Genes Behind the Clots

Every year, millions face the hidden danger of blood clots, leading to serious health challenges. Thrombosis is a complex biological process, regulated by a balance between the formation and breakdown of blood clots. But what if the key to preventing these clots lies in our genes?  

Although the connection between genetics and thrombosis has been studied for some time, recent advancements in genomic technologies have noticeably accelerated discoveries in this area. Randal Westrick, Ph.D., associate professor of bioengineering and biological sciences, is making significant progress in identifying the genetic factors that regulate two key proteins involved in blood clotting, as well as their roles in thrombosis.

Plasminogen activator inhibitor-1 (PAI-1) and Trem-like transcript-1 (TLT-1) are hemostatic proteins that reside in specialized structures within platelets. When these proteins are released into the bloodstream, they play crucial roles in regulating the formation — and dissolution — of blood clots. PAI-1 inhibits fibrinolysis (the process by which clots are broken down), while TLT-1 facilitates clot formation by helping to bind the protein that forms the structural basis of blood clots to platelets. Both proteins play vital roles in hemostasis, but the genetic regulation of their expression, particularly in platelets, remains poorly understood. 

Using mouse models, Dr. Westrick and his laboratory team, which includes OU bioengineering and biological sciences students, examined PAI-1 and TLT-1 levels in different inbred mouse strains. The results revealed substantial variation in both PAI-1 and TLT-1 levels across these strains, laying the foundation for understanding how genetic differences can influence an individual’s risk for thrombotic disease.

“For example, the CAST strain exhibited lower plasma soluble TLT-1 levels, compared to other strains, while strains like 129S1 and DBA had higher plasma PAI-1 levels. These findings suggest that genetic differences — not environmental factors — drive these variations,” Dr. Westrick explains.

To further investigate the genetic basis of these differences, the researchers performed crosses between CAST and DBA strains to produce second-generation offspring. By assessing the levels of PAI-1 and TLT-1 in these offspring through quantitative trait locus analysis, they identified significant loci on chromosomes 5, 6 and 13 that regulate plasma PAI-1 levels.

“In addition, we saw gender differences in PAI-1 expression, with certain strains exhibiting notable differences between males and females. These findings highlight the importance of considering gender as a factor in genetic studies of hemostasis and thrombosis,” Dr. Westrick adds.

Within the framework of Dr. Westrick’s research, Kailey MacFadyen, an undergraduate student majoring in bioengineering, undertook a study of a different protein, Plcb4 — a gene that regulates cellular signaling pathways crucial to thrombosis. 

“To explore how Plcb4 affects blood clotting, we created mice with this gene knocked out. We observed that these mice showed changes in body weight and slight deviations in blood clotting times, but no major issues with platelet activation (a key part of clot formation). This suggests that Plcb4 might help regulate clotting and could potentially be targeted for new treatments to prevent excessive blood clots without major side effects on coagulation,” MacFadyen shares, while discussing the results of her work.

Similarly, bioengineering student Arina Rodionova, who recently received the Best Poster Presentation award at the 2024 Midwest Platelet Conference, explored how genetic changes affect thrombosis by focusing on the F3 gene, which controls tissue factor (TF).

“Thrombosis begins when TF binds to coagulation factor VII, triggering the clotting process. This is regulated by tissue factor pathway inhibitor (TFPI). We noticed that reducing the expression of TFPI in mice with a mutation called Factor V Leiden caused lethal clotting issues. After screening the mice, we discovered a genetic variant (MF5L6) that helped a subset of mice survive by lowering F3 expression. We identified two new genetic variants near the F3 gene that may regulate its expression, providing new insights into how thrombosis is genetically controlled,” Rodionova says.  

Like PAI-1 and TLT-1, Plcb4 and F3 highlight another layer of genetic control over thrombosis, where small shifts in cellular processes can influence the risk of thrombotic diseases. 

The next steps in Dr. Westrick's research include refining the genetic mapping of PAI-1 and TLT-1 loci to a higher resolution, which will allow for the production of genome-edited mice to confirm the role of specific genetic variants. These efforts align with broader goals in the field of thrombosis research, where pinpointing genetic influences — such as those identified in the Plcb4 and F3 studies — could lead to the development of more targeted therapies for clotting disorders, paving the way for precision medicine approaches, based on an individual’s genetic profile.

Additionally, a major goal of the research is to identify the enzyme(s) that cut(s) TLT-1 off the surface of platelets, producing soluble TLT-1 and opening up new avenues of research into how TLT-1 regulates clotting and immune function. 

Dr. Westrick's innovative research is supported by multiple American Heart Association, National Science Foundation and National Institutes of Health grants, including funding from the National Heart, Lung and Blood Institute. For more information on Dr. Westrick’s work in the Cardiovascular Bioengineering and Genomics laboratory, contact him via email at [email protected]