Hippocampal CREB Reduction and Susceptibility to Chronic Unpredictable Stress

Rat having electrodes inserted into cranium

Students

2020
College

Faculty

Professor of Pharmacology

Project Summary

This summer I had the opportunity to work in Dr. Julie Blendy’s laboratory under the mentorship of postdoctoral fellow, Dr. Melissa Manners. The lab has previously published a body of work studying the role of the transcription factor cAMP response element-binding protein (CREB) in depression and antidepressant treatment. In this ongoing project, we will be examining how deletion of CREB from the hippocampus affects response to the chronic unpredictable stress (CUS) protocol, which induces depression-like behaviors in mice. It has previously been demonstrated that deletion of CREB in the hippocampus induces an antidepressant-like state. Thus, we hypothesize that deletion of CREB in the hippocampus will produce a resilience or reduced susceptibility in the CUS model. 

 

My main role in this project is to perform stereotaxic surgery to delete CREB from the hippocampus. To do this, I first anesthetize a mouse and secure its head to an apparatus with a three-dimensional coordinate system. This allows me to precisely measure the location of the hippocampus. I then drill two small holes on each side of the skull where I can later insert the needle of a syringe. At each of these four injection sites, a small volume of a viral vector containing Cre recombinase is infused. Cre recombinase recognizes molecular targets called LoxP sites that are inserted in a critical portion of the CREB gene, and then excises this portion of the gene. After 6 weeks, CREB expression is knocked down by over 50%. We will then test our hypothesis by conducting CUS on both wild-type and CREB-deleted mice, and evaluate the anxiety and depression like phenotype of these mice. 

 

I am fortunate to be an integral part of this project from its infancy and therefore have gained experience in optimization and troubleshooting of both molecular and behavioral protocols. In conducting PCR to identify mouse genotypes, I learned how to troubleshoot molecular biology protocols. I also spent time focusing on hippocampal injections. I conducted several practice surgeries in order to accurately and reliably inject the hippocampus. In this process, I learned that even very minor deviations from the protocol could result in improper injections. Throughout this process I learned that research does not always run smoothly, however, with diligence, thoughtfulness, and practice, we were able to overcome obstacles. 

 

My time at the lab has been an invaluable educational experience. I have learned a great deal about the scientific process, collaborative work, and what goes in to planning and executing basic scientific research. I also have a better understanding of potential research based career paths. Overall, it has been an extremely enriching experience and I plan to continue working at this lab to see this project to completion.