.
Commonly, STR analysis is performed for human identification, although alternative approaches like the analysis of deletions and insertion polymorphisms (DIPs) have recently been become commercially available. What are the main benefits or limitations to analyzing DIPs?
The amplicons of DIP markers are very small, so they work better for partially degraded DNA, low copy numbers of DNA, and hair and bone samples. Because they are biallellic markers, combinatorial use of dozens of DIP markers can reach the same discrimination level as the current STR systems.
Furthermore, DIP markers are compatible with current STR testing platforms, i.e., capillary electrophoresis. There is no stutter peak when using DIP markers and it is also easier to get the correct genotyping results.
How important is the pre-analytical part of the forensic process — sample collection, stabilization, and extraction — for the overall results? What advice would you give to increase the chance to get a profile when working with challenging samples?
I think this is the most important step. Only when you have high-quality DNA can you get a high-quality DNA profile. Otherwise, you will only get a partial DNA profile or even no result from DNA genotyping. The QIAamp DNA Investigator Kit works well for purifying limited amounts, or heavily degraded, DNA.
What are the future activities of your group?
Besides routine casework, we will go deeper into identity testing for difficult casework samples, complex kinship testing, species identification for casework samples and tissue samples, and we intend to develop related technical solutions.
What QIAGEN products do you use in your work?
As mentioned, we use the QIAamp DNA Investigator Kit for DNA purification. The Investigator HDplex Kit and Investigator Argus X-12 Kit are part of our paternity testing workflow. We also use the QIAGEN Multiplex PCR Kit for PCR, and the PyroMark PCR Kit on the PyroMark Q96 ID for Pyrosequencing.
Professor Hou, thank you for your time.
