Jenni Hällfors’ dissertation highlights the pleiotropic effects of nicotine receptors
M.Sc. Jenni Hällfors’ thesis entitled "Nicotine Dependence – Identifying the Contribution of Specific Genes” focuses on identifying genes predisposing individuals to smoking behavior and nicotine dependence. This topic is of outmost importance, since according to World Health Organization, tobacco is still one of the biggest public health threats the world has ever faced, killing more than 7 million people a year.
Jenni Hällfors graduated from the University of Helsinki in 2010 having genetics as her major subject. In 2009 she joined Professor Jaakko Kaprio’s research group as a research assistant and started her thesis work soon after.
– My excellent supervisors, Jaakko Kaprio and Anu Loukola, and the group’s various fascinating research topics made the decision to continue with the thesis project easy for me, Jenni says.
Jenni’s thesis consists of three publications and one manuscript currently being under review. She has utilized both Finnish twin cohorts and population-based samples and performed linkage, candidate gene and genome-wide association analyses.
In two of the publications she concentrated on the thus far best characterized smoking behavior locus on chromosome 15, which harbors three nicotine receptor subunit genes. She was able to confirm the earlier association findings and show that variation within this locus explains approximately 1% of the inter-individual differences in the daily smoking quantity. Interestingly, nicotine receptor variants were also shown to associate with alcohol consumption and BMI.
– These results are an exciting example of pleiotropy, one gene influencing two or more seemingly unrelated traits. Notably, the effect on BMI was only seen when the smoking status of the participants was taken into account. Nicotine receptor variants were shown to contribute to higher BMI in those people who have never smoked and to lower BMI in those who are current smokers.
As part of the thesis work, she also conducted a genome-wide association study aiming to identify novel variants explaining smoking behavior related traits, such as smoking quantity and nicotine withdrawal symptoms. The pinpointed genes highlighted the importance of neurotrophin signaling pathway in smoking behavior.
During the past year, Jenni has been quite busy combining the thesis project with a family life with two little boys. In the future, she would be interested in transitioning from academia to industry.
– The findings of my thesis improve our knowledge of the genetic factors affecting smoking behavior and nicotine dependence, but bigger samples and large collaborations are still needed to get this field further. Although studying genetics of complex traits is always challenging, I have really enjoyed this challenge, Jenni concludes.
M.Sc. Jenni Hällfors will defend her doctoral dissertation in the Faculty of Medicine, University of Helsinki, on 2 June 2017 at 12:00. The public examination will take place at the following address: Biomedicum Helsinki, Seminaarihuone 3, Haartmaninkatu 8. Dosent Päivi Onkamo, University of Helsinki, will serve as the opponent, and Professor Jaakko Kaprio as the custos.
The dissertation is also available in electronic form through the E-thesis service.